Abstract
Geological activity on icy planets and planetoids includes cryovolcanism. Until recently, most research on terrestrial permafrost has been engineering-oriented, and many related phenomena have received too little attention. Although fast processes in the Earth’s cryosphere were known before, they have never been attributed to cryovolcanism. The discovery of a couple of tens of meters wide crater in the Yamal Peninsula aroused numerous hypotheses of its origin, including a meteorite impact or migration of deep gas as a result of global warming. However, the origin of the Yamal crater can be explained in terms of cryospheric processes. Thus, the Yamal crater appears to result from collapse of a large pingo, which formed within a thaw lake when it shoaled and dried out allowing a large talik (that is layer or body of unfrozen ground in a permafrost area) below it to freeze back. The pingo collapsed under cryogenic hydrostatic pressure built up in the closed system of the freezing talik. This happened before the freezing completed, when a core of wet ground remained unfrozen and stored a huge amount of carbon dioxide dissolved in pore water. This eventually reached gas-phase saturation, and the resulting overpressure came to exceed the lithospheric confining stress and the strength of the overlying ice. As the pingo exploded, the demarcation of the crater followed the cylindrical shape of the remnant talik core.
Highlights
Volcanism shaped the surface of some larger rocky bodies in the Solar System, but currently it is restricted to the Earth and Io
The crater was found in the summer of 2014 in the central Yamal Peninsula at N69.970965 E68.369575, 30 km southeast of the Bovanenkovo gas field
The Yamal crater is located in a zone of ice-rich continuous permafrost of −1 °C to −5 °C mean annual temperatures, with a bulk ice content of 30–65 vol %, frequently confined to thick lenses of ground ice
Summary
For the separate analysis of the mineral matrix of ground and ice a cut core was placed in plastic bags and thawed at ambient temperatures (8–15 °C). At high ice content of the sample, the melted water was trapped by ICP−MS protocol. With the sampling, the following parameters of the solution were determined: electrical conductivity using a conductivity meter Expert 002 and potentiometric measurement of pH, Eh and the activity of fluoride ions. Potentiometric measurements were conducted with the pH-meter Expert-001 and ion-selective electrodes silver chloride reference electrode EVL-1M3.1. The redox potential was determined using two electrodes - glass redox EO-01 and a platinum EVP-1. The combination of these electrodes allows to determine the parameters of potential-reaction. For studies of the gas composition a standard volume of core (400 cm3) was placed in a sterile glass container with 100 cm[3] of saturated sodium chloride solution. The content of macro components was determined by X-ray fluorescence
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