The subduction zones where oceanic plates sink beneath the continents produce volcanic arcs such as those that make up the “rim of fire” around the Pacific Ocean. The volcanoes are fed by molten rock ...

Earth’s deep interior may hold water equal to today’s oceans, challenging long-held views of how the planet became habitable.

The big picture: Theia is a hypothetical ancient planet that orbited the Sun during the formation of the solar system. According to the giant-impact hypothesis, this protoplanet collided with Earth ...