January 7, 2015 is Old Rock Day!
Did you know? By dating the zircons embedded within the Acasta gneiss (the rock above-which happens to be the oldest known rock), geologists have determined its age to be 3.96 billion years. This rock’s composition establishes it as part of a continent, indicating that continents existed nearly four billion years ago.
Did you know?
Most of the ocean floor is made of basalt. This igneous rock continues to flow out of Earth from chains of underwater volcanoes known as “mid-ocean ridges.