So-called effusive volcanoes, like Puy de la Vache in Auvergne, form following the convergence or separation of two tectonic plates. These phenomenons allow magma to rise through cracks in the earth's crust. Inside volcanoes, the lava is stored in a magma chamber before going up the chimney and out through the crater. When erupting, the volcanoes emit fluid lava and project volcanic rocks. The projections of effusive volcanoes are less violent and lava less viscous and gaseous than in the explosive volcanoes.