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In the main crater there is the lake of Kaali, with the diameter, depending on the water level, from 30-60 m and the depth from 1-6 m. The lake feeds on ground water and precipitation. The thickness of the bottom sediments of the lake is nearly 6 m and their age is about 4000 years.
The vicinity of Kaali is a moraine level, where the thickness of the clayey basal till near the main crater is about 1 meter, with the thick microbedded dolomites of the Upper Silurian Paadla Stage under it. The Kaali meteorite hit, so to say, two-ply target – the clayey basal till and the underlying dolomites. 
Thus, the craters are filled with peculiar material, formed by the mixture of dolomite pieces of various size, basal till and humus. The upper part of the wall consists of the material thrown out of the crater during the explosion, and of dolomite layers tilted at an angle of 25…90°. The mean thickness of the uplifted bedrock complex is 10 m and it has been split into 9 separate shifted blocks, each up to 50 m wide. The filling between the dolomite blocks is quite clayey in the upper part of the wall, lower down dolomite shingle prevails. The dolomite blocks are underlain by pulverized dolomite, up to 6 m thick, in a lens form. This light grey dolomite powder formed as a result of the explosion and contains dolomite pieces of different sizes. |
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At the bottom of the crater lies a 8…10 m thick highly fractured and displaced layer of dolomite breccia. Geophysical investigations have revealed that the dolomite layers around the crater are heavily split to the depth of 40…50 m. The zone of destruction more than twice exceeds the area of the visible crater.
The main crater of Kaali is a typical explosion crater. The meteorite falling at cosmic velocity exploded when it collided with the earth, and created the crater with a surrounding mound of uplifted bedrock. The meteorite itself pulverized in the explosion and dispersed in the rising cloud of dust. Hereby, no meteoritic fragments preserved in the main crater.
The smaller craters, locally known as dry lakes, are shallow bowl-shaped hollows. However, vague and in some cases interrupted mounds can mostly be traced on the banks of the secondary craters. Hazel thicket grows in most of the dry lakes. These are impactcraters and meteorite fragments were gathered in them. |
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At the end of the 1970ies and the beginning of the 1980ies, the systematic investigation of pulverized meteoritic matter (i.e. types and distribution of particles with the diameter less than 1 mm) began, first in the Kaali crater field and its immediate neighbourhood, later all over Saaremaa, Muhu and Western Estonia. It appeared that the distribution of the pulverized meteoritic matter was irregular and divided into rather complicated fields. |
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Ivan Reinvald (1878-1941)
In 1927 I. Reinwald was sent to Saaremaa to prospect for gypsum or salt deposits near Kaali, and if possible, find an explanation for the genesis of the Kaali craters. The hypothesis of the meteoritic origin of the craters I. Reinwald published in 1928, but it was only in 1937 that he found the first 30 meteorite fragments from the secondary craters 2 and 5. |
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Agu Aaloe (1927 - 1980)
In the years 1955-1980 Agu Aaloe specified the shape of the craters, their geological construction and the distribution of the meteoritic matter in the craters as well as in the crater field. He initiated the extension of the geological reserve of Kaali and the building of the exhibition pavilion, where information can be obtained about meteorites and the investigation of the Kaali craters. |
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I.Reinwald and A. Aaloe have a considerable share in the investigation of the Kaali craters. In their honour, a modest memorial stone stands on the front lawn of the Kaali schoolhouse.
Since the death of A. Aaloe the investigations have been concentrated on the study of the meteoritic matter and the peculiarities of its distribution, and the tracing and dating of soil and rock particles melted in the explosion, which occur in the marsh sediments of the neighbourhood |
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