Complex crater

Complex craters are a type of large impact crater morphology.

Above a certain threshold size, which varies with planetary gravity, the collapse and modification of the transient cavity is much more extensive, and the resulting structure is called a complex crater. The collapse of the transient cavity is driven by gravity, and involves both the uplift of the central region and the inward collapse of the rim. The central uplift is not the result of elastic rebound which is a process in which a material with elastic strength attempts to return to its original geometry; rather the uplift is a process in which a material with little or no strength attempts to return to a state of gravitational equilibrium.^[1]

Complex craters have uplifted centers, and they have typically broad flat shallow crater floors, and

Diameters of craters where complex features form depends on the strength of gravity of the celestial body they occur on. Stronger gravity, such as on Earth compared to the Moon, causes rim collapse in smaller diameter craters. Complex craters may occur at 2 kilometres (1.2 mi) to 4 kilometres (2.5 mi) on Earth, but start from 20 kilometres (12 mi) on the Moon.[5]

If lunar craters have diameters between about 20 kilometres (12 mi) to 175 kilometres (109 mi), the central peak is usually a single peak, or small group of peaks. Lunar craters of diameter greater than about 175 kilometres (109 mi) may have complex,

• Impact crater – Circular depression in a solid astronomical body formed by the impact of a smaller object
• Impact structure – Geologic structure formed from impact on a planetary surface
• Multi-ringed basin – Crater containing multiple concentric topographic rings
• Peak ring (crater)
   – Roughly circular ring or plateau, possibly discontinuous, surrounding an impact crater's centerPages displaying short descriptions of redirect targets
• Traces of Catastrophe, 1998 book from Lunar and Planetary Institute - comprehensive reference on impact crater science

References