e Pacific Ring of Fire. Type of volcanoes. Not all volcanoes are the same shape even though they all begin as a crack or hole in the ground. As the volcanoes erupt, lava and ash build up forming the cone of the volcano. If running lava from the volcano forms a gently sloping shape it is called a shield volcano. This lava can flow for many miles before it becomes cold. The eruption from this type of volcano is not very violent. If the lava is sticky and hardens quickly, the volcano will have steep sides. This is a composite cone or stratovolcano. MSH is a stratovolcano. This type of eruption is the most violent. Stratovolcanoes are the most common type on earth. They are composed of almost equal amounts of ash and thick lava flows. This layering of ash and lava gave it the name of strato. The magma is extremely powerful and can form steep slopes of up to 35 degrees. These volcanoes are not usually very big and occur along the subduction zone, mostly around the Pacific Ocean. Subduction is the process of one plate of the earth's crust moving under another plate. MSH is also called a composite volcano because it erupts both lava and ash. Dormant and Extinct Volcanoes If a volcano shows no signs of life for thousands of years it is thought to be extinct. If a volcano shows activity, even slight movement, it is dormant. Volcanoes that have violent eruptions between long periods of no activity are usually stratovolcanoes. Volcanoes that are inactive and not expected to erupt in the near future are called dormant volcanoes. Volcanoes that are never expected to erupt again are called extinct. All of the volcanoes in the Cascade Range where MSH is found are dormant volcanoes. Approximately 50 or so volcanoes erupt every year. The International Association of Volcanology defines active volcanoes as one that has erupted in historic times. Historic can mean 200 years in Hawaii or 3,000 years in the Mediterranean depending if there are historical re...
