One thing that is very noticeable down here in the Antarctic is how dry the air is. It is in fact the driest continent on earth.
Warm air can carry a lot more moisture than cold air. This moisture is actually invisible vapour (gas). When you breathe out on a frosty day, the warm moist air from your lungs becomes chilled and forces the water to condense into tiny liquid drops which appear as a cloud. This phenomenon once allowed me to appear as if I were smoking a cigarette at school (it was a plastic imitation) which successfully ‘wound up’ my teacher without leading to any painful consequences for myself or my lungs.
On Planet Earth – we could compare the hot and humid equator
with our lungs breathing out. Due to the warmth there, the air expands, becomes
less dense and rises. As it rises it expands further and cools, having to release
its moisture as rain (hence the tropical rainforests) and then flowing away
towards the North or South as high level dry air. After a somewhat involved
journey which may include sinking to the surface and rising again, this air
finally reaches one of the Poles eg Antarctica,
where it is now very cold and sinks to the surface. It has nowhere to go but
outwards, blowing away in all directions from the centre of the continent. The
dome like profile of the ice sheets also encourages these dry cold winds to
blow faster and faster towards the coastlines. So it is the windiest continent
Here at McMurdo, we are told to look out for banks of low
cloud (which is the windblown surface snow) looming up from the South - a sure
sign of bitter winds. I took the second and third photos last year - this year has been relatively quite so far...
So, if the air is so dry, and it therefore snows very little (a very few centimeters a year on most parts of the continent) how come there is about 4000 meters of snow and ice piled up over the landscape? - It has accumulated over many thousands of years and has never melted away due to the temperatures staying well below zero.
So this was all to tell you why we have to drink so much water continually through each day to avoid dehydration and a dry throat. I have just done a quick survey of 20 people working near by to me in the ANDRILL offices. Of the total, 17 of them had a bottle of water or drink beside them, and three did not. I was actually quite surprised at these three. On further enquiry I learned that each of them do regularly drink, but there mugs or bottles were just temporarily somewhere else.
Another related thing is that because of the dryness, static
electricity builds up very quickly. Whenever I take my jacket off and
hang it onto a metal hook there are usually crackling noises and an
electric shock. A great way to start the day!
Things are changing slowly at McMurdo. The population has now reached just about maximum capacity with about 1200 people on Base. This is partly because the Summer contingent that are headed onwards to the South Pole Station are unable to travel due to exceptionally cold temperatures. They are still well below -50 degrees at the Pole- the threshold below which the Hercules aircraft are unable able to land safely.
Another change is that the sun has climbed a bit higher in its path through the sky and no longer hides behind the horizon at night. It circulates through the sky, skimming the horizon to the south at midnight, and traveling up to a point about 23.5 degrees higher when it gets to the opposite (north) side of the sky at noon.
There is a convenient sundial on the base, which I can now use 24/7 to tell the time (if I want to go outside and look!). Look for the shadow to find what the time was when I took the photo of it last night.
If you look carefully at the picture there are a few interesting points to notice.
The shadow producing stick (gnomon) is leaning at an angle of 12 degrees towards the South. If we were at the South Pole itself it would be pointing straight up, as the sun would be traveling more or less horizontally around the sky from right to left. Because we are instead at latitude -78deg, we are 12 degrees north of the South Pole, and the axis of the suns daily path is tipped by that amount towards the South. So it’s simplest to tip a sundial in the same way to keep the gnomon lined up with the Polar Axis. That way the interval between each hour will stay simply 360 degrees/24 hours = 15 degrees
The letter GN and GW stand for Grid North and Grid West which represent the directions depicted on a map of the area. Doesn’t it seem a bit odd that Grid West should be pointing in almost the opposite direction to True West? I had to think about this for a minute or two. If you look at a map of Antarctica, the reason for it may become clear. Have a go and email me your ideas if you like!
An exciting day today!
We saw the first cores of the sea bed. These were retrieved by pushing a hollow core barrel out of the steel tube (which is called the sea riser). This riser has been dangling 940 meters all the way down from the surface to within a few inches of the sea floor. As it moved slowly from side to side with the tides, the drillers pushed the core barrel out under high pressure to grab some length of core from the upper layers of mud.
The very first of the cores were used for analyzing the chemistry of the water locked within the spaces between the particles. This process tells the scientists about the chemical processes happening near the surface, and how conditions are for living organisms. By analyzing the oxygen isotopes in the pore water, it will be possible to tell whether there was once a thick ice sheet that actually completely froze down to the sea bed (a higher proportion of relatively light isotopes will suggest a glacial rather than oceanic origin for the water). This would only happen if an ice sheet were big enough to push out all the sea water from the area. However this pore water analysis involves squashing the water out of the cores, and so the core is basically flattened in the process.
These six new cores we saw this morning were the first ones
to be left intact.
Remember that the most recent part of the sediment has been laid at the top of the pile, so as you go down the core you are going further back in time.The cores were quite short – the longest about half a meter, but it is thought that that depth represents about 20 000 years of time – taking us right back into the peak of the last ice age!
In the cores we could see different layers. There were fine grained muddy layers, with quite a few larger pebbles lodged in them. These dropstones as they are called, are the boulders and pebbles that have been scraped off the land by the glaciers, and then taken out to sea before being dropped to the depths when the ice melted and released them. They are a classic deposit found below ice shelves or areas of ocean that contain icebergs.
There was also a turbidite layer – this is a layer of sediment deposited by a submarine avalanche flowing off a nearby underwater slope. By carefully studying the particles, the scientists will soon be able to tell where the avalanche came from. It is made of volcanic fragments, which can be analysed to find which nearby volcano they belong to.
The upper part of the cores contain a proportion of tiny fossil plants (diatoms) and parts of silica sponges, revealing the transition to more open water, where the sunlight was able to penetrate because the ice has retreated. One of these diatoms is called Fragilariopsis kerguelensis (Try saying that that ten times with your mouth full!) The amazing thing about this little plant is that it has been discovered in the North Atlantic having been transported by deep ocean currents moving from Antarctica via the Pacific and Indian oceans!
It was great to see the way that different information is already starting to build possible elements of a climate history...
drilllers and scientists out there at the drill site are carefully
setting up the initial extraction of samples of the soft surface
sediments. This is a different and more complicated process from the
hard rock drilling that will happen when the deeper layers are
reached. A maximum of three meters of the soft material can be
extracted at a time - and the process is done in a different place for
each additional three meters of depth to be sampled. At a certain
point, when the sediment gets harder (probably within 9 meters depth)
the drill bit will be changed to a rotary cutter and progress will
speed up. This will be a big moment, and will jolt the whole machinery
of the science analysis teams into action. There will be day and night
shifts with most people working atleast 12 hours each day. It is
absolutely fascinating to learn about the technical intricacies of how
the technicians feel and test their way blindly into the sea floor one
kilometer below them
So at the moment there is a
relatively quiet waiting time, with everyone preparing in their own
ways. Yesterday several of us went for a walk up the 5km (3 mile) Hut
Point Ridge track. This is on the opposite side of McMurdo to
Observation Hill. It was a windy day, so we were well wrapped up. To
protect my face I had on my insulated face shield, neck gaiter,
windproof fleece hat, ski goggles and ECW hood.
We set out first for Scott's Hut - a short walk out of the base. Then we started to climb the ridge above. The wind was very strong in places, and by the time we got to the flatter area at the top there was a steady gale blasting snow across the ground. Behind us there were views across the sea ice, past the air runway to the Transantarctic Mountains. Ahead was the huge white dome of Mount Erebus, to the left we could see along the coastline of Ross Island, and to our right and below was McMurdo Station with Observation Hill and the distant Ice Shelf behind. The track veered around to the right, past the satellite receivers of Arrival Heights (a restricted area we had to stay clear of) and back down to the creature comforts of "town".
After dinner, I did the walk again, this time in the opposite direction, the wind was calmer and the views impressively expansive.
