Precambrian Continents

The oldest parts of the continents began forming nearly four billion years ago, shortly after the Earth’s formation.

These continents grew when smaller land pieces, called microcontinents, collided with each other, making them larger.

The oldest parts of the continents are called cratons. Geologists study the rocks from these continents to learn about Earth’s earliest days, a time called the Precambrian.

Inside the cratons, geologists found felsic igneous rocks made mostly of light minerals like quartz.

Cratonic rocks often contain rounded sedimentary grains, which indicate erosion from preexisting rocks and provide evidence of ancient rivers or seas.

Another rock found in cratons is greenstone, a metamorphosed volcanic rock. Today, greenstones are found in ocean trenches, where two tectonic plates collide, and one sinks beneath the other, showing that subduction zones existed billions of years ago.

Earth’s continents have occasionally merged to form massive supercontinents. One of the most well-known is Pangaea. However, before Pangaea, there was Rodinia, which contained about 75% of Earth's total continental landmass.