[1][2] The name was coined by geologist William Thomas Blanford, who accompanied the British Expedition to Abyssinia in 1868,[3] after the Imba Alaje mountain.

Locally they are covered by Pliocene shield volcanoes, such as the Simien Mountains, or Mount Guna.

These flows have been deposited on the lower Ashangi Basalts and locally on intra-volcanic sedimentary rock.

Like all volcanic rocks, the Alaji Basalts originate from initial melting of the Earth's mantle.

In the mineralogy of the trachytes one notices especially the by twinning of feldspar minerals and a small amount of altered pyroxenes.