Researchers believe they have found the Earth’s largest water reservoir around 643 km underneath North America, inside mantle rock. This water is not in a form familiar to us—it is not liquid, ice or vapour. This fourth form is water trapped inside the molecular structure of the minerals in the mantle rock.
North-western University geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt have found deep pockets of magma beneath North America, a likely signature of the presence of water at these depths. The discovery suggests water from the Earth’s surface can be driven to such great depths by plate tectonics, eventually causing partial melting of the rocks found deep in the mantle.