Gardnos Impact Structure, Norway
Tuesday, 26. May 2009, 14:38:50
Three meteorite impact craters have so far been recognised in Norway. The Gardnos structure was the first impact structure to be recognised. The Mjølnir crater (in the Barents Sea) was recognised just a couple of years after Gardnos. The Ritland crater outside Stavanger is apparently not yet really recognised, or at least not yet confirmed in The Earth Impact Database.
The Gardnos impact has been dated to 546 ± 5 million years old. Today it is about 5 km in diameter, and was created by a meteorite with an estimated diameter of 200-250 m and a velocity of around 20 km/sec.
A 400 m long core was drilled within the Gardnos structure in 1992, penetrating sediments and impactites (suevite and Gardnos breccia). The sedimentary post-impact deposits have been intensively studied and described in several papers. The Gardnos breccia was produced during impact by fracturing of target rocks, formed during the shock wave propagation. In the typical Gardnos Breccia angular white granitic or quartzitic clasts are embedded in a dark matrix. In central parts of the crater, a sheet of suevite breccia is found overlying the Gardnos Breccia. The creation of Suevite is a result of the enormous amount of energy released by the meteorite impact. The rock consists of rock melt, glass and rock fragments (see image below).
The complex crater is well exposed, easy accessible and conveniently located along the main road between Oslo and Bergen, just 170 km from Oslo. In addition, its great exposures offer a magnificent section through several different typical impact lithologies. The Gardnos structure is visited annually by about 20,000 tourists and geologists. It is possible to drive in to the centre of the crater. There are two trails through the surrounding natural region, with information signs describing the geology of the area. There is also a new information centre.
The Precambrian basement of the area consists mostly of granitic gneisses, along with quartzites and banded gneisses.
The Quaternary glaciers excavated the weaker crater-infill rocks and thereby refreshed some of the original crater shape.
An Excursion guide to Gardnos meteorite crater from Oslo University was at the time of writing available as pdf file. Click here for download. (Authors: Elin Kalleson, Tom Jahren and Henning Dypvik, Department of Geoscience, University of Oslo).
• http://www.gardnos.no/servlets/dispatcher?siteNodeId=584122&languageId=2
• http://www.unb.ca/passc/ImpactDatabase/images/gardnos.htm
In Norwegian:
• http://www.forskning.no/artikler/2009/mai/220027
Image of Suevite from the Ries crater in Germany:
The Gardnos impact has been dated to 546 ± 5 million years old. Today it is about 5 km in diameter, and was created by a meteorite with an estimated diameter of 200-250 m and a velocity of around 20 km/sec.A 400 m long core was drilled within the Gardnos structure in 1992, penetrating sediments and impactites (suevite and Gardnos breccia). The sedimentary post-impact deposits have been intensively studied and described in several papers. The Gardnos breccia was produced during impact by fracturing of target rocks, formed during the shock wave propagation. In the typical Gardnos Breccia angular white granitic or quartzitic clasts are embedded in a dark matrix. In central parts of the crater, a sheet of suevite breccia is found overlying the Gardnos Breccia. The creation of Suevite is a result of the enormous amount of energy released by the meteorite impact. The rock consists of rock melt, glass and rock fragments (see image below).
The complex crater is well exposed, easy accessible and conveniently located along the main road between Oslo and Bergen, just 170 km from Oslo. In addition, its great exposures offer a magnificent section through several different typical impact lithologies. The Gardnos structure is visited annually by about 20,000 tourists and geologists. It is possible to drive in to the centre of the crater. There are two trails through the surrounding natural region, with information signs describing the geology of the area. There is also a new information centre.
The Precambrian basement of the area consists mostly of granitic gneisses, along with quartzites and banded gneisses.
The Quaternary glaciers excavated the weaker crater-infill rocks and thereby refreshed some of the original crater shape.
An Excursion guide to Gardnos meteorite crater from Oslo University was at the time of writing available as pdf file. Click here for download. (Authors: Elin Kalleson, Tom Jahren and Henning Dypvik, Department of Geoscience, University of Oslo).
• http://www.gardnos.no/servlets/dispatcher?siteNodeId=584122&languageId=2
• http://www.unb.ca/passc/ImpactDatabase/images/gardnos.htm
In Norwegian:
• http://www.forskning.no/artikler/2009/mai/220027
Image of Suevite from the Ries crater in Germany:
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