Volcanoes Lecture Review

Flashcards covering vocabulary related to volcanoes.

Volcano

A natural vent or fissure in the earth's crust through which hot gaseous molten or solid materials may escape to the surface.

Volcanism

The process by which liquid rocks, or magma is forced through vents into the earth's crust or onto its surface.

Pacific Ring of Fire

A circle around the Pacific Ocean where about 75% of volcanoes are situated.

Extrusive Volcanic Landform

Formed when magma is poured onto the earth's surface, forming volcanoes and lava plateaus.

Intrusive Volcanic Landform

Created by magma cooling inside the crust, forming sills, dykes, batholiths, and laccoliths in surrounding rocks.

Batholith

A large, dome-shaped reservoir of magma located deep within the earth's crust.

Dyke

A sheet-like intrusion of magma lying across or discordantly at an angle to the bedding planes of rocks.

Sill

Masses of magma injected or flowing horizontally parallel to the rock layers along the bedding planes.

Laccolith

A type of rock that appears like sheet-like intrusions injected within the layers of sedimentary rocks; pressure causes a dome or mushroom-like appearance.

Basic Lava

Lava that is low in silica (40%), mobile, and flows in a liquefied state, mostly in thin sheets for long distances.

Acidic Lava

Lava that is high in silica (65%), viscous, and relatively immobile, solidifying quickly at the surface.

Active Volcano

A volcano that is currently in the process of eruption.

Dormant Volcano

A volcano that has not erupted for a long time but shows signs of seismic activity.

Extinct Volcano

A volcano that has not erupted in recorded history.

Cinder

Pumice or scoria, stones filled with bubbles, ejected from volcanoes.

Tuff

Material formed from ash and dust ejected from volcanoes.

Bombs

Large globular rocks greater than 65mm across ejected from volcanoes.

Lapilli

Small fragments of lava ejected from volcanoes.

Pyroclastic Flow

Avalanches of fiery gases, ash, and rocks ejected from a volcano.

Nuee Ardente

A glowing, cauliflower-shaped vertical cloud of hot ash, gas, and rock fragments ejected from a volcano during an eruption.

Shield Volcano

Volcanoes shaped like a bowl or shield in the middle with long, gentle slopes made by basaltic lava flows.

Composite Volcano

Steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash, and rock debris.

Ash and Cinder Cones

The simplest types of volcanoes; circular or oval cones made up of small fragments of lava from a single vent.