Correct Answer: D
Explanation:
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.
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.
In this case, the velocity of the plates doesn't sum to zero at all, as is usual.
It sums to 15 millimetres a year, which is huge.
The scientists surmised a plate was missing from the equation.
To find its boundaries, researchers mined a catalogue of multi-beam 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.
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.
Earthquakes along diffuse boundaries tend to be small and less frequent than along transform faults.
Therefore 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.
This suggests the possibility of another plate.