GEOL 200 Earth’s Fury: Lecture 11 Magma Fragmentation and Volcanic Hazards

This set of flashcards provides key vocabulary and definitions related to volcanic processes, fragmentation, eruption styles, and associated hazards.

Bubble Growth

The increase in size of gas bubbles in magma, which can occur through diffusion, decompression, and coalescence.

Fragmentation

The process by which magma transitions from a continuous liquid state, containing bubbles, to a continuous gas state containing pyroclasts.

Basaltic Eruption Style

Eruptive behavior that depends on the relative velocity between bubbles and magma, with distinct types such as Hawaiian and Strombolian eruptions.

Critical Vesicularity Criterion

A threshold of approximately 70% vapor volume in which bubble walls become thin and fragile, leading to shattering during fragmentation.

Phreatic Eruption

An eruption caused by external water hitting hot magma, resulting in steam explosion.

Lahar

A destructive mudflow associated with volcanic activity, often resulting from melting ice or mixing with water.

Pyroclastic Flow

A fast-moving current of hot gas and volcanic matter that flows down the slopes of volcanoes.

Glass Transition

The process during which magma cools and becomes brittle, leading to fragmentation in high viscosity magmas.

Overpressure Strength Criterion

When bubble pressure exceeds the strength of the surrounding melt, leading to fragmentation as a result of rapid decompression.

Effusive Eruption

An eruption characterized by the outpouring of low-viscosity magma, typically resulting in lava flows.

Explosive Eruption

An eruption characterized by high gas content, often resulting in explosive outcomes such as pyroclastic flows and ash dispersal.

Mafic Lava Flows

Lava flows that are low in silica and viscosity, often forming smooth surfaces known as pahoehoe or more rugged surfaces known as a'a.

Volcanic Hazards

Various dangers associated with volcanic eruptions, including ash fall, lava flows, pyroclastic flows, toxic gases, and lahars.