The volcano contains a 0.7 x 1.6 km elliptical summit crater

The volcano contains a 0.7 x 1.6 km elliptical summit crater with several steep-sided pit craters, one of them containing a lava lake. Another larger 1.8 x 3.1 km wide depression, elongated parallel to the trend of the Erta Ale range is located to the SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the northern flank of Erta Ale.