erik simpson
2024-05-10 22:02:25 UTC
Ancient crystals suggest early Earth had land and freshwater
"The zircons represent a rare report from the mysterious Hadean, the
geological time period that ended about 4 billion years ago, 500 million
years after Earth’s formation. The planet, originally a ball of magma,
had cooled off and formed a crust. Somehow, perhaps from a bombardment
of water-rich asteroids, it had accumulated a global ocean. Earth may
have remained watery for quite some time—at least until tectonic
processes began to recycle Earth’s crust into its interior, and magma
bubbled up in chains of island volcanoes that eventually fused into
continents.
Much of this is guesswork, because almost no rock survives from the
Hadean. The oldest rock with a reliable age—a gneiss from Canada—is 4.03
billion years old. The only surviving material from before then are
zircons, found embedded in younger rock, which are as much as 4.4
billion years old. “Just about any information that we can get from
these Hadean zircons is useful because it’s our singular record of the
Earth’s first 500 million years,” says geologist Stephen Mojzsis of the
HUN-REN Research Centre for Astronomy and Earth Sciences."
https://www.science.org/content/article/ancient-crystals-suggest-early-earth-had-land-and-freshwater
"The zircons represent a rare report from the mysterious Hadean, the
geological time period that ended about 4 billion years ago, 500 million
years after Earth’s formation. The planet, originally a ball of magma,
had cooled off and formed a crust. Somehow, perhaps from a bombardment
of water-rich asteroids, it had accumulated a global ocean. Earth may
have remained watery for quite some time—at least until tectonic
processes began to recycle Earth’s crust into its interior, and magma
bubbled up in chains of island volcanoes that eventually fused into
continents.
Much of this is guesswork, because almost no rock survives from the
Hadean. The oldest rock with a reliable age—a gneiss from Canada—is 4.03
billion years old. The only surviving material from before then are
zircons, found embedded in younger rock, which are as much as 4.4
billion years old. “Just about any information that we can get from
these Hadean zircons is useful because it’s our singular record of the
Earth’s first 500 million years,” says geologist Stephen Mojzsis of the
HUN-REN Research Centre for Astronomy and Earth Sciences."
https://www.science.org/content/article/ancient-crystals-suggest-early-earth-had-land-and-freshwater