Earth’s plate tectonics traced back to a “tipping point” 3.2 billion years ago. The Earth’s surface is constantly changing today, with tectonic plates shifting and moving, forming mountain ranges, ripping apart the seafloor, and causing massive earthquakes. Geophysicist Dave Stegman of the Scripps Institution of Oceanography in La Jolla and colleagues used observational data and computer models to develop a new formula for how the speeds of Earth’s plates depend on the size and edges of subduction zones. About 200 million years ago, the continent of Pangea broke apart into two huge pieces, with the supercontinent Laurasia to the north and Gondwana to the south.