Geology Reference
In-Depth Information
Figure 3.24. Detail of the
impact process, showing the
contact and compression
stage and the generation of a
shock wave that expands
radially from the point of
contact. Decompression of the
target after passage of the
shock wave sets material into
motion along excavation
flow-paths and ejection of
material to form the crater
cavity. The most intense
deformation occurs closest to
the point of contact, leading
to vaporization and melting
of material; with distance
from the point of contact,
rocks are shock
metamorphosed, fractured,
and brecciated (reprinted
from Icarus, 59, Melosh, H. J.,
Impact ejection, spallation,
and the origin of meteorites,
234
260, Copyright (
1984
),
with permission from
Elsevier).
-
Figure 3.25. Lunar crater Euler (27 km in
diameter), showing typical impact depression,
central peak, terraced walls, and ejecta deposits,
including continuous and discontinuous ejecta,
and secondary craters formed by blocks ejected
from the primary crater (NASA AS 17
-
2923).
