Volcanoes & Tectonics Lecture Notes

Vocabulary flashcards covering key terms, processes, lava types, volcano classifications, hazards, and tectonic settings discussed in the lecture notes.

Volcano

A hill or mountain formed by the accumulation of magma, ash, and rock around one or more vents.

Vent

An opening in the Earth’s crust through which magma, gas, and ash are ejected during an eruption.

Subduction

The process in which one tectonic plate is forced beneath another at a destructive (convergent) boundary.

Ring of Fire

Narrow belt of violently active volcanoes encircling the Pacific Ocean; hosts ~75% of the world’s active volcanoes.

Destructive (Convergent) Boundary

Plate margin where two plates move together, often causing subduction and explosive volcanoes.

Constructive (Divergent) Boundary

Plate margin where two plates move apart, allowing magma to rise and form effusive volcanoes.

Rift Zone

Region created by divergent plates (oceanic or continental) where the crust is pulled apart and magma upwells.

Mid-Atlantic Ridge

Sub-marine constructive boundary in the Atlantic where seafloor spreads; Iceland sits on this ridge.

East African Rift Valley

Continental rift formed by divergent movement of the African plate, marked by volcanic activity.

Hot Spot

Stationary mantle plume of abnormally hot magma that forms chains of volcanoes as the plate above moves, e.g., Hawaii.

Seamount

Sub-marine volcanic mountain that may grow to become an island if eruptions continue.

Active Volcano

A volcano that has erupted recently and is expected to erupt again (e.g., Mt St Helens).

Dormant Volcano

A ‘sleeping’ volcano that has erupted in the last 2 000 years but not recently; may erupt again (e.g., Mt Kilimanjaro).

Extinct Volcano

A ‘dead’ volcano that has not erupted for at least 10 000 years and shows no signs of future activity (e.g., Mt Elgon).

Magma Chamber

Sub-surface reservoir where molten rock is stored before an eruption.

Crater

Funnel-shaped hollow at the summit of a volcanic cone, formed by eruptive activity.

Composite (Strato) Volcano

Steep-sided cone composed of alternating layers of lava and ash; typically at destructive boundaries.

Shield Volcano

Broad, gently sloping cone built entirely of fluid basic lava; common at constructive boundaries and hot spots.

Lava Dome

Small, steep volcanic mound formed by thick, acidic lava that piles up over a vent.

Caldera

Large depression formed when a volcano’s summit collapses or explodes, often filling with water (e.g., Yellowstone).

Basic (Basaltic) Lava

Low-silica, runny magma high in iron, magnesium, and calcium; produces gentle, frequent eruptions.

Acidic (Andesitic) Lava

High-silica, viscous magma that cools quickly and erupts violently but infrequently.

Pyroclastic Flow

Fast-moving, super-heated cloud of ash, gas, and rock fragments that races down volcanic slopes.

Volcanic Bomb

Large, molten rock fragment hurled from a volcano that solidifies as it falls.

Ash Cloud

High plume of fine volcanic ash ejected during an eruption; can travel great distances.

Lahar

Mudflow composed of volcanic ash and water that can bury settlements and landscapes.

Convection Currents (Mantle)

Circular motions in the mantle that drive plate movement by rising hot material and sinking cooler material.

Effusive Eruption

Gentle volcanic eruption characterized by steady lava outpouring and low explosivity.

Explosive Eruption

Violent volcanic activity that blasts ash, gas, and pyroclasts due to high gas pressure in viscous magma.

Plate Tectonics

Theory describing the movement of Earth’s lithospheric plates and associated phenomena such as volcanoes and earthquakes.

Fold Mountains

Ranges formed by the collision and upward buckling of two continental plates (e.g., Himalayas); typically lack volcanism.

Geothermal Energy

Renewable power generated from heat of magma near Earth’s surface, common in volcanic regions.

Fertile Volcanic Soil

Nutrient-rich soil created by weathered lava and ash, ideal for agriculture near volcanoes.

Seismic Monitoring

Use of instruments such as seismographs to detect earthquakes and tremors that may precede eruptions.

Prediction & Evacuation

Strategies—based on monitoring—that allow early warning and movement of people away from erupting volcanoes.

Secondary Cone

Smaller cone formed on a volcano when magma finds a new route to the surface after the main vent is blocked.

Conduit (Pipe)

Passage through which magma travels from the chamber to the surface.

Parasite (Side) Vent

Smaller outlet on the flank of a volcano through which magma may erupt.

Volcanic Hazards to People

Dangers such as lava flows, ash fall, poisonous gases, pyroclastic flows, lahars, and volcanic bombs.

Volcanic Hazards to Environment

Effects including forest fires, habitat loss, ash-induced vegetation stress, and greenhouse-gas emissions.

LED C vs MED C Vulnerability

Greater deaths in LEDCs due to weaker monitoring, poorer structures, limited healthcare, and inefficient evacuation.

Seafloor Spreading

Process at mid-ocean ridges where new oceanic crust forms as magma rises and solidifies.

Conservative Boundary

Plate margin where plates slide past each other; typically no magma generation but may host shield volcanoes where thin crust allows leakage.

Plate Buckling

Upward folding of colliding continental plates, forming mountains without subduction or volcanism.

Tectonic Plate

Rigid segment of Earth’s lithosphere that moves over the asthenosphere and interacts at boundaries.

Yellowstone Caldera

Massive volcanic depression in the USA measuring 37 × 18 mi, produced by a continental hot spot.