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Secrets of Antarctica's fossilised forests

Posted: Wed Jun 22, 2011 7:13 pm
by edfrank
7 February 2011 Last updated at 20:34 ET

Secrets of Antarctica's fossilised forests
By Howard Falcon-Lang Royal Holloway, London

http://www.bbc.co.uk/news/science-environment-12378934


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Dinosaurs once foraged beneath the Southern Lights in Antarctica
It may be hard to believe, but Antarctica was once covered in towering forests.

One hundred million years ago, the Earth was in the grip of an extreme Greenhouse Effect. The polar ice caps had all but melted; in the south, rainforests inhabited by dinosaurs existed in their place. These Antarctic ecosystems were adapted to the long months of winter darkness that occur at the poles, and were truly bizarre. But if global warming continues unabated, could these ancient forests be a taste of things to come? One of the first people to uncover evidence for a once greener Antarctic was none other than the explorer, Robert Falcon Scott. Toiling back from the South Pole in 1912, he stumbled over fossil plants on the Beardmore Glacier at 82 degrees south. The extra weight of these specimens may have been a factor in his untimely demise. Yet his fossil discoveries also opened up a whole new window on Antarctica's sub-tropical past.
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Re: Secrets of Antarctica's fossilised forests

Posted: Wed Jun 22, 2011 9:26 pm
by jamesrobertsmith
I've always been so happy that I had parents who--while having had no formal education--were extremely well read. They would pile science books on me by the dozens so that I knew all about evolution and geology by the time I was six years old. My dad used to take me to the barber shop and impress the locals with my knowledge of prehistoric animals. My mom was telling me about plate tectonics before it was being taught in colleges--an effect of various professors stopping by to discuss politics with my dad who was an old style working class intellectual (and the owner of a popular Atlanta bookstore).

One of the books my mom and dad gave me to read when I was eight years old had a chapter on Antarctic fossils. So it seems as if I've always been aware that Antarctica was once much warmer and comfortable to life than it is now.

Re: Secrets of Antarctica's fossilised forests

Posted: Wed Jun 22, 2011 11:14 pm
by James Parton
I remember seeing something on this on some show on dinosaurs a while back. It was quite fascinating how those dinos survived the dark antarctic night.

Re: Secrets of Antarctica's fossilised forests

Posted: Thu Jun 23, 2011 4:58 am
by Joe
100 million years ago, the Antartic wasn't at the south pole!

Re: Secrets of Antarctica's fossilised forests

Posted: Fri Jun 24, 2011 3:21 am
by KoutaR
From about 100 myr ago (later Cretaceous) the crust of Australia and New Zealand begin separating from Antarctica. By this time Antarctica is already positioned over the South Pole.
http://www.discoveringantarctica.org.uk/alevel_1_2.html

Re: Secrets of Antarctica's fossilised forests

Posted: Fri Jun 24, 2011 10:31 am
by jamesrobertsmith
Yep. It was already polar by the Cretaceous when it was relatively warm there. Ice and snow were there, but not common and likely fleeting.

When I was a kid, one of the professors from GA Tech who would visit the house from time to time explained the movements of the continents to me. Later, my mom explained it in even simpler terms for my eight-year-old ears. I don't recall hearing the term "plate tectonics", but when I finally began to hear of it in my later teens I already knew what it was. (The professor may have been Bud Foote who was actually an English professor--but it may have been somebody from the science department. Foote was the guy who visited my dad most often, though.) In the 1960s it was largely discounted and thought to be a fantasy by many geologists.

Re: Secrets of Antarctica's fossilised forests

Posted: Sat Jun 25, 2011 5:17 am
by Joe
Kouta Räsänen wrote:
From about 100 myr ago (later Cretaceous) the crust of Australia and New Zealand begin separating from Antarctica. By this time Antarctica is already positioned over the South Pole.
http://www.discoveringantarctica.org.uk/alevel_1_2.html
that article says, "After this time, Gondwana slowly split apart to create Antarctica as a separate continent, and Antarctica has gradually moved away from the other southern continents towards its present polar position."


