thumb|right|The crater as viewed from near the rim

thumb|right|The main crater is nearly circular. When the water level is low, rocks can be seen penetrating the surface in the middle of the crater.

thumb|right|Tilted [[Dolomite (rock)|dolomite bedrock in the walls of the main crater]]

Kaali is a group of nine meteorite craters in the village of Kaali on the Estonian island of Saaremaa. Most recent estimates put its formation shortly after 1530–1450 BC (3237 ± 10 <sup>14</sup>C yr BP). It was created by an impact event and is one of the few impact events that has occurred in a populated area (others are Henbury craters in Australia and Carancas crater in Peru).

Before the 1930s, there were several hypotheses about the origin of the crater, including theories involving volcanism and karst processes. Its meteoritic origins were first conclusively demonstrated by Ivan Reinvald in 1928, 1933 and 1937.

Formation

The impact is thought to have happened in the Holocene period, around 3,500 years ago. The estimates of the age of the Kaali impact structure (Saaremaa Island, Estonia) provided by different authors vary by as much as 6,000 years, ranging from ~6,400 to ~400 years before current era (BCE). Analysis of silicate spherules in Estonian bogs show that the possible age of the impact craters could be approximately 7,600 years. A study based on elevated iridium signal in a nearby bog suggested the much younger age of 4th century BC. The craters were formed by a meteor with an estimated impact velocity of between with a total mass of between 20 and 80 metric tonnes. According to some researchers the meteor arrived from the north-east.

At an altitude of , the meteor broke into pieces and fell to the Earth in fragments, the largest of which produced a crater with a diameter of and a depth of . The explosion removed approximately of dolomite and other rocks and formed a tall, extremely hot gas flow. Vegetation was incinerated up to from the impact site. There is the possibility that an even larger fragment fell into the sea, triggering seismic waves, and tsunamis up to 20-30 m high in the Baltic Sea, feeding the Norse mythology too

Kaali as a cult site

Lake Kaali is best known as a meteorite crater. When the meteorite fell on Saaremaa, it was already quite densely populated and caused a catastrophe for the locals. Those who survived may have interpreted this phenomenon as the death of the sun. The dates for the formation of the lake vary, but according to the latest data it would have been between about 1600 and 800 BC.

Archaeological excavations on Lake Kaali in 1976-1979 revealed a fortified settlement on the northeastern side. Most of the finds allowed the settlement to be dated to the pre-Roman Iron Age (500 BC-50 AD), although there were also a few finds that dated to the 8th-6th centuries BC. The unusual location of the settlement suggests that it is more of a cult site than any other structure. maintain that the event featured prominently in regional mythology. It was, and still is, considered a sacred lake. There is archaeological evidence that it may well have been a place of ritual sacrifice. At some point during the early Iron Age, the lake was surrounded by a stone wall long, with a median width of about and an average height of .

Finnish mythology has stories that may originate with the formation of Kaali. One of them is in runes 47, 48 and 49 of the Kalevala epic: Louhi, the evil wizard, steals the Sun and fire from people, causing total darkness. Ukko, the god of the sky, orders a new Sun to be made from a spark. The virgin of the air starts to make a new Sun, but the spark drops from the sky and hits the ground. This spark goes to an "Aluen" or "Kalevan" lake and causes its water to rise. Finnish heroes see the ball of fire falling somewhere "behind the Neva River" (the direction of Estonia from Karelia). The heroes head in that direction to seek fire, and they finally gather flames from a forest fire.

According to a theory proposed by Lennart Meri, it is possible that Saaremaa was the legendary Thule island, first mentioned by ancient Greek geographer Pytheas, and the name Thule could have been connected to the Finnic word tule '(of) fire' and the folklore of Estonia, which depicts the birth of the crater lake in Kaali. Kaali was considered the place where "The sun went to rest."

References

  • About Kaali crater on the official Saaremaa website
  • Kaali crater - Osiliana
  • Photos of the Kaali crater
  • Impact tectonics
  • Interactive panoramic aerial view of the Kaali crater area