Zones of Volcanism
What is volcanism
The process that describes all the activity associated with discharge of magma, hot fluids and gases
What is the conduit?
Tubelike structure where molten rock travels through to reach Earth's surface
What is tephra?
The fragments of volcanic material ejected during explosive eruptions are collectively
Magma containing less than about 50% silica, typically from upper mantle melting, produces these relatively quiet eruptions
basaltic magma
What are batholiths
Intrusive igneous bodies that form large, irregular masses covering at least 100 km² and often found in mountain interiors
What two plate boundaries do most volcanoes form on?
Convergent and divergent
What is the vent on a volcano?
The opening where lava comes out of the volcano
Fissures
Magma with 50–60% silica commonly found at oceanic‑continental subduction zones is named this.
andesitic magma
What are stocks
smaller, irregular plutons similar to batholiths but of lesser extent
This belt, is also called the Pacific Ring of fire, is the larger volcanic belt around the Pacific Plate.
Circum-Pacific Belt
What is a crater?
What are pyroclastic flows?
Rapid, hot clouds of ash and gas that flow down volcano slopes at high speed are known as this.
Magma with more than about 60% silica, high viscosity, and high gas content that fuels very explosive eruptions is called this.
rhyolitic magma
What is a laccolith
lens-shaped pluton with a rounded top and flat bottom, often doming overlying rock layers
Volcanoes that form where an oceanic plate slides under a continental plate are typically this type of eruptive style.
Explosive
What are calderas?
Much larger depressions — up to about 100 km across — formed when a volcano collapses are called these.
What are flood basalts
When long cracks erupt large volumes of lava forming extensive flat areas
What two factors affect the formation of magma?
Temperature and pressure
What is a sill
type of pluton intrudes parallel to rock layers and usually forms close to the surface.
What are hot spots?
Isolated volcanic centers form above unusually hot, stationary plumes of mantle material.
A volcano with broad, gently sloping sides built from successive nonexplosive lava flows is this type
Shield volcano
This property, influenced by temperature and silica content, describes a magma’s resistance to flow
Viscosity
A pluton that cuts across existing rock layers by intruding into cracks is known as this.
A dike