Ethiopia Mountain

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Earthquake distribution in Ethiopia

The Afar Depression, the Main Ethiopian Rift and the Escarpments constitute the main seismic belts in Ethiopia. These regions belong to East African Rift system and their seismicity can be explained in terms of plate tectonics.

According to the theory of plate tectonics the earth’s surface may be divided into a number of rigid spherical caps whose boundaries are the seismic belts of the world. It is the relative motion between these caps, or plates, which causes earthquakes.

There are three major types of plates boundaries at which the relative motion occur. The first type is a boundary created when two plates are moving apart from one another.

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Ethiopia’s Tectonics

Precambrian tectonics
Three Precambrian are present, Lower, Middle and Upper. They are clearly separable in structural style. The rocks of the Lower Complex from large blocks separated and surrounded by folded belts of the Upper Complex.

The Middle complex is minor in extent, filling some troughs in the Lower Complex. The Upper Complex appears to consist of two north-south trending belts which join together in northern Ethiopia.

Mesozoic-Cenozoic tectonics
The major tectonic elements are
1. The Ethiopian plateau
2. The Somali plateau
3. The Danakil uplift
4. The Aisha uplift
5. The Rift System

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The major characteristics of Ethiopia’s relief and landscape

The major characteristics of Ethiopia’s relief and landscape which have been summarised above are also illustrated in the cross-sections which have been associated with the relief map. In particular, these cross-sections serve to illustrate:

(a) the highly dissected character of the landscape over much of Ethiopia’s territory
(b) the limited extent to which flat surfaces are present in Ethiopia.

The highly dissected nature of the landscape has proved a barrier to the development of internal surface communications and has resulted in the long-term isolation of many communities in mountainous area difficult of access.

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Ethiopia and its Relief

The specific features of the various relief and drainage area are considered later in the atlas. This map is concerned with the general characteristics of the relief of the country.

The major physical features are the results of the extensive and spectacular faulting which cracked the old crystalline block of the African continent along its eastern side producing features which stretch from Africa’s juncture with the eastern end of the Mediterranean Basin to Mozambique in the South.

The uplifting which resulted produced the high plateau – lands which are characteristic of the central regions of Ethiopia and which stand at a general elevation of between 2000 and 2500 metres above sea level.

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The outer lowlands of Ethiopia

The outer lowlands of Ethiopia are to the west of the western highlands, and to the east and south of the south eastern highlands.

Areas of ancient crystalline lowlands, in northern Eritrea, northwestern Welega and southern Borena, have inselberg topography, isolated hills scattered over the well-developed plains.

The Baro-Akobo basin forms a vast, flat lowland area in western Illubabor. In the lower course of the Baro river and its tributaries the water does not flow during the rains but forms extensive impassable swamps and marshes.

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The lower rift valley in Ethiopia

The lower rift valley is generally of low altitude, (300-700 metres) being mainly large plains and low table land.

In Dalol-Asale district, the land falls to about 110 metres below sea level. Active volcanoes are numerous here. Some lakes in the hot Danakil depression have dried up and become salt flats.

(Source: National Atlas of Ethiopia)

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The central lowlands of Ethiopia

The central lowlands Ethiopia from Chew Bahir to the Gulf of Zula between the walls of the two highlands, are covered with recent volcanic material and patches of older and new lava and recent sedimentary materials.

The lakes sub-region, from Ziway to Chamo, is a relatively higher area than the Afar plain. East flowing rivers from the western highlands, the Meki, Bilate, and westward flowing rivers from the eastern highlands, replenish the waters of the Upper Rift Valley lakes.
 

(Source: National Atlas of Ethiopia)

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The south eastern highlands

The south-eastern highlands include the highlands of Sidamo, Bale, Arsi and Harerge. The highlands in this region are made up of volcanic rocks, but where the rivers cut deep, crystalline rocks are exposed.

The South Eastern Highlands have high mountains on their western rim, but no clear-cut boundary to the east, for they have a continuous slope running from the highest peak, Mt. Batu (4,308 metres), towards the south-east lowlands.

The areas of higher land are separated by the Wabe Shebele and the Genale rivers and their tributaries. Within the areas of higher elevation are found remnant, flat-topped tablelands known as ‘Ambas’ and jagged peaks isolated by river-eroded gorges and ravines.

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The western highlands

The western highlands are massive with an average height of 2000-25000m. They slope gradually to the west and terminate in extended lowlands starting from Tigray Administrative Region to the southern part of Gamo Gofa.

The highlands include many sub-divisions or blocks separated by the deep, steep-sided valleys of the major rivers.

For example, the Tekeze separates the Tigray and Gonder massifs; the Blue Nile divides the Gojam, Shewa-Welega massifs; the Omo river separates the Kefa and Shewa-Gamo Gofa massifs. The elevations of the escarpments are lower towards the west, but are high and steep towards the Rift Valley in the east.

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Topography

Ethiopia is a country of great geographical diversity with high and rugged mountains, flat topped plateaus, deep gorges, incised river valleys and rolling plains.

Over the ages, erosion, volcanic eruptions, tectonic movements and subsidence have occurred and continued through millennia to accentuate the unevenness of the surface.
Altitudes range from the highest peak at Ras Dejen, 4620 meters above sea level, down to the depression of the Kobar Sink, about 110 meters below sea level.

Most of the country consists of high plateau and mountain ranges with precipitious edges dissected by the numerous streams which are the tributaries of the major rivers such as the Abay (Blue Nile), Tekeze, Awash, Omo, Wabe Shebele, Baro-Akobo, etc.

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