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23 October 1964
Vol 146, Issue 3643

About The Cover

Submarine lava flow of pillowed, tholeiitic basalt erupted from the earth's mantle onto the west flank of the East Pacific Rise. This primary oceanic basalt contains much less potassium, uranium, and thorium than most other oceanic and continental basalts. Depth of water, 2400 meters. See page 477. [Fred Dixon]