Ethiopian Mountains

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.

This is typically found at a mid-oceanic ridge where new plates are being formed. The East African Rift system belongs to this category. Such boundaries are called accreting or diverting boundaries.

The second type of boundary is created where two plates are moving towards one another. This is called converting boundary.

Oceanic trenches like the Marianas and certain mountain ranges, such as the Himalayas are located along such boundaries. The third type of plate boundary occurs along transform faults where the relative plate motion is parallel to the boundary.

In all three types of boundaries strain accumulates slowly over a period of years. The abrupt release of this accumulated strain generation disturbance in the earth’s crust and this disturbance is known as an earthquake. Such earthquakes are generally associated with faulting volcanic activity.

Historical records over the last 600 years and recent instrumental observations show that there have been earthquakes in Ethiopia mainly in the Afar Depression, the escarpments, and the main Ethiopian rift.

Explanation of earthquake parameters employed in producing the earthquake distribution map is given subsequently.

Epicentre and focal depth
The initial disturbance which sends out the main waves is confined to a limited region of the earth’s interior whose linear dimensions do not ordinarily exceed the order of a few kilometres.

The centre of this confined region is called the focus (sometimes the hypocentre) of the particular earthquake.

The point of the earth’s outer surface vertically above the focus is known as the epicentre while the distance from the epicentre to the focus is called the focal depth.

In general focal depths are grouped in three categories, namely, shallow (0km-60km), intermediate (61km-300km), and deep (301 km-700 km). Almost all of the earthquakes that occur in Ethiopia are of shallow focal depth.

Magnitude
Earthquake size as determined by instruments is measured on a logarithmic scale called the Richter Magnitude Scale. Earthquake magnitude is related to the energy released during the occurrence of an earthquake. Empirically this is given by:
Log E = 5.8 + 2.4m
where m is the body wave magnitude and E is the energy in ergs.

Earthquakes with magnitude greater than five can cause destruction over a restricted area while earthquakes with, say, magnitude 4.5 can cause slight damage near the epicentre.

As can be inferred from the map there have been numerous earthquakes in Ethiopia whose magnitudes are greater than, or equal to, 5 (red).

These earthquakes have either been felt or caused damage. For example, the 1961 E.C. (1969) earthquake at Serdo, Central Afar, had a magnitude of 6.5 and completely destroyed the town killing 24 people and injuring 167 others.

Earthquakes whose magnitudes are less than 5 (green) are also shown on the map. In some area such earthquakes also caused damages; example, Awara Melka area, 1973 E.C. (1981). Earth quakes whose magnitudes are not determined (blue) are mainly from historical records.

(Source: National Atlas of Ethiopia)

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

The Ethiopian plateau is an uplifted block limited on the east by the Rift System and declining on the west to the Sudan plain. The eastern margin of the plateau is elevated to between 3,000m and 4,000m while, towards the west, the plateau surface descends to between 1,200 and 1,000 metres.

The Somali plateau bounded on the west by the Rift System, is at elevations of 3,000m to 3,500m on the west, and declines gradually eastward to the Indian Ocean.

The Danakil uplift appears to be a northwesterly trending horst block with a core of Precambrian rocks and Mesozoic sedimentary rocks on the limbs. The Danakil uplift continues to the northwest as the Buri peninsula. It may continue buried under Quaternary volcanics to the Gulf of Zula.

The Aisha uplift in its northern part has a crudely anticlinal structure with Jurassic limestone in the core and Cretaceous sandstones on the limbs.

Numerous north-south faults subdivide the uplift into several horst-graben blocks. In its southern part the Aisha uplift consists of a second uplifted block bounded to the southwest by a large sinistral fault.

The Rift System consists of the Red Sea rift, Afar, the Main Ethiopian rift and Lake Stefanie and Lake Rudolf rifts. The Red Sea rift is bordered on the west by the escarpment of the Ethiopian plateau.

The margin of the Red Sea rift is interpreted as a series of stepfaulted blocks, the coastal plain forming one such step.

The Afar rift is a triangle bordered in the west and south by the escarpments of the Ethiopian and Somali plateaus, and in the northeast and east by the Danakil and Aisha uplifts.

The Danakil depression, the Erta Ale, Alayta and Tat Ali volcanic ranges, and the Gawwah, Dobi and Tendaho graben form prominent features in northern Afar. Southern Afar consists of two marginal depressions parallel to the margins of the Ethiopian and Somali plateaus, and a central relatively uplifted part.

