Glover Bluff crater
Encyclopedia
Glover Bluff is a meteorite
crater
located about 4 miles (6.4 km) south of Coloma, Wisconsin
in the United States
.
It is 8 kilometers (5mi) in diameter and the age is estimated to be less than 500 million years (Cambrian
or younger). The crater is exposed at the surface.
The Glover Bluff impact site is among the least studied in the world, in part because for years the uplifted central area has been actively quarried for dolomite
beneath the moraine
left by retreating glaciers. Ironically, the very evidence supporting a meteoritic impact uncovered in the quarrying process is systematically being destroyed. Such evidence includes a central bulge, dipped strata, the presence of “shatter cone
s” (although no longer as common as they may once have been), and, “impact breccia
.” There are “red” and “yellow” varieties (more of a brick red and tan yellow) and sometimes a mixture of the two. The breccia contains many broken fragments (or shards) of quartzite and other rocks.
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
located about 4 miles (6.4 km) south of Coloma, Wisconsin
Coloma, Wisconsin
Coloma is a village in Waushara County, Wisconsin, United States. The population was 461 at the 2000 census. The village is located within the Town of Coloma.- History :...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
It is 8 kilometers (5mi) in diameter and the age is estimated to be less than 500 million years (Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
or younger). The crater is exposed at the surface.
The Glover Bluff impact site is among the least studied in the world, in part because for years the uplifted central area has been actively quarried for dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
beneath the moraine
Moraine
A moraine is any glacially formed accumulation of unconsolidated glacial debris which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past glacial maximum. This debris may have been plucked off a valley floor as a glacier advanced or it may have...
left by retreating glaciers. Ironically, the very evidence supporting a meteoritic impact uncovered in the quarrying process is systematically being destroyed. Such evidence includes a central bulge, dipped strata, the presence of “shatter cone
Shatter cone
Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions...
s” (although no longer as common as they may once have been), and, “impact breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
.” There are “red” and “yellow” varieties (more of a brick red and tan yellow) and sometimes a mixture of the two. The breccia contains many broken fragments (or shards) of quartzite and other rocks.