The Earth: A Very Short Introduction (Very Short Introductions) by Martin Redfern

Author:Martin Redfern [Redfern, Martin]
Language: eng
Format: epub, mobi
Publisher: Oxford University Press
Published: 2003-06-25T16:00:00+00:00

Drilling the seas

From 1968 the ocean floor was sampled directly and scientifically by the US-led Deep Sea Drilling Program using a drilling vessel named the Glomar Challenger. This was superseded in 1985 by the international Ocean Drilling Program using the improved JOIDES Resolution. Around 200 separate two-month-long voyages or legs have taken place, with core samples drilled at intervals along each. The deepest holes exceed 2 kilometres, and overall thousands of kilometres of core samples have been recovered. Many of them include varying depths of sediment down to volcanic basalt beneath. They all tell stories about their origins and the changing conditions of climate and ocean. Far from eroding land and river deltas, sedimentation rates are much lower. At high latitudes the sediments include clay and rock fragments rafted on icebergs which have melted and dropped their load. Elsewhere, wind-blown dust from deserts and volcanic ash makes up a greater proportion of deep-water sediment, sometimes accompanied by micro-meteorite dust, sharks’ teeth, and even the ear bones of whales.

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