As you can see from the
photos the landscape is mainly black or white - well at first sight
anyway. Perhaps strangely, the absence of colours actually makes you
more sensitive to what you see. I find myself noticing subtle shades of
white, grey, yellow, orange. It is as if your eyes become hungry for
differences in texture and colour that would normally not stand out at
all. I have quickly and happily realised that the views never look the
This morning I set out for the short walk up observation hill just above McMurdo Station. It is one of the few walks for which it is unnecessary to sign out from the base. I wrapped up very warmly, with several layers and my big ECW (extreme cold weather) jacket over the top, ski goggles and a face mask that protected me completely from the wind. At the entrance to the main building I strapped on some attachable studs to give my feet extra grip, and off I went.
There was quite a strong breeze blowing as I left Mactown behind me and clambered up patches of snow lying in areas of gravel and volcanic boulders. Up higher the ridge became more distinct, and the cross wind was blowing snow sideways. I soon found out that to the right of the ridge the drifting snow was much harder to climb than the crest itself which was swept clear and had a layer of good hard snow for my studs to push in to.
Well at last we are here. It has been a very busy and exciting time, and there is a lot I could describe.
We flew from Christchurch in a C17 which is a huge US military plane. Very spacious and faster than the Hercules I traveled in last year. In only 5 hours we landed on the frozen sea ice that is used as an airport for McMurdo Station and the smaller New Zealand Station, Scott Base
McMurdo station has over 900 people staying at the moment. It is a strange ugly settlement. Looking across the central area you see large concrete and metal buildings, linked by telegraph wires. When the noise of the freezing wind stops for a while, you hear the sound of humming from every building, - and large trucks and four wheel drive vehicles cruise slowly passed or stand waiting with their engines endlessly running. People are few to be seen outdoors - they pace purposefully from one building to another. There are over 100 buildings; each has a number, but nothing to indicate its use from the outside. Everything from a sea water distillation plant, a chapel, hydroponics greenhouse, a shop, machine storage sheds and workshops, and 11 accommodation blocks.
We are settled into our accommodation units and have been briefed about everything from outdoor safety, environmental care, helicopter travel, recreation possibilities, tents, lighting stoves, and water conservation.
Last night I went for a walk at 1am. The sun actually sets at this time of year at about midnight, and rises again at 3am. It wasn’t dark at 1am though, more like a colourful sunset, which quietly and unnoticeably turned into sunrise without a dark time in between. Before breakfast this morning I went for a short run from the accommodation block to Hut Point – about 1km away... The temperature was about – 25˚C and with a strong breeze the wind-chill made it about -40˚C. It was good to get a feeling for how cold that is! Especially when running into the wind. Parts of my face that were not covered by my neck gaiter, 2 hats, jacket hood and ski goggles were instantly in pain. These conditions are by no means described as “bad”. They are “weather condition 3” (i.e. normal) as opposed to condition 2 or 1 which become progressively harsher. No-one is allowed to move outside in condition 1, which means that you are stuck in whatever building you are in, for as many hours or days that the storm lasts! Thankfully that doesn’t happen too often, but I do think i might get a stash of food into my room...
Here in New Zealand we are having a day of
cold southerly winds and rain. This blasts straight off the Southern Ocean -
the only thing between us and Antarctica. It
makes me think of that cold white wilderness where these winds must ultimately
My snow caving expedition was a success. Thirteen of us slept under the snow. It took about three hours to dig the snow cave, but amazingly, we had plenty of room. It even felt rather warm! On the next day we climbed up the steep slopes to the top of Ruapehu and had a great view of the crater lake and clouds far below us.
Well that was a few days ago. Tomorrow I intend to travel back up there again. This time to do some skiing with my youngest daughter. It is to be our treat before my absence from home for two months. I’m hoping that the weather will improve and that there will be a pile
of fresh snow for us, as well as perfect
calm and sunshine!
After I return from the mountain again I will have to get more serious about
packing and other final preparations. I will fly to Christchurch and meet the rest of the team on
17th October, ready for our scheduled flight to the ice on the 19th.
Thank you to all of you who have sent messages to me so far. I will be away fro a few days, and can be back in touch on Monday.
September 22, 2006
It’s quite something to be part of all this. But spending hours in front of a
computer screen seems a long way away from that bleak, wild, cold place that is
the reality of Antarctica.
So for now I am putting information together, spreading the word and planning a cold night in a snow cave with some of my students this weekend. We will be digging ourselves in above one of the ski fields on Ruapehu - our snow covered volcano in the centre of the North Island. That should be a nice precursor to a visit to the coldest place on earth...
So, if you are reading this - do feel free to send me a message, introduce yourself and ask any questions that you may have about Antarctica and the ANDRILL project. I will be updating this blog more as the journey south begins...
Cheers for now
Since the soft sediment cores were retrieved, there has been a lull in core extraction while the drillers have been repositioning the sea riser (steel tube down which the drill is operated). It is presently being pushed into the sea floor and is at about 17 meters depth. When the drillers are satisfied that it is well enough embedded they will pour a special cement down the riser which will flow out of the end and make a water tight seal to allow the continuous rock drilling to start. So we still expect to be waiting for a couple of days before we start to get into the routine of dealing with a daily batch of core for analysis.
In the meantime there has been plenty to do – people on the day shift usually come into the lab and office area between 7 and 8 am. For me the day usually includes lots of emailing, writing, organising audio interviews with scientists, and a whole variety of other activities including meeting and talking with a lot of people.
Each morning at 9.30 we have a science update meeting in which the latest news from the drill rig is described, and individuals give presentations about their work which is invariably fascinating
It is, for example, wonderful to be told in detail by Lionel Carter of Victoria University in New Zealand, how the Ross Ice Shelf visible right outside the Crary Lab window, is one of the main physical drivers of the world’s ocean circulation! It is hard to grasp that this is the largest ice shelf in the world – about the size of Spain, and 800 km across. Huge quantities of sea water circulate underneath it and become cooled by about half a degree C before recirculating out to the open sea. Then, during the winter months, an area of the surrounding Southern Ocean the size of the Antarctic continent itself, freezes into sea ice about 1 – 2 meters thick. As the water freezes it leaves it’s salt behind – so the water just below the ice is now very dense – due to its cold temperature as well as it’s very high salt content. In addition there are areas of open water, called polynyas, caused by the freezing winds blowing off the continent and pushing the sea ice away. These open water areas are chilled further by the winds (down to about -2˚C – the salt content allows the water to stay liquid below O˚C). As the surface water rolls down into the depths due to the increased density, it is replaced by an upwelling current in a continuing process. All of this super cold dense water eventually reaches the bottom of the Southern Ocean, and slowly slides northwards, past New Zealand and into the central Pacific. From there it goes on its world tour through the Indian and Atlantic Oceans, gaining and releasing its heat, rising and sinking, until it finally returns to Antarctica again, after perhaps 1000 years.
McMurdo Station and Scott Base are actually beach resorts. Believe it or not there is going to be a “beach party” at Scott Base tonight. It will be interesting to find out how far the beach attire will be adhered to for any outside activities… I don’t see many people lying in the sun. However, there are one or two seals that lie on the frozen sea ice doing a pretty good job of looking warm and relaxed.
The seals around here are Weddell seals. They move in and out of the water by using the tide cracks – fissures along the sea edge caused by the rise and fall of the sea. Here at McMurdo the tides actually occur once a day instead of twice. (For those interested this is because the phase of the moon actually has very little effect compared to the monthly rhythm of the moon ascending and descending in the sky. This means there are no spring or neap tides, but that every two weeks the tides die out altogether, and then return to a maximum of about a meter rise and fall. )
This afternoon a group of us went walking across the sea ice to the ice runway. It is strictly forbidden to wander off from the flagged routes... A characteristic sign of danger is a seal lying on the ice. This will invariably mean there is some sort of water hole nearby, which may be partly frozen over and therefore hard to see before it is too late. The seals use their teeth to bite through any ice that starts to block up their door in and out of the water.
We had spotted a seal on the ice runway road. But by the time we set out for a closer look it had started to move away. We found its trail – it was bleeding a little and followed it for some distance alongside the road. The rule about wildlife here is that you are not supposed to do anything that will change the behaviour of an animal. So we kept quite a long distance away from the seal and finally turned back.
