Geology midterm 3

Volcanism

The geological process of eruption of magma from below the Earth's crust.

Magma

Molten rock beneath the Earth's surface.

Decompression melting

Melting that occurs when pressure decreases without a temperature change.

Volatiles

Substances like H2O and CO2 that lower the melting temperature of rocks.

Viscosity

A measure of a fluid's resistance to flow; higher viscosity means thicker fluid.

Silica content

The proportion of silicon dioxide (SiO2) in magma, influencing its properties.

Effusive eruption

A type of volcanic eruption characterized by the outpouring of lava without explosive activity.

Pyroclastic flow

A fast-moving current of hot gas and volcanic matter that flows down from a volcano.

Shield volcano

A type of volcano with broad, gentle slopes formed by low-viscosity basaltic lava flows.

Stratovolcano

A volcano characterized by steep profiles and explosive eruptions, built from alternating layers of lava and ash.

Cinder cone

A small, steep-sided volcano formed from the explosive eruptions of basaltic magma.

Lava flows

The movement of molten rock from a volcano during an eruption.

Lahar

A volcanic mudflow made of water and volcanic ash.

Hotspot

A volcanic region thought to be fed by underlying mantle that is anomalously hot.

Divergent boundary

A tectonic plate boundary where two plates are moving away from each other.

Convergent boundary

A tectonic plate boundary where two plates are moving towards each other.

Partial melting

The process where only some minerals in a rock melt, forming magma.

Gas content

The amount of dissolved gases in magma which affect eruption style.

Tectonic plate

A massive slab of the Earth's lithosphere that moves and interacts with other plates.

Caldera

A large volcanic crater formed by a major eruption leading to the collapse of the volcano.

Pillow lavas

Rounded lava formations that occur when lava erupts underwater.

Volcanic dome

A mound-shaped protrusion resulting from the slow extrusion of viscous lava.

Basalt

A dark, fine-grained volcanic rock that is low in silica.

Rhyolite

A light-colored, high-silica volcanic rock.

Subduction zone

An area where one tectonic plate moves under another and is forced to sink into the mantle.

Creep

A very slow form of mass movement where soil and rock move down a slope.

Debris flow

A fast-moving mixture of water, rocks, and organic matter that flows down a slope.

Earthquake triggering

An event that can initiate mass movements by shaking the ground.

Gravity

The constant force pulling materials downwards, affecting slope stability.

Angle of repose

The steepest angle at which a sloped surface formed by loose material is stable.

Magma chamber

A reservoir of magma located beneath the Earth's surface.

Lava tube

A natural conduit formed by flowing lava beneath the hardened surface of a lava flow.

Tsunami

A series of ocean waves caused by disturbances such as earthquakes or volcanic eruptions.

Landslide

The movement of rock and soil down a slope due to gravity.

Friction

The resistance encountered when moving over a surface, affecting slope stability.

Chemical alteration

The process of minerals changing composition, often leading to decreased cohesion.

Frost wedging

A mechanical weathering process where water seeps into cracks, freezes, and expands.

Skid resistance

The ability of materials to resist sliding and maintain stability on slopes.

Runout distance

The distance that material moves down a slope after a mass movement.

Avalanche

A large mass of snow, ice, and debris that rapidly flows down a mountain.

Geological hazard

A natural process that poses a risk to life, property, and the environment.

Seismic waves

Waves of energy caused by earthquakes or volcanic eruptions that travel through the Earth.

Eruption column

A column of gas, ash, and volcanic rock that rises into the atmosphere during an explosive eruption.

Thermal energy

Heat energy that can contribute to the melting of rocks and formation of magma.

Hydrothermal system

A geologic system in which heated water interacts with rocks, often related to volcanic activity.

Pleistocene Epoch

A geological timescale of the last 2.6 million years, marked by ice ages and volcanic activity.

Sedimentary strata

Layers of sedimentary rock that can provide insight into geological history.

Basin and range

A geological region characterized by alternating mountain ranges and desert valleys.

Transform fault

A type of fault where two tectonic plates slide past each other horizontally.

Conditions of Slope Instability

Factors that contribute to slope failure, including excessive rainfall, earthquakes, vegetation removal, and geological structure.