On Kilimanjaro six glacial episodes are recognized. At the principal volcanic center of Kibo these were interrupted by volcanic activity. The smaller volcanic center of Mawenzi has been extinct longer, and the glaciations have been super-imposed. Shira, the lowest of the three volcanoes in the group, has been only slightly affected by glaciation. The successive glacial episodes are named the First, Second, Third, Fourth (Main), Little, and Recent, of which the Third was the most extensive; however, most of the obvious glacial features belong to the Fourth Glaciation which covered about 150 sq mi. The Little and Recent Glaciations are smaller in extent and post-Pleistocene. The climatic pattern was probably similar at all times to that of today, and the thickest and longest glaciers were generally always on the south and west slopes. Comparison with other glaciated regions in East Africa shows some similarities, and a similar sequence has been suggested for the East African pluvial periods.