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 earths 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 [tamu.edu]
Nature Article: http://www.nature.com/news/quest-to-drill-into-earth-s-mantle-restarts-1.18921 [nature.com]
BBC News: http://www.bbc.co.uk/news/science-environment-34967750 [bbc.co.uk]