Figure 19.

(a) Schematic showing a two-layer crust (red and blue layers) and mantle (pink layers) that is impacted, creating a transient crater and ejecta during the excavation stage. (b) One of several possible basin-forming scenarios where collapse of the transient is inward (Baker et al., 2016). This is presumably related to a central uplift and inward collapsing walls through faulting and graben formation. Black arrows signify the predominant directions of which gravitational flows may occur. Following the inward collapse, the impact structure would consist of a series of faults and grabens associated with primarily shallow crustal megabreccia from gravitational flows. Impact melt sheets (green) are also expected to have formed, predominantly within the central basin area. (c) Another of several possible basin-forming scenarios where collapse of the transient crater occurs outward (Baker et al., 2013). From hydrocode model results, we may expect the central peak to collapse outward. The putative flow associated with this collapse is possibly able to form megabreccia, which would be more deeply derived.