This week’s Imaggeo on Mondays is brought to you by Dmitry Demezhko, who describes how Patomsky crater may have formed and why it keeps scientists puzzling…
Patomsky crater, also known as Patomskiy crater or the Patom cone, sits in the Irkutsk Region of Eastern Siberia. The site is a curious cone with a crater at the top and a small mound in the center. The cone totals some 39 metres in height and stretches more than 100 metres in diameter (at the base of the cone).
The crater was discovered in 1949 by Russian geologist Vadim Kolpakov and for a long time it was considered to be an impact structure with a meteoric origin. Later, Viktor Antipin suggested it could be a nascent volcano. But neither meteoritic nor volcanic matter was found there. The crater consists of proterozoic limestone and sandstone debris and, to date, there is no consensus among scientists regarding the crater’s origin.
During a short expedition in August 2010 we conducted a gravimetric survey at the crater and surrounding area, aiming to evaluate its internal structure. The gravity field shows that surface negative anomalies, where the gravity is unusually low, have deep “roots” and a joint source at depth. But the crater’s gravity field differs greatly from the fields of other well-known impact structures, suggesting that it may not have formed during a meteoric impact.
We suggest this structure formed in two stages. During the first stage tectonic processes similar to mud volcanism created a porous vertical channel. In the second stage, cryogenic processes would have played an important role in breaking apart the rocks to form the cone and crater.
There is a lot of mysticism and superstition surrounding Patomsky. Local residents call the crater “a fabulous Eagle’s Nest” and say that both people and animals bypass it. We didn’t sense anything mystical while working in the crater though – and this cute little animal lives quite comfortably there.
By Dmitry Demezhko, Institute of Geophysics UB RAS, Yekaterinburg
Alekseyev, V. R. Cryovolcanism and the mystery of the Patom Cone, Geodynamics and Tectonophysics, 3, 289-307, 2012 (in Russian)
Demezhko D.Y., Ugryumov I.A., Bychkov S.G.: Gravimetric studies of Patom Crater. In: Patom Crater. Research in the 21st Century. Publishing House of the Irkutsk State University, Irkutsk, p. 42–50, 2011 (in Russian)
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