This edifice is composed of ashy tephra, usually spewed out by Strombolian eruptions. Unlike stratovolcanoes, many Scoria cone volcanoes have only one eruption event. These wide, relatively short volcanoes occur when low-viscosity lava flows out with minimal explosiveness, such as in Hawaiian eruptions. Near the summit, the edifice gets a little steeper, giving the volcano a slightly raised center. Photo courtesy USGS Mauna Loa, a shield volcano in Hawaii.
Volcanic activity can also produce other interesting structures, such as calderas and lava domes .
Calderas, large crater-shaped basins, form when eruptions drain a magma chamber and the volcano edifice collapses into the empty space. These often fill up with water, creating round lakes, such as Crater Lake in Oregon. This creates a domed plug at the top of the volcano, which may continue to grow over time. Inc. All rights reserved. Simply register for a free Postbox in the country where your merchant is located.