The surface of Earth's moon is covered with craters.
Rocky planets like Earth and Mars all have craters on their surfaces. Against the barren landscape of a planet like Mars, these craters are obvious; on Earth, they can be harder to see. Such craters can result from the impact of a meteoroid, comet or asteroid, or from a volcanic explosion within the planet itself.
Collapse Calderas
A collapse caldera is a form of volcanic crater. It occurs when a volcanic eruption releases so much material and magma that a void forms beneath the volcano. The volcano then collapses in on itself, creating a large depression. One such crater formed almost 8,000 years ago in what is now Oregon, when Mount Mazama exploded. The resulting collapse caldera had a five-mile diameter, and was one mile deep. Today, this caldera is known as Crater Lake.
Explosive Calderas
As their name implies, explosive calderas result from massive volcanic explosions. These explosions can occur when silica-rich magma beneath a volcano traps large bubbles of superheated gas. As this magma rises to the surface, the resulting pressure change causes the gas to expand. The pressure generated by this rapid expansion can blow up an entire volcano, leaving nothing but a crater.
Simple Impact Craters
A simple crater, or pit crater, is usually just a few miles across, and comprises a smooth, bowl-like shape with debris distributed around the crater's rim. These are the smallest impact craters, and generally result from the least powerful impacts.
Peak Craters
Peak craters typically result from larger impacts. Behaving like water, the impacted crust rebounds upward, while the debris from the sides of the crater runs back toward the center of the depression. This causes a central peak to form. In peak-ring craters, a central peak also forms; however, it grows so high that it can't support itself and collapses outward, forming a ring of smaller peaks near the middle of the crater.
Multi-Ring Impact Basins
The most powerful planetary impacts cause waves to spread outward across the planet's crust, like the ripples that form when you drop a pebble into water. The waves cause ruptures that produce a terrace-like series of concentric rings. These impact basins may extend for hundreds of miles.
Tags: result from, beneath volcano, central peak, collapse caldera
