Volcanic Structures and Eruptive Styles
- Some volcanoes are only 30 meters high and formed during a single eruptive phase that may have lasted only a few days.
- Volcanic landforms come in a wide variety of shapes and sizes, and each structure has a unique eruptive history.
- Volcanic activity usually begins when a crack develops in the crust as magma moves forcefully toward the surface.As the gas-rich magma moves up this linear fissure, its path is usually localized into a circular conduit or pipe, that terminates at a surface opening called a vent.
- Located at the summit of most volcanoes is a somewhat funnel-shaped depression called a crater.
- Gases that come from the vents of a volcanoes are called fumaroles.
- Shield volcanoes are produced by the accumulation of fluid basaltic lavas and exhibit the shape of a broad, slightly domed structure that resembles a warrior's shield.
- Scoria cones are built from ejected lava fragments that take on the appearance of cinders or clinkers as they begin to harden while in flight.
- Cinder cones are the most abundant of the three major types of volcanoes.
- Earth's most picturesque yet potentially dangerous volcanoes are composite cones or stratovolcanoes.
- A conical shape, with a steep summit area and more gradually sloping flanks, is typical of many large composite cones.