The Main Ethiopian Rift extends for 500km from 90 30’N to 4045’N. The Rift floor varies in elevation from 1,000m to 2,000m. The Northern segment of the Main Rift is 70km to 80km wide, within the north a median trough extending from southern Afar.

The central segment of the Main Rift, 280km long and 70km to 80km wide, extends from the Yerer fault to Lake Abaya. Lakes Langeno, Shala and Abijata, to mention the major ones, fill the central depression in this segment.

The southern segment of the Main Rift consists of the Abaya-Chamo Rift, the Amaro Horst, the Galana graben and several other features.

The Lake Stefanie Rift is a narrow, north-south trending graben 100km long by 25km to 30km wide. It is bounded on both sides by steep tectonic escarpments consisting of two to three step-faulted blocks. This graben stretches to the Kenya border.

The Lake Rudolf rift is a tectonic depression which includes the Turkana basin in Kenya and the Lower Omo valley in Ethiopia. The latter widens southward between north-southtrending escarpments, and is filled with Pliocene-Quaternary lacustrine and alluvial sediments.

(Source: National Atlas of Ethiopia)

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.

In the present day, although the major road system and the pattern of penetration and feeder roads has increased very significantly, road construction over this difficult terrain remains an expensive enterprise and maintenance costs are high.

On the other hand, differences in elevation and therefore of climate conditions have provided the scene for a wide variety of cropping patterns in agriculture.

The extreme differences in altitude coupled with high rainfall have also created the conditions for a very high potential in the production of hydro-electric power.

Extensive plains are found only in the eastern Welo and Harege Regions, and in the southern half of Sidamo and Bale Regions.

The western ‘panhandle’ of the Gambela area is the only example of a flood plain in the flat area between the Baro and Akob rivers.

Less extensive but agriculturally important area of high flat plateauland are to be found in the central highlands, particularly in northern Shewa, western Welo and parts of Gojam and Gonder Regions.

(Source: National Atlas of Ethiopia)

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.

However, the cracking also produced the clearly defined rift valley structures formed between parallel fault lines as the main blocks continued their upward movement. The floor of the Rift Valley, which stretches from the Red Sea through, (and includes the adjacent Afar Plains), south and over the border into Kenya.

It separates the main plateau area which occupies the western half of Ethiopia from the plateaulands of the south west, and, in the central regions of the country, stands at around 1000 metres below the general level of the plateaus.

Major features of the Ethiopian landscape the therefore the lines of the great escarpments overlooking the Afar plains.

These converge in the latitude of Addis Ababa to produce the Rift Valley lakes region which is a major area of inland drainage. In addition, fault structures have produced escarpments along the western borderlands of Ethiopia.

Three smaller features, the through of the lower Omo river, the highlands of the Afar horst bordering the Red Sea, and the area of the Kobar sink (Afar Depression) which is around 110 metres below sea level, are also the result of faulting.

The earth movements which affected the continental block in the eastern African region were associated with widespread volcanic activity which produced thick deposits of hard plateau basalts.

These are responsible for the flat surfaces which are characteristic of many areas in the highlands. The Bale Mountain area, for example, is the largest area of land above 10,000 metres on the continent of Africa.

However, continuing volcanic activity resulted in the building up of higher mountain areas which now dominate the plateau surface several regions, the most notable being the Simen Mountain Massif which rises to 4620 metres above sea level in Ras Dejen.

Other examples are Abuye Meda (4000 metres) which dominates the eastern escarpment area, Mt. Chilalo (4139 metres) in Arsi, Mt. Batu (4307 metres) in the Bale mountain region, Tulu Welel (3302 metres) in Western Welega Region, and Mt. Guge (4200 metres) in north eastern Gamo Gofa Region. Volcanic mountain structures are also found on the fringes and on the floor of the Rift Valley system. Examples are Mt. Wechecha (3385 metres), Mt. Ziquala (2989 metres) and Mt. Chubbe (2592 metres) in the Lakes Rift region.

The Pluvial Periods in Africa, (comparable with the Ice Ages of more northern latitudes), were responsible for the further shaping of the Ethiopian landscape, and produced the deep gorges which have dissected the high plateau lands.

