Scientists discover new tectonic plate

"We think there's another plate we're missing," researcher Tuo Zhang said.
By Brooks Hays  |  Aug. 14, 2017 at 12:41 PM
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Aug. 14 (UPI) -- A team of researchers from Rice University in Texas have discovered a new tectonic plate off the coast of Ecuador. There were 56 plates; now, there are 57 -- and researchers think there could be one more to find.

Scientists discovered the microplate -- which they've dubbed "Malpelo" -- while analyzing the movements of what they believed to be the convergence of a trio of plates.

Researchers were studying the coming together of a major tectonic plate and two smaller plates. The edges of the Pacific lithospheric plate roughly form the Ring of Fire, a region of volcanic activity. Filling in the gaps between larger plates are smaller plates. Just west of the Galapagos Islands, the Pacific plate is met by Cocos and Nazca.

The intersect plates don't collide head on. Nor do they slip over and under one another, such as the case at a subduction zone. The plates rotate around each other, like a series of gears.

By measuring the rates of seafloor spreading and the angles at which the plates slip by each other, researchers can estimate the speeds at which plates spin.

"When you add up the angular velocities of these three plates, they ought to sum to zero," Rice geophysicist Richard Gordon said in a news release. "In this case, the velocity doesn't sum to zero at all. It sums to 15 millimeters a year, which is huge."

The scientists surmised a plate was missing from the equation. To find its boundaries, researchers mined a catalogue of multibeam sonar soundings. Anomalies in the data suggested the presence of a new plate east of the known Panama transform fault, a region originally believed to be part of the Nazca plate.

Their analysis -- detailed this week in the journal Geophysical Research Letters -- revealed the presence of a diffuse plate boundary running from the Panama fault east to a deep ocean trench off the coasts of Ecuador and Colombia.

"A diffuse boundary is best described as a series of many small, hard-to-spot faults rather than a ridge or transform fault that sharply defines the boundary of two plates," Gordon said. "Because earthquakes along diffuse boundaries tend to be small and less frequent than along transform faults, there was little information in the seismic record to indicate this one's presence."

When researchers crunched the seafloor spreading and boundary angle numbers again, they still couldn't zero out their equation.

"The nonclosure around this triple junction goes down -- not to zero, but only to 10 or 11 millimeters a year," researcher Tuo Zhang said. "Since we're trying to understand global deformation, we need to understand where the rest of that velocity is going. So we think there's another plate we're missing."

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