from the poking-the-bear dept.
The continuation of many previous quests to drill into the Earth's Mantle will begin shortly in the Indian Ocean. A team of scientists and engineers led jointly by Henry Dick of the Woods Hole Oceanographic Institution, and Chris MacLeod from Cardiff University will use the scientific drilling ship JOIDES Resolution to bore 2km into the ocean floor in the first of a series of three planned missions to the South-West Indian Ridge. The ultimate aim of the mission is to find and understand the "Moho Boundary", this is a point in the earth's crust where the seismic waves from earthquakes abruptly change their speed of travel. The current explanation of the Moho boundary is a simple change in rock types from the crust to the mantle, however, this operates on untested assumptions about the structure of the Earth's crust and mantle. The team have a theory that the mantle structure is more complicated, and that ingress of ocean water can cause large structural changes. This is the key theory they plan to test with this drilling mission.
"The Moho is pretty uniform everywhere across the ocean basins, and because of that everyone has assumed that the ocean crust is very uniform and therefore, by inference, very simple," explains Prof MacLeod. "But if we're right here, it changes the game completely. If the Moho seismic boundary is actually an alteration boundary from water penetration into the mantle, it means we know a lot less about the ocean crust than we did."
Expedition Site: http://iodp.tamu.edu/scienceops/expeditions/indian_ridge_moho.html
Nature Article: http://www.nature.com/news/quest-to-drill-into-earth-s-mantle-restarts-1.18921
BBC News: http://www.bbc.co.uk/news/science-environment-34967750
Back in the beginning of December the JOIDES Resolution, a scientific drilling vessel, began Expedition 360 to drill the deepest hole into the Earth and reach the mantle. The Expedition ended at the end of January with a 789 meter hole, which is short of their goal of 1300 meters. They do have the distinction of having drilled the 5th deepest hole into the solid crust, and they did return both the longest single piece and the widest single piece of hard rocks recovered for scientific purposes. They hope to be able to return to the drill site to continue drilling in a future expedition.
The next expedition for the JOIDES Resolution started on January 30, and will run through March 31, 2016.
Expedition 361: South African Climates will drill core six sites on the southeast African margin and Indian–Atlantic ocean gateway to better understand the relationship between the Agulhas Current -- the strongest western boundary current in the Southern Hemisphere -- and the development of climate in southern Africa during the Pliocene/Pleistocene periods.