An impact structure, or astrobleme (meaning "star wound") is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure.
The vaguely circular Lake Dellen water system, in Sweden, was formed by an impact crater 89 million years ago (some will even say 100+ M ya), placing the impact in the Late Cretaceous, when the area was hit by a meteorite.
The initial resulting impact crater measured about 19 kilometers in diameter. Nowadays it's only half that size. The impact resulted in the area containing the rock Dellenite (a rock intermediate in composition between Rhyolite and Dacite), which has become the provincial rock.
In contrast to an impact structure, an impact crater is the surface expression of an impact structure. In many cases, on Earth, the impact crater has been destroyed by erosion, leaving only the deformed rock or sediment of the impact structure behind. This is the fate of almost all old impact craters on Earth, unlike the ancient pristine craters preserved on the Moon and other geologically inactive rocky bodies with old surfaces in the Solar System.
Asteroid 7704 Dellen was named after it.
An installation of the Sweden Solar System representing Pluto and Charon lies near the southern lake; the pillars holding the model objects are made of dellenite.
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Sources: Magasin Hälsingland (summer issue 2022) and Wikipedia.
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