Steinheim crater
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The Steinheim Basin is incurred by a meteorite impact crater in Steinheim in the Baden- Württemberg district of Heidenheim.
Appearance
The Steinheim basin is nearly circular with an average diameter of about 3.8 kilometers. In the center of the basin rises a hill which Steinhirt, some 50 feet above the present crater floor, while the crater floor itself is around 100 meters below the surrounding plateau of Albuch.
In the crater is the town of Steinheim.
Formation
The Steinheim Basin was formed about 14-15 million years ago the impact of a diameter estimated at about 100-150 meters large meteorite at a speed of about 20 kilometers per second ( 72,000 km / h ). It was explosively released an energy of about 1018 joules (equivalent to approximately 18,000 Hiroshima bombs), which further led parts of the Ostalb to an immense devastation. It first created a crater with a depth of about 200 meters, in the center of the spring-back rock formed an approximately 100 -meter-high central peak.
After the impact, a crater lake silted up later and was drained by the Wental formed. The fossils found in the up to 50 meters thick lake sediments suggest that the Steinheim Basin is simultaneously created with the approximately 40 kilometers to the northeast Ries Ries in the so-called event. Thus it was in the cosmic body, the impact left by the two craters, an asteroid, which was accompanied by a smaller satellite. An iron ( or stone -iron ) meteorite is thought to be Steinheim impactor In more recent studies.
Geology and Paleontology
The crater wall is composed of shifted and tilted Jurassic Kalkschollen. Some of the limestones are also smashed and form a breccia of different sizes, angular fragments. Drilling has shown that the crater floor is filled below the lake sediments with breccias, which consist of rock material that has been thrown up by the impact, and then fell back into the crater is ( Rückfallbrekzie ). In places, show the Impaktbrekzien of the Steinheim basin suevitischen a character. The central peak consists mainly of limestone and sandstone of the middle and upper Jurassic, which are found in undisturbed storage outside of the crater only about 300 meters depth.
In the limestone of the central uplift also called Strahlenkalke were found. That surface structures are formed by passage of the impact of the pressure wave through the rock. Strahlenkalke were first recognized in 1905 in the world Steinheim Basin and described, but without that its origin could be explained. Today, they are also known from numerous other terrestrial craters and are considered clear indicators for an impact.
The lake sediments are rich in fossils from the Miocene, so that the Steinheim Basin is one of the most important sites for this era. In addition to numerous finds of vertebrates ( including fish, reptiles, birds and mammals) are the sediments mainly due to the fossil snail shells found masse known ( so-called Steinheim snails sand ). In 1862, the paleontologist Franz Hilgendorf examined the body of the freshwater snail Gyraulus, a genus of the family plate screw, and noted that the case shape from the older to the younger sedimentary layers slowly changed. The worm finds were thus the first confirmation of the published in 1859 by Charles Darwin 's theory of evolution.
In the Steinheim district Sontheim is the 1978 opened Meteor Crater Museum, which is also the starting point for a geological trail through the Steinheim Basin.
Gallery
The central hill
Limestone cliffs " Steinhirt " on the top of the central hill
Strahlenkalk from the Steinheim Basin