The central regions of Ethiopia are most characteristic of this plateau and gorge landscape where river beds are often 2000 metres below the general level of the plateau surface, and where the hard surface basalts have resulted in abrupt edges to the gorges, overlooking a series of lower terraces which mark the underlying layers of softer sedimentaries.

The most well-known and the largest of these features is the gorge of the Abay (Blue Nile) river.

In general, the inclinations produced by uplift have resulted in the development of river systems which drain the highlands towards the north-west and the south-east, with closed river basins associated with the Rift Valley system between these two.

Ethiopia’s relief thus contributes to drainage towards both the Mediterranean Sea and Indian Ocean.

Limited area in Ethiopia lie below the 500 metre contour line. These are to be found adjacent to the Red Sea (including the area which has sunk below sea level); in the eastern and south-eastern extremities of the Ogaden area and Bale region, including the middle section of the Wabe Shebele valley and in the Gambela panhandle in western Ethiopia where the courses of the Baro and Akobo rivers enclose a section of the Sudan plains.

The Ethiopian relief includes therefore a range of altitudes stretching from below sea level to nearly 4600 metres above sea level, although, within these latitudes, this is not sufficiently high to bring the landscape within a permanent snow line as is the case in eastern Africa to the south. Within these extremes, about 50% of the land surface is above the 1500 metre contour line.

Traditional descriptions of the landscape (which are also associated with the broader classification into ecological zones) define:

(a) Woorch (the coldest highlands above 3500 metres)
(b) Dega (the cool highlands above 2500 metres)
(c) Woyna-Dega (warm lands between 1500 and 2500 metres)
(d) Kolla (the hot and relatively low lying lands below 1500 metres)
(e) Haroor (the hottest lowlands below 500 metres)

(Source: National Atlas 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.

The lower Omo and Kibish basin are south of the Maji and Korma highlands on the northern shore of the Lake Rudolf. Much of this area is swampland where the Omo river enters this lake.

(Source: National Atlas of 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)

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)

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.

The highest peaks in the country are in Gonder Region. Ras Dejen (4,620 metres) is an example. 44% of the high peaks of over 4,000 metres are found in this region.

The Afar Hills are limited in area and altitude but form a different region because they are at a higher altitude than the adjacent Afar lowlands.

This range of mountains is an isolated region stretching from the Gulf of Zula to the northern part of Djibouti Republic. The Afar Hills have steep sides and deep valleys and some volcanic peaks rise to an elevation of about 2,500 metres.

Among the significant lowland area are the central lowlands of the Rift Valley and outer lowlands surrounding the highlands.

(Source: National Atlas of Ethiopia)

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.

Gorges are found along the upper courses of the big rivers such as the Tekeze, Abay (Blue Nile), Omo, Wabe Shebele, which flow in deep canyons but widen out to broad and shallow valleys in their lower courses.

On the Addis Abeba-Debre Markos all-weather road at the Abay bridge, the bed of the Abay River is 1,500 metres below the general level of the plateau.

The general area of the central lava highlands and massifs consists of the Gonder, Welo, Gojam highlands, Shewa plateaus, some higher parts of Welega, and parts of Gamo Gofa and Ilubabor Administrative Regions.

The North Central Massifs (Gonder, Gojam and Welo) generally have a rugged surface with high elevation.

They include basins such as the Tana depression. The Shewa plateaus are dissected on almost all sides and form the watersheds of the Abay, the Awash and the Gibe drainage systems.

The South Western Plateaus (Gamo Gofa, Illubabor and Welega) receive the heaviest rainfall in Ethiopia, and are, as a result, very much dissected by the Gibe, and Baro rivers and the tributaries of the Abay river (Didessa, Dabus, Guder and Anger).

(Source: National Atlas of Ethiopia)

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.

Since the country is located within the tropics, the physical conditions and variations in altitude have resulted in a great diversity of climate, soil and vegetation.

The Great Rift Valley separates the Western Highlands and the South Eastern Highlands, and the highlands on each side give way to vast semi-arid lowland areas in the east and west and especially in the south of the country.

 (Source: National Atlas of Ethiopia)

In this generalized soils record only the dominant soil types are indicated. The area percentages given for each soil unit are the percentage of occurrence of the soil type over the country as dominant soil, as well as in association with other soil types.

The nomenclature used is the FAO/UNESCO legend for the soil map of the world 1966 E.C (1974).

