Volcanoes and Volcanism Overview

Study Notes

Volcanoes are openings in the Earth's crust that allow hot magma, ash, and gases to escape.
Volcanism encompasses all volcanic activity, from magma formation to eruptions.
Volcanoes are named after Vulcan, the Roman god of fire.

Volcanoes form when tectonic plates collide, forcing magma from the mantle to the surface.
This occurs at oceanic-continental boundaries, where the denser oceanic plate is subducted beneath the continental plate.

A crack in the Earth's crust extends to the surface and widens.
Smoke escapes through a vent.
Molten rock, or magma, erupts from the vent, often accompanied by ground shaking.
Magma reaches the surface and flows as lava.
Lava cools and solidifies, accumulating around the vent.
A cone-shaped landform develops.
The cone grows into a volcano.

Magma Chamber: A large underground reservoir of molten rock (magma) that feeds the volcano.
Vent: An opening in the Earth's crust through which magma, gases, and ash escape.
- Main Vent: The primary channel for magma flow.
- Secondary Vent: Smaller openings on the volcano's sides.
Crater: A bowl-shaped depression at the volcano's summit, formed by explosive eruptions or summit collapse.
Caldera: A large depression formed when a volcano collapses into itself after an explosive eruption.
Ash Cloud: A cloud of volcanic ash and gases released during an eruption.
Conduit (Pipe): The tube-like passage connecting the magma chamber to the vent.
Parasitic Cone: A smaller cone formed on the side of a larger volcano by secondary vents.
Fumaroles: Openings that release volcanic gases like steam, carbon dioxide, and sulfur dioxide.
Volcanic Bombs: Large fragments of lava that solidify in the air before falling to the ground.
Tephra: A general term for all volcanic debris, including ash, pumice, and bombs.
Sill: Flat rock formed when magma hardens in a crack in the volcano.
Flank: The side of the volcano.
Lava Flow: The movement of molten rock that pours out of a volcano.

Pahoehoe: Smooth, ropy lava that flows slowly.
A'A: Rough, clumpy lava that flows quickly and forms a jagged crust.
Blocky Lava: Lava with irregular surfaces and large, smooth-sided, angular blocks.

Molten rock with temperatures ranging from 700 to 1,200 °C.
Color changes with temperature:
- Bright yellow over 1,000 °C
- Orange (800-900 °C)
- Dull red (600-700 °C)