Today's Science Times has a piece by Kenneth Chang summing up advancements by geologists suggesting that the earth some four billion years ago was a relatively calm place, and not hellishly hot as previously thought."Geologists now almost universally agree that by 4.2 billion years ago, the Earth was a pretty placid place, with both land and oceans," writes Chang of the ancient Hadean period [bottom of chart at right].
Advancements in geophysics and geochemistry paint a new picture of early Earth using "mineralogical analysis of small hardy crystals known as zircons embedded in old Australian rocks" through which scientists were able to determine the presence of water, consistent with conditions in which "life could have emerged hundreds of millions of years earlier" than previously thought possible, in conjunction with the geologic processes of plate tectonics, writes Chang.
Cited in Chang's piece is work by the University of Wisconsin-Madison's John W. Valley. Chang writes:
"In 2001, two groups, one led by Dr. Harrison and the other by John W. Valley of the University of Wisconsin, reported that the Australian zircons formed during the Hadean period as long ago as 4.4 billion years and were later embedded in the younger, 3-billion-year-old rocks."
Fascinating stuff and reassuring as always to read of science at work, toppling old views as new evidence and analyses come to the fore.
"'We thought we knew something we didn’t,' said T. Mark Harrison, a professor of geochemistry at the University of California, Los Angeles. In hindsight the evidence was just not there. And new evidence has suggested a new view of the early Earth," writes Chang.
One wonders what goes through the minds in the people forming the political base of today's Republican Party which denies evolution and an Earth older than 6,000 years old. At least nobody is being arrested for heresy.
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