The plate tectonics that cause earthquakes, build mountains and split continents may have started when Earth was in its infancy, new research finds — significantly earlier than many scientists previously thought.
The new study suggests plate tectonics started more than 4 billion years ago — not long after the planet formed 4.5 billion years ago. In this era, known as the Hadean, Earth was fresh and piping hot, with an ammonia-and-methane atmosphere imbued with enough water to eventually condense into a planet-wide ocean. During this period, Earth cooled enough to have a solid outer crust.
