Word: lava
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...propel these great land masses away from the rift valley remains one of geology's great mysteries. According to Geologist Wilfred Bryan of the Woods Hole (Mass.) Oceanographic Institution, the submarine explorers found indications that contrary to some theories, the continents are not forced apart by powerful lava flows at the site of the rift valley. If massive eruptions of lava were forcing the continents apart, Bryan says, the crews of the subs would have seen giant volcanoes like those in Hawaii. But they spotted only small mountains-a sign of minor uplifting by forces beneath the earth...
...lava flows that the deep divers found in the rift valley were hardened into all sorts of bizarre configurations...
...beginning to bite into the solid rock that they were looking for. Analysis of the core samples brought to the surface identified it as granite about 600 million years old. The find proved that the rock was continental shelf and not ocean basin crust, which is primarily basalt (solidified lava), which in the South Atlantic is no more than about 130 million years...
...revolutionary new view of geology called "plate tectonics," the earth's outer shell consists not of a single solid mass but of half a dozen or so giant plates on top of which the continents drift like extremely slow-moving ice floes. It was the gradual outpouring of lava from deep within the earth's mantle along the mid-Atlantic rift valley that began to split North America from Europe, Africa and South America some 225 million years ago. Even now, as fresh material attaches itself to the plates, the continents are being pushed apart at a barely...
...accretion of debris in orbit around the earth. As the debris-drawn by lunar gravity and ranging in size from tiny pebbles to huge boulders many miles across-crashed into the enlarging moon, it eventually generated enough heat to turn the lunar surface into a sea of molten lava. Slowly, as the bombardment lessened, the lava cooled and hardened into a crust that was then cratered by the impact of the remaining debris. When the rain of rocks eventually ended some 3.9 billion years ago, the moon's surface was covered by great craters and basins. Other changes were...