A. Orithic Acrisols (4.5 %)
These soils have a distinct argillic B horizon and a low base saturation. The topsoil can have a coarse texture.

Orthic Acrisols occur mainly on sloping terrain. They have limited agricultural potential. The soils are chemically poor; the contents of weatherable minerals is generally low; the PH is less than 5.5. and available P contents are very low.

Physically these soils have few limitations. The rooting depth might be limited by the argillic B horizon, or by rock at shallow depth.

The moisture storage capacity is, depending on the depth of the soil, moderate to good. Only when the topsoil is very sandy do tillage operations create problems like compaction or erosion.

Be. Chromic, Eutric and Calcic Cambisols (7.5%)
These soils have a cambic B horizon and a base saturation of 50 per cent or more. Chromic Cambisols have a strong brown or red colour.

Those with a calcic horizon or with lime accumulation are Calcic Cambisols. The latter mainly occur in limestone areas with limited precipitation.

Most Cambisols have little agricultural value, as they occur dominantly on slopes, are often shallow of have many stones or rock outcrops. Where Cambisols are deep and not stony they are good for agriculture.

Bh. Dystric and Humic Cambisols (2%)
These soils have a low base saturation and a cambic B horizon (Dystric Cambisols) or a deep umbric A horizon. The latter are Humic Cambisols. They mainly occur at high altitude. Dystric Cambisols are found on steep slopes in high rainfall areas.

Their agricultural value is limited, as they occur on slopes, they are shallow and have many stones or rock outcrops.

Bv. Vertic Cambisols and Vertic Luvisols (3%)
These soils are Cambisols and Luvisols with vertic properties. As the Vertisols, these vertic soils have fairly good, but limited agricultural potentialities. Land preparation is difficult, dry soils are hard and wet soils are sticky.

Only during a short period is the moisture condition of the topsoil favourable for tillage practices. Chemically these soils have no limitations.

H. Rendzinas, Haplic and Luvic Phaeozems (4%)
These are soils with a mollic A horizon. Rendzinas and Haplic Phaeozems mainly occur in the highlands, where soil depth is often limited by hard rock at shallow depth.

Rendzinas have only a mollic A horizion resting directly on calcareous rock.
Their agricultural value is limited, because generally they occur on steep slopes, rooting depth is small and there are many stones and rock outcrops. when they are deeper, they are suitable for agriculture.

Luvic Phaeozems have an argillic B horizon. They occur in the Rift Valley. As most of them are sodic, their agricultural value is limited.

I. Lithosols (17%)
These soils are less than 10 cm thick, developed over hard rock. They occur on steep slopes and in area with very limited precipitation. These soils have no agricultural potential.

J. Calcaric and Eutric Flovisols (8.5%)
Fluvisols are young soils developed in recent alluvial deposits of river plains, deltas, former lakes and coastal areas.

Soil conditions are highly variable. In arid regions many soils are saline. Fluvisols with calcareous material are Calcaric Fluvisols, those which are non-calcareous, having a base saturation of 50 per cent or more, are Eutric Fluvisols.

Fluvisols are generally good agricultural soils and often intensively used, although land use has to be adapted to floods, inundations or high groundwater.

L. Chromic and Orthic Luvisols (5%)
Luvisols are soils with an argillic B horizion and a base saturation of 50 per cent or more. Those with a strong brown or red B horizon are Chromic Luvisols.

Most Luvisols have good agricultural potentialities. Base saturation is high and they have weatherable minerals. In soils with a heavy textured B horizon, permeability might be low, and drainage and good root distribution can be hindered.

Nd. Dystric Nitosols (7.5%)
Nitosols are deep, clayey red soils with an argillic B horizon. Dystric Nitosols have a base saturation of less than 50 per cent. They are found on almost flat to sloping terrain in high rainfall areas.

They have rather good potentialities for agriculture. These soils have very good physical properties. They have a uniform profile, are porous, have a stable structure and a deep rooting volume. Their moisture storage capacity is high.

Chemically these soils have some restrictions. The base saturation is rather low, PH’s are less than 5.5 and available P contents are low.

Ne. Eutric Nitosols (5%)
Eutric Nitosols are Nitosols with a base saturation of 50 per cent or more. They are found on almost flat to sloping terrain in the highlands.

They are among the best agricultural soils. Their physical properties are similar to those of the Dystric Nitosols. Chemically these soils are better, although available p contents are low.

