I have written about some of my interests, oceanography, chocolate, pretty men so I thought it was about time to bring on the impact craters. I'll start with one that's been tamed.
This is the Steinheim crater with the village of Sontheim. Lucky broadbanders can GoogleEarth it at Latitude N48deg41' Longitude E10deg4'.
It's diameter is 3.8 kilometres and has an approximate age of 15 million years. It's a complex crater with the wooded area being the central uplift.
Complex craters are formed when gravity causes the initially steep crater walls to collapse downward and inward. The central peak forms as the deep crater floor rebounds from the compressional shock of impact. Think of a stone dropped from height into a bowl of water.
The peak consists of material that has been intensely fractured, shows faulting and shocked metapmorphism which is the irreversible chemical of physical changes in rocks by shock waves.
Now here is one in the wild. Bosumtwi is located 30 kilometres south of Kumasi in Ghana. Latitude N6deg30' Longitude W1deg25' and is 10.5 kilometres in diameter and approx 1.03 million years old. The centre of the crater is completely filled by Lake Bosumtwi and has a preserved well-defined central uplift structure near the northwest-central part of the lake.
This is one of the youngest impact craters on earth and the heat in the crater would have taken 10-20,000 years to dissipate.
Climate researchers have drilled into the 250 metres of mud at the bottom of the lake to take samples of deposits recording a million years of the African climate going back through several ice ages. The lake is ideal for this as it's shielded from stong winds and no rivers flow through to stir up the sediments, the layers of which go undisturbed to the very bottom of the crater.