Friday, February 26, 2010

Off in deep water with ice-rafted debris

We are approaching the end of the drilling operations. We need to leave here four days from now to make it to Hobart on time. We are drilling in the distal end of a fan now in nearly 4000 m water depth and find laminated silts and clays and occasional rock clasts. These rock clasts are most likely ice-rafted debris, rock eroded by glaciers, that then calved and produced icebergs. The debris then gets carried off-shore by icebergs, which melt and release the rock debris so that it can fall to the sea floor. For a decent recent calving event see for example this website from NASA. It shows a series of images documenting the recent calving of the Mertz Glacier Tongue near to where we are drilling. You may have heard about it on the news, it is going on right now.

However, not all icebergs in this area originate at the Wilkes Land coast. Here in this core section is a piece of volcanic rock that may have come from the Ross Sea. I was there two years ago with the Antarctic Geological Drilling program (ANDRILL). There are several volcanic islands there that are composed of volcanic rocks like this one. (See the posts on this blog from 15-16 Oct. 2007.) A glacier may have eroded it there and icebergs may have carried it out here.

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