Q. Calcic Arenosols (5%)
These are coarse-textured soils. The sub-soil has the characteristics of a cambic B horizon, but does not classify as such, because the soil texture is too coarse. Arenosols are developed on sandstone.

Arenosols have very limited agricultural potentialities. They have a low water retention, are very permeable, have a low natural fertility and a low CEC. Rooting depth is often restricted by limited soil depth.

R. Calcaric and Eutric Regosols (11%)
Regosols are soils without profile development, consisting of loose, non-alluvial soil material.

They occur in areas with little precipitation; or on steep slopes subject to severe erosion. Those with lime accumulation are Calcaric Regosols. Eutric Regosols have a base saturation of 50 per cent or more.

They have limited agricultural value, especially where soil depth is limited. Water retention in Regosols is low.

T. Humic, Mollic and Vitric Andosols (1%)
Andosols occur in volcanic regions. They are formed in volcanic ash material. The ash material being very light, their bulk density is less than .85 g/cm3. Vitric Andosols have more than 60 per cent volcanic glass, they occur in rather arid zones.

Mollic Andosols have a mollic A horizon, Humic Andosols have an umbric A horizon. The latter mainly occur in cool and humid regions, at altitudes.

Most Andosols are good for agriculture. They can absorb much water and are very porous. The CEC is high (35-70/me/100gr soil) and the organic matter content is often high. Some Andosols, especially in the rift valley, have a high sodium content and thus a limited agricultural value.

V. Chromic and Pellic Vertisols (10%)
These are heavy clay soils in flat areas, having a pronounced dry season during which they shrink and have deep cracks in a polygonal pattern.

During the wet season the clay swells and causes pressure in the sub-soil. Pellic Vertisols are dark, usually occupying areas which are water-logged during the rainy season. Chromic Vertisols are brownish and better drained.

Vertisols have fairly good, but limited agricultural potentialities. Land preparation is difficult, dry soils are hard and wet soils are sticky. The moisture condition of the surface layer is only during a short period favourable to prepare land.

Another difficulty is that the permeability of the subsoil is very low. Very often these soils are flooded or have stagnant water during the rainy season.

The soil has a high water retention, but relatively a small amount of water is available for plant growth. Rooting depth might be restricted because of the swelling and shrinking properties of the soil.

Chemically these soils are good. The CEC is very high (often over 70 me/100g soil) and the base saturation is over 50 per cent, mainly with Ca+++ and Mg++ ions.

Free CaCo3 is often present as nodules in the profile. When precipitation is limited, salinity problems might occur. Because of the low permeability and the difficult drainability of the subsoil, it is very difficult to improve such soils.

X. Haplic, Calcic and Luvic Xerosols (5%)
Xerosols are soils in arid and semi-arid regions, with a weakly developed A horizon. Those with an argillic B horizion, mostly at shallow depth, are Luvic xerosols.

Those without a calcic horizon are Haplic Xerosols, those with a calcic horizon are Calcic Xerosols.

The calcic horizon may harden, forming a petrocalcic horizon.
The agricultural value of Xerosols is low, except when they can be irrigated and when physical properties are good for irrigated crops.

Y. Gypsic Yermosols (3%)
The moisture regime of these soils is aridic and they have a weakly developed ochric A horizon.

They consist of highly gypsiferious parent material, and have a gypsic horizon. The gypsic horizon may harden, forming a petrogypasic horizon.
Gypsic Yermosols are not suitable for agriculture in irrigation projects.

Z. Gleyic and Orthic Solonchaks (4.5%)
Solonchaks are highly saline soils containing soluble salts that influence plant growth. These are poor soils because most plants cannot grow at all.

Most solonchaks are Orthic Solonchaks. If they have hydromorphic properties within the first 50 cm, they are called Gleyic Solonchaks.

In saline soils that have a moderate to rapid permeability to a depth of at least 3 m, and that can be drained, the harmful soluble salts can be washed out, and carried away, in drain water. When this is completed, soils may have agricultural potential, although it is necessary to take care that salts do not accumulate in the rooting zone again.

(Source: National Atlas of Ethiopia)

The basement upon which all younger formations were deposited contains the oldest rocks in the country, the Precambrian, with ages of over 600 million years.

They are exposed in areas where the younger cover rocks have been eroded away; namely, in parts of Harerge, Sidamo, Bale, Ilubabor, Gojam, Welega, Gonder, and Tigray Administrative Regions.

