Suavjärvi crater
Encyclopedia
Suavjärvi is a lake and impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 in the Republic of Karelia
Republic of Karelia
The Republic of Karelia is a federal subject of Russia .-Geography:The republic is located in the northwestern part of Russia, taking intervening position between the basins of White and Baltic seas...

, Russia about 50 km north of the town of Medvezhyegorsk
Medvezhyegorsk
Medvezhyegorsk , formerly known as Medvezhya Gora and Karhumäki, is a town and the administrative center of Medvezhyegorsky District of the Republic of Karelia, Russia. Population: 15,800 ....

. The approximately 3 km wide Suavjärvi lake is located in the centre of the crater.

The crater is 16 km in diameter and it is estimated to be about 2.4 billion
1000000000 (number)
1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 109....

 (2.4 x 109) years old, placing it in the Archean
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...

Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...

 boundary. That makes it the oldest known impact crater on Earth. Not much of the crater has survived, although some shock
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

 features like large blocks composed of impact breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....

have been found.
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