Судлаачид 70 жилийн турш эрдэмтдийн анхаарлыг татсаар ирсэн Патомын тогооны үүслийг хий болон мөнх цэвдгийн нөлөөгөөр тайлбарлах таамаглалыг дэвшүүллээ.
Зүүн Сибирийн Патомын өндөрлөгт орших, ойролцоогоор нэг сая тонн жинтэй, 40 метр өндөр шохойн чулуун овоолгыг анх 1949 онд геологич Вадим Колпаков нээснээс хойш түүний үүслийн талаар маргаан өрнөсөөр ирсэн. Орон нутгийнхан “Галт бүргэдийн үүр” хэмээн нэрлэдэг энэхүү байгууламжийг солирын нөлөөгөөр үүссэн гэх таамаглал олон арван жил давамгайлж байсан ч сүүлийн үеийн судалгаанууд үүнийг няцааж байна. Иркутскийн геохимийн хүрээлэнгийн судлаачдын 2008 онд хийсэн шинжилгээгээр уг овоолгоос солирт агуулагддаг никелийн агууламж маш бага байгааг тогтоосон юм.
Геофизикч Дмитрий Демежкогийн удирдсан баг “Doklady Earth Sciences” сэтгүүлд нийтэлсэн судалгаагаараа солирын онолоос татгалзаж, газрын гүнээс ялгарах хий болон мөнх цэвдгийн нөлөөллийг гол хүчин зүйл гэж үзжээ. Тэдний таамагласнаар, газрын гүнээс ялгарсан хий чулуулгийг нэвтлэн гарч, улмаар хур тунадас болон хайлсан ус хөлдөж, гэсэх мөчлөгийн дагуу чулуулгийг буталж, дээш түрснээр өнөөгийн хэлбэрээ олсон байх магадлалтай юм.
Ойр орчмын шинэс моддын цагираг дээр хийсэн шинжилгээгээр уг байгууламж 500 орчим жилийн өмнө бүрэлдэж эхэлсэн гэж үздэг. Түүнчлэн 1841-1842 оны хооронд чулуу нурж, моддыг гэмтээсэн ул мөр үлдсэн нь тухайн үед хүчтэй өөрчлөлт явагдсаныг гэрчилдэг. Судлаачид уг бүс нутагт хийсэн гравиметрийн болон цахилгаан хайгуулын хэмжилтээр гадаргуугийн дор сийрэгжсэн бүс, босоо сувгууд байгааг илрүүлсэн нь хийн нөлөөллийн таамаглалыг дэмжих нотолгоо болж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
In the forests of the Patom Highlands, in eastern Siberia, a pale mound of broken limestone rises about 40 meters above the larches. It is roughly 160 meters across at the base, weighs an estimated one million tons, and has a crater at its top with a smaller hill sitting in the middle, like a target seen from the sky. Geologists have argued about how it formed ever since it was first described in 1949.
The trees growing on and around it have turned out to be some of the best witnesses. Some of them still carry scars left by rocks that came tumbling down its slopes in the 1840s.
The most recent explanation comes from geophysicist Dmitry Demezhko, of the Bulashevich Institute of Geophysics in Yekaterinburg. In a study published in Doklady Earth Sciences, he sets aside the meteorite theory that dominated the debate for decades and looks underground instead, to gas escaping from depth and to the freezing ground of the Siberian permafrost.
A Cone That Does Not Look Like an Impact
The structure sits in the Bodaibo district, in the north of the Irkutsk region, near the upper reaches of the Lena River. Geologist Vadim Kolpakov described it in 1949 during a mapping survey and proposed that it had been created by a falling meteorite. Locals called it the “Fiery Eagle’s Nest,” and the formation is now known as the Patom crater, after a nearby river.
The meteorite idea drew doubts almost immediately. In 1951, the geologist S. V. Obruchev suggested instead that a jet of gas and steam had burst through ground weakened by faults. Another researcher, A. M. Portnov, later linked the crater to a fragment of the Tunguska object that exploded over Siberia in June 1908, but a 1963 expedition by the Siberian Committee on Meteorites concluded that its formation was far more complex than a single impact.
