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Plate tectonics started at least 3.5 billion years ago

Yosemite National Park’s Half Dome

ROCK OF AGES  Plate tectonics may have started as early as 3.5 billion years ago on Earth. That recycling of Earth’s surface leads to the separation of light-colored continental crust (exposed here at Yosemite National Park’s Half Dome) from darker, denser oceanic crust.  

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Plate tectonics may have gotten a pretty early start in Earth’s history. Most estimates put the onset of when the large plates that make up the planet’s outer crust began shifting at around 3 billion years ago. But a new study in the Sept. 22 Science that analyzes titanium in continental rocks asserts that plate tectonics began 500 million years earlier

Nicolas Greber, now at the University of Geneva, and colleagues suggest that previous studies got it wrong because researchers relied on chemical analyses of silicon dioxide in shales, sedimentary rocks that bear the detritus of a variety of continental rocks. These rocks’ silicon dioxide composition can give researchers an idea of when continental rocks began to diverge in makeup from oceanic rocks as a result of plate tectonics.

But weathering can wreak havoc on the chemical makeup of shales. To get around that problem, Greber’s team turned to a new tool: the ratios of two titanium isotopes, forms of the same element that have different masses. The proportion of titanium isotopes in the rocks is a useful stand-in for the difference in silicon dioxide concentration between continental and oceanic rocks, and isn’t so easily altered by weathering. Those data helped the team estimate that continental rocks — and therefore plate tectonics — were already going strong by 3.5 billion years ago.

Animals

Old barn owls aren’t hard of hearing

By Helen Thompson 7:05pm, September 19, 2017
A new study suggests that older barn owls hear just as well as younger ones.
Astronomy,, Planetary Science

These are Cassini’s parting shots of the Saturn system

By Lisa Grossman 12:09am, September 15, 2017
In its last hours before plunging into Saturn’s atmosphere, the Cassini spacecraft turned its cameras to some of the system’s well-known features.
Planetary Science

The Cassini probe dies tomorrow. Here’s how to follow its end

By Helen Thompson 2:30pm, September 14, 2017
Science News is on the scene at NASA’s Jet Propulsion Laboratory for the big finish of the Cassini mission to Saturn.
Astronomy,, Planetary Science

So long, Titan. Cassini snaps parting pics of Saturn’s largest moon

By Lisa Grossman 4:05pm, September 13, 2017
The last swing past Saturn’s largest moon sent Cassini heading directly towards the planet — and showed how future spacecraft will explore other moons.
Astronomy,, Planetary Science

Final flyby puts Cassini on a collision course with Saturn

By Lisa Grossman 4:00pm, September 11, 2017
A “last kiss goodbye” with Saturn’s largest moon sent the Cassini spacecraft on its final trajectory into the planet’s atmosphere.
Astronomy,, Planetary Science

Pluto’s pits, ridges and famous plain get official names

By Lisa Grossman 6:05pm, September 7, 2017
From Adlivun to Voyager, the International Astronomical Union officially names 14 surface features on the dwarf planet.
Animals,, Biophysics

Why bats crash into windows

By Helen Thompson 2:00pm, September 7, 2017
Smooth, vertical surfaces may be blind spots for bats and cause some animals to face-plant, study suggests.
Particle Physics

The results from a slew of experiments are in: Dark matter remains elusive

By Emily Conover 8:00am, September 6, 2017
Scientists continue the search for particles that make up the universe’s missing matter.
Archaeology,, Anthropology,, Human Evolution

People may have lived in Brazil more than 20,000 years ago

By Bruce Bower 7:00am, September 5, 2017
Stone Age humans left behind clues of their presence at a remote Brazilian rock shelter.
Anthropology,, Psychology

Spiritual convictions and group identities inspire terrorist acts, study finds

By Bruce Bower 11:00am, September 4, 2017
Sacred values and becoming one with comrades fuels terrorist acts, a report finds.
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