Mien
Key facts
- Country
- Sweden
- Diameter
- 9 km
- Age
- 121 ± 2 million years
- Location
- 56.42° N, 14.87° E
Lake Mien, a round lake about 5 km across in the forests of Småland, southern Sweden. Boulders of impact melt rock lie on islands and shores.
Mien is an impact structure about 9 km across in southern Småland, Sweden, whose centre is filled by the round Lake Mien.
What it hit. About 121 million years ago, in the Early Cretaceous, an asteroid or comet struck granite and gneiss of the Baltic Shield. The heat of the impact melted some of the rock, which cooled into impact melt rock, a fine-grained, often glassy rock. This rock is found on islands in the lake and in boulders around its shores.
Proof of impact. Study of the melt rock and breccias found quartz and feldspar with shock features, confirming that Mien is an impact structure. The structure was recognised in the 1960s.
Age. Argon dating of the melt rock gives an age of about 121 million years, plus or minus about 2 million.
Why it matters. Mien is one of the youngest impact structures in Sweden, and its melt rocks have been used to study how impact melts form and cool. The impactor is unknown.
Visiting. The lake is surrounded by forest and farmland. Ask landowners' permission before exploring.
Did you know?
Islands in Lake Mien contain rock melted by the impact.
Mien formed in the Early Cretaceous, when dinosaurs ruled the land.
It is one of the youngest impact structures in Sweden.