Aloes and Lilies of Ethiopia and Eritrea

INTRODUCTION
mountain scenery around the edges of the plateau, such as
the Semien Mountains with its dramatic jagged pinnacles,
precipices and gorges. The faulting was followed by, and
alternated with, the eruption of large amounts of ash and
coarser material, forming the Trap Series.
Ethiopia’s largest lake, Lake Tana, is the result of the
damming of a large natural drainage area on the western
plateau. The Blue Nile disgorges from the Lake and
has carved a deep, steep­sided gorge as it runs in an arc
around the eastern and southern sides of the lake. The Tis
Isat Falls close to the lake are where the Blue Nile runs
over the edge of an ancient lava flow.
More recent volcanic activity is associated with
the development of the Rift Valley, activity being
concentrated within the Rift and along the edges of the
adjoining plateaux and also in the Danikil Depression.
Plugs of old volcanoes are seen throughout the highlands.
Hot springs are frequent in many areas and earth tremors
are not uncommon. The recent sediments (conglomerate,
sand, clay, and reef limestone) which accumulated in the
Afar Depression and at the northern end of the main Rift
Valley are of Quaternary age.
Geography
Ethiopia is located between 3° and 15°N and 33° and
48°E. It is a large (1.12 million km²) and highly diverse
country. It is a country of dramatic contrasts, with Ras
Dashen (Dejen) in the Semien mountains reaching to
about 4620 m to the Afar Depression in the Danikil
Desert sinking to 115 m below sea level. Some parts
the highlands are dissected and form sharp peaks on the
horizon, giving the impression, as one observer remarked,
of “a country with a table upside­down" (Fig. 1).
Although much of the interior consists of highland
plateaux, these are interrupted by deep gorges and valleys
formed by the large rivers and their tributaries such as the
Abay (Blue Nile), Tekeze, Mereb, Awash, Omo, Genale,
Wabishebelle and Baro. The African Rift Valley divides
the country in two: the north­western highlands on one
side and the south­eastern highlands on the other. Both
these highland systems gradually decrease in elevation
to form vast arid or semi­arid lowlands in the east, west,
and southern parts of the country. The Rift Valley is itself
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