Every day when I come into the Crary Lab after breakfast I walk past a cabinet with some fascinating items on display. My favorite is the skull of a crabeater seal – these live on the edge of the pack ice unlike the Weddell seals which live in the more solidly frozen sea ice zone. Crabeaters feed mainly on krill – the little shrimp like beasties that live in their trillions in Antarctic waters. What amazes me is the teeth of this seal – they are branched – looking like they have little fingers. This allows the seal to gobble a mouthful of krill and squeeze out the water through its teeth like a sieve before swallowing. Not so far different from the krill munching style of a blue whale!
The drill progress is going slow but sure and at the moment a wad of cement that was pushed down the sea riser into the sea floor has been forced out and around the riser to form a water tight seal. This is now hardened and is being drilled out of the tube to prepare for the actual rock drilling.
Yesterday was a good day to take some time out of the lab and go for a long walk. Matteo and I signed out from the Fire House, took an emergency radio and headed up the hill away from the sea to check out a place called Castle Rock. It is across a high white plateau. Flagged all the way of course, it has two emergency shelters on the way in case of bad conditions. We stopped in the second of these for lunch. They are red and rounded, and appropriately named ‘apples’.
A little further we reached Castle Rock, sidled around it and climbed it by the only recommended route. The rocks are rough, brown coloured and contain abundant lumps of black basalt. This makes for excellent friction for your feet. It is an enjoyable scramble and has a fixed rope up one section where a slip on the snow would definitely be the end of you. At the top we had an amazing 360 degree view, and we spent a good while fossicking around to check out the rocks
The outcrop was formed by a volcano that erupted in water almost two million years ago. The hot rock combined with the water created the altered light coloured minerals that make up the overall colour. Somehow this liquid magma must have ripped through a basalt lava and included all the fragments in its explosions.
After we carefully descended the rock, we continued in a loop down the hill and along the edge of the sea ice towards Scott Base. On the way we passed a guy skiing along under kite power. Now that looked like fun! From Scott Base we added a little extra onto our walk by continuing around the Armitage Loop. This takes you way out onto the sea ice instead of the normal road over the hill to McMurdo. This brought our total distance covered to about 22 Km, a good appetizer for yet another big evening meal…
Yesterday was an interesting day for three of us teachers. In the afternoon, Betty, Matteo and I went to the drill site for a guided tour. To see the whole thing operating in reality was quite a revelation.
The road there goes from McMurdo, over a rise beside Observation Hill, and descends to the ice beside Scott Base. The road passing from the land to the ice is built up a bit to cover any tide cracks, and then follows a flat groomed trail out onto the ice shelf (Scott Base is at the boundary between the thin sea ice and the very thick ice shelf).
It is a strange sight out on the ice to see the white shrouded tower of the drill. The cover helps keep the drillers warm but more importantly to stop the hydraulic fluids that are used, from freezing. Tamsin Falconer from Victoria University, Wellington, New Zealand gave us a really thorough tour of the buildings (made of converted freezer containers linked together) as well as the drill rig itself. We were shown how the fresh core is pulled up, and then posted through a hole in the wall of one of the containers. Inside it is carefully studied to look for fractures and other structures which are measured and recorded.
Then it is cut into one meter lengths, and put through a scanner which takes a complete digital photograph of the outside of the core. This highlights structures like faults and folds, which tell the story of past earth movements in this region of Antarctica. Whilst the core was pulled up from the ground it has turned a bit. How can the structural geologists find out which way these faults and folds were facing when the rock was in its original position? There is a very clever way that they do this and I will describe it in my next posting.
After the scanning, the core is sent through another machine which measures a lot of different physical properties, such as the magnetic qualities of the core, how well electricity passes through it (resistivity – which indicates how much sea water is in the rock and therefore how much pore spaces there are), and how fast sound waves travel through it which is indicative of the density.
We had a good look at the drillers at their posts, the layout of the drill mast and the platform on its hydraulic stand that compensates for the sea tidal movements. We also visited the “mud room” where the drill fluid is mixed before being pumped down the sea riser to lift up the drill cuttings (rock fragments) and cool the drill bit. This fluid comes all the way back up the sea riser and is cleaned and recirculated.
So all too soon our time was up and we jumped in our 4 wheel drive tracked wagon for the ride back home.
This will give you an impression of one of the first analyses that is made on the cores. It is a process that is carried out at the drill site after an initial visual study of the rock, and before the core gets disturbed or changes colour due to chemical reactions with the air
The scientists involved are Terry Wilson, Tim Paulsen, and assistant technicians: Andreas Laufer, Cristina MillanThe first picture is showing some scientists doing an inititial check on a core
This research is based on digital photographs of the whole of the outside surface of each piece of rock core. The second pic shows the scanner that is used, with a core on rollers to turn it as the image is taken. The images show the three dimensional structures and allow detailed studies of past sedimentary environments, palaeomagnetism and earth movements
They analyse the orientation of bedding planes, unconformities, joints, folds and faults.
What is the procedure?
The core is cut into one meter lengths, placed on a scanner with a roller mechanism and a digital image is made of the whole surface. This is then displayed two dimensionally as if a rolled up sheet of paper were laid out flat. (third pic) Details of structures can be studied in a way which is much easier than when just looking at the core itself. The resolution of the images is 250 pixels per inch, allowing fine details to be studied under high magnification (This uses software called 'Corelyzer' created specially for ANDRILL)
When a core is drilled and brought to the surface, it gets rotated
from its original position in the ground. A further technique to calculate its
original orientation with respect to North and South is required. Now this is clever!
A televiewer (a special camera using sound waves - so not needing any light) is later lowered down the drill hole, creating a second set of images. These show details of the rock all around the sides of the borehole. The televiewer images are oriented with a magnetic compass, so when they are matched with the rock core images, it is possible to calculate the original orientation of the core pieces. (The fourth picture shows a borehole image next to the core image). This now means that any structures observed can be analysed in relation to the regional geology. For example, sedimentary structures may show ancient water current directions; folds and faults will reveal the alignment of ancient stresses in the Earth’s crust; and the magnetic orientation of iron rich minerals in ancient lavas will reveal the polarity of the Earth’s magnetic field when the volcanic layers were cooling down.
When all this information is combined with other disciplines such as microfossils, stratigraphy and petrology, a detailed understanding of the geological history of the area is possible over the time range covered from the lowest piece of core up to the most recent at the surface of the sea floor.
This might include a description of what major earth movements happened, how sediments were eroded and deposited, how the ice shelves and ice sheets changed with the climate, what volcanoes erupted, and how different life forms changed over time.
In the final picture of a rock sequence there are folds, faults
and unconformities. if you know some basic geology, have a closer look and try to answer these questions
Firstly just to say
that some of your email addresses must have been not quite correct as my
responses have failed to get through. I love to read your messages and
questions, so be careful to write you email correctly so I can get back to you!
Today I would like to tell you how the rock cores are studied and discussed at McMurdo:
Every morning there is a meeting where the rock cores are put out on view and discussed before the different scientists select points that they wish to sample and analyze. It is a very exciting part of the day, as the latest finds get to be talked about. Remember that the drilling and logging of the core are happening continually 24 hours a day. Here is an overview of the process:
There are three reports given to update us each morning:
First Jim Cowie of Antarctica New Zealand gives a description of how the drilling has progressed over the last 24 hours, including any difficulties or notable successes. Next, Larry Krissek gives an overview of the latest lengths of core that have been fully described and logged. This includes a computer diagram of the cores (PSICAT software -see pics one and two) so that we can have a visual idea of the different layers in the rock sequence.
Next we have a “Core Tour” where we all go and see the cores laid out on tables.
The cores have been scanned at the drill site to find how
dense and fractured they are, brought to the lab here at McMurdo, and sliced up
the middle into two halves. One half is immediately wrapped up and boxed to be
shipped away to Florida
as the “archive core” for future reference. The “working half” is photographed and
put through a machine that measures the chemistry of the rocks exposed at the
core surface. Then the cores are set up so that they can be easily seen by everyone.
Lionel Carter (pic #4)gives an account of how all the physical features of the cores seem to piece together in terms of a geological and environmental history. This is a fascinating occasion as the different specialists contribute their ideas about what they have found in the cores, and what these clues add up to.
