Igneous Rocks at Mount Bisoke, Northwest Rwanda

Crater Lake, Mount Bisoke, Rwanda

One of my most rewarding hiking experience in Rwanda has always been climbing Mount Bisoke in the Northwest of my country, Rwanda (East Africa). Even though it is not an exceptionally difficult climb for many, it is visually gratifying while remaining a physical challenge. The mountain is covered with different habitats; predominantly, a bamboo forest and bushes of rare plants at the summit that are home to the rare mountain gorillas. It is about 3,700 meters high and is situated on the border of Rwanda and the Democratic Republic of the Congo—although a large part of it, including its summit, is on the Rwandan side.

But most importantly, Mount Bisoke is an active volcano whose last recorded eruption dates back in 1957. Its summit is currently filled with a Crater Lake of breathtaking beauty. It is part of similarly forest-covered volcanoes that form the Virunga Mountain Range. Of most interest to me is the type of soil and rock found in the area. Indeed, many experts believe that Bisoke’s magma is of Trachyandesite basaltic type, which produces an extrusive igneous rock with an intermediate/mafic composition. Dark colored, Bisoke’s rock allows limited free quartz but more alkali feldspar and other mafic minerals. Therefore, the weathering process of Bisoke’s basaltic type of rock has endowed the area with the most fertile soil of the country.

Fertile Land at the Foot of Mount Bisoke, Rwanda

Source:

Global Volcanism Program, 2013. Visoke (223050) in Volcanoes of the World, v. 4.7.6. Venzke, E (ed.). Smithsonian Institution. Downloaded 25 Mar 2019 (https://volcano.si.edu/volcano.cfm?vn=223050). https://doi.org/10.5479/si.GVP.VOTW4-2013

Balasubramanian, V., Sekayange, L. (1991). “Effects of tree legumes in hedgerows on soil fertility changes and crop performance in the semi-arid highlands of Rwanda.” Biological Agriculture & Horticulture.