Earth’s tectonic plate motion is jittery

Science : Earth’s continents are continually shifting, and the pace of their movement is irregular, sometimes rapid and sometimes slow. Researchers at the EarthByte program at the University of Sydney in Australia have been studying the complex interplay between deep-Earth and surface processes and have developed a computer model that breaks down tectonic plate movements into 1-million-year intervals. They have found that although the plates tend to shift about 4 cm per year, they can move as fast as 20 cm per year over geologically brief time periods of 10 million years or so. And oceanic plates appear to move faster than continental plates. What causes the plates to speed up and slow down is still not entirely understood. The researchers say that rising plumes of molten rock in Earth’s mantle could provide lubrication between it and the continents, and rocky protrusions on the underside of the massive continents may create drag to slow them down. The group plans to look next at ancient plate movement before the breakup of Pangea into multiple continents.