Often there are mysteries that can only be understood when some further analysis has been done.
When someone wants to take a sample from the core they put a flag beside the exact place. You can see that the volcanic layer in photo #7 has several flags. It must be important!
Some of the features of the core that are studied carefully are:
Sedimentary features – laminations (layering - see pic #5) mean that the sediment has been affected by water currents. Quite a lot of the stuff we see has no layers – which suggests it has been dumped from the base of overlying ice. Also the amount of sorting of the particles is significant too – glacial deposits from within the ice are typically an unsorted mixture of all sizes of angular fragments.
recognizable as pebbles that have melted out of ice bergs and landed in the mud
on the sea floor. Sometimes the sediment is hard and compacted, showing that
the ice was actually thick enough to sit on the sea bed and squash down onto
the sediments below. (see pic #6)
Clasts – (rock
fragments including dropstones) - These can be angular – or rounded (therefore
worn down) which says something about how they have been transported from their
place of origin. Also different clast types can be identified showing where
they originated from in the mountains which tells us about the movement of the
glacier ice. You can see different coloured clasts in pics #5 and #6.
Volcanic layers –
(pic #7) These might be deposited directly by an underwater eruption, or by ash falling
onto open water, or they could have been transported by water currents. If they
are in their original position, they are extremely useful because they can be
dated precisely using radio active isotopes (although it takes several months
for the results to be known).
Fossils – Scientists who study tiny fossils are called micropalaeontologists. They take small samples of muddy layers to look for remains of microscopic plants (eg diatoms) or animals (eg foraminifera). These allow dating of the cores, because over time different species of these creatures evolved. They have been studied from ocean cores all around the world. Ocean currents can wash them under an ice shelf, but they will be more abundant when there is no overlying ice in the area, as they need sunshine in order to live in the sea. In pics #7 and #8 you can see diatom scrapings being taken from the core using tooth pics. Only a very small amount is needed to look for diatoms.
Magnetism: The earth’s magnetic field reverses every half million to one and a half million years (very roughly), through geological history. This means that a compass needle would point the other way around after such a change. Because rocks contain small amounts of iron minerals they are slightly magnetic. Tiny particles settling on the sea floor tend to line up with the earth’s magnetic field as they do so. If their magnetism is measured it is possible to find out the direction of the earth’s magnetic polarity at the time the rocks were deposited, or when they cooled and crystallized as a liquid volcanic material. This is useful for dating purposes.
So far (to November 13th) about 60 meters of core has been described, with plenty more on its way. A typical sequence that seems to be repeating through the core so far is as follows, with the oldest part below:
3. Muds with volcanic layers and microfossils
Relatively warm open water marine conditions, with (or
without?) an ice shelf floating above.
2. Layered sand or silt
Mixed glacial and marine conditions with the grounding line
(edge of an ice sheet) nearby, and water currents moving the sediment.
1. Unsorted diamictite (mixed glacial deposit) sometimes compressed.
Full glaciated (ice age) conditions with an ice sheet filling up the sea right down to the bottom.
The last photo shows how a high resolution digital photo is shown on the Coralyzer computer programme. This software was developed for ANDRILL. It is possible to zoom right in to the core images and see details magnified to a very high quality of definition. This allows the scientists to discuss tiny details of the core as well as large sections of it, without having to look through boxes that have been packed away. Also a lot of other information from the different scans is included alongside the images, wich helps to put all the information together in a very accessible way.
Well that is a pretty full geology lesson. Well done if you managed to follow it! Let me know if any of it isn’t so clear!
Before I say a few words about what the rock cores have been showing us over the last couple of days, I will explain a little bit about ice and ocean deposits.
The diagram shows how a land based ice sheet flows out to
sea to become a floating ice shelf. As long as its base is in contact with the
ground, even if this is below sea level, it is still an ice sheet. As soon as
the ice starts to float (as the sea gets deeper or as the ice gets thinner),
but is still attached, it is an ice shelf.
The line along which an ice sheet lifts off the sea floor to
become an ice shelf is called the grounding line though it is probably better
to think of a grounding zone, perhaps 100km wide, which is the general area of
ice grounding in relatively stable conditions.
When we look at the rock core, the sediments are different
depending on which situation was occurring, ice sheet, ice shelf, or open water
(perhaps with ice bergs floating around). The different rock types therefore
clearly indicate differing climate (temperature) conditions at the time they
were laid down
Ice Sheet sediments
– mixed sized particles, little or no layering (except perhaps from some water
flow under the ice), few if any fossils, sediment compacted under the weight of
the ice. (see photo #2))
Ice Shelf sediments:
some layered sediments mixed with dropstones, and some microfossils in a few of
the layers. Some of the sediments are likely to be disrupted by sliding and
slumping if they are from near to the grounding line.
Open Water Marine sediments: these will have a high proportion of mud layers, with a lot of microfossil content (because the sunlight allows photosynthesis of the tiny planktonic plants). Currents will have produced laminations and there will still be dropstones from ice bergs (see photos #3 and #4)
Volcanic layers can occur from an underwater eruption. If
ash falls from above, and ice is covering the sea, it is will not fall directly
on to the sea floor, but may eventually get there by indirect processes. This
can often be seen in the way the particles are arranged in the layer
The core that was logged and ready for sampling yesterday
was very exciting to the scientists here. After several sequences of thick
glacial deposits, with a few thin mud and volcanic layers in between
(representing warmer times when the ice must have thinned and retreated
somewhat, but still occurred as a thinner floating ice shelf in the area),
there has been a dramatic change in the appearance of the sequence.
There is a much thicker layer of laminated (layered) mud, with hardly any dropstones. There are also layers very rich in diatoms and other microfossils, and even a few fragments of larger shellfish. This appears to represent an environment where open water conditions existed in the sea above. What this means is that at this time – likely to be within the last million years, the Ross Ice Shelf was much smaller than it is today, in a very warm interglacial period. This is getting to the heart of some of the key questions of the ANDRILL programme (about how much and how fast the ice shelves and ice sheets grew or shrank with time). Did the Ross Ice Shelf disappear completely in this past warm period?
If so will we be able to find out how fast such a change
occurred? There is a lot of excitement here in McMurdo at the moment as the
rock core is starting to give hints and clues about these questions. It will
take a lot more drilling and a lot more analysis before the answers are fully
What is very helpful about the deposit is that there are
some volcanic layers
which will be good for dating the core here - you can see a thick greyish pumice layer in part of the section in photo#4. Also there are rich microfossil assemblages which will help refine the timescale too, and say a lot about the marine environment at the time.
Well that’s it from me today. Tomorrow,
weather permitting, I will be on a flight out to the dry valleys. This will be a major
highlight of the Antarctic experience for me. The weather is a bit unstable right now though - a cold wind is whipping up snow all around , so fingers crossed!
Well the helicopter tour of the Dry Valleys was postponed today due to cloudy and windy conditions - so I'm hoping for better weather soon!
In the meantime there is a strange thing happening on the ground here, particularly on sunnier days. Inspite of the air temperature being well below zero degrees centigrade (eg -5 deg C or 23 deg F), puddles of water appear in places near the snow patches of the gravel streets of McMurdo. This has nothing to do with any artificial heating or volcanic thermal activity, but is an entirely natural process. Can you work out what is happening? I just took the picture a minute ago - it shows the air temp being below freezing (about 29 deg F this time, or - 2 deg C), and water all over the place.
Here is a picture of some rocks in the snow - have a close look - it may be a helpful clue.
I will send a token prize to anywhere in the world for the person who sends me the most convincing answer by 9am Monday morning New Zealand Time. (Sunday afternoon in the US). It will be a card signed by three ANDRILLIAN scientists of your own choice (!) some stickers and a cloth ANDRILL patch.
Have a think and send me your idea. Good luck!
I have just returned from probably the most spectacular
landscape I have ever seen.
I had the privilege of flying by helicopter on a tour of some of the “Dry Valleys” in the Trans Antarctic Mountains. Before I write further about this experience, you should understand that I have been fascinated by mountains and by Antarctica for most of my life, and still I was unprepared for the impact of this wilderness.
