Caucasus Mountains

Long ago, a small sea lay where the mountains are now.

Pieces of Earth's crust pushed together and closed the sea. The land was squeezed up into mountains.

The Caucasus sits at the northern edge of the collision between the Arabian plate and the Eurasian plate. Geologists think an ocean basin once lay here, perhaps 350 to 400 kilometers wide at its widest.

These geologists propose that, as the plates pushed together, the basin began to close about 35 million years ago. Around 5 million years ago, an old chain of volcanoes called the Lesser Caucasus arc collided with a block of crust called the Scythian platform, forming the Greater Caucasus. Another study suggests that rocks across the range have been brought up toward the surface quickly since the Pliocene.

Cowgill, Forte and colleagues (AGU, 2016) explain the Greater Caucasus as the result of post-collisional Cenozoic closure of a relict Mesozoic back-arc basin on the northern margin of the Arabia-Eurasia collision zone. From detrital zircon provenance, they estimate a maximum basin width of about 350 to 400 km and propose that closure began about 35 million years ago, at the initial (soft) Arabia-Eurasia collision, leading to hard collision about 5 million years ago between the Lesser Caucasus arc and the Scythian platform.

Apatite fission-track ages reported by Wang and colleagues (AGU Fall Meeting, 2014) suggest rapid exhumation across the range since the Pliocene, fastest along the central axis, where metamorphic grade is highest.

Rivers of ice called glaciers sit high on the mountains.

The glaciers are getting smaller. Scientists use pictures from space to measure them.

Storms from the Atlantic Ocean and the Mediterranean Sea bring moisture to the Caucasus, especially to the west. That snow feeds glaciers: in 2000, scientists counted 2,186 of them, and almost 70% of the range's glaciers lie in its high central part.

Using satellite pictures, the same scientists found that the glaciers' total area shrank by about 23% between 2000 and 2020. The glaciers in the east, most of them very small, are shrinking fastest, likely because small glaciers lose area faster.

Tielidze, Nosenko, Khromova and Paul mapped glacier outlines manually from Landsat, Sentinel-2 and SPOT images. In 2000 the range held 2,186 glaciers covering 1,381.5 ± 58.2 km²; by 2020 the area was 1,060.9 ± 33.6 km², a loss of 23.2 ± 3.8%, or about 1.16% a year. Loss was fastest in the eastern Greater Caucasus (about 1.82% a year), where most glaciers are very small.

Mediterranean and Atlantic cyclones bring moisture from the west and southwest; annual precipitation reaches about 3,200 mm on the southern slope of the west and declines eastward. The authors say the larger eastern losses are likely related to the smaller size of glaciers there, since relative area loss increases as glaciers get smaller; the Elbrus Massif, dominated by large glaciers, lost area most slowly.

Big, wild forests grow in the western Caucasus. Only wild animals graze the high meadows there.

European bison were brought back to live in these mountains.

UNESCO protects the Western Caucasus, more than 275,000 hectares at the far western end of the mountains. It is one of the few large mountain areas in Europe where people have not changed nature much. Its high meadows have only ever been grazed by wild animals, and its untouched forests stretch from the lowlands up to the high slopes.

The area is where the mountain kind of European bison comes from, and where bison were brought back. Across the wider Caucasus region, there are about 6,500 kinds of plants, and a quarter grow nowhere else. A conservation fund, CEPF, lists the Caucasian tur as endangered.

UNESCO inscribed the Western Caucasus in 1999 under criteria (ix) and (x). It covers more than 275,000 ha about 50 km northeast of the Black Sea and has a remarkable diversity of geology, ecosystems and species. UNESCO calls it of global significance as a center of plant diversity: subalpine and alpine pastures grazed only by wild animals, undisturbed mountain forests from the lowlands to the subalpine zone, and the place of origin and reintroduction of the mountain subspecies of the European bison.

The Critical Ecosystem Partnership Fund counts some 6,500 vascular plant species in the wider Caucasus biodiversity hotspot, a quarter of them endemic, and lists the Endangered Caucasian tur (Capra caucasica) among its threatened mammals.

High up in the mountains, the air has less oxygen. Climb slowly and rest.

Tell a grown-up if your head hurts.

High mountains have thin air. The US Centers for Disease Control and Prevention (CDC) says travelers who sleep at 2,450 meters or higher without getting used to the height first can get altitude illness, and children can get it just as easily as adults. The CDC's main advice is to go up gradually.

PlayOwl's advice for the forests: stay on marked trails and watch wild animals from a distance.

The CDC's Yellow Book notes that any traveler who has not acclimatized and sleeps at 2,450 m or higher, and sometimes lower, is at risk of altitude illness; children are as susceptible as adults, and fitness does not lower the risk. Its checklist: ascend gradually and, above 3,000 m, raise sleeping altitude by no more than 500 m a day, with an extra day for every additional 1,000 m. The average elevations of all three sectors of the Greater Caucasus are above 3,000 m.

In the Western Caucasus, PlayOwl's own advice is to keep to trails and leave wildlife undisturbed, so the meadows stay grazed only by wild animals.