Manson Impact Structure Morphology
The form and structure of the crater's impact
by Raymond R. Anderson
Study of the Manson Impact Structure (MIS) Drill cores, cutting samples from water wells, and seismic data has led to a good understanding of the geometry of the well-preserved impact structure. The sequence of events that formed the MIS was typical of most complex impact structures (impact structures with central peaks).
A hypervelocity impact excavated a crater by vaporizing, melting, and brecciating target materials, ejecting them form the crater and depositing them as proximal and distal deposits. Additionally, some target material was physically pushed down and out, lifting up the crater rim. At its maximum diameter this cavity is called the transient crater (because it is short-lived).
As the transient crater reached its maximum size, its internal pressures had dissipated sufficiently that it could no longer hold up the uplifted crater rim. Gravity began to pull the uplifted rim down, creating an annulus of down-dropped blocks (the terrace terrane) and forcing up a central peak.
The MIS drill and seismic data define a broad central peak (about 6 km in diameter) and a broad terrace terrane (about 7 km wide) forming an annular ring at the outer edge of the crater.