The cone sits on a hillside, so its height above the slope ranges from about 10 meters on one side to nearly 38 meters on the other. Its base is not quite round, measuring 150 to 160 meters in one direction and 120 to 130 in the other, according to mapping by researchers from the Irkutsk institutes of the Russian Academy of Sciences. A ring-shaped ridge about 80 meters wide surrounds a pit 12 to 15 meters deep, and the central hill is about 34 meters across at its base.
No Trace of a Meteorite in the Rocks
Expeditions in 2006 and 2008 produced the first geological map of the cone and sampled every type of rock on it. Geochemists Viktor Antipin and Alexander Fedorov, of the Vinogradov Institute of Geochemistry in Irkutsk, found that the limestones in all parts of the crater have the same composition as those of the surrounding bedrock, which dates to the Neoproterozoic, more than 540 million years ago. Their 2008 analysis found very low levels of nickel, an element that meteorites usually carry in abundance.
The structure of the cone also argues against a single violent event. The ring-shaped ridge is made of two parts formed at different times, the inner one older and heavily weathered, the outer one made of fresh, dark crystalline limestone. The central hill, the least weathered part of all, appears to have formed last, and an impact would have created all of these features at once.
Blocks of sandstone and schist mixed into the limestone tell another part of the story. They were carried up from deeper layers and became heavily enriched in calcium and strontium on the way. Oxygen isotopes in the limestone show that it reacted with water hotter than 100°C, and the team concluded in 2015 that the cone was most likely produced by a phreatic explosion, a blast of superheated steam, possibly fed by magma rising into water-soaked rock.
Trees Hit by Flying Stones
The age of the cone was settled largely by counting tree rings. Larches in this part of Siberia commonly live 600 years and can reach 1,100, but the oldest trees found near the crater were only 400 to 480 years old. That gap points to a mass toppling of trees about 500 years ago, and places the start of the crater’s formation in the late 15th or early 16th century.
The trees at the foot of the cone recorded something more dramatic. Plant scientist Viktor Voronin, of the Siberian Institute of Plant Physiology and Biochemistry, found that many of them were tilted, broken or scarred by impacts from stones in 1841 and 1842. One larch growing right at the base of the slope stopped growing almost completely in 1843 and died in 1876, while another fell over onto the rubble and kept living, with half its roots still in the soil.
Forest fire was ruled out, since none of the trunks showed burn damage. The researchers concluded that the ground shifted violently as a new load of rock piled up on the outer ridge, sending blocks rolling down the slopes, and that at times the activity was explosive enough for sharp rock fragments to pierce the larch trunks and stay lodged in them. The trees on the central hill were the youngest of all, with the oldest only 71 years old when sampled, which suggests that the last part of the cone took shape well into the 20th century.
Chemical scanning of one larch, using synchrotron radiation in Novosibirsk, revealed one more clue. Between 1852 and 1859, the strontium content of its rings doubled. The team linked this to hot, carbon dioxide-rich fluids rising through the limestone and leaching out strontium, which the tree then absorbed through its roots.
Gas From Below, Ice From Above
Demezhko’s team took a different route to the problem, measuring what lies beneath the cone. During a short expedition in August 2010, they ran a gravity survey of the crater and the surrounding area. As he explained on the European Geosciences Union’s blog, the gravity field looked nothing like that of known impact structures, such as Siberia’s giant Popigay crater.
His 2025 study combines those measurements with electrical soundings of the subsoil. The cone sits exactly above a zone of slightly lower gravity, about 0.6 milligals, a tiny difference that indicates less dense, more broken rock. Deep below lies a broad decompacted zone, from which narrower channels rise toward the surface, and one of them reaches the ground directly under the crater. The electrical survey also found layers of graphite-rich sandstone and steep fault zones along which blocks of rock have been pushed over one another.
From these data, Demezhko proposes what he calls a gaseous-cryogenic hypothesis. In a first stage, gas escaping from depth broke through the rock and opened a vertical, permeable zone. Much later, rain and meltwater seeped into this fractured column, which was frozen in the permafrost, and the repeated cycles of freezing broke the rock apart and pushed it up into the cone that stands today.
The site remains hard to reach, deep in the taiga of the Bodaibo district, and research there has depended on short summer expeditions. Local residents say that people and animals avoid the “Eagle’s Nest.” Demezhko noted that his team felt nothing mystical while working there, and photographed a chipmunk living comfortably inside the crater.
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