Kaali Craters

Kaali Craters / Beskrivning

Eighteen kilometers from Kuressaare towards Kuivastu is the location of Estonia's most unique geological object, Kaali lake.
Early explorers considered the ring-shaped Kaali crater as a volcanic depresion or a karst hole formed due to the dissolution of limestone, gypsum or salt. The meteoric origin of the lake basin was first suggested by J. Kalkun-Kaljuvee in 1922. In 1937 Ivan Reinvald collected 30 fragments of meteoritic iron from the collateral craters. The analysis of the fragments showed that the cosmic body which fell to the Kaali area belonged to the most frequent type of iron meteorite, coarse octahedrite, with the contents of Fe and Ni amounting to 91.5 and 8.3%, respectively.
The structure of the craters and the distribution of meteoritic material suggest that the meteorite fell from the east-northeast at an angle of 45 deg. The initial mass of the meteorite could have been 400 to 10 000 tons, mass at impact was 20 to 80 tons, initial velocity upon entering the atmosphere was 15 to 45 kilometers per second, velocity at impact ranged from 10 to 20 kilometers per second.
By passing through the atmosphere the meteorite heated and broke into pieces at an altitude of five to ten kilometers, falling to Earth as a meteorite shower. As a result, the main crater, 110 meters in diameter and 22 meters in depth, and at least eight collateral craters with a diameter of 12 to 40 meters and a depth of one to four metes, were formed.
The craters or their embankments do not contain marine sediments. Therefore the craters cannot be older than the time the area emerged from the sea. The explosion scattered into the air abundantly fine particles of soil and rock, which by melting formed glassy spherules. These spherules have been found in mires and lake sedimets in the vicinity of the craters. The age of the layers of peat with microimpactites is 7500 to 7600 years, which is the most probable age of the Kaali craters.

(text: www.saaremaa.ee)