Central peak
A mountain or cluster of hills in the middle of a complex crater, made of rock pushed up from deep below.
A central peak forms in the final seconds to minutes of a large impact. The blast first digs a deep, temporary cavity. That cavity is unstable, and the squeezed rock beneath its floor rebounds upwards, much as water leaps up in the centre after a stone drops into a pond. In rock, the rising mass freezes in place as a peak or a group of hills.
Central peaks are scientifically precious because they bring deep layers to the surface. On the Moon, spacecraft study peaks to learn what lies kilometres under the crust. On Earth, the uplifted rocks in eroded peaks often carry clear impact evidence such as shatter cones and shocked minerals.
Tycho on the Moon has a beautiful central peak, easy to spot through a small telescope near the line between lunar day and night. On Earth, Gosses Bluff in Australia's Northern Territory is the worn-down remains of the central uplift of a crater formed around 140 million years ago. The original crater has eroded away, leaving a striking ring of hills about 5 kilometres across. Peaks form only in craters above a certain size; in bigger ones, a peak gives way to a ring of peaks.
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Level: Explorer Ages 10 and up