Teach Astronomy - Volcanoes on Venus
Автор: Teach Astronomy
Загружено: 2010-07-07
Просмотров: 612
Описание:
http://www.teachastronomy.com/
Radar mapping of the surface of Venus has given us some clues as to the volcanic history of our sister planet. Venus has huge volcanoes ranging in size up to 5 to 6 miles high. There is evidence that the entire surface of Venus was re-surfaced by volcanoes and magma 500 to 800 million years ago. This is quite unlike the situation on the Earth, where although there is volcanic activity, it's possible to find relatively young and relatively old surfaces. Almost the entire surface of Venus has roughly the same age. Astronomers speculate that convective super-plumes of hot magma in the mantle caused this violent episode of volcanism. Venus may have been resurfaced a number of times in its history. Yet, Venus does not have tectonic activity or large-scale movement of the lithospheric plates. At first sight, this is hard to understand, given the active volcanism, but it's probably because Venus has a thicker lithosphere than the Earth, and a different type of interaction between the lithosphere and the mantle.
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