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
Nisga'a Memorial Lava Bed Provincial Park legend that accounts for the lava as well as geological causes. The park has waterfalls, pools, cinder cones, tree moulds, lava tubes, spatter cones, a lava-dammed lake, caves and other features created by lava flows. The park aims to protect moose, goats, marmots, bears and many other species of wildlife. The park covers 178.93 square kilometres in area. It is believed to be the site of Canada's most recent volcanic eruption and lava flow, a geological disaster that killed an estimated 2,000 people. The source of the eruption was the Tseax Cone. Large lava flows dammed the Nass River and