The Precambrian contains a wide variety of sedimentary, volcanic and intrusive rocks which have been metamorphosed to varying degrees.

The basement in the south and west of the country, where granitic rocks and gneisses predominate, has been more strongly metamorphosed than Preecambrian sequences in the north.

Though in many cases strongly folded and foliated, the rocks in the north, which include the youngest formations yet known in the Precambrina, have generally undergone only weak metamorphism, reflecting the relatively low temperatures to which they have been subjected since their deposition.

The Precambrian or basement rocks contain most of the presently known metallic deposits of Ethiopia. In particular, the gold deposits of the northern, western and southern regions all occur in these rocks, where they are associated with fractured quartz reefs or sulphides.

Under favourable conditions, these deposits have given rise to major placer deposits along river beds, as in the Kibre Mengist (Adola) area.

Copper, zinc and lead sulphides have been found in the weakly metamorphosed volcanic facies (greenschists) of these old rocks. Similarly occurrences of potentially exploitable talc and nickel deposits are associated with ultrabasic bodies, and it is in a layered body of this type that platinum mineralisation occurs at Yubdo in Welega Administrative Region.

There are considerable possibilities of finding other economically exploitable deposits of these minerals in the Precambrian series, while major intrusions and dykes contain good potential for other minerals.

Most of these Precambrian rocks are relatively impermeable, and have been subjected to several orogenic episodes since their formation.

These processes, combined with the rifting associated with the development of the Red Sea and the East African-Ethiopian Rift Valley, have resulted in considerable fracturing and shattering. Major water resources are associated with these fracture zones.

At the end of Precambrian times uplift occurred; this being followed by a long period of erosion. Any sediments which were deposited during Palaeozoic interval, which lasted some 375 million years, have been largely removed by erosion.

Some, shales and deposits of glacial origin, were laid down in northern Ethiopia during this period.

Subsidence occurred in the Mesozoic which began some 225 million years ago, and a shallow sea spread initially over the Ogaden and then extended further north and west as the land continued to subside.

New sandstone was deposited on the old land surface. Deposition of mudstone and limestone followed as the depth of water increased. The subdivision of the Mesozoic sequence and younger sediments on the map into approximate age categories is largely based on palaeontological evidence.

In the west of the country, sedimentation ended with the deposition of clay, silt, sand, and conglomerate brought in from the land as the sea receded due to uplift of the land mass. In the southeast, gypsum and anhydrite were precipitated on inter-tidal flats.

In the Ogaden there was a fresh invasion of the sea in late Mesozoic times during which the sequence of sedimentation was repeated, ending again with the precipitation of gypsum and anhydrite.

The same cycle of sedimentation was reported yet again in the Ogaden during the Teritary period. It ended with the deposition of conglomerates.

Mesozoic rocks are considered to have the greatest potential for oil and gas deposits. The presence of such deposits is dependent on the original existence of organic materials mostly of marine origin in sediments which were buried to form the so-called source beds.

In these beds, which may now be represented by shales or stromatoloid reef limestones, the organic material was altered by the pressure of the overlaying sediments and a build-up of heat into oil and gas which migrated into nearby permeable (reservoir) rocks.

The Mesozoic of southern Ethiopia contains few favourable structures for oil, beign only weakly folded; nevertheless, there remains a reasonable possibility of the occurrence of stratigraphic traps.

Outcrops of the Mesozoic in the north and west are considered as less favourable, due to the possible terrestrial nature of the rocks in the north and the probable thinness of the rocks in the west.

The mp emphasizes the necessity for additional studies in these areas.
Metallic minerals have not be discovered to date in the Mesozoic rocks but the occurrences of limestones and saline deposits shown on the map point to the need to prospect these formations further for lead, zinc and silver ores.

Rocks of this age also represent major reserves of glass sands, cement limestones and other industrial minerals.

Extensive fracturing occurred in the early Cenozoic (this interval started 65 million years ago), although major displacement along the fault systems of the Red Sea, Gulf of Aden and East African Rifts did not occur until later in the Teritary.

Faulting was accompanied by widespread volcanic activity which led to the formation of vast quantities of basalt lava over the western half of the country.

This was accompanied by, and alternated with, the eruption of large amounts of ash and coarser fragmental material, forming the Trap Series. Several shield volcanoes, also consisting of alkali basalts and fragmental material, then developed around the eastern edge of the Lake Tana depression and southwest of Goba.

