Lava broad, shallow slopes formed from predominantly effusive eruptions of relatively fluid basaltic lava flows, to steeply-sided stratovolcanoes (also known as composite volcanoes) made of alternating layers of ash and more viscous lava flows typical of intermediate and felsic lavas. A caldera, which is a large subsidence crater, can form in a stratovolcano, if the magma chamber is partially or wholly emptied by large explosive eruptions; the summit cone no longer supports itself and thus collapses in on itself afterwards. Such features may include volcanic crater lakes and lava domes after the event. However, calderas can also form by non-explosive means
Hell's Half Acre Lava Field lava plain is located in Bingham and Bonneville counties in the state of Idaho. The site is about in size. The area where a former lava lake existed is marked by a long by wide depression near the summit of the lava field. Ten circular pits and two large lava tubes are also located near the summit. Two major lava flows, each about long by wide, extend from the main lava field to the south and southwest. These two lava flows surround "Morgans Pasture," a kipuka (or older geologic feature which was not covered by lava). More recently, scientists studying