There are about 450 recent volcanic centres, of which about 400 are lava domes and 50 small stratovolcanoes,[13] the latter of which include many recent cones[6] which are accompanied by lava flows whose length reaches 20 kilometres (12 mi).[14] Among the older volcanoes of Atakor are the peaks Assekrem and Tahat,[7] the latter of which is the highest summit in the Hoggar.[15] Some of these volcanoes have craters, including double craters, and others are eroded to the point that only volcanic necks remain,[16] while lava domes include shapes from steep pillars to short stubby lava flows[17] and are responsible for much of the field's scenery.[18] Some of these lava domes and necks penetrated older basaltic layers.[19] Among the stratovolcanoes is the Oued Temorte cone, which is 300 metres (980 ft) high, 800 metres (2,600 ft) wide and has erupted an over 10 kilometres (6.2 mi) long lava flow. It has also erupted volcanic ash, lapilli and slag.[20]