Шаблон:Infobox rockunit
The Ashangi Basalts are the earliest Tertiaryvolcanic rocks in north Ethiopia, hence they are in the lowest position. These dark porphyriticbasalts are separated from the Mesozoic formations below it by basal conglomerates. The basalts hold phenocrysts that developed before the magma reached the earth surface. These basalts are weathered, partially eroded and have a sub-horizontal stratification, particularly at the lower part. This series was created during the first period of the flood basalt eruptions in north Ethiopia, in the Oligocene.[1][2][3]
These volcanic rocks formed through melting of Earth's mantle. After magma generation, lava flowed out over the surface, in successive flows. Some part of it disappeared within the next 1 to 3 million years due to weathering and erosion, while other parts remained present. Within the basalt, columnar joints occur as a result of cooling; they are visible along the flanks of the ridges. The columnar joints are perpendicular to the surface of the lava flows; they are mostly vertical, but may also be strongly inclined. The lower succession, the one that overlies the Amba Aradam Formation and the Adigrat Sandstone holds vertical and closely spaced columnar joints. A common characteristic of the columnar joints observed in the Ashangi Basalts is their pentagonal or hexagonal shape (in plan view).[2]
The Ashangi Basalts are made of coarse-grained plagioclase minerals, surrounded by a matrix of fine-grained plagioclases and pyroxenes; some iron oxides are also present.[2]
