Why does the East African plateau around Lake Victoria have few volcanic rocks?

The East African plateau surrounding Lake Victoria is characterized by a lack of volcanic rocks because it was primarily formed through the thermal expansion of the lithosphere rather than through volcanism.1

While much of the broader East African region has experienced significant volcanic activity associated with the East African Rift System, the specific high plateau area holding Lake Victoria does not contain volcanic rock and is only intersected by small, minor rift valleys. This plateau stands at a high elevation due to the heating and subsequent uplift of the underlying mantle, a process that does not inherently require the extrusion of volcanic material. In contrast, the higher peaks found elsewhere in East Africa, such as Kilimanjaro and Mount Kenya, are volcanic in origin and were formed by lavas ejected from fissures during the development of the rift valleys.123