There were eight ANDRILL participants on board including New Zealand’s professor Peter Barrett who has been studying the geology of Antarctica since 1962. He gave us a commentary on the geology as the perspectives slowly changed on our journey.
Flying initially over the 30 kilometers (20 miles) of frozen
sea that separates Ross
Island from the Antarctic
mainland, some volcanic cones piercing through the ice as islands caught my
attention (pic #1). Then, reaching the
mountain area, we flew up the Blue Glacier, and then over the Ferrar Glacier, past the Cathedral Rocks (pic #2) towards a peak called Table Mountain. This was going to be our first drop off point – where we were going to have a close look at the ancient Beacon Sandstone, from a time when desert conditions prevailed in the area. Unfortunately the winds were too strong for a safe landing, so the pilot pulled away when we were about 3 meters of the ground. After a couple of further attempts in other locations, we were informed that landing was a “no go” today. Disappointing yes – but who could complain when even to be on this flight was such a unique opportunity?
As we continued our flight past the Beacon Valley, I was trying to drink in every impression and taking endless photographs. Unbelievably, the land surface here is about 10 million years old! There is a remarkable feature called “patterned ground”, where the process of freezing and thawing of the ground ice creates an improbable landscape of hexagons fitting together geometrically (pic #3).
In the distance we could see the infinite horizon of the Polar Plateau (East Antarctic Ice Sheet) with it’s huge slow moving tongues of ice sliding slowly down the valleys below us. Unfortunately its cold winds were to blame for our inability tread the mountains below.
The peaks that we passed are spectacular. They have been rising slowly over the last 40 million years. Because they are so cold, they do not get eroded as fast as mountains in other parts of the world (which fall apart more quickly due to the constant freezing, melting and refreezing of ice in the rock crevices). So these faces are steep and of great vertical height. They show a fantastic cross section of the rock formations which form a relatively uncomplicated basic sequence. Cutting their way down the steep faces were glacier and icefalls, each one unique in its shape or structure.
After following the Taylor Valley in a homeward direction, we landed for refueling at Marble Point. Here there is a small stopover landing pad, inhabited by three staff whose job it is to manage the refueling of aircraft through the summer months. We had a short lunch break, and a walk across the landscape before the last leg of our journey back to Ross Island. Our pilot took us close up to a large flat (tabular) ice berg, waiting to be released from the clutches of the sea ice that it was surrounded by. The weather deteriorated as we drew near to Mactown once more, with poor visibility and snowfall to welcome us “home”. I know that I will never forget the impression of grand, remote beauty that I experienced today.Julian
So for those of you who have been pondering over the problem I posed about the snow melting when air temperatures are below freezing, I have the pleasure of announcing that Aly King of the 6th grade, Mickle Middle School, Lincoln, Nebraska , USA was the first person to send in the most comprehensive answer. Well done Aly!! A small package is on it’s way to you from Antarctica!
Quite a few people suggested that the rocks might have a high salt content which would depress the freezing point. This was a very sensible hypothesis – but in fact not the main reason.
There were some clues in the blog I wrote – one was where I said that this melting happens on sunnier days, and the other was the photo of the rock in the snow. You may have noticed that the snow is melted near to the rock – which is due to the fact that the darker surface is warmed by the sunlight even though the air stays cold. Note that I said the air temperature was below freezing, but I avoided mentioning the rock temperature!
This is an aspect of the albedo effect. Clean snow has a high albedo and reflects around 90% of the sun’s light whereas the dark rocks will absorb most of it and become warmed up in the process. Air actually absorbs very little of the sun’s heat, so the rocks get warmer than the air just above them and can then melt the snow that is close by.
There are all sorts of interesting consequences that this effect
can produce – such as rocks sinking into the ice that they are resting on, and
dust that is scattered within an ice layer gradually accumulating on the
surface as the ice around it melts away. In the photo, the dirty snow has melted faster than the clean white stuff and is therefore at a lower level.
So for the record, Aly sent two messages – the first was on the right track, and the second one clarified that it was the rock that was getting warmed first.
“I think the snow melted because the sun hit the snow and it heated up the surface but not the air around it and it would make sense because you said it was on a sunnier day!”
“The dark rocks are absorbing the heat of the sun thus melting the snow and ice around it!!!!!”
I am interested that Aly comes from Lincoln
which is also the international head quarters of the science management office of ANDRILL. I wonder
of there is something in the water people drink there that makes them
interested in what goes on in Antarctica? Thanks to all those of you who sent me your ideas.
“PQ to HQ”
Yesterday and today have been a break for most of the scientists and technicians, as a technical step is carried out at the drill site. Now that the hole is at 230 meters depth, the drill diameter is being reduced from PQ size (which produces a core of 83mm diameter) to HQ size (which will drill 64 mm cores). This allows continuation of drilling as the depth increases, and the friction on the drilling tube gets higher. What the drillers are doing is leaving the PQ drilling tube in place to line the borehole, and repeating the cementing process to improve the seal around the end of the tube. When the cement is dry, they will send down the smaller drill, cut through any cement left in the tube and carry on drilling out thinner diameter cores.
Interesting fact: the drillers have been noticing that as the rock cores have been pulled up from deeper levels, they have been expanding slightly due to the release of pressure! So reducing the diameter of the drill bit will also help prevent the cores getting jammed in the pipe as they are pulled up.
In the meantime…
One of the most amazing experiences for anyone staying at
Scott Base or McMurdo Station is to travel north up the coastline of Ross Island
and visit the huts of Ernest Shackleton and Robert Scott. The pause in drilling
operations has allowed most of us to take a trip to visit these places either yesterday or today.
It is a journey back into the days of the heroic era of antarctic history, around one hundred years ago. At that time, clothing and equipment were relatively primitive, there were no radios, no lightweight freeze dried food packets, no search and rescue teams on standby. Transport was by boat, and then on foot or with the help of ponies or dog teams. (One thing that has endured though is the tent design from that time – Scott Polar pyramid tents are the main accommodation for small science groups out in the field to this day!)
When these men traveled into the remote and unexplored interior of Antarctica, they would sometimes be away for months at a time. Many of the stories of their adventures describe unbelievable physical and mental hardship. Some of these early explorers never returned – they fell into crevasses, died of cold and starvation, fell into the sea or simply disappeared never to be seen again.
Shackleton's hut at Cape Royds is the furthest away (about 30km) from McMurdo. It is a small wooden building on a rocky area right beside a large colony of Adelie penguins. Around the outside are boxes of supplies, the remains of a stable and a few dog kennels. An old weather station is nearby, along with piles of empty rusting tins – the rubbish pile of a century ago. Inside is a single large room, with bunks made of packing crates, a kitchen area, stove, and very simple furniture.
Every ledge is lined with food tins, bottles, bits of clothing and a myriad of items used in daily life by Shackleton and his men.
We had a close up look at the penguins nearby – clustered in groups with nests made of pebbles. The wind was blowing hard – which made me appreciate the incredible ability of these creatures to live in this icy world with no cover from the elements. Some of them were in the distance below, waddling across the sea ice, while others faced the challenge of searching for rocks to improve their home, whilst simultaneously guarding their own nest from neighbours out on a similar mission.
Watching the whole scene with interest were a few predatory skuas (antarctic sea birds) that would create an anxious reaction whenever they came up close to the penguins.
From Cape Royds we back tracked towards McMurdo for about 10 km. Scott’s hut at Cape Evans is much larger than Shackleton’s. The windows were snowed over, which made the interior very dark. However we had brought torches which allowed us to look around. In the entrance area there are tools, buckets and wooden skis hanging from the walls. A passage leads past a pile of seal blubber, and a box of broken eggs (presumably from penguins) to the pony stables. Here are various boxes, bales of straw, even small snow shoes with straps to fit to ponies’ legs.
Back in the entrance a door leads to the main room and living quarters for the men. In the centre is a large oblong table with chairs around it. Around the walls are bunk beds, a laboratory, a dark room and a kitchen crammed with tins and bottles of food as well as cooking equipment. Captain Scott had his own small ‘room’ with his bed, and on a nearby table lies a dead penguin, an old newspaper, and various other items. Everywhere is the clutter of supplies, personal belongings and scientific equipment.
