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Spreading Plants Best:
Gomphocarpus (Asdepias fruticosa) is a member of the milkweed family. Its flowers are small, white, and intricate in design. But this plant is grown for the pods, which form yellow to greenish brown balls, each covered with soft, green spikes. They are large, spreading plants best started at least six weeks before the last spring frost in order to guarantee flowering. Space 12 inches apart. Although listed as tender annuals, plants will survive fall temperatures of - 26°F.Vine and Matthews used the reversals of the earth's magnetic field to test the hypothesis of sea-floor spreading in an ingenious way. Precise measurements of the magnetic field in the oceans showed that large areas of the seabed are magnetized in long, narrow strips of alternately high and low magnetization, and the suggestion was made that this is due to sea-floor spreading during reversals of the magnetic field. Molten rock rising on the axis of an ocean ridge would cool and become magnetized by the earth's field. Spreading would carry these magnetized rocks laterally away from the ridge on both sides.
As the magma cools, new crust is created and becomes part of the moving plates. This is the phenomenon of sea-floor spreading. Spreading rates, though slow, are not negligible. The Atlantic is opening up by 2cm (0.75in) a year. The fastest rate is found at the East Pacific Rise, which creates 10cm (4in) of new crust every year - that is 1,000km (620 miles) in the short geological time of ten million years.
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