Volcanism is caused by magma, which either rises directly to the earth's surface from the upper regions of the earth's mantle or, in the majority of cases, gathers in a magma chamber, several tens of kilometres deep, at the base of the earth's crust, from which magma rises at irregular intervals and causes volcanic eruptions. Volcanism in the Eifel is thought to be partly caused by the Eifel hotspot, a place where hot material from deep in the mantle rises to the surface, and partly by melt-ascent at deep fractures in the Earth's crust. Research has shown that the volcanism is still active; the Eifel region is rising by 1-2 mm per year and there are escaping gases, for example, carbon dioxide (CO2) in the Laacher See.