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Impact Melt Rock

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Impact melt rocks are basically volcanic rocks, such as basalt lava, and they attest to the extreme conditions generated by the impact event. Pressures and temperatures in the target rocks surrounding the point where the asteroid or comet hits are so high that large volumes or rock can be instantaneously melted. Pieces of this melt can cool rapidly to form glass and be incorporated in suevites. However, so much melt is produced sometimes that it forms a pool in the central parts of an impact crater to form crater-fill deposits. This pool of melt then cools slowly over time and solidifies to form a new rock, an impact melt rock. An impact melt rock typically contains only a few fragments of target rock, and up to 25% fragments in extreme cases. If the melt contains a lot of fragments of target rock, it is then classified as an impact melt breccia. Impact melt rocks can be found in crater-fill deposits and in ejecta deposits of impact structures.

See impact melt rocks in the Ries impact structure

Example of an impact melt rock (10% fragments of original rock) in our Impact Rock Kits
Example of an impact melt rock (10% fragments of original rock) in our Impact Rock Kits
Photo: F. Chuang, Planetary Science Institute
Location: Polsingen, an area near the northwest rim of the Ries impact structure, Germany

Aerial view above a 80 meter thick sheet of impact melt rocks. Note the "columnar joint" structure of the rocks.
Aerial view above a 80 meter thick sheet of impact melt rocks. Note the "columnar joint" structure of the rocks.
Photo: D. Wilton
Location: Mistastin impact structure, Labrador, Canada

Closeup view of impact melt rock samples collected in the field. Note: rock hammer is 30 centimeters tall.
Closeup view of impact melt rock samples collected in the field. Note: rock hammer is 30 centimeters tall.
Photo: G. Osinski, University of Western Ontario
Location:
Mistastin impact structure, Labrador, Canada

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