Unwanted Noise On The Terrestrial Tape Recorder
The hypothesis of continental drift and sea-floor spreading depends heavily upon the strip-like magnetic anomalies that parallel the active ocean ridges. Molten material pushing out along these ridges spreads out, solidifies, and is magnetized by the prevailing terrestrial magnetic field. Thus, the spreading sea floor becomes a "tape Recorder" preserving the record of changing terrestrial polarity over the past several hundred million years. As one drills into this thin conveyor-belt/tape-recorder, one would expect to encounter only rocks of one polarity. Not so! Some of the holes drilled by the Deep Sea Drilling Project have passed through several polarity zones. To illustrate, core 395A from the mid-Atlantic ridge is magnetized normally for the upper 170 meters, reversely for the next 310 meters, and normally again for 40 meters. Is the tape-recorder idea therefore incorrect? Some scientists argue that it is and that the whole modern edifice of plate tectonics is suspect.
(Anonymous; "Testing Vine-Matthews," Open Earth, p. 28, April 1979.)