Duvalo in Kosel in the former Yugoslavia in geography textbooks for elementary education was described as a rare geological phenomenon, the only active volcano in the Balkans. According to the Institute of Geography at the Faculty of Natural Sciences and Mathematics in Skopje, Duvalo is not a volcano, there was no outflow of magma, but a crack from which gases emerge.
It is located near the village of Kosel, in the basin of the Koselska Reka that flows into the Ohrid Lake. The fumarole’s height is 740 meters above sea level. It is a 0.5 m diameter crater and a depth of about 30 cm from which sulfur dioxide and carbon dioxide are released. The smell of sulfur is about three kilometers in diameter. Duvalo is protected as a monument of nature.
Similar occurrences in North Macedonia are found on some hills in the Kumanovo-Kratovo region, on Kozuf mountain in two places, from Kavadarci and Gevgelija side and in the Kratovo-Zletovo region near the villages of Beli and Plesnitsa.
There are two theories on the origin of Duvalo. Although the active phenomenon is considered to be the last “living volcano” in the Balkans, it can not really be claimed with certainty when it exists and whether it was once an active volcano since there was no spill of magma on the surface. From a scientific point of view, it is a matter of several fractured cracks or miniature craters, the largest with a diameter of 50 cm and a depth of 30 cm, from which the openings of carbon dioxide and sulfur dioxide are opened, and experts say that this phenomenon is at the same time the moss and sulfate.
Gases and vapors cause an unusual, unpleasant smell of rotten egg to spread. The smell intensity depends on the concentration of the vapor and the weather conditions. In dry periods, it raises and the smell is stronger, and in the rain, you are listening to insidious bumps. In May 2014, there was increased activity with heavy smoke, but it was determined that there was no seismic activity and that it was a natural phenomenon after heavy precipitation and tectonic movements that then affected the region.
The locals remember the legend that Duvalo is part of the rampage of the Vesuvius volcano that is connected to the Adriatic Sea and that also Kosovrasti at the Debar baths are in same line – whose hot and healing waters have the same distinctive odour. They are accustomed to that smell from which there is no harm, except for copper wire appliances that quickly rush and rust. Sulfur is said to be healing and helps with various types of diseases, but it is also poisonous in larger concentrations – every animal that dwells for a long time in Duvalo dies, and a lump of white sulfur destroys all kinds of insects, especially cockroaches and taffytes.
According to one legend, the name of the village of Kosel comes from the word in Turkish meaning sulfur. In the Ottoman era, the gunpowder was processed from this sulfur country, before the Ilinden uprising was supplied by Thessaloniki merchants for the production of an explosive, and even the Romans used it to make some kind of matches. The Duval phenomenon certainly has the potential to become a kind of tourist attraction for guests who visit this region.