More recent volcanism is associated with the development of the Rift Valley, activity being concentrated within this structure and along the edges of the adjoining plateaux.
Volcanism has persisted to the present in the Afar region conglomerate, sand, clay, and reef limestone which accumulated in the Afar Depression and at the northern which accumulated in the Afar Depression and at the northern and of the main Rift Valley.

Sediments which accumulated in former lakes occur at the south end of the Afar, in the main Rift Valley and in the Omo valley. Undifferentiated Quaternary sediments and superficial deposits occur intermittently along the Sudanese and Kenyan borders.

Oil and gas deposits may be present in some of the Teritary deposits but in general the rocks of Cenozoic age in Ethiopia are of potential economic importance because of their extremely large salt deposits.

These include not only the common rock salt traditionally worked in the Afar region but also deposits of potassium and magnesium salts.

Furthermore, the geothermal activity associated with the many Cenozoic deposits has given rise to metallic mineral occurrences-copper and manganese in particular, concentrated as a result of leaching of the rocks by saline solutions.

Iron ores, and possibly even aluminium ores (bauxite), developed on the volcanics as a result of intense weathering and may prove to be of economic interest
The underground water resources of the Cenozoic are of great importance.

The often lenticular nature of the beds necessitates detailed investigation but, given suitable recharge areas, the deposits can be considered as highly favourable for water exploitation.

(Source: National Atlas of Ethiopia)

The Entoto Mountains (also called the Entoto Hills) lie north of Addis Ababa (capital of Ethiopia), in the Oromia Region.

Mount Entoto is part of the Entoto mountain chain, reaching 3,200 meters above sea level.

It is also a historical place where Menelik II dwelled and established his palace, when he came from Ankober and founded Addis Ababa. Established on these remarkable peaks, Addis Ababa is the highest capital in Africa. It is considered a sacred location and holds many monasteries.

They are known for their views over the capital, and are the location for Addis Ababa’s immediate predecessor as capital.

These mountains are home to:

• numerous churches,
• a museum of religious costume, and
• a park

Keywords: Entoto Mountains, churches,

In Ethiopia, the most widespread mountain ranges on the highlands are the Simiens, which lie straight north of Gonder and mount to the fourth highest peak in Africa, Ras Dashen (also known as Ras Dejen), whose height is usually given as 4,620m.

Combined with a visit to Ras Dashen:

• The castles and churches of the ancient capital of Gondar
• The rock carved churches of Lalibela
• The island monasteries on Lake Tana

During the rainy season crops grow well on the rich volcanic soils of the highland plateau but roads are very muddy. From September to June the weather is much drier and so the recommended time to visit Ethiopia is most likely between September and Christmas.

The Simien Mountains are really the edge of a huge volcanic plateau and dramatic cliffs drop down to the hot lowland plains to the north. Infrequent volcanic plugs rise out of the plains and provide a challenge to climbers..

A part of the Simien Mountains has been designated a National Park and within this area the remnants of the once magnificent Afro-Alpine moorlands are being protected from the further infringement of cultivation. High altitude vegetation such as:

• the remain fine stands of groundsels
• ericas
• lobelias and other high altitude vegetation are grown in the area

 Bird life is very rich and there are also quite good chances of seeing:

• the rare Walia Ibex and
• the Simien Fox as well as
• the Gelada Baboons

Keywords: Gonder, Ras Dejen, Ras Dashen, Lalibela, Tana, Walia Ibex, Gelada Baboons,

The Bale Mountains (they are also known as the Urgoma Mountains) are a range of mountains in the Oromia Region of southeast Ethiopia, south of the Awash River.

The Bale Mountains comprise:
• Tullu Demtu, the second-highest mountain in Ethiopia (4377 meters), and
• Mount Batu (4307 meters)
• The Web River, a tributary of the Jubba River, rises in these mountains east of Goba
• The Bale National Park covers 2,200 square kilometers of these mountains

Many Ethiopia’s endemic animals shelter in The Bale Mountains. These include:

• The Ethiopian Wolf, found on the Sanetti Plateau, which is the highest moorland in Africa.
• The Harenna Forest, situated to the south of the mountains which is a largely unexplored area thought to contain many undiscovered species of reptile as well as lion, leopard and various types of antelope.

