Great tension developed in the crust, probably related to changing plate motions far to the west.
Olympus Mons may have formed just after the plate motion stopped.
The overall driving force for plate motion and its energy source remain subjects of ongoing research.
It has been proposed that these are the result of plate motion which on Earth makes volcanic arc islands.
The plate motion is much too slow to "keep the magma occupied".
The remaining 0.6 inch of relative plate motion was unaccounted for.
Since the mid-1980s a direct means of measuring present rates and directions of plate motion has become available.
The sources of plate motion are a matter of intensive research and discussion among earth scientists.
The new finding, the team said in Nature, may add new understanding to the riddle of what drives plate motion.
Through tectonic plate motion the western half of the volcano moved north at about 1.5cm per year.