GEOG 1150: Physiographic Regions and Basic Geomorphology of British Columbia

Comprehensive vocabulary flashcards reviewing fundamental geology, rock types, plate boundaries, terrane accretion history, volcanism, and glacial processes in British Columbia.

Intrusive Igneous Rock

Rock formed by the slow cooling of magma beneath the Earth's surface, characterized by large crystal grains (e.g., granite).

Extrusive Igneous Rock

Rock formed by rapid cooling of lava at the Earth's surface, characterized by a fine-grained, glassy texture with no visible crystal structure (e.g., tuff).

Sedimentary Rock

Rock formed through the weathering and erosion of existing rocks, followed by the deposition, compaction, and cementation of mineral particles or organic matter into layers.

Strata

Horizontal layers or beds in which compressed and cemented sediments solidify into rock over time.

Metamorphic Rock

Rock created deep beneath the Earth's surface when pre-existing rock is structurally and mineralogically transformed by heat, pressure, or chemical fluids without melting.

Protolith

The original, unmetamorphosed parent rock that undergoes transformation by heat, pressure, and time into a metamorphic rock (e.g., mudstone transitioning to shale and slate, or limestone to marble).

Continental Drift

The hypothesis proposed in $1912$ by Alfred Wegener stating that all landmasses were once joined in a single supercontinent called Pangaea before breaking apart.

Craton

The ancient, structurally stable foundation or basement core of a continent, representing the oldest portion of a tectonic plate (e.g., the ancestral North American craton dating back over $600\text{ million years}$).

Accretion Belt

A geological zone along the edge of a continental craton where migrating crustal blocks (terranes) have collided and become welded to the continental margin.

Western Cordillera

The distinct physiographic region comprising the mountain systems that cover nearly all of British Columbia and the Yukon.

Spreading Boundary

A divergent plate boundary where tectonic plates move apart and upwelling magma solidifies to construct new crust (e.g., Explorer Ridge, Juan de Fuca Ridge).

Cascadia Subduction Zone

A convergent plate boundary along the Pacific Northwest where denser oceanic plates (Explorer, Juan de Fuca, Gorda) are forced beneath the North American Plate at approximately $4\text{ cm/year}$.

Transform Boundary

A plate boundary where tectonic plates slide horizontally past one another, neither generating nor destroying lithospheric crust (e.g., the Queen Charlotte Fault).

Orogeny

Crustal deformation driven by tectonic forces that results in the uplift and building of mountain ranges.

Thrust Fault

A geological fault line formed under horizontal compressive stress, pushing rock strata upward and causing older rocks to be placed on top of younger rocks.

Terrane

A migrating crustal fragment that travels across ocean basins and eventually collides with and welds onto a continental margin through tectonic accretion.

Intermontane Superterrane

A composite assemblage of four offshore terranes—Stikinia, Cache Creek, Quesnellia, and Slide Mountain—that collided with western North America between $181$ and $150\text{ Ma}$.

Foreland Belt

The eastern structural belt of the Canadian Cordillera formed when the collision of the Intermontane Superterrane folded and faulted the margin of ancestral North America.

Omineca Belt

The geological belt representing primarily the leading edge of the accreted Intermontane Superterrane, characterized by uplifted, marine sedimentary rocks rich in fossils.

Insular Superterrane

A large terrane complex that collided with the western margin of North America between $84$ and $40\text{ Ma}$, uplifting the Coast Mountains (Coastal Belt) and Insular Mountains (Insular Belt).

Tectonic Relaxation

A phase occurring around $60\text{ Ma}$ where compressive pressure on the Rocky Mountains ceased, causing crustal down-dropping and the opening of interior grabens/valleys like the Rocky Mountain Trench and Okanagan Valley.

Garibaldi Volcanic Belt

A linear chain of composite volcanoes in southwestern British Columbia formed by the subduction of the Juan de Fuca and Explorer plates beneath the North American Plate.

Stikine Volcanic Belt

A volcanic belt in northwestern British Columbia produced along crustal rift zones and diverging tectonic fractures.

Anahim Volcanic Belt

An east-west volcanic chain across central British Columbia created by crust moving over a stationary mantle hot spot.

Batholith

An extensive subsurface body of intrusive igneous rock formed when large chambers of molten magma rise into the crust and cool slowly.

Ring of Fire

A major tectonic belt bordering the perimeter of the Pacific Plate where intense seismic activity and active volcanism frequently take place.

Nass Valley Lava Beds

The volcanic feature in northwestern British Columbia formed by Canada's most recent volcanic eruption, occurring in the $1770\text{s}$.

Pleistocene Epoch

The geological epoch spanning from $1.65\text{ million}$ to $10,000\text{ years ago}$, marked by $18$ distinct advances of glacial ice sheets across North America.

Ice-Free Refuge

An unglaciated enclave that remained uncovered during glacial maxima, allowing biological populations to survive while surrounding lands were under ice.

U-Shaped Valley

A wide, steep-walled, flat-floored glacial trough produced when an alpine glacier widens, deepens, and straightens a pre-existing V-shaped river valley.

Glacial Till

Unsorted, unconsolidated sediment containing particles from clay to large boulders, deposited directly by melting glacial ice (common across the Cariboo Plateau).

Glacial Flour

Fine, silt-sized rock particles pulverized by glaciers that stay suspended in meltwater, scattering sunlight and creating a vibrant turquoise-blue water appearance.