How did volcanism affect the formation of East African lakes?

Volcanism has played a significant role in shaping the East African lakes by altering drainage patterns and influencing the physical environment of the basins.

Key impacts of volcanic activity include:

• Drainage Blockage: Volcanic eruptions have frequently interrupted existing drainage systems. For example, the eruption of the Virunga Mountains created a volcanic dam that separated Lake Kivu from Lake Edward. This event blocked Kivu’s original northward drainage toward the Nile and forced a reversal of its flow to the south through the Ruzizi River into Lake Tanganyika.12
• Shoreline and Basin Shaping: Volcanic activity has contributed to shaping lake shorelines and, in some instances, blocking drainage to form or modify basins.13
• Biological and Chemical Effects: Intense volcanic activity around the shores of Lakes Edward and George has been linked to a significant reduction in their organic content, as evidenced by the fossil record. Additionally, some lakes are characterized by high concentrations of volcanic substances, such as the methane and hydrogen sulfide found in the deep waters of Lake Kivu.12