Pumice is a highly vesicular rock produced in explosive volcanic eruptions. Central America is geologically active with volcanic eruptions and earthquakes occurring from time to time. Pillow basalt is also produced by some subglacial volcanic eruptions. Their subterranean movements were said to be the cause of volcanic eruptions and earthquakes. The area contains numerous large volcanic eruptions. El Salvador has a long history of destructive earthquakes and volcanic eruptions. The mountains formed from the remains of the magma chambers which fed volcanic eruptions. These spots are thought to represent lava freshly released by volcanic eruptions. Volcanoes are the primary landforms built by repeated eruptions of lava and ash over time. The gas phase is extremely important in propelling volcanic eruptions. The VEI itself is inadequate for describing the atmospheric effects of volcanic eruptions. Associated with these eruptions were pyroclastic flows. It has been the site of some of the youngest volcanic eruptions in Canada. The lunar maria represent ancient flood basaltic eruptions. The lava emitted in eruptions at Nyiragongo is often unusually fluid.