What is believed to be the oldest known section of the earth's crust, estimated to be 3.8 billion years old, has been charted in Greenland.
The section of volcanic rocks found in southwestern Greenland was formed as the sea floor split apart, and its age may help determine when the earth's plate tectonics system was set in motion.
Scientists have pondered when the movement in the earth's crust, which is composed of several plates, began. The old age of the Greenland rocks suggests that it began early in the earth's 4.5-billion-year history.
The international team of researchers was headed by Norwegian geologist Harald Furnes of the University of Bergen. Details of their survey were published in the March 23 issue of the scientific journal Science.
Movement in the earth's crust can help explain phenomena like seismicity, volcanism and continental drift.
The crust fits together like puzzle pieces or plates, and when they move away from each other, magma from the core of the earth forms new crust.
At other boundaries, known as subduction zones, one plate pushes underneath another, deep into the Earth where it melts into the magma.
However, the Greenland rocks discovered by Furnes and his team were pushed to the surface rather than into magma, offering the possibility to date the rock.