In a paper published last month in the Open Journal of Geology, four researchers from the Ivane Javakhishvili Tbilisi State University of Georgia traced the old glaciation of the Caucasus Mountains from the 17th to 19th century during the Little Ice Age. These mountains are the highest mountains in Europe. Despite being remote, studying their processes can aid in the understanding of global climate history.
In this study, it is remarkable that the team had a robust methodology comprising a rigorous review of local knowledge and sources from the indigenous people as well as the analysis of rock samples collected during their expeditions. Reading a collection of folklore from the mountain communities by A. Krasnov, the team was able to reconstruct the advance of local glaciers that stretched all the way down to the populated mountain valleys during that epoch. This collection served as a first-hand account on the extent of glaciation based on the location of the villages.
Divided into the Greater Caucasus in the North and the Lesser Caucasus in the south, the Caucasus mountain region in West Asia stretches between the Black Sea and Caspian Sea. It is formed from the tectonic plate collision between the Arabian and European plates, occupying territory in Georgia, Armenian, Azerbaijani, Russia, Turkey and Persia. According to a local Georgian Svanetian poem by Nizardze, glacier advances had reached a distance of up to 17km during the peak of the Little Ice Age.
The existence of Russian topographic maps from the second half of the 19th century also helped form a broad picture of the latest glaciation. This knowledge was then further corroborated with other sample data collected in the team’s expedition.
The first technique used was petrography, which is the classification of rocks based on physical structure and mineral content. Present-day block debris from moraines could be reconstructed with this information to find out their main centers and from thereon, historical glacier movement and distribution boundaries.
The second technique used was palynology, which is the study of microscopic matter. It was used to identify the genesis of loose sediments from moraines. Using 590 pollen samples, the fossilized plant spectrum in the loose sediments were analyzed to explore if weathering of the moraines occurred as a result of glaciation or fluvial action and the time periods they occurred in. Information about whether the rocks were covered in ice at that point in time would allow researchers to estimate the extent of glaciation.
“The glaciers completely filled the river valleys of the Greater Caucasus, passed the foothills and covered some of the piedmont valleys. It is supposed that the strongest glaciation took place in the Terek (the northern slope) and Kodori (the southern slope of the Greater Caucasus) river basins as well as in the Enguri and Rioni basins,” the research notes.
Until today, the actual mudflow activity in the Caucasus is still rather intensive (especially in the east). However, it appears that in the past it was even more intensive due to the tectonic shoves, rock falls and catastrophic thaw of large glaciers during highly dynamic glacial epoch. Based on the traces of glaciers, the Caucasus ancient snow-line is still about 700 to 1000 meters lower than the contemporary one.
Research suggests that the minor glacial epoch experienced by the Caucasus Mountains was intensified by the South European covering glaciation. However, the team believes that atmospheric circulation processes and regional tectonic movements are the main drivers of the glaciation.
The Little Ice Age remains the heart of geological research in the Caucasus Mountains since it is the last stage of glacial advance in the region. Hence, the geological mystery on the relative importance of the drivers for minor glacial epoch is still being debated.