Thomson and his colleagues analyzed sediments drilled from the ocean floor just offshore of Lambert Glacier, as well as from onshore moraines, the rock piles pushed up by glaciers. Tests on minerals in the sands and muds helped them figure out when and how fast the surface eroded.
Here's what the sediments say: From about 250 million to 34 million years ago, the region around Lambert Glacier was relatively flat, and drained by slow-moving rivers, Thomson said. About 34 million years ago, which coincides with a cooling of Earth's climate, big glaciers appeared, shaping the spectacular valley now hidden under thick ice.
"It seemed like it occurred very early on, 34 [million] to 24 million years ago," Thomson said. Erosion slowed dramatically as the ice sheet stabilized about 15 million years ago, he said.
Some 5,250 to 8,200 feet (1.6 to 2.5 kilometers) of rock have since disappeared, ground down by glaciers and carried away by the ice, according to the study.
"Glaciers can carve deep valleys quickly — and did so on Antarctica before it got so cold that the most of it got covered by 1 or 2 miles [1.6 to 3.2 km] of thick, stationary ice," Peter Reiners, a UA geologist and study co-author, said in a statement.
Clues to buried mountain range
Lambert Graben extends about 375 miles (600 km) inland, ending at one of Antarctica's most enigmatic features — an entombed mountain range called the Gamburtsev Mountains. Buried under the ice, the mountains rose during Gondwana's rifting. Geologic evidence suggests two pulses of upliftfrom rifting events about 250 million years ago and 100 million years ago pushed up the jagged peaks.
But Thomson and his colleagues did not find evidence in the sediments for a second uplift phase 100 million years ago. The river sands contain minerals from the Gamburtsev Mountains, and the tiny grains suggest the mountains got their height with one tectonic push.
"This underscores both the mountain range's remarkable age and the extraordinary degree of subglacial landscape preservation," writes Darrel Swift in an accompanying article in Nature Geoscience. Swift, a geologist at the University of Sheffield in the United Kingdom, was not involved in the study.
Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook or Google+. Original article onLiveScience's OurAmazingPlanet.
- Images: The Majestic Transantarctic Mountains
- Video - Antarctica: Solving Geologic Mysteries
- Images: Scientists at the End of the Earth
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8 Comments
Add CommentIt won't be long before will get a look at it again the way global warming is accelerating. Perhaps our grand kids grand kids anyway.
Reply | Report Abuse | Link to thisOne day there will be a mile of ice above NYC. It's citizens (our descendants) will have, long ago migrated to the rapidly expanding lands of Florida, as sea level drops by 50 meters. Problem is... nobody can say exactly WHEN that will happen... only that it is becoming overdue. GK
Reply | Report Abuse | Link to thisWTF? Not overdue, was possible, but not anymore.
Reply | Report Abuse | Link to thisModels of the globe Static and Dynamic www.mammoths.narod.ru prove, that the Earth casually appeared in Solar system (~800 thousand years), these models of the globe have proved, what changes in time II, III, IV stages have particularly taken place, millions years is a leisure fiction
Reply | Report Abuse | Link to thisNot just possible, but probable, and some humans actually believe that they can stop it by accident. That would be funny, if it weren't so sad.
Reply | Report Abuse | Link to thisSavov. Nice fun stuff on that link. No data of course, just lots of speculations. Where is the raw data that generated these speculations? Might be fun to try to recreate your conclusions from real data, maps, etc. Could you explain your methods a bit more?
Reply | Report Abuse | Link to thisem_always_right: When you say another ice age is not possible, you are most likely wrong. Warming changes salinity in water, which could cause Gulf Stream and Japan Current to stop the engine that keeps coastal regions moderate, triggering another ice age (like the mini-ice-age in 1600's). The Pilgrims of course did not say WTF when it was so cold in UK, they just headed out for warmer shores, or so I was told long ago.
Reply | Report Abuse | Link to thisTo mclayton200
Reply | Report Abuse | Link to thisThe past of a planet the Earth includes many millions years when this planet was in system of planets of other Galaxy, thickness of a firm environment was measured (thousand in km). At occurrence of the Earth in an orbit of the Sun practically all planet has fused, as consequence was proceeded with global tectonic changes, II stage has terminated in cardinal change of volume and a geographical kind of the planet, the escaped inhabitants now appeared on a flexible and thin environment of a planet (Ms). During III stage this environment repeatedly turned in an equatorial plane, this "work" was carried out by thermal energy of the Sun, at total weight of ice domes which changed in limits (150 - 450 million км3). On last site of the schedule the environment of a planet has burnt through, as result, the thermal stream of bowels has practically kindled all ice (except for 29 million км3), the level of Ocean thus has raised on size (~ 450 м), thus, “ the Bible flood ” it, unfortunately a reality. So, with the beginning of IV stage the water elements has tired out inhabitants of a planet on top (Ms), the present abnormal level of Ocean and abnormal weight of an ice dome obliges inhabitants to predict variants of events in which IV stage will terminate. However “ the Science about the past of a planet ” has taken very strange position in relation to Dynamic model of the globe of a planet the Earth