Erta Ale is an isolated active basaltic shield volcano situated in the Afar Region of northeastern Ethiopia, a badlands desert area located at the border with Eritrea. Compared to other volcanoes, Erta Ale has a relatively low-elevation (613 m) because it is surrounded by an area below sea level, one of the most inhospitable on earth. It is well known for its two lava lakes at the summit which occasionally overflow and for being the longest-existing lava lake (of the five lava lakes in the world). In the local Afar language, Erta Ale means “smoking mountain” and its southernmost pit received an apocalyptic name, “the gateway to hell”. (a similar “gate” is located in Turkmenistan).
“Shield volcanoes form when rock deep in the Earth heats to its melting point and rises through conduits and fractures until it punches through the crust. Unlike explosive stratovolcanoes, like Mount St. Helens in Washington state, lava oozes out of shield volcanoes at a more lethargic pace.
Shield volcanoes are the biggest volcanoes on earth. They are short but wide with widths 20 times their heights. Their typical gradient is gentle at the bottom, near 2-3 degrees, with a steeper slope of 10 degrees near the top and they level out at the summit, producing the shield-like shape.” (via Physics Buzz)