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GEOLOGIC FEATURES OF THE MANSON IMPACT STRUCTURE
The Manson impact structure appears at the bedrock surface, but
there is no visual evidence of the crater on the surface land
because it is concealed under 70 - 300 feet of glacial till. Like
other complex impact craters, the Manson impact structure has
three distinct features. The central peak is the mound of rock
found at the center of the crater. Surrounding the central peak
is an area known as the crater moat. The terrace terrane is the
outermost crater feature, which forms a ring around the crater
moat.
(The word "terrain" refers to the land surface, usually the topographic
relief. The word "terrane" refers to the entire rock package (the
total crust) in an area. Terrane is an appropriate term for the
Manson crater regions because it refers to the characteristics
of the entire rock package, not just the surface.)
The 12 cores obtained in the early 1990s penetrated the three
major regions of the Manson impact structure: the terrace terrane,
crater moat and central peak. In-depth studies of the core samples
determined that the Manson impact structure was comprised of the
following six types of impact rocks.
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