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Description of a Shield Volcano Eruption

The three major types of volcanoes are differentiated by their structure. The stratovolcanoes build up from the accumulation of thick viscous lava flows. Cinder cones develop from violent eruptions with monstrous explosions ejecting cinders and smoke high into the air before falling back to the earth in conelike formations around the volcano opening. Shield volcanoes build up slowly from layers of fluid basaltic lava that flows out of fissures in the earth. They become some of the largest volcanoes on the planet.

Hot Spots
- The Galapagos Islands also host shield volcanoes.
  
  The volcanoes of the Hawaii Islands and the Galapagos Islands are characteristic shield volcanoes that form over a hot spot or a tectonic plate boundary in the earth's mantle. Here, fissures in the earth's crust allow the magma to force its way up and out through the cracks. The lava flows out in all directions and gradually builds increasingly large circular deposits known as shield volcanoes.
Lava Tunnels
- Kilauea lava flows in Hawaii.
  
  Shield volcanoes build slowly, and one characteristic feature is that tunnels form within the existing lava layers. They provide interior channels for the lava flow so that it remains warm longer and travels to the existing edge of the shield lava where it breaks out and spreads the lava further. Magma is the molten material below the earth's crust. Once it reaches the surface of the earth as it boils out of the volcano, it is called lava. Its temperature ranges from 700 to 1,300 degrees Celsius.
Rift Zones
- Volcanic crates are common sights in Hawaii.
  
  Most shield volcanoes form along the rift zones in Eastern Africa or in the Atlantic Ocean where the tectonic plates are pulling apart, creating fissures that the lava can penetrate. Two exceptions are the Hawaiian Islands and the Galapagos Islands, which form over hot spots in the Pacific Ocean. Hot spots are weak spots where the magma breaks through in the earth's crust and are not located near rift zones. As the crust moves over the hot spot, it creates an island arc.
Calderas
- Mauna Kea stands out on the horizon in Hawaii.
  
  Large circular depressions called calderas form from the original opening at the volcano's summit where the magma flows out of its chamber. The eruption and removal of large volumes of magma may result in a weakening of the overlying rock that then collapses into the caldera. Craters are smaller circular depressions created by explosions that occur during eruptions of stratovolcanoes and cinder cone volcanoes.

Nature