An impact on the Moon is thought to have launched the partially molten or vaporized material into orbit.
The partially molten mass cooled as a large block, with gravity flattening its upper surface.
Partially molten basalt in the mantle wedge moves upwards until it reaches the base of the overriding crust.
Instead of a watery ocean, however, evidence suggests that Io has a layer of partially molten rock over 50km thick.
The model that seemed to work well had a partially molten asthenosphere, which is the upper-most layer of the mantle.
He conceded that the reservoir of partially molten rock under Yellowstone extends to a depth of 125 miles.
Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids.
The Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess a partially molten core.
Around the core is a partially molten boundary layer with a radius of about 500 kilometers.
Kirk and Spock soon encounter a creature which looks like an animated clump of partially molten stone.