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.   

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!

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

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…

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.

The scientists involved are Terry Wilson, Tim Paulsen, and assistant technicians: Andreas Laufer, Cristina Millan

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

• Assuming the rock is the same way up as when it formed,which of the two coloured layers would be the oldest?
• What are two features at the boundary of the green and yellow layers which indicate that a phase of earth movements occurred before the yellow layers were deposited?

•  What is one feature that indicates earth movements occurred after the yellow layers were deposited?

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 State University 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.

Dropstones are 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.

Interpretations:

So far (to November 13^th) 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:

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.

Computer Logging:

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!

Julian

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

Breaking News

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 clear.

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!

Julian

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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!

Julian

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.

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 6^th 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.

Julian

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.

Julian

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!

Julian

 

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 the Transantarctic 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 the ice. 

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?

Julian

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:

 

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 moment.



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!

Julian

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 below freezing.

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 ...

Julian

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…

Julian

 

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.

R.W. Richards

August 14 1916

Losses to Date

Hayward

Mack

Smyth

Ship (?)

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

Julian

 

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.

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.

Julian

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,

Julian