There is an atmosphere of tragedy in this hut as several of its occupants (including Scott himself of course) left it never to return. Their bodies are to this day frozen deep into the ice shelf several days walk away to the South. The last photo shows the beds of Evans, and lead scientist Edward Wilson (who died with Scott on the epic return from the South Pole in 1912).
To spend time in this place left me feeling humbled by the courage of these great individuals of antarctic history, and moved by the tragedy of their story.
However, since the change of the drill from 83 to 63 mm diameter, the pace of drilling has speeded up dramatically. The smaller size allows faster cutting.
And also, with the narrower cores, it is now possible to pull out 6 meter sections each time rather than just the 3 meter lengths which were retrieved so far.
So in the last 24 hour period, a record of over 70 meters of core was retrieved! This has taken the drill to 420 meters below the sea floor level as of this morning. This fast rate of progress is very encouraging as it is allowing us to catch up for some of the delays that occurred in the initial drilling phase. It may also offset future delays caused problems yet to be encountered.
At about 700 meters depth the diameter of the drill tube (or
‘drill string’) will be reduced again to NQ size which is only about 45 mm. The
first picture shows the three different sizes of drill bits, and the next one shows some HQ core next to a section of PQ size.
So it’s all full steam ahead in the lab as the lengths of core get delivered and the scientists attempt to keep up with the flow. I have been helping three teams today:
The palaeomagnetic team - taking samples from the core every meter. These are tested to find the direction of the earth’s magnetic field when the sediment was being deposited, to help with dating the core;
the microfossil team - helping to prepare and study slides of foraminifera (single celled animals) – which will help fill in the dating jig saw puzzle
the clasts team who study all the individual fragments of rock that are included in the sediment. This gives information about the source regions of the sediments, and therefore the pathways of the ancient glaciers and ice sheets. Sometimes there are over 150 individual clasts in a single meter of the core, each of which is identified and classified.
Well – a busy day for all, and no doubt more tomorrow!
Ross Powell – one of our two co-chief scientists – is a specialist in the research of sediments that are created where glaciers flow off the land and into the sea. He gave a presentation here recently to describe some of this research. It allows scientists to interpret what different sedimentary structures in the cores actually show of the past conditions in which they were deposited. I came away from his talk realizing how complex the story actually is in reality…
When a glacier or ice stream (which is a fast moving part of an ice sheet) moves into the sea and starts to float, we get a glacier tongue. If the floating ice is wide and fed by more than one source, it is called an ice shelf.
The Mackay glacier is a river of ice flowing slowly through
Mountains to drain 6500km² of the giant East Antarctic Ice
Sheet. It is about 140km long and narrows to a neck about 4 km wide, moving at
a rate of about 200 m per year. When it reaches the sea, it starts to float and
extends as an intact tongue of ice about 4 km long. (Back in 1911, a party from
Captain Scott’s team measured it to be 12 km in length at that time). At the leading
edge, ice bergs break off and float away.
A lot of the basic processes that occur under glacier tongues also happen with ice shelves. Ross has worked over several years on the Mackay glacier tongue about 150km north of McMurdo. He has studied the sediments under the ice which is very helpful for understanding the ANDRILL rock cores being pulled up from beneath the much larger Ross Ice Shelf.
One of the cool things that Ross did was to send down a Remotely
Operated Vehicle (ROV) to take film and photos from under the glacier.
As the glacier travels in its upper reaches, it erodes the
bedrock, which gets included as a debris rich layer in the lower 20 meters of
Lower down the glacier, this debris starts to melt out, to form an underlying bed of glacier rubble (called till), which the glacier rides over.
Once in the sea, the ice starts to become buoyant at the ‘grounding zone’ where sea water is able to circulate under it. This speeds up the melting process at the glacier base. As the lower part of the glacier melts in this way, eroded rocks embedded in the lower layer rain down onto the sea floor. The fresh meltwater is relatively light compared to the dense salty sea water. So it flows upwards along the lower surface of the ice and when it reaches the ice front it wells up to the sea surface like water coming up from a spring.
The rained out debris forms a wedge of sediment made up of
particles of all shapes and sizes. Water currents can create small layers in
the sediment with features like ripples and also some diatoms can get washed
into this area.
The front of this wedge periodically avalanches down into deeper water to create characteristic slumped and layered mudslide deposits. These often show a layered structure which indicates water movement, with larger particles at the base, getting gradually finer upwards (as the smaller particles stay suspended in the water for longer).
The above diagram shows a simplified version of the different sediments formed. On the left are the random sized chunks left under the ice. On the right are the open water diatom rich muds with dropstones, whilst in between are the sediments rained down from the melting glacier ice.
The last diagram shows an idealized version of a rock core from a retreating ice shelf or glacier tongue. If you imagine a point that is initially under the glacier, the sediments deposited there would change as the retreating glacier moves back and the sea takes over.
Can you think how the sediments might be different where the ice was advancing instead of retreating?
Now that we have a basic picture of the sorts of sediments that deposit under an ice shelf, (see last blog entry ‘Where Ice meets Water’) let's look at some real examples from this morning's core tour. They are all from between 440 and 470 meters below the sea floor and are tentatively dated at 3.5 million years old. Take a good look and admire! You are witnessing scientific discovery happening today!
Although the core sections have been put side by side in the picture, they actually come from different levels one above the other, and show that the ice shelf was moving back and forth over long periods of time, depositing a succession of different sediments in a vertical sequence.
Now let’s go further and play with our model diagram from
last time, and look in more detail at what would happen when the ice retreats. How
will this affect the gradually building up layers of sediment below?
Firstly it is important to remember that although the front edge of the ice would now be shrinking back, the ice is always traveling from the land (left of the diagram ) to the sea, bringing its rock debris along like a conveyor belt.
Because the ice doesn’t reach so far out to sea, the open marine conditions exist nearer to the coast, so the diatom rich muds now start to build up over the original glacial rainout and till deposits. If you follow the diagram you can see how the sediments vary depending on the location. Don’t forget that such diagrams (models) are only a help to our understanding. In reality these sediment layers are sometimes tens of meters thick, and extend over hundreds or thousands of square kilometers of the sea floor!
Now for good measure lets warm up the ocean a bit more so that the ice disappears off the screen:
The open marine sediments now start to blanket the whole area. Even places well away from the original ice shelf now show fewer ice rafted dropstones - wherever we look at the sediment there will be evidence for the retreat of the ice. Can you visualise how sediment cores would look from different points on our imaginary sea floor?
So the next step would be to create an ice age once more and see what happens when our model ice shelf expands out to sea again:
This is a bit more messy, especially when the ice gets so thick that it no longer floats and starts to grind up the sediments below it. Unfortunately for the geologist, this can destroy some of the precious evidence of previous events. Just like someone crumpling up the critical pages of a history book!
As the ice thickens and advances again over the original sediments, they can get bulldozed along into a pile of reworked debris under the grounding zone. Further out the ice covers the sea, preventing diatoms from living in the water. However their dead skeletons can drift under the ice for quite a distance due to currents. Again, the changed conditions are affecting the whole area. But because of the disruption of some of the sediments, it is hard to know if the whole story is shown or not.
So finally take a look at these examples of our core. The first represents a 20cm section showing the recession of the ice shelf, and a transition from glacial till below to marine diatom mud higher up - one of the Ross Ice Shelf's many previous disappearing acts discovered by ANDRILL. The core on the right shows a mud layer being overlaid by glacial till - the ice returning. The million dollar question for all of us is: can we find out how quickly these shifts occured? and what was their effect on the most important part of the story - the land based ice around the Ross Ice Shelf that is responsible for global sea levels?
If you were happy to read the last two blogs about interpreting the rocks in the sediment cores, here are three more examples that give their own small part of the story:
The weather here has been warming up a lot over the last week or two. On some days temperatures have even been above zero at times, making it possible to walk around without a jacket occasionally.
