Posts Tagged ‘earthsciences’

Piece of crust stolen from Texas found in Antarctica

29 Aug

You’ve likely heard of Pangaea (not the one that sounds similar from Avatar), but you may not realize that it wasn’t the first supercontinent; several have been identified from the rock record. About a billion years ago, a supercontinent named Rodinia formed from the collision of a number of cratons which comprise parts of today’s continents. Evidence of the collisions that built Rodinia remains in a geological remnant called the Grenville mountain range.

Collisions of continents compress the crust between them, driving up a range of mountain peaks. We see a process like this going on today in the Himalayas, where the Indian plate is pushing northward into the Eurasian plate. With time, however, erosion will level out these mountains.

The Appalachian mountain range no longer reaches the impressive heights it once did because it has been eroding for over 400 million years. Deep in the roots of the Appalachians, though, we can see evidence of an even older mountain range that has long-since eroded from sight. The remnants of the Grenville range extend along the East Coast of the United States, but also continuing north into Canada as well as south through Texas and into Mexico. 

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Why so cold? The last refuge of Antarctica’s forests

28 Jun

We know Antarctica as an unfathomably cold wasteland, suitable for little beyond penguins and foolhardy researchers. But it hasn’t always been like that. At times in the distant past, plate tectonics and warmer climates have combined to cover Antarctica with lush forests, dinosaurs, and even marsupials. A paper published in PNAS details the final transition from habitable continent to the inhospitable ice cap that has developed over the past 40 million years. Its results describe the ecosystems that survived in the last unglaciated corner of Antarctica before the ice sheet swept away the last remnants of terrestrial life.

To accomplish this, the team behind the paper set out to read the history recorded in the sediment around the Antarctic Peninsula (Antarctica’s "tail"), which would have been the last piece of the continent to be covered by an ice sheet. They used seismic imaging of the sedimentary layers offshore to identify locations with sediment from the desired age range.

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