Tuesday, December 12, 2006

Unique Antarctica

Just walking around the Dry Valleys you may stumble (literally and figuratively) upon many interesting wonders of nature. Here are a few examples:

Mummified seals and penguins: Carcasses of seals and penguins have been found in the Dry Valleys over 30 miles away from the sea. This is not the result of a sea level drop, but simply because the seals and penguins have “lost their way.” Scientists say that when seals travel, some follow cracks in sea ice that lead them far from open water. When winter comes and they are far from open water, they become extremely stressed, perhaps causing their navigational systems to deteriorate. At this point, seals either try to return overland before winter sets in or share a breathing hole in the ice created by another seal. Often the seals choose the former and cannot find their way back, ending up in the Dry Valleys and other areas. The seals and penguins appear to be in pretty good shape but this can be very misleading because some are hundreds of years old. The very dry, cold weather makes it hard for any organic material to break down (this is also why prevention is the best remedy for pollution in the Dry Valleys).
One of the many mummified seals you may find in the Dry Valleys. I think this one is a Leopard Seal.
Kenyte: Kenyte (a type of phonolite) is a volcanic rock type found only in Antarctica and Kenya. It is so rare because it contains minerals that do not usually occur together. The kenyte in Antarctica comes from Mt Erebus, 20 miles from McMurdo station. The heat in the caldera of this volcano is not uniform, causing differing viscosities and temperatures within the same lava body. These varying conditions allow several families of minerals to form in an environment that would normally support only one type.

Kenyte. The lenses are made of a mineral called microcline.

Venefacts: A venefact is a rock that has been sculpted by the wind. Wind speeds get so high in Antarctica (especially in the winter) that large sediment particles become entrained and effectively sandblast a regular piece of granite or other rock into an abstract sculpture. The largest and most stunning of these venefacts can be found on high ridges where the wind whips through notches.

One of the many venefacts on a high ridge. We found some that were 5 or 6 times as large as this one.

Blood Falls: You can only stumble across this one if you’re not looking very closely. Blood Falls is an outflow of subglacial water at the terminus of the Taylor Glacier in the Taylor Valley. The researchers studying this landform believe that a large quantity of iron-rich seawater became trapped in the glacier, part of which is released and oxidized each year. This creates a striking frozen waterfall that looks like the glacier is bleeding.

Blood Falls emerging from the Taylor Glacier. Lake Bonney is in the foreground. The glacier face (not including the brown sediment) is about 50 feet high.


George said...

In the foreground of the picture of "blood fall" there appears to be a lake, or puddle, of liquid water. Is this a bit of a mirage, or is it too cold to be liquid? If it is, to get that smooth, it seems like it must have been liquid at some point.

Also, you mentioned that scientists surmise that the "blood falls" comes from trapped sea water; does this ice have a salt content? I am under the impression that the salt is somehow lost in long-frozen water; is this correct? If so, why weren't the iron particles lost as well?

Emily said...

The Taylor Glacier and Blood Falls terminate at Lake Bonney. The lakes are "permanently frozen" but every summer a moat develops around the edge due to warmer meltwater input. So yes, what you are looking at in the foreground is the moat of Lake Bonney, beginning to thaw for the summer season.

As for the trapped seawater, I had the same questions myself. Not a whole lot is known about the mechanics of Blood Falls, but to partly answer your question: no, the glacier has no (or negilgible) salt content. I am not sure about the mechanisms for trapping the seawater (I'll ask around) but presumably the seawater was salty enough that it never froze, retaining it's salt and iron contents.

Wally said...

Any explanation as to why the kenyte is only found in Antarctica and Kenya? Was the lava created in both places in the same scientific era? Seems odd since they are so far apart.

Emily said...

The only reason it can be found in both places is because it is very rare for partial melting to occur in a lava body. So of all the volcanoes in the world, only these two have the right conditions to produce kenyte. It is not actually the same lava body in both places- it is produced independently in Antarctica and Kenya. Hopefully that answers your question.

Kevin said...

Blood Falls is pretty awesome, even if it sounds like the title of a bad horror film.

Emily said...

I asked around about the potential mechanisms for trapping a large amount of saltwater within a freshwater glacier. The consensus seems to be that during the last interglacial (warm period), sea level was higher and thus the Taylor valley looked much like a fjord. As the next glacial maximum arrived and glaciers advanced, sea level fell and the ocean receded from the valley. The low spots were left with saline lakes. One of these lakes was situated on an iron rich rock formation, and so the seawater became iron "infused," if you will. As the Taylor glacier advanced, it captured this lone, iron-rich body of saltwater within it's mass.

To further answer the question about Kenyte, both the Kenyan and the Antarctica variety are relatively recent geological productions. So even though you could say they were formed in the same time period, that does not indicate their relatedness.

Anonymous said...

have they found any life in blood falls?

Anonymous said...

i have sample of kenyte soda trachyre cape royds victoria land
antartica from shackelton's expedition and ithas a number with s173 i don't knowhow old it is (is it rare?)my email is minituna150@hotmail.com write to me brandon

Anonymous said...

i think it is swee that you have been to shakeltons boat place we were reading about that in school today