Ring of Fire and Plate Tectonics

Vocabulary flashcards covering key geological terms, processes, and features discussed in the lecture on the Pacific Ring of Fire.

Ring of Fire

A 25,000-mile arc around the Pacific Ocean where about 75 % of Earth’s volcanoes and 90 % of its earthquakes occur.

Stratovolcano

Tall, cone-shaped volcano built from layers of viscous, silica-rich lava and ash; common all along the Ring of Fire.

Blocky Lava

Thick, highly viscous lava that breaks into angular blocks as it moves, indicating high silica content and explosive potential.

Viscosity

A fluid’s resistance to flow; higher viscosity in lava traps gases and leads to explosive eruptions.

Silica

The mineral (SiO₂) that increases lava viscosity; more silica equals stickier lava and more violent eruptions.

Magma

Molten rock beneath Earth’s surface that may contain dissolved gases and water; feeds volcanic eruptions.

Dissolved Gas

Volatile components (e.g., H₂O, CO₂) held in magma under pressure; their release drives explosive eruptions.

Pyroclastic Flow

Super-heated avalanche of ash and gas racing down volcano slopes at >100 mph and ~1,300 °F after column collapse.

Hornblende

A water-bearing mineral whose crystals in volcanic rocks signal the presence of water during magma formation.

Subduction

Process where an oceanic plate bends and sinks beneath another plate, recycling crust and generating magma, quakes, and trenches.

Oceanic Trench

Deep linear depression marking a subduction zone; the Pacific trenches outline the Ring of Fire’s outer edge.

Seafloor Sediments

Layers of mud, volcanic ash, and organic material on the ocean bottom that ride into trenches with subducting plates.

Carbon-12 (C-12)

A stable carbon isotope enriched in organic matter; its presence in volcanic gases links magma to ocean sediments.

Phytoplankton

Microscopic marine plants whose remains enrich seafloor sediments with carbon-12, later released in volcanic gases.

Fumarole

A volcanic vent emitting steam and gases; sampling reveals magma chemistry and water sources.

Megathrust Earthquake

A colossal quake (> M 8) occurring on the sloping contact between a subducting plate and an overriding plate.

Tsunami

Series of large sea waves triggered by seafloor displacement during events like megathrust earthquakes.

Mantle Convection

Slow, heat-driven circulation in the semi-solid mantle that drags tectonic plates across Earth’s surface.

Pacific Plate

Earth’s largest tectonic plate; its boundaries form most of the Ring of Fire.

Plate Tectonics

Theory describing the movement of rigid lithospheric plates over the asthenosphere, causing quakes, volcanism, and mountain-building.

Mid-Ocean Ridge

Undersea mountain chain where rising magma creates new oceanic crust and pushes plates apart.

Black Smoker

Hydrothermal vent on mid-ocean ridges that ejects superheated, mineral-rich water, evidencing new crust formation.

High-Precision GPS

Geodetic system measuring Earth-surface motions to millimeter accuracy, revealing plate movements (~3 in/yr in North America).

Seismic Station

Instrumented site that records ground vibrations; networks map earthquake depth, location, and plate interactions.

Seismic Ribbon

Linear zone of earthquake foci that slopes landward, tracing the descent of a subducting plate.

Accretionary Wedge

Chaotic mix of scraped-off ocean sediments piled against a continent at a subduction zone, e.g., Chugach Mountains.

Cook Inlet

Alaskan waterway hosting Augustine Volcano, a prime study site for Ring of Fire volcanology.

Augustine Volcano

Active Alaskan stratovolcano that erupted in 2006; classic example of viscous, gas-rich Ring of Fire volcanism.

Thermal Imaging

Remote-sensing technique that maps surface heat, used to monitor lava buildup and flow paths during eruptions.

Plume Collapse

Failure of an eruption column, leading to pyroclastic flows down volcano slopes.

Mantle

Layer of hot, deformable rock between Earth’s crust and core; source region for most magmas.

Oceanic Crust

Dense, basaltic crust formed at mid-ocean ridges and recycled at subduction zones.

Continental Crust

Thicker, less dense crust forming Earth’s continents; overrides subducting oceanic plates.

Aleutian Islands

Arc of Alaskan islands formed by Pacific Plate subduction; northern segment of the Ring of Fire.

Seafloor Spreading

Creation of new oceanic crust at mid-ocean ridges, balancing crust lost to subduction.

Convection Current

Circular flow pattern in a fluid (or mantle) driven by temperature differences, powering plate motion.