The field is a low-relief expanse of volcanic rocks occasionally interrupted by volcanic cones which covers an area of -, making it the largest of the basaltic volcanic fields of Northern Africa. Its eruption products reach a thickness of in the central sector in the form of stacked lava flows, the total volume of volcanic rocks has been estimated to be about . The Al Haruj al Aswad (Black mountain) field in the northern part of Haruj and Al Haruj al Abyad (White mountain) south are considered to be subdivisions of the main Haruj volcanic field with Aswad covering a much larger surface than Abyad, or even two separate volcanoes that started overlapping each other during the Pliocene.