In addition to wildlife the Bale Mountains National Park offers exceptional trekking opportunities from the park headquarters at Dinsho.

Dodola is a useful base for traveling around these mountains. Dodola is the gateway to the Bale Mountains, one of Ethiopia’s most important attractions in the south-east of the country.

The mountain trekking destination of Dodola has been developed only recently. Tour guide books have not yet started referring to it.

Think about it as a genuine ‘insider’ tip-off. Whether you are operating tours in Ethiopia or traveling on your own, including Dodola in your program is highly recommended.

Expand your image of Ethiopia further than the historic northern route and the southern tribes diversification.  Complete your impressions on Ethiopia with a exclusive experience of great mountain forests, perfect streams, etc.

Keywords: Tullu Demtu, Mount Batu, Web River, Jubba River, Goba, Bale National Park, Sanetti Plateau, Harenna Forest, Dinsho, mountain trekking,

For many Ethiopia is seen as dry and sandy land. But in contradiction this country is full of wonderful mountains of which one is Ras Dashen (alternatively Ras Dashan or Ras Dejen). It’s the highest mountain in Ethiopia.

The widely-quoted elevation of 4,620 metres is inconsistent. A more recent DGPS Franco-Italian survey measured a slightly higher elevation of 4,549 metres, which agrees more closely with the most recent elevation supplied by the Ethiopian mapping authority.
Ras Dashen is the highest mountain in Ethiopia, and the highest of the Simien range, a group of eroded mountains that rises gorgeously from the surrounding 9,000 foot plateau in northern Ethiopia.

Despite the overall high elevation of Ethiopia, the Simien range is the only place in the country that is regularly snow-covered in Winter.

Though there are no active volcanoes today, the mountains are composed of basalt volcanic rock.

In the midst of the Simien range, Ras Dashen is a cluster of nine rocky peaks. The mountain trails of the Simien Range are dotted with many small agricultural villages.

Keywords: Ras Dashen,

The most extensive mountain ranges on the highlands are the Simien Mountains, which lie directly north of Gonder and rise to the fourth highest peak in Africa, situated about 100km north of Gonder to the east side of the Axum road.  The Simien Mountains is one of Africa’s largest rages, studded with at least a dozen peaks topping the 4,000m mark. Other notable heights include: • Mounts Biuat (4,437 m) and
• Abba Yared (4,460 m) These comprise Ras Dashen (also spelt Ras Dejen), the highest point in Ethiopia and the fourth highest peak in Africa. The western side of the range, excluding Ras Dashen, was designated as the Simien Mountains National Park in 1969, and the entire range was listed as a UNESCO World Heritage Site in 1979. The major attractions here are spectacular scenery. Besides, you will have the opportunity to see three of Ethiopia’s four endemic large mammal species in the area: • The Walia Ibex,
• Gelada Baboons and
• A few Ethiopian wolves
.
The Semiens are remarkable as being one of the few spots in Africa where snow recurrently falls.Despite their ruggedness and altitude, the mountains are scattered with villages linked by tracks.

 Historically populated by Ethiopian Jews (they are also called ‘Beta Israel’ meaning the House of Israel), who after frequent attacks by the zealous Christian Emperors in the 15th century pulled out from the province of Dembiya into the more defensible Semien mountains. First talked about in the Monumentum Adulitanum of the 4th century AD (which portrayed them as “inaccessible mountains covered with snow” and where soldiers walked up to their knees in snow) The occurrence of snow was indisputably witnessed by the 17th century Jesuit priest Jerónimo Lobo. Although the later traveler James Bruce claims that he had never seen snow in the Semien Mountains, the 19th century explorer Henry Salt not only documented that he saw snow there (on 9 April 1814), but gave details the reason for Bruce’s failure to see snow in these mountains — Bruce had ventured no further than the foothills into the Semiens. The area is access is by foot or mule. It would be unrealistic to set aside fewer than four days to see the Simiens (including travel to or from Gonder); six days – or even longer – would be betterAlthough the ideal way to explore the Simien Mountains is over several days hiking or trekking, the new road into the national park makes a full-day trip from Gonder a realistic and more and more popular tour. A more inexpensive alternative is the half-day trip to Kosoye viewpoint 32km from town along the Simien road.

Keywords: Gonder, Simien Mountains, Axum road, gelada baboon, Walia ibex, Ras Dejen,