Glover Bluff crater
Glover Bluff is a meteorite crater located about south of Coloma, Wisconsin in the United States. It is 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 cones” (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.