Antarctica Was Once Home to Rivers, Forests

2023-11-06 12:05:17来源：网络

Antarctica Was Once Home to Rivers, Forests

南极洲曾经是河流、森林

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　　By Dan Novak

　　05 November 2023

　　Antarctica has not always been a land of ice and snow. Earth's southernmost continent once was home to rivers and forests full of life.

　　Scientists are using satellite observations and radar imagery to look deep under the ice. The researchers report finding a large ancient landscape buried under the continent's ice sheet. It is full of valleys and ridges, shaped by rivers before being covered by glaciers long ago.

　　The landscape is located in East Antarctica's Wilkes Land area bordering the Indian Ocean. It covers an area about the size of Belgium. The researchers said the landscape appears to date to at least 14 million years ago and perhaps beyond 34 million years ago, when Antarctica entered its deep freeze.

　　"The landscape is like a snapshot of the past," said Stewart Jamieson. He is a professor of glaciology at Durham University in England and co-leader of the study published in the journal Nature Communications.

　　"It is difficult to know what this lost world might have looked like before the ice came along, but it was certainly warmer back then," Jamieson added. "Depending how far back in time you go, you might have had climates that ranged anywhere from the climate of present-day Patagonia through to something more approaching tropical."

　　Such an environment likely would have been populated by wildlife, Jamieson said. But the area's fossil record is too incomplete to know which animals may have lived there.

　　The ice above the ancient landscape measures about 2.2 kilometers to 3 kilometers thick, said study co-leader Neil Ross. He is a professor of polar science and environmental geophysics at Newcastle University in England.

　　The researchers said the surface of the planet Mars is better known than the earth surface below the ice in Antarctica. They said one way to learn more would be to drill through the ice and take a piece of the earth below. This could uncover evidence showing ancient life, as was done with samples taken in Greenland dating back two million years ago.

　　Some earlier studies have uncovered ancient landscapes beneath Antarctica's ice including mountains. But the landscape discovered in the new study was the first of its kind.

　　Right before 34 million years ago, Antarctica's landscape and wildlife was likely similar to today's cold temperate rainforests. That includes places like Tasmania, New Zealand and South America's Patagonia area, Ross added.

　　Antarctica was once part of the Gondwana supercontinent that also included what is now Africa, South America, Australia, the Indian subcontinent and the Arabian Peninsula. But it eventually split off in a process called plate tectonics.

　　Jamieson said the researchers think that when Antarctica's climate was warmer, rivers flowed toward a continental coastline that was created as the other land masses broke away. When the climate cooled, he said, some small glaciers formed on hills next to the rivers, with valleys deepening as glaciers eroded.

　　When the climate cooled even more, an ice sheet grew which covered the whole continent, Jamieson added. Eventually, "the landscape got preserved, likely for 34 million years."

　　I'm Dan Novak.

　　Dan Novak adapted this story for VOA Learning English based on reporting by Reuters.

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　　丹·诺瓦克

　　2023年11月5日

　　南极洲并不总是冰天雪地。地球最南端的大陆曾经是充满生命的河流和森林的家园。

　　科学家们正在利用卫星观测和雷达图像来观察冰层深处。研究人员报告发现了一个巨大的古代风景埋藏在大陆的冰原下。它充满了山谷和山脊在很久以前被冰川覆盖之前，由河流塑造而成。

　　该景观位于东南极洲靠近印度洋的威尔克斯陆地区域。它覆盖的面积大约有比利时那么大。研究人员表示，这种景观似乎可以追溯到至少1400万年前，甚至可能超过3400万年前，当时南极洲进入深度冻结状态。

　　“景观就像一个快照斯图尔特·贾米森说。他是英国杜伦大学的冰川学教授，也是发表在该杂志上的这项研究的共同领导人《自然·通讯》.

　　“很难知道在冰出现之前，这个失落的世界可能是什么样子，但那时肯定更温暖，”贾米森补充道。“根据你追溯到多远的时间，你可能有这样的气候变化从现在巴塔哥尼亚的气候到更接近的气候热带的."

　　杰米森说，这样的环境很可能会有野生动物。但是该地区的化石记录太不完整，不知道哪些动物可能在那里生活过。

　　这项研究的合作领导者内尔·洛斯说，古代景观上方的冰厚约2.2公里至3公里。他是英国纽卡斯尔大学的极地科学和环境地球物理学教授。