PROVIDENCE, R.I. -- Scientists say they have discovered the thinnest portion of the Earth's crust -- a 1-mile thick, earthquake-prone spot under theAtlantic Ocean where the American and African continents connect.
The discovery will help geologists and oceanographers better understand the formation of the planet's outer skin, Donald W. Forsyth, an asociate professor of geology at Brown University, said Tuesday.
The find, which must still be confirmed by seismic tests, was made by Forsyth, graduate student Roger Prince and oceanographer Robert S. Detrick of the University of Rhode Island.
They used an instrument that measures barely detectable variations in gravitational pull to pinpoint the thin crust, which is just north of the equator at the juncture of the crusts of the American and African continents.
'The main thing we're trying to do in this study and others is figure out the mechanics of the sea floor, particularly the mechanics of a ridge in the fracture zone,' Forsyth said. 'We're trying to find out how it works -- the basic process of crustal formation.
'It's definitely basic science. No one's going to make a million dollars on this discovery,' he said.
For comparison, the Earth's crust ranges from a thickness of 40 miles below mountainous Tibet to 4 miles on the ocean bottom. The scientists' measuring device was able to distinguish the crust from the mantle below because the crust is less dense than the subsurface.
So, the higher gravity meant there was less crust and more dense mantle near the surface.
The thin area is estimated to be 6 to 10 miles wide and 12 to 15 miles long. The thin crust is located along the Mid-Atlantic Ridge, the area where the blocks of crust that make up the American and African continents meet.
The ridge is similar to the San Andreas fault in California, including its potential for earthquakes because of the tension created by the massive, shifting crustal plates. But there is no need to worry about a giant tidal wave or the thin crust cracking and draining the ocean, Forsyth said.
If a crack did develop, water would probably cool the usually molten, denser mantle below and form another layer of crust, Forsyth said.
'The water isn't going to go down this hole in the crust,' he said. 'The crust can be seen as floating on a more dense mantle. The ocean's on top because it's the least dense material.'
The scientific team plans to return to the area next October to doublecheck the discovery with seismic waves, Forsyth said.