Chyulu Hills

The 100-km-long NW-SE-trending Chyulu Hills volcanic field is located 150 km E of the Kenya Rift. It contains several hundred small cones and flows, including numerous recent cinder cones. Two of these, Shaitani and Chainu, erupted during the mid-19th century. Volcanic activity began about 1.4 million years ago with eruptions in the northern Chyulu Hills and migrated to the SE, where a large number of Holocene cones are found. Many of the cinder cones are aligned along dominantly NW-trending older faults and younger NNE-trending fissures. The silica contents of the lava flows increased with time. Early flows consisted of foidites; later Holocene lava flows are basanites and alkali basalts. Six tephra deposits from Lake Chala were attributed by Martin-Jones et al. (2020) to Pleistocene eruptions in the Chyulu Hills (~87-16.8 ka), along with one Holocene mafic cryptotephra 14C dated at about 4.2 ka.