[3] It covers an area of some 40,000 km2 (15,000 sq mi)[citation needed] in the modern-day Syrian Arab Republic, Jordan, and Saudi Arabia.

[9] Activity began during the Miocene; an earlier eruptive stage at the southeastern end of the volcanic field, occurred during the late Pleistocene and the Holocene.

[12][13] The Jabal al-Druze, al-Safa and Dirat al-Tulul volcanic fields, among others, form the northern and Syrian part of the ḥarra.

The Saudi Arabian portion of the Harrat Ash Shamah volcanic field extends across a 210 km (130 miles)-long, roughly 75 km (47 miles)-wide northwest-southeast-trending area on the northeastern flanks of the Wadi Sirhan and reaches its 1,100 metres (3,600 ft) high point at Jabal al-Amud.

[17] Although the region as a whole is too dry for rainfed agriculture, seasonal wetlands such as the Qa' Shubayqa are used for growing cereals after they are flooded by winter rains.