So being on the shores of Ross Island, it is of course thoroughly logical to want to take a dip in the cool, refreshing, perhaps even quite bracing -Antarctic sea water…
The idea was triggered by a conversation with Erika Schreiber.
She is working on a project that involves scuba diving below the sea ice to
study the rich marine life on our doorstep.
She told me how she had done the “Polar Plunge” and jumped into the
water without a wet suit.
Just five minutes walk from the lab here there is a dive hut. (the orange hut in the pic) Inside there is a trapdoor in the floor with a hole drilled through
the ice for the divers to get in and out of the sea.
The idea of a refreshing bathe was of course instantly appealing – surely anyone visiting Antarctica would want to take the opportunity to have a quick dip in the uniquely chilly water at -2˚ Celsius! – Ah yes that does sound chilly though…
Unfortunately the idea didn’t seem to go away and I woke up
the next day wondering about when the best time to go to have a dip would be.
Erika confirmed that she would be assisting two divers in her team – Bruce Miller
and Jon Sprague - at 1pm and afterwards, around 2 o’clock would be the ideal
I also learnt that there was a history to the Polar Plunge idea. To fully qualify as a polar plunger you have to be completely naked and stay in the water for at least 10 seconds. Under the circumstances, the ten seconds rule was more scary for me than the notion of stripping my clothes off in front of a few people. I was feeling increasingly nervous at the prospect of what I was in for, but got some psychological support when Stefan, one of the ANDRILL team, also expressed an interest in going for a dip too.
Well – we went ahead as the pictures testify – and although it was VERY cold, and we did make some interesting grunting and yelping noises, I am actually able to say that the thought was worse than the reality – mind you – I was quite terrified beforehand, so perhaps that wasn’t so surprising!
Lastly I have to mention that the divers were telling us how
rich and unique the marine life is. I have posted one of their pictures – you
can see many more such amazing photos on their site at: www.clemson.edu/biosci/faculty/moran/lab/Antarctic_research/Field/Index.html
Check it out! It is easy to understand how anyone might get hooked on becoming a marine biologist in Antarctica!
Here in the lab is a marine aquarium where we can look at some of the variety of sea animals without having to become highly qualified divers. It amazes me that these colourful creatures actually thrive in such waters.
My favourite is the ‘touch tank’ – when I put my hand in to say hello
to the sea spider I get a reminder of how cold that water really is…a few
seconds is all it takes! Ouch!
As well as leaping into the cool briny Antarctic sea waters, there has been a variety of other mad activities recently here at McMurdo. It seems that we need very little excuse to go nuts around here…
When those tough early explorers of Antarctica
came down here on their expeditions, they usually had to spend the winter in
their camps, in order to be ready in the early spring to launch out on their
journeys into the unknown interior.
Shackleton, Mawson, Amundsen and Scott - Tough guys of Antarctica
To pass the time during those very cold, dark months, they would keep up their daily routines, carry out scientific experiments and organize activities to keep themselves preoccupied and in good spirits. So on occasion they would have dress up parties, which gave them an opportunity to clown around and see the funny side of things.
This tradition of letting your hair down is upheld every
year at Scott Base, and is now known as the Skirt Party. The basic rule is that
you are not allowed into the bar unless you are wearing a skirt or dress,
irrespective of whether you happen to be male or female. About a week ago this
event came around and was taken up enthusiastically (perhaps a little too enthusiastically)
by a large number of the ANDRILL team.
Naish and Powell. The tough Co Chiefs of ANDRILL
Well for the sake of the participants I had better not go into further details – but suffice
to say a good and thoroughly sensible time was had by all.
A couple of days later there was the UNDRILL 700. This was a
running race to commemorate the attainment of 700 meters of depth in the
ANDRILL drill hole. The main challenge was to run the distance wearing only
your underwear - a particularly silly thing to do in Antarctica
of all places. Fortunately the temperature on the day was only a few degrees
Even so, gasping in cold dry air for those few minutes took its toll on several individuals (me in particular) who instantly developed rasping coughs for a short while. The picture shows Rob McKay well in the lead, with the rest of us trying to keep up somewhere back there in the distance.
So the next event wasn’t so much a matter of letting your hair down, but getting it shaved off. This was a charity fundraiser evening, again at Scott Base. Volunteers stood up on a small stage while the privilege of cutting all their hair off was auctioned off to the highest bidder. Over $4000 dollars was raised for a child cancer charity.
Lastly on a much more sensible note, I did a cross country ski trip with Rob McKay and Huw Horgan. We followed the Armitage Loop trail which goes out onto the sea ice and follows a big bend around Observation Hill for 8 km (5 miles) to Scott Base.
I am hoping that you can see a similarity between me and Captain Scott on his skis. Perhaps when I grow up I could be an heroic Antarctic Adventurer too ...
One of the most readily accessible walks from McMurdo is the climb up Observation Hill which is a great view point for looking across the McMurdo Ice Shelf and to the surrounding mountains. I have always felt my attention drawn to the spectacular view even whilst concentrating on my steps up the rocky slopes.
This changed recently when Davide (one of our Italian scientists) returned from a walk around the hill, having found lava bombs amongst the rubble.
Lava bombs? The image of molten rock being hurled down the slopes to the accompaniment of volcanic explosions and billows of smoke captured my imagination. Suddenly I realised that by looking at the view I had been blind to what was under my feet. I was inspired to find out more about the geology of Observation Hill. (picture of eruption courtesy of USGS).
Later that evening after work, I set out with Rob – who is ever enthusiastic for any outdoor adventure – and we circumnavigated the hill at about mid height, with our eyes more open to the different rocks we could find. A later conversation with Phil Kyle – one of our resident volcanologists with ANDRILL, inspired me to take another look the next day. This time I climbed from the bottom to the top to get a look at the rocks at different levels.
Although by its shape it is easily recognized as a small volcanic cone, there are a couple of different rock types which make up the peak.
The lower part is made of basalt lava. When this erupted from an earlier, now obscure crater, it was relatively fluid. The particles often flew up from the vent and solidified quickly whilst spinning in mid air. Because the outer part of an airborne fragment cools quickest, the pieces often have a glassy or fine grained skin, with a more rough crystalline texture on the inside, which you can see on the ones that are broken.
The basalt is a very dark red or black rock. In the loose rubble underfoot we found several good examples of ‘spindle bombs’. Other shapes included more rounded ‘cannon ball’ forms as well as ‘welded spatter’ pieces that landed and stuck together whilst still not quite hardened.
These various rocks looked very fresh – as if they had erupted within the last few years. However I was told by Phil that the eruption had been dated at about 1.2 million years ago! In a temperate or tropical country the fragments would have been weathered by the action of water and heat, but here on the frozen continent, little had altered them through all those years.
The upper part of Observation Hill is made of a more silica rich lava called Phonolite (named originally in Germany where similar rocks were found to ‘ring like a bell’). This is the grey greenish rock that you can see above the basalt in the photos. The extra silica makes it a stickier (more viscous) lava that will have oozed out more steadily, and piled up into a more steeply sided cone.
Close up I could see flow features, and also little black lumps of a mineral called kaersutite (a titanium hornblende). Some of these had eroded out of the rock and were strewn around in the dust.
Once I got to near the top of the hill, I decided to sit and look at that beautiful expansive view once more. I had found my close up look at observation hill fully absorbing, and now it was time to take in the big picture again…
A couple of days ago I had a second opportunity to visit the historic huts of Shackleton and Scott. This was now my third visit since last year (see earlier blog ‘Frozen in time – November 22nd’). My sense of awe only seems to have increased with each trip.
Both Scott and Shackleton each made more than one expedition to Antarctica. The three huts they built along the shore of Ross Island over the early years of the 1900s were used more than once by successive teams. Supplies that had been left behind were sometimes lifesavers for later occupants.
Before leaving I was interested to learn more details of the history, and one aspect particularly fascinated me. This is the tale of Shackleton’s Ross Sea support party who were sent to this side of the continent while Shackleton, on his third visit to the ice, attempted to make the first ever crossing of Antarctica by starting on the other side, in the Weddell Sea.
Shackleton never even set foot on the mainland of Antarctica as his ship ‘Endurance’ got frozen in to the
sea ice and was slowly crushed.
