Volcanoes

The lava of volcanoes is molten rock, called magma. Some magma rises straight from the earth’s mantle to the surface. Some is stored in a magma chamber in the crust, where the gases collect and help to drive the magma out. The upper part of the mantle, under the earth’s crust, is nearly molten. Magma contains several gases, and bubbles of this expand near the surface and drive the magma out as an eruption. Volcanic eruptions vary from place to place, mainly according to how fluid or gaseous the lava is. The highest active volcanoes on land are in the Andes, in South America. The highest of these is Ojos Del salada, which is 6885 meters high. But even larger volcanoes rise from the floor of the Pacific Ocean and form the islands of Hawaii. Mauna Loa, on Hawaii, is probably the largest active volcano in the world. It rises 4170 meters above sea level, but its base is 5180 meters below sea level. This base is roughly oval in shape: 119 kilometers long and 85 kilometers across. The lava from Hawaiian volcanoes is very liquid and flows for long distances. Mauna Loa erupts about every 3.5 years. The near by Kilauea crater, south- east of the main volcano, is filled with red-hot lava.