THE BASALT COLUMNS OF RACOȘUL DE JOS

This geosite (geological site) was declared a Natural Monument in 1962 (IUCN Category III). Volcanic activity here occurred approximately 1.2 million years ago, and at that time, there was either a lava flow or a lava lake at least 15 meters thick.

As lava begins to cool, it contracts. The interior remains extremely hot (1100–1250°C) while the edges cool more quickly. Because lava occupies less space in its solid state than in its fluid state, cooling leads to the formation of contraction cracks within the lava mass. The separation of basalt columns occurs along these cracks.

Tall basalt columns indicate slow cooling under stable conditions (with no additional magma supply from depth). The cooling of large lava masses can take several months. Most often, the columns form pentagonal and/or hexagonalshapes.

Basaltic lava rocks often contain xenoliths originating from the Earth’s upper mantle, which were carried upward by basaltic magma from depths of approximately 65–90 km beneath the Perșani Mountains.

Stone quarrying in this area began around 1872.