During the last Ice Age, the Bohinj Glacier extended across the Vrata Valley and through the region of Dežela all the way to the gates of Radovljica. This large glacier experienced crisis periods during the warmer interglacial phases. The present-day Triglav Glacier is not a remnant of that ancient glacier. The Triglav Glacier (traditionally called Green Snow due to the bluish-green color of its ice) was once the largest glacier in Slovenia. Its remnants lie on the northeastern slope below the summit of Triglav.
In the 16th century, the extent of the Triglav Glacier was smaller than in 1957, as can be inferred from conditions in the High Tauern, where gold and silver were mined in tunnels near the glacier margins in the 16th century, only to be re-covered by advancing ice. In Slovenia, the Institute of Geography at the Slovenian Academy of Sciences and Arts (SAZU) began systematic monitoring of glacier conditions in 1946.
Due to elevation, only Triglav and the Triglav Glacier are suitable for observing the boundary of permanent snow. This boundary is not fixed—it shifts over time and even from year to year. In 1955, researchers discovered dead ice beneath moraine debris on the Triglav Glacier. Based on mapping the glacier’s edge, its area was determined to be 46.9 hectares, which aligns with the first recorded measurement from 1888, citing 45.9 hectares (Richter). Between 1946 and 1952, the glacier’s area fluctuated between 13 and 16 hectares (Gams).
The growth or decline in glacier thickness depends on the balance between snowfall and melt. For Triglav, the boundary of permanent snow was estimated at an elevation of 2700 meters. Due to warm climate conditions, the Triglav Glacier likely did not exist during the last third of the Middle Ages. By the mid-19th century, however, it covered around 40 hectares. This period, when Eastern Alpine glaciers were at their largest, is known as the Little Ice Age.
A major factor in the glacier’s decline was the reduction in October precipitation. This month had previously contributed to snow accumulation, but began providing less and less. Increased summer rainfall, on the other hand, accelerated ice melt. The condition of the glacier is most affected by average summer temperature and the number of sunshine hours. It was precisely the temperature during the melting season and the amount of snowfall during the accumulation season that led to rapid retreat after 1983 and complete disintegration after 1991.