Notice the word "gradually".

I still don't think Antartica was in its present postion 100 M years ago- it may have been moving in that direction, but I doubt any continent fails to move for long, other than Africa which I think is believe to have moved very little.
Joe

Re: Secrets of Antarctica's fossilised forests

Posted: Sat Jun 25, 2011 10:01 am
by KoutaR
Joe,

You omitted the beginning of the paragraph you referred. Here it as a whole:
Some 200 million years ago, Antarctic continental crust was joined with South American, African, Indian, and Australian continental crust making up a large southern land mass known as Gondwana (the southern part of the supercontinent called Pangea). After this time, Gondwana slowly split apart to create Antarctica as a separate continent, and Antarctica has gradually moved away from the other southern continents towards its present polar position.
Antartica was not in its present postion 100 M years ago. 100 Ma its edge has passed over the South Pole.

Kouta

Re: Secrets of Antarctica's fossilised forests

Posted: Mon Jun 27, 2011 5:08 pm
by edfrank
How Antarctica Got So Cold
Jun 27, 2011 3:02 PM ET
By Charles Q. Choi, OurAmazingPlanet Contributor

http://www.ouramazingplanet.com/antarct ... zingPlanet
Antarctica continent

The coldest continent, Antarctica, became that way by progressively cooling over the past 37 million years, scientists have found.

Antarctica was once significantly warmer than today. Just prior to 40 million years ago, past studies found, the continent was home to diverse vegetation and experienced average temperatures between 30 and 51 degrees Fahrenheit (minus 1 and 10 degrees Celsius). It is hotly debated as to why Antarctica then grew colder.

Drilling down

To help solve the mystery, scientists collected seismic data and drilled out tubes of sediment up to more than 100 feet (30 meters) long during two cruises in the northernmost Antarctic Peninsula area. The task wasn't always easy.

"You spend a lot of time lowering drill pipe to the seafloor only to have an iceberg approach and force you to pull pipe and move to another location," said researcher John Anderson, a marine geologist at Rice University. "As you can imagine, this was frustrating, but expected."

The researchers next reconstructed the region's climate and vegetation history by analyzing fossilized spores and pollen, marine organism remains, and sand and pebbles. Materials deposited in sediment are laid down in layers, and therefore can be pinned down to general points in time if these layers were not later disturbed.

They found that 37 million to 34 million years ago, reduced concentrations of atmospheric carbon dioxide coincided with increased mountain glacier formation. From 34 million to 23 million years ago, vegetation primarily consisted of woodlands and tundra dominated by conifers and southern beech. Limited pockets of this tundra were still present until 12.8 million years ago, with this long transition from a temperate alpine region to one of cold and ice continuing until nearly the present day.

"We have long suspected that climate cooling in Antarctica was gradual, based on a large body of evidence from onshore and offshore; however, recent studies have suggested a much more abrupt cooling and associated glaciation due to rapid draw down of carbon dioxide at the end of the Eocene (34 million years ago)," Anderson said. "Our results support cooling at this time, but also indicate that the demise of the Antarctic climate was gradual and that the onset of full glacial conditions and evolution of the Antarctic Peninsula ice sheet occurred over many million years."

The investigators suggest the gradual opening of ocean passageways around Antarctica that isolated the continent helped explain why it progressively cooled. These passageways resulted in currents that flowed around Antarctica, which disrupt ocean currents that would normally transport heat from nearer the equator toward the South Pole, Anderson told OurAmazingPlanet.

Current climate change

This progressive cooling contrasts sharply with the rapid warming trend the Antarctic Peninsula has seen for at least a half-century.

"It is always helpful to place current climate change in the context of natural change," Anderson said. "The fact is the rate of climate change in the Antarctic Peninsula over the past few decades is unprecedented in terms of the rate of change and the geographic extent of change, and this supports other evidence, such as the current unprecedented rate of sea-level rise, that humans are significantly altering Earth's climate."

The scientists detailed their findings June 27 in the journal Proceedings of National Academy of Sciences.
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