Word: silt
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Dates: during 1940-1949
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...When silt sinks slowly to the bottom of an ocean or lake, the magnetic particles in it line up with the earth's magnetic field like tiny compass needles. When the silt hardens into rock, the magnetic particles are "frozen" so that they cannot move. The Carnegie scientists found that even when the rock layer is folded by geological forces, the magnetic particles keep their alignment, pointing accurately around the curves of the folds. Even in layers known to be 200 million years old, the rock keeps its magnetism...
...series of rock samples 10 million to 100 million years old which they took from flat-lying strata in the western U.S. proved to have a magnetism pointing in about the same direction as present-day compass needles. The conclusion was that when the rocks were laid down as silt, the earth's magnetic field was about as it is today...
...been unable to get out. Perhaps the bank of a prehistoric river caved in on it. It sank down into the cold, Pleistocene mud, which kept out the air and preserved the body. With the coming of winter, the mammoth was frozen solid; the river kept on dropping silt. Moss and peat kept the body insulated...
...between July and October, a great gush of muddy water floods the narrow, fertile valley. For the ancient Egyptians, who did not demand too much of their sacred river, the flood was fine. They built mud dikes around the fields, and caught the flood water in shallow basins. The silt settled to the bottom, keeping the soil fertile, millennium after millennium. When the water. was gone, the peasants planted their crops, often without plowing or other preparation, in the wet soil...
When SESP came to Cametá in 1944, the town's 550 families were getting their drinking water from the silt-laden Tocantins River. Their only plumbing facilities were the jungle bush behind their rickety shacks. Cametá had no doctor, and there is no record of how many Cametenses died each year from dysentery, hookworm, malaria and typhus, but these and other communicable diseases accounted for 55% of all deaths in the Amazon region which includes Camet...