His epic journey of survival is one of the most incredible and gripping stories of adventure ever told. However, an equally desperate drama was unfolding on this side of the Pole with the other half of the expedition.
After landing on Ross Island in January 1915, a group of the team set out on a first journey to leave supply dumps for Shackleton. Returning after two months of desperate struggle, starvation, frostbite and exhaustion, they discovered that their ship had been torn from it’s anchor and blown out to sea in a storm with many of the crew on board, They had no idea whether the ship floundered and the crew were lost – (in fact they did survive but could not return due to the sea ice conditions). So now ten of the group were marooned and lacking most of the food and supplies which had been left on the ship. They survived by living off whatever they could find in the huts and by hunting seals and penguins.
Still they had a mission to complete. They wanted to set up more depots for Shackleton closer to the Pole – little did they know that he was never going to need them. So in October 1915, nine of them set off again, pushing heavy sledges with the help of only four surviving dogs. On this 4 ½ month journey they pushed supplies of food and fuel for Shackleton whilst they themselves starved, at one point cutting their rations to a few lumps of sugar and half a biscuit per day. Exhausted and desperate, they suffered from snowblindness, scurvy, and frostbite. Some members of the team pushed on. One man, Spencer Smythe, died. Another had to be left behind and rescued after his comrades, who could drag him no further, had gone ahead to kill some seals for food at Hut Point (here at McMurdo).
Five of them were now cut off from Cape Evans (Scott’s second and better supplied hut to the north) by the open sea water. After two months two of the team made a desperate bid to cross the slowly freezing sea ice and were lost in a blizzard, believed to have been blown out to sea on an ice flow.
The remaining group waited for better conditions and then moved to Cape Evans to meet the rest of the party.
There on the side of one of the bunk beds, one of these survivors wrote a few words which encapture the anxiety and suffering they were going through.
August 14 1916
Losses to Date
They were finally rescued in January 1917 by Shackleton himself who, having survived his own harrowing epic, learned of their plight and came to find them. Imagine the relief they must have felt at the sight of the ship when they had no certainty of being picked up at all!
The signature of the great man himself on a packing case in the Cape Royds hut.
Whilst visiting the other hut (Shackleton’s) at Cape Royds,
it was of course imperative to see the penguin colony again.
This time the birds were sitting on eggs.
There were large ponds at the edge of the sea ice
with seals wallowing in the green water.
On the ground were some mummified
penguin chick corpses.
Life and death as usual on the icy continent...
On our way home another sight had us all captivated. A lone
emperor penguin was walking slowly across the empty sea ice.
The wind was blowing streamers of snow along the surface of the ice at his feet. The penguin stopped to look at us, then as we left, it turned and slowly waddled along into the emptiness
People have long used the earth’s magnetic field to help them find their orientation whilst traveling through unfamiliar territory. In outdoor activities we are always advised to trust the compass over any other more subjective judgment such as our ‘sense of direction’. I once forgot this rule on a foggy mountain top and found myself going in precisely the opposite direction to the one I was supposed to be going in. Oops!
However the magnetic field of the earth is actually something that changes it’s strength and direction constantly over time.
Year by year, the position of the magnetic poles moves around, making it necessary to adjust the magnetic correction when using a map and compass.
Depending where you are on the Earth, a magnetized needle hanging in balance on a string, will align itself with the way the earth’s magnetic field lines up at the surface. This means that at the equator it will be horizontal, pointing north - south, whilst the further north or south you go, the more steeply the needle will dip towards the ground. Here in Antarctica we are very near to the South Magnetic Pole (SMP), and the magnetic field is at about 80 degrees to the surface. At the SMP itself, the needle would point straight down into the ground.
On much longer timescales, the magnetic poles do something rather dramatic – they actually swap their polarity. This means that a
compass needle with the red end pointing north would swing around to point it to
the south instead. These events are called magnetic reversals.
This doesn’t happen overnight – it follows a gradual weakening of the intensity of the geomagnetic field and the switch then takes perhaps 7000 years to happen, during which a compass would be fairly useless anyway, pointing randomly anywhere. The interval between reversals is vary variable, from a few tens of thousands to several hundred thousand – even millions - of years.
This phenomenon has been used to great advantage by people
investigating the geology of the earth.
Minerals that contain iron compounds are like little magnets. Simply by sitting in the crust they become magnetized.
If a molten lava containing iron cools and solidifies, the iron minerals that crystallize will tend to become magnetized in alignment with the earth’s polarity at that time. The temperature at which they will do this is very specific to a particular mineral. For example magnetite – an iron mineral, Is able to be magnetized when its temperature is below 580 ˚C. If the temperature rises above this amount again all the magnetization will be lost.
Similarly, if a sediment made of tiny particles contains magnetic minerals, they will tend to line up with the earth’s magnetic field as they consolidate on the bottom of sea.
As long as the rocks don’t then get moved from their original position, they can act as memories of the earth’s magnetic polarity at the time they formed.
Measurements of these magnetic alignments can be made by spinning a sample of the rock within an electric coil, to generate a very slight electric current. This is done for four different orientations of the sample to find the magnetic orientation in three dimensions.
So by measuring the magnetism of rocks regularly down a
geological sequence, (such as the ANDRILL rock core) these reversals can be
picked up. They have been well studied from other parts of the world and the
exact times of the reversals are well known. The diagram shows this magnetic 'bar code' of the Earth - the numbers on the left represent millions of years - very much the timescale that applies to the top half of our ANDRILL core.
This means that when used along with other dating methods (fossil assemblages, radiometric dating of volcanic rocks and mollusc shells) palaeomagnetism can give vital information about the ages of rock layers in a sequence.
The ANDRILL core is being sampled every meter of its length to test whether the magnetic alignment is normal or reversed. It is exciting to listen to the different scientists compare notes to work out the ages of the different layers of the ANDRILL core.
One of the fun things you can do in Mactown is get hold of a bicycle. This opens up possibilities for a more exciting approach to some of the local hikes.
The pictures show a couple of the local scenic possibilities – the first is the Castle Loop track – (about 15 km). It is mostly on snow or ice – which can prove tricky depending on the conditions. When it's soft you sink right in - and easily come to a grinding halt. When it is icy, you fall over...The ideal is hard packed snow, which we did have for most of the way round. The very exciting bit is a steep downhill section going from Castle Rock itself down to the ice shelf at sea level.
The second route is the much shorter Hut Point Ridge (5km). This is an excellent biking challenge, starting with a stiff climb on the road out of town, then the spectacular ridge track and a challenging descent down a steep rubbly track back home.
The drill is now at 1100 meters below sea level. This is already deeper than any previous rock core drilled on the continent. If there are no unforeseen problems, all bodes well for the attainment of target depth of 1200m and more by Christmas Day – the last day of drilling.
After that the geophysicists will have their chance to lower various gadgets down the drill hole to make further recordings. Then the drill and all the associated equipment will be packed up and hauled back to Scott Base, ready to be deployed again next year for another drilling on the sea ice, a little further out from McMurdo.
There is an abundance of new discoveries waiting to be analysed in more detail in the core. This is now the work of the scientists through next year. They will clarify the dating of the sequence and consolidate all the information gleaned from the different rock layers and microfossils. There is no doubt that this drilling will live up to all expectations and more in terms of producing new understandings of Antarctic climate history.
So I have come to the point of writing my final words on this blog as an ANDRILL outreach educator for 2006. Tomorrow I will return to New Zealand, and a day later I will be at home again.
I have now been in Antarctica for two months - witnessing, learning and participating. The experience has been huge and unforgettable – every single day has been full. I am left with a sense of gratitude for having had such an amazing opportunity. There are many people to whom I owe my thanks. The ANDRILL management, all the scientists, my ARISE teacher colleagues, and also my patient and generous family at home.
I would also like to thank all those of you who wrote to me with your comments and questions. It has been most enjoyable interacting with you. Do continue to do so – I will be continuing with ANDRILL outreach activities through 2007, and the scientific results of the project will continue to expand.
So I will wish you all the best for the season, wherever you are on this beautiful planet,