Zhamanshin
Key facts
- Country
- Kazakhstan
- Diameter
- 14 km
- Age
- about 900,000 years
- Location
- 48.40° N, 60.97° E
A shallow, eroded basin about 14 km across in the steppe of north-western Kazakhstan, with scattered pieces of impact glass on the ground.
Zhamanshin, in the steppe of north-western Kazakhstan, is one of the youngest large impact craters on Earth. It lies in a flat, open landscape of grassland and low hills, in the Aktobe region. It is famous among collectors and scientists for the unusual glass it produced.
The impact. About 900,000 years ago an asteroid struck the steppe, forming a crater about 14 km across. Because it is relatively young, the crater still has a clear basin shape, though erosion has worn down its rim and sediments have partly filled it. The target rocks included a mix of sedimentary and metamorphic rocks.
Glass from the impact. The heat of the impact melted large amounts of rock, and some of this melt formed natural glass. Two main kinds are found. Zhamanshinite is a dark, often frothy impact glass that formed in and around the crater. Irghizites are small, dark, glassy droplets and strands, often only a few millimetres to a centimetre across, which formed when molten material was thrown into the air and cooled rapidly. Irghizites are similar in some ways to tektites, the natural glass objects found in strewn fields far from some craters, and they have been studied to understand how tektites form.
Recognition. Zhamanshin was identified as an impact structure in the 1970s, when scientists recognised the impact glasses and found shocked minerals. Since then, it has been studied by scientists from Russia, Kazakhstan and elsewhere.
A young crater. Zhamanshin's age makes it one of the youngest impact craters of its size anywhere. Very few craters larger than about 10 km are known from the last couple of million years; another is Bosumtwi in Ghana. An impact of this size today would cause devastation over a large region, though it would not threaten life on a global scale.
Why it matters. Zhamanshin gives scientists a well-preserved example of a young crater of medium size, and its glasses provide insights into how impacts melt rock and how glass forms when molten material is ejected. Because it is young, the crater has not been changed much by erosion, so scientists can study features that are usually lost in older craters.
Visiting. Zhamanshin lies in a sparsely populated area of the Kazakh steppe, reached by rough tracks. Visitors need suitable vehicles and local knowledge. Collecting and exporting geological material from Kazakhstan may be subject to regulations, so check the current rules before taking any samples.
Did you know?
Zhamanshin is one of the youngest impact craters larger than 10 km on Earth.
Irghizites, small glassy droplets from the impact, resemble tektites.
The crater lies in the open steppe of north-western Kazakhstan.