Image courtesy of Pete Mouginis-Mark, Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa

Hawaii is well known to have been created from volcanic activity, and the geologic hotspot below the islands is the most studied in the world. In this image, we see a type of lava flow known as pahoehoe at Kilauea. The image was used to illustrate a December Science article titled “Mantle Shear-Wave Velocity Structure Beneath the Hawaiian Hot Spot.”

The lava flow originates from well below the surface of the Earth to the layer known as the mantle. The mantle, a cross-section between our planet’s crust and outer core, is an extremely hot layer of the planet, where temperatures range between 500 to 900 °C (932 to 1,652 °F) at the upper boundary with the crust to over 4,000 °C (7,230 °F) at the lower boundary with the core.

Image courtesy of Pete Mouginis-Mark, Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa.

This deep, dark region retains heat from the hot gas and dust that formed Earth about 4.5 billion years ago.

The middle layer, the mantle, is solid rock, but it is hot enough to flow slowly, like Silly Putty. The movement, called convection, brings hot rock from the lower mantle to the surface. Cooler rock at the top of the mantle sinks.

The overall effect of convection is to create “conveyor belts” that transport the giant plates that form Earth’s crust. Mantle rock rises close to Earth’s surface along the mid-oceanic ridges. Some of the mantle rock melts, rises further, and, and where melt forms, rises, warms rock above it, which cools crystallizes to and to forms new ocean crust. As ocean the new crust moves away from a ridge, it cools and become denser, eventually sinking back into the mantle.

“As the continental plates are carried along on this conveyer belt, they may crash together (the Himalayas), slide past one another (California), or separate (Baja California),” says Goodwin. Over hundreds of millions of years, the continents have merged and re-separated in their continual movement around the globe. This movement explains why fossils of tropical animals are found in Antarctica, she says.