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
Ice-marginal lava flow activity and erosion. In the late 1800s, a debris flow from the Barrier created a large boulder field which gave Rubble Creek its name. Conditions are so bad that the area directly below the lava damn is considered uninhabitable and dangerous to human life. Hoodoo Mountain A second example of ice-marginal lava flows can again be found in British Columbia, this time near the border of Alaska. The Hoodoo Mountain Volcano is located in Northwestern British Columbia The volcano formed underneath a glacier, making it a subglacial formation. The Hoodoo Mountain Volcano is a flat-topped stratovolcano as a result of