Steinheim
Key facts
- Country
- Germany
- Diameter
- 3.8 km
- Age
- about 14.8 million years
- Location
- 48.68° N, 10.07° E
A shallow, round basin about 3.8 km across on the Swabian Alb, with a central hill, the Klosterberg, rising from its flat floor and the town of Steinheim am Albuch inside it.
Steinheim, on the Swabian Alb in Baden-Württemberg, is the smaller sister of the Nördlinger Ries. Its basin is only about 3.8 km across, but it holds a special place in science twice over: once for its shatter cones and once for its fossil snails.
The impact. Steinheim formed about 14.8 million years ago, at the same time as the Ries, about 40 km to the east. Many geologists think both craters were made by a pair of objects travelling together, perhaps a binary asteroid, though some still debate whether the impacts were truly simultaneous. The Steinheim impactor was perhaps 100 to 150 m across.
A central hill. Unlike most craters of its size, Steinheim has a clear central uplift, a hill called the Klosterberg, which rises from the flat basin floor. Central uplifts form when rock beneath the crater rebounds upwards after the impact, and they are typical of larger, complex craters. Steinheim is one of the smallest craters on Earth with such a well-developed central peak.
Shatter cones. Steinheim's limestones are famous for their shatter cones, cone-shaped fracture patterns with fine, branching grooves, created when a powerful shock wave passed through the rock. Shatter cones at Steinheim were described in the early twentieth century and are among the finest examples in the world. Today they are one of the key tests geologists use to identify impact structures.
Evolution in a crater lake. After the impact, a lake formed inside the crater. Its sediments are packed with fossil freshwater snails of the genus Gyraulus. In 1866 the German naturalist Franz Hilgendorf studied these snails and noticed that their shapes changed gradually from layer to layer, from flat coils to tall spirals and back again. He interpreted this as a lineage changing over time, making it one of the first fossil sequences used to support Darwin's theory of evolution, published just seven years earlier. The Steinheim snails are still studied by palaeontologists today.
Visiting. The town of Steinheim am Albuch lies within the crater. The Meteorkrater-Museum, in the village of Sontheim im Stubental, explains the impact and displays shatter cones and fossil snails. A geological trail leads around the basin and onto the Klosterberg, with views across the crater. Collecting fossils and rocks is restricted at many sites, so check local rules before taking samples.
Why it matters. Steinheim is an important example of a small complex crater and, together with the Ries, it gives scientists a rare chance to study two craters formed by what may have been a single event.
Did you know?
Fossil snails from Steinheim's crater lake were used in 1866 to support Darwin's theory of evolution.
Steinheim and the Ries probably formed at the same moment, about 40 km apart.
Its central hill, the Klosterberg, is unusually well developed for such a small crater.