Mount Chilalo is an isolated, extinct

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the g ...

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

in southeastern

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

. Its highest point (4036 m or 13,241 ft a.s.l.), in the

Arsi Zone Arsi () is a Zones of Ethiopia, zone in Oromia Region of Ethiopia, named after a clan of the Oromo people, Oromo, who inhabit in the area. Arsi is bordered on the south by Bale Zone, on the southwest by the West Arsi Zone, on the northwest by Ea ...

of the

Oromia Region Oromia (, ) is a Regions of Ethiopia, regional state in Ethiopia and the homeland of the Oromo people. Under Article 49 of 1995 Constitution of Ethiopia, Ethiopian Constitution, the capital of Oromia is Addis Ababa, also called Finfinne. The ...

, is located in Arsi Mountains National Park on the border between the

Hitosa Hitosa () is one of the woredas in the Oromia Region of Ethiopia. The woreda of Lude Hitosa was separated from Hitosa. Part of the Arsi Zone, Hitosa is bordered on the south by Digeluna Tijo, on the southwest by Tiyo, on the west by Batu Dugda, o ...

and

Tiyo Tiyo (T'í'o, or طع) is a coastal town in east-central Eritrea, the capital of the Are'eta district in the Southern Red Sea region. Nearby towns and villages include Anrata Arata ()Afar af (Arraqta) is a coastal village in eastern Eritrea. ...

woreda Districts of Ethiopia, also called woredas (; ''woreda''), are the third level of the administrative divisions of Ethiopia – after ''List of zones of Ethiopia, zones'' and the ''Regions of Ethiopia, regional states''. These districts are f ...

(). The mountain has an elliptical base (about 30 by 20 kilometers), whose major axis lies NNE-SSW or parallel to the predominant tectonic trend. Chilalo rises with gentle slopes for more than 1500 meters from the top of the plateau. At the summit, there is a large, almost circular

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

about 6 kilometers in diameter, whose southern rim is considered to be the mountain's summit. Mount Chilalo last erupted in the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. One authority identifies Mount Chilalo as a late Trap Series volcano. The geologist Erik Nilsson claimed to have identified traces of

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...

on Chilalo, as well as on its neighbor Mount Kaka down to about 3400 meters, which he dated to the "Last Pluvial Period".Erik Nilsson
"Traces of Ancient Changes of Climate in East Africa: Preliminary Report"
''

Geografiska Annaler ''Geografiska Annaler'' is a scientific journal published by the Swedish Society for Anthropology and Geography in Stockholm, Sweden. The journal is founded in 1919. Since 1965 the journal is published in two series A and B. Series A deals with ar ...

'', 17 (1935), pp. 13f Although this mountain is located south of the

East African Rift The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago. It was formerly considered to be part of a l ...

, along with Mount Gugu to the north and Mount Kaka to the south, it is considered, geologically speaking, part of the

Ethiopian Highlands The Ethiopian Highlands (also called the Abyssinian Highlands) is a rugged mass of mountains in Ethiopia in Northeast Africa. It forms the largest continuous area of its elevation in the continent, with little of its surface falling below , whil ...

Notes

Mountains of Ethiopia Stratovolcanoes of Ethiopia Ethiopian Highlands Geography of Oromia {{Oromia-geo-stub