The Ocean Drilling Program has deepened a hole in the eastern Pacific Ocean to a depth of 2 km into the ocean floor, the deepest hole ever drilled into the ocean crust.
Plans call for deepening the hole later, said Dr. Philip D. Rabinowitz, ODP director.
"What we can learn from this one site can either confirm what has been theory or open up new ways of thinking about the dynamics of Earth's system," Rabinowitz said.
The Joides Resolution drill ship, registered as Sedco/BP 471, drilled in 3,400 m of water and deployed more than 5 km of drill string in Hole 504B on ODP leg 140.
Texas A&M University operates and staffs the drill ship and retrieves cores from strategic sites around the world.
Lamont-Doherty Geological Observatory of Columbia University, Palisade, N.Y., is responsible for downhole logging.
Until drilling Hole 504B, west of Ecuador, scientists were limited by seismic recordings and their own imaginations to visualize the three layers of ocean crust.
By penetrating two of the layers, they can replace the layer-cake concept with a complex, three dimensional model.
OCEAN FLOOR STRATA
Scientists involved in the ODP say that reaching still deeper is critical to understanding how the ocean crust forms and interacts with the overlying oceans.
Sediments overly hard volcanic rocks in the shallowest layer of ocean crust.
The second layer has lava flows underlain by massive eruptions of frozen magma, called sheeted dikes, that fill the fractures in ocean crust.
Scientists believe the third layer represents the frozen remains of extinct magma chambers, great pools of molten rock that lie beneath the mid-ocean ridges and produce the sheeted dikes of the second layer.
The magma in the chambers cools slowly and crystallizes into coarse-grained rocks called gabbros, which have never been documented in position in an undisturbed section of ocean crust.
Hole 504B represents at this time the only hole in the world in which scientists have the possibility of observing the transition into the third layer.
The hole was drilled well into the transition zone between the second and third layers but did not break through into the third layer. Many of the lavas drilled contained fragments of gabbros that clearly had been carried up from depth.
Drilling into the third layer will allow scientists to study directly the processes by which lavas evolve, crystallize, and erupt.
Learning more about these processes provides the best way to test new theories and perhaps revolutionize understanding of marine geology and geophysics, ODP said.
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