Chapter 22: Earth Science
Describe the internal structure of a volcano and how volcanos form
Relate the types of volcanic eruptions to the characteristics pf magma.
Describe the different types of volcanoes and where they are typically located.
Describe several types of igneous features and how they are formed
Volcano, magma chamber, pipe , vent, crater, caldera, hot spot, shield volcano, cinder cone, composite volcano, batholith, sill, dike, volcanic neck
Formation of a volcano
Volcano: Is a mountain that forms when magma reaches the surface.
Deep inside Earth, between the molten iron core and the thin crust at the surface, there is a solid body of rock called the mantle.
When rock from the mantle melts, moves to the surface through the crust, and releases pent-up gases, volcanoes erupt.
It is estimated that around 80% of the Earth’s surface, above and below sea-level, originated because of volcanic activity.
Magma chamber: Before an eruption, magma often collects in a pocket called a magma chamber.
Pipe: Magma rises to the surface in a narrow, vertical channel.
Vent: An opening in the ground where magma escapes to the surface.
Crater: At the top of the central vent in most volcanoes is a bowl-shaped pit.
Caldera: Is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption.
Quiet and Explosive Eruptions
Volcanoes erupt explosively or quietly, depending on the characteristics of the magma.
A non-explosive eruption produces quiet outpourings of lava. Non-explosive eruptions are generally associated with shield volcanoes.
During an explosive eruption these materials are blasted out of the volcano at supersonic speeds. Explosive eruptions are generally associated with composite volcanoes.
Location and Types of Volcanoes
Most volcanoes occur along plate boundaries or hot spots in the crust.
Hot spot: are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere.
Hot spots are not linked to arcs and may not be associated with ocean ridges.
There are four major types of volcanoes, classified according to their shape, composition of their magma, and the way they erupt.
Composite Volcano: which are the most common type of volcanoes, generally steep-sided cone shaped mountains most of which have a crater at the summit and erupt with different kinds of lava, ash, and rock .
Shield Volcano: are wide gentle-sloping volcanoes that have low viscosity lava