VOLCANOES How they work

WHAT IS A VOLCANO? A mountain or hill having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from earth’s crust. If there is a weak spot in the crust the magma will up into these openings, and will form a large pocket of melted rock, called a magma chamber.

PARTS OF A VOLCANO The crater is the bowl shaped indent where the vent is located. The pipe is a passageway in the volcano in which the magma rises through to the surface during an eruption. The vent is an opening at the Earth’s surface.

HOW ARE VOLCANOES FORMED? Volcanoes are formed when magma from within the Earth's upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger. The lower part of the Earth’s crust and the upper part of the mantle begin to melt, forming magma. This magma is not as dense as the rock surrounding it, so it rises. When the magma reaches the surface it is called lava, and the lava forms a volcanic mountain or plateau.

DIFFERENT TYPES Cinder Cones are circular or oval cones made up of small fragments of lava from a single vent that have been blow in into the air, cooled and fallen around the vent. Composite are steep sided volcanoes composed of many layers of volcanic rocks, usually made from high viscosity lava, ash, and rock debris Shield volcanoes are shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows. Lava domes are formed when erupting lava is too thick to flow and makes a steep sided mound as the lava piles up near the volcanic vent.

CINDER CONE

COMPOSITE VOLCANO

SHIELD VOLCANO This is a picture of Mauna Loa in Hawaii, which is the largest volcano on earth.

LAVA DOME

ERUPTION