What did Earth look like 3.2 billion years ago? New evidence suggests the planet was covered by a vast ocean and had no continents at all.
Continents appeared later, as plate tectonics thrust enormous, rocky land masses upward to breach the sea surfaces, scientists recently reported. They found clues about this ancient waterworld preserved in a chunk of ancient seafloor, now located in the outback of northwestern Australia.
Around 4.5 billion years ago, high-speed collisions between dust and space rocks formed the beginnings of our planet: a bubbling, molten sphere of magma that was thousands of miles deep. Earth cooled as it spun; eventually, after 1,000 to 1 million years, the cooling magma formed the first mineral crystals in Earth’s crust.