Mousa Ali (, , ) is a

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 ...

located on the

tri-point A triple border, tripoint, trijunction, triple point, or tri-border area is a geographical point at which the boundaries of three countries or subnational entities meet. There are 175 international tripoints as of 2020. Nearly half are situated ...

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 ...

Eritrea Eritrea, officially the State of Eritrea, is a country in the Horn of Africa region of East Africa, with its capital and largest city being Asmara. It is bordered by Ethiopia in the Eritrea–Ethiopia border, south, Sudan in the west, and Dj ...

and

Djibouti Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...

. The volcano is the highest point in Djibouti. The volcano's summit is truncated by a

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 ...

, which contains

rhyolitic Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals ( phenocrysts) in an otherwise fine-grained groundmass. The miner ...

lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...

s and

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

s. The last known eruption occurred before the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

epoch. Mousa Ali is situated at the tri-point of the

Tadjourah Region The Tadjourah Region , ) is a region in north-central Djibouti, the largest of its six regions. With its capital at Tadjourah, it has an area of . It lies along the Gulf of Tadjoura, and the coastal city of Tadjoura. The region has active salt ...

, the Southern Red Sea Region of

, and the

Afar Region The Afar Region (; ; ), formerly known as Region 2, is a Regions of Ethiopia, regional state in northeastern Ethiopia and the homeland of the Afar people. Its capital is the planned city of Semera, which lies on the paved Awash, Ethiopia, Awash� ...

Geography

The mountain has two distinct

summit A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. The topographic terms acme, apex, peak (mountain peak), and zenith are synonymous. The term (mountain top) is generally used only for ...

s, the higher being the south one with an

elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...

of 2,021 metres. The north summit in

has an elevation of 1,871 metres. Both summits are separated by a large

, about 1 km (0.71 mi) wide and 1514 metres deep. Mousa Ali, in the northern part of the

Great Rift Valley The Great Rift Valley () is a series of contiguous geographic depressions, approximately 6,000 or in total length, the definition varying between sources, that runs from the southern Turkish Hatay Province in Asia, through the Red Sea, to Moz ...

region, has

on its northern flank, Ethiopia on the west, and

the east and south. The Djiboutian town of

Dorra Dorra () is a village in Djibouti in the mid-north of Tadjoura Region, the largest region. It is located about 237 kilometers north-west of Djibouti City and 65 km (40 mi) south of the border with Eritrea and east of the border with E ...

is 36 km to the south-southeast, the Ethiopian volcano Manda-Inakir is 22 km to the southwest, and the road from the Ethiopian town of Manda to the Eritrean port of

Assab Assab or Aseb (, ) is a port city in the Southern Red Sea Region of Eritrea. It is situated on the west coast of the Red Sea. Languages spoken in Assab are predominantly Afar language, Afar, Tigrinya language, Tigrinya, and Arabic. After the Ita ...

is 19 km to the northwest.

Wildlife and flora

The mountain is home to an abundance of wildlife, lush vegetation, flowering shrubs and trees and various plants.

History

Two sects of Afar live in the area. They are collectively known as Adrúmmi, from 'Adó rum li or "white as Byzantines." The position of Ali Mousa as the tripoint between

and

is not the result of an agreement between the three countries. In December 1948 the British administering Eritrea refused to attend a meeting with the other two parties to determine the exact location of their tripoint, set in a 1908 treaty as 60 km inland from the Red Sea. British administration of Eritrea ended in 1952, and with increasing Ethiopian administration over the ensuing decade, and incorporation into Ethiopia from 1962 to 1993, the boundary was internal, not international. In 2002, the Eritrea-Ethiopia Boundary Commission established the tri-point at the Mousa Ali summit; Ethiopia had pressed for it to be further east, nearer to Dadda'to, Djibouti.

Climate

The temperature of Mousa Ali usually ranges from 7 °C to 17 °C in December and January, and 16 °C to 26 °C from June to September. The weather on the mountain can be very erratic, sometimes severe.

Gallery

File:On the summit of Moussa Ali looking at the Caldera.jpg, On the summit of Moussa Ali looking at the Caldera. File:View of Mousa Ali from the southwest side.jpg, View of Mousa Ali from the southwest side.

References