Earth continued to cool and solidify. Water vapor condensed into water, which covered Earth’s surface.
A thin layer of basalt and granite (a very hard type of rock) formed a permanent crust under the ocean. Land masses known as greenstone belts, made mostly of granite, formed the ancient cores of our modern continents. These belts also contained most of the world’s deposits of gold.
Continental shields, large, low areas of stable rock in Earth’s crust, were created by the greenstone granite colliding to form what is called basement rock. This became the foundation of the continents.
Rocks from this time are currently exposed—and virtually unchanged—in North America, Africa, and Australia.