Oceanic crustal drilling by R. V. Glomar Challenger at 15 sites in the North Atlantic has led to a complex picture of the upper half kilometer of the crust. Elements of the picture include the absence of the source for linear magnetic anomalies, marked episodicity of volcanic activity, ubiquitous low temperature alteration and evidence for large scale tectonic disturbance. Comparison sections in the Pacific and much deeper crustal drilling are needed to attack problems arising from the North Atlantic results.

Depth gives the basement penetration.

Supplement to: Hall, J Michael; Robinson, Paul T (1979): Deep crustal drilling in the North Atlantic Ocean. Science, 204(4393), 573-586