GEOL 101 Chapter Notes - Chapter 5: Olympus Mons, Stratovolcano, Magma Chamber
Document Summary
Volcanoes are vents at which molten rock (lava), pyroclastic debris, gas, and aerosols erupt at the earth"s surface. The characteristics of a lava flow depend on its viscosity, which in turn depends on its temperature and composition. Pahoehoe flows have smooth, ropy surfaces, whereas a"a" flows have rough, rubbly surfaces. Andesitic and rhyolitic lava flows tend to pile into mounds at a volcano"s vent. Pyroclastic debris includes powder-sized ash, marble-sized lapilli, and apple to refrigerator sized blocks and bombs. Some debris falls from the air and some settles from pyroclastic flows. The summit of an erupting volcano usually includes a crater. Collapse of a volcano, when a large magma chamber drains, can yield a much larger bowl-shaped depression called a caldera. A volcano"s shape depends on the style of eruption. Stratovolcanoes (composite volcanoes) can become quite large and consist of alternating layers of pyroclastic debris and lava. The type of eruption depends on the lava"s viscosity and gas content.
