[OANNES Foro] Pacific. The fiery birth of Earth's largest ocean exposed

[Mario Cabrejos]

Nature

doi:10.1038/nature.2016.20334

 

A volatile arrangement of tectonic plates millions of years ago gave us the
Pacific.

The fiery birth of Earth's largest ocean exposed

 
<http://www.nature.com/news/the-fiery-birth-of-earth-s-largest-ocean-exposed
-1.20334?WT.ec_id=NEWS-20160728&spMailingID=51933150&spUserID=MTc2NjE2MjAwMA
S2&spJobID=964075662&spReportId=OTY0MDc1NjYyS0#auth-1> Alexandra Witze

27 July 2016

 
<http://www.nature.com/news/the-fiery-birth-of-earth-s-largest-ocean-exposed
-1.20334?WT.ec_id=NEWS-20160728&spMailingID=51933150&spUserID=MTc2NjE2MjAwMA
S2&spJobID=964075662&spReportId=OTY0MDc1NjYyS0>
http://www.nature.com/news/the-fiery-birth-of-earth-s-largest-ocean-exposed-
1.20334?WT.ec_id=NEWS-20160728&spMailingID=51933150&spUserID=MTc2NjE2MjAwMAS
2&spJobID=964075662&spReportId=OTY0MDc1NjYyS0

 

http://www.nature.com/polopoly_fs/7.38074.1469628625!/image/Pacific%20plates
_c0089968_900px.jpg_gen/derivatives/landscape_630/Pacific%20plates_c0089968_
900px.jpg

NOAA/Science Photo Library

A computer model simulates the seafloor in the North Pacific.

 

The Pacific Ocean was born from a geological spasm that started 190 million
years ago, when
<http://www.nature.com/news/new-origin-seen-for-earth-s-tectonic-plates-1.14
993> Earth's crust ripped apart and fresh lava welled up from below. Now, a
new analysis suggests that this seafloor birth was a lot more complex than
researchers had thought.

The study is a rare step forward in understanding the origin of the Pacific,
one of geology's most enduring mysteries.

"This is one big piece of the puzzle that we've now put into place," says
Lydian Boschman, a geologist at Utrecht University in the Netherlands. She
and her colleague Douwe van Hinsbergen report the discovery on 27 July in
Science Advances
<http://www.nature.com/news/the-fiery-birth-of-earth-s-largest-ocean-exposed
-1.20334?WT.ec_id=NEWS-20160728&spMailingID=51933150&spUserID=MTc2NjE2MjAwMA
S2&spJobID=964075662&spReportId=OTY0MDc1NjYyS0#b1> 1.

Oceans are born at unstable seams in Earth's crust,
<http://www.nature.com/news/unusual-indian-ocean-earthquakes-hint-at-tectoni
c-breakup-1.11487> where plates pull apart, allowing molten rock to fill the
gap and solidify. The fresh crust pushes older crust away from the seam and
towards the edge of a continent. Eventually, the ocean crust crashes into
continental crust and, through the process of plate tectonics, gets
<http://www.nature.com/news/seabed-samples-cast-doubt-on-earthquake-risk-for
-pacific-northwest-1.15655> sucked down and recycled deep within the planet.

Because of this continuing cycle of creation and destruction, no seafloor is
older than about 200 million years. To see how oceans behaved further back
in time, geologists must try to reconstruct the three-dimensional geometry
of long-vanished crustal plates.


Mind the gap


Boschman and van Hinsbergen studied the oldest part of the Pacific plate,
which lies just east of the Mariana Trench. Previous work suggested that the
Pacific was born in what's known as a geological triple junction, with fresh
seafloor spreading outward from each of three intersecting ridges. But that
configuration is geologically stable; in the south Atlantic Ocean, a similar
triple junction has endured for more than 100 million years without forming
a new plate. "There's no reason to," says Boschman.

Instead, she says, the Pacific must have been born at an unstable type of
triple junction. The three intersecting seams would have had to have been
transform faults, in which the two sides of a fault slide past one another.
California's San Andreas fault moves in this fashion.

Three transform faults coming together would have created a triangular gap
in the centre. "A triple junction with ridges is not going to make a new
plate," says Boschman. "A triple junction with transform faults does." The
configuration was probably an accident, she adds.

The work shows how basic thinking about plate tectonics can still yield
surprises, says Bernhard Steinberger, a geophysicist at the GFZ German
Research Centre for Geosciences in Potsdam, Germany. "This is one of those
rare cases where a discovery could be made simply by an elegant thought," he
says.

Boschman would like to push even further back in time, to unravel the
history of the ocean that preceded the Pacific and surrounded the
supercontinent Pangaea. She is currently doing fieldwork in Costa Rica,
looking for evidence of ancient seafloor rocks scraped up on the side of the
continent as the ocean crust was dragged under and destroyed.


 <javascript:;> References


o    Boschman, L. M. & van Hinsbergen, D. J. J. Sci. Adv. 2, e1600022 (2016)
<http://dx.doi.org/10.1126/sciadv.1600022> Article  <javascript:;> Show
context

 



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