Mt. St. Helens is in the Cascade Range. A central vent is a main tube or passageway that magma travels on its way from the magma chamber to the opening of a volcano. A cinder cone is a volcano that is made of only pyroclastic debris. A cone is a hill of lava or pyroclastic debris that develops around a vent. A dike is a table of igneous rock that cuts across other rock.
Igneous rock is rock that cooled and became solid beneath the surface of the earth.
A volcanic dome is a mound that is created when very thick magma is squeezed out of a volcano and forms a dome above and around the vent. A dormant volcano was active in the historical past but is not currently active. A dormant volcano may become active again sometime in the future. A quick movement or shaking of the earth caused by the release of stress or strain on rocks. An earthquake swarm is a bunch of small earthquakes which may precede a volcanic eruption.