The Hummeln structure was confirmed, in 2015, as an
impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...
in Småland province, Sweden. It is a wide depression within Lake Hummeln and is estimated to have formed between 470 and 443 Ma ago, during the
Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya.
T ...
.
Description
The depression was first described in 1826 but was considered to be the result of
volcanism
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...
or
tectonics
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...
topography
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary sc ...
gave the first hints of an impact event. More conclusive evidence was found recently when scientists from
Lund University
, motto = Ad utrumque
, mottoeng = Prepared for both
, established =
, type = Public research university
, budget = SEK 9 billion Siljan crater, found
shocked quartz
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal. These pl ...
breccia
Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix.
The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...
that firmly established the structure's impact nature.
It has also been suggested that this structure, the nearby
Granby crater
Granby is an impact crater in Östergötland, Sweden, located to the southeast of Vadstena. It is estimated to have formed about 470 million years ago (Middle Ordovician
The Ordovician ( ) is a geologic period and system, the second of six pe ...
, and other coeval small craters in
Baltoscandia
Baltoscandian Confederation or Baltoscandia is a geopolitical concept of a Baltic–Scandinavian ( Nordic) union comprising Denmark, Estonia, Finland, Iceland, Latvia, Lithuania, Norway, and Sweden. The idea was proposed by a Swedish Profe ...
may be connected to the
Ordovician meteor event
The Ordovician meteor event was a dramatic increase in the rate at which L chondrite meteorites fell to Earth during the Middle Ordovician period, about 467.5±0.28 million years ago. This is indicated by abundant fossil L chondrite meteorites in ...
of 470 Ma.
See also
*
Ordovician meteor event
The Ordovician meteor event was a dramatic increase in the rate at which L chondrite meteorites fell to Earth during the Middle Ordovician period, about 467.5±0.28 million years ago. This is indicated by abundant fossil L chondrite meteorites in ...
*
Granby crater
Granby is an impact crater in Östergötland, Sweden, located to the southeast of Vadstena. It is estimated to have formed about 470 million years ago (Middle Ordovician
The Ordovician ( ) is a geologic period and system, the second of six pe ...