Geologist and volcanologist Ade Edward suspects that the rock mounds found by residents in the Lubuk Alung District area, Padang Pariaman Regency, West Sumatra Province, Indonesia, are columnar joints.

Based on the results of physical observations in the field, he said that the rocks in the mound found in Lubuk Alung were a type of basaltic andesite rock.

Andesite rocks are light gray in color, while basaltic rocks are more gray or close to black.These rocks are formed due to the freezing process of magma below the earth's surface, which then seeps through cracks or fractures.

In the process of changing mass from liquid to solid, shrinkage and hardening occur, resulting in a phenomenon that forms columns, which are called columnar joints.

The age of the rocks that are thought to be columnar joints in Lubuk Alung is probably between 40 and 60 million years. However, to confirm this, research and assessment are needed to determine the exact age of the rocks.

This columnar joint structure is very rare and rarely found, even in Indonesia. If you dig deeper, it is estimated that the rock structure resembles the Hong Kong National Geopark.

SOT : ADE EDWARD, geologist and volcanologist
Time Code : 01.32 - 02.41

"Why is it rare because it forms far below the surface of the ground? Because it is a solution and is formed from a magma breakthrough, but it forms underground. If it breaks through to the surface, it becomes lava and eventually becomes a volcano, but if it doesn't break through to the surface below, it is just frozen. Because it's that old. A long time ago, namely 40 to 60 million years ago, plus the Bukit Barisan area, Sumatra was an active tectonic area that was uplifted so that what was previously several kilometers below the earth could emerge to a height. This is a height of around 100 meters above sea level, and this is considered rare. "Because it can be the highest in Indonesia. In other areas, the position is lower, so the cliffs are not too thick and high when we find them, while in this one, the cliffs are higher, so we can see the columnar joint structure."