May 25, 2021
The Two Fundamental Processes
Originally published October 6, 2011
images from NASA Earth Observatory
The solar system has 8 planets, more than a hundred moons, tens of thousands of asteroids, billions of comets and trillions of pieces of space dust. All were created and/or modified by impact collisions, and all of the hard bits larger than a few hundred kilometers have been modified by volcanism. Here, from the Earth Observatory, are examples of these two most fundamental processes. On the right is the currently erupting Nabro caldera in Ethiopia - it is about 7 km in diameter. Dark ash has been blown to the south and west, the pinkish lava flow was erupted in June and in this false color IR image the pink is due to heat still escaping as the flow cools. The bright red indicates a currently erupting flow, perhaps in a lava lake. The other image is of a barely recognizeable circle - the 8 km wide Bigach impact crater in Kazakhstan. On Earth, impact craters are typically much harder to identify than volcanoes. That is because impact craters don't form very often - Bigach is a young one having impacted 5 million years ago. Nabro, obviously, is still forming. On the Moon, volcanism slowed down a lot about 2.5 b.y. ago and stopped a billion years ago, but impact cratering continues at a slow pace. Earth's atmosphere destroys projectiles that form craters smaller than a few hundred meters, but on the Moon, small craters are now being discovered that formed since Apollo.
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Yesterday's LPOD: What is Undarum?
Tomorrow's LPOD: Ptolemaic Sunset