The Last Word: Roger Searle; Dropping Into the Ocean.(Interview)

Byline: Ginanne Brownell

Roger Searle is going down under--way under. Last week the Durham University geophysics professor and a group of fellow scientists set sail from Tenerife aboard the [pounds sterling]40 million research ship RSS James Cook. They are investigating a hypothesis that part of the earth's crust is missing. Halfway between the Canary Islands and the Caribbean lies what one of Searle's colleagues called "an open wound on the surface of the earth." Nearly 100 kilometers of seafloor seems to be, in effect, missing. The scientists will spend several weeks investigating why this area did not develop a normal crust and how it appears to challenge current tectonic-plate theories. With the Atlantic waves crashing around him, Searle spoke to NEWSWEEK's Ginanne Brownell by satellite phone from Tenerife. Excerpts:

BROWNELL: A huge hole in the bottom of the ocean sounds pretty dire.

SEARLE: It's not just a big hole--it's much more subtle than that. Tectonic plates are thin, rigid shelves that slide around on the surface of the earth. The interior of the earth is ductile, a little bit like hard toffee. These plates move apart from each other at mid-ocean ridges--such as the mid-Atlantic ridge--leaving a gap, which has to be filled somehow. The earth's mantel moves up very slowly to fill up that gap. As it does, some of it can melt, and produce magma, or molten rock. Magma can then be erupted from volcanoes, making its way to the seafloor. Most of the earth's crust is essentially a buildup of volcanoes and volcanic products. The ocean floor has a six-kilometer stack of volcanoes underneath it. What people have found in the last decade in the area we are going to is that there are 10 to 100 kilometers where that volcanic crust is just missing. The question: why is it missing?

How was the gap discovered?

A lot of science comes from random exploration, and over the years people have taken samples of seafloor rocks. There are clear characteristic patterns that we can recognize about the normal volcanic crust--long, thin volcanic ridges, which run parallel to the plate boundary and are close together. That pattern is missing where we are, and instead of these long, thin parallel ridges, you see a much more blocky structure. If you throw a pile of spaghetti down on the kitchen floor, it will tend to line up in parallel ridges, whereas if you throw down a pile of walnuts, you get a much more blocky surface. It ...