Magma chamber of magma chambers can be mapped using seismology: seismic waves from earthquakes move more slowly through liquid rock than solid, allowing measurements to pinpoint the regions of slow movement which identify magma chambers. As a volcano erupts, surrounding rock will collapse into the emptying chamber. If the chamber's size is reduced considerably, the resulting depression at the surface can form a caldera. Magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is under great pressure, and, given enough time, that pressure can
Geology of the United States ago. Most of the lava flooded out in the first 1.5 million years: an extraordinarily short time for such an outpouring of molten rock. The Snake River Plain stretches across Oregon, through northern Nevada, southern Idaho, and ends at the Yellowstone Plateau in Wyoming. Looking like a great spoon scooped out the Earth surface, the smooth topography of this province forms a striking contrast with the strong mountainous fabric around it. The Snake River Plain lies in a distinct depression. At the western end, the base has dropped down along normal faults, forming a graben structure. Although there is extensive