Scientists discovered an expanse of rock in Greenland as a remnant of Earth's crust dating back 3.8 billion years.
Writing in the journal Science on Thursday, a team led by Harald Furnes of the University of Bergen in Norway said these ancient layered rocks from southwestern Greenland originally were formed on the sea floor of primordial Earth.
They are made up of thin sheets of formerly molten rock, and look a bit like a multilayered cake. They contain a mix of volcanic rocks associated with the formation of new crust.
Plate tectonics is a theory broadly accepted by geologists relating to the movement of the gargantuan plates that make up the planet's surface. These plates, largely corresponding to the continents, are in constant gradual motion.
Over millions of years, these plates move vast distances. Where they come together there can be significant geological activity like earthquakes, volcanoes and the creation of mountain ranges.
The fact that most of the continents look like puzzle pieces that fit together -- with the western African coastline roughly matching with the east coast of South America -- represents visual evidence of plate tectonics.