Plate Tectonics I: Key Observations

A set of vocabulary flashcards reviewing observational lines of evidence for plate tectonic theory from the lecture notes.

Bimodal Elevation Distribution

The global topographical pattern in which Earth's surface elevation clusters around two primary peaks: ocean floor basins at approximately $-4.5\,\text{km}$ and continental landmasses at $0.5\,\text{km}$.

Deep Sea Trench

Long, narrow oceanic depressions that occur directly adjacent to linear mountain chains (such as west of the Andes) or alongside volcanic island chains (such as south of the Aleutian Islands).

Seismicity and Volcanism Distribution

The global pattern where active young volcanoes and earthquake epicenters are strongly concentrated along narrow linear or arcuate belts rather than evenly distributed across the planet.

Hawaiian-Emperor Seamount Chain

A continuous linear chain of volcanic islands and underwater seamounts in the Pacific Ocean with active volcanoes located at the southeastern end and older, extinct seamounts extending to the northwest.

Hawaiian Hotspot Age Progression

The systematic increase in volcanic age toward the northwest along the Hawaiian chain, ranging from active volcanism at Hawaii ($0.8\,\text{Ma}$ to present) to Kauai ($3.8\text{--}5.6\,\text{MY}$) and Midway ($25\,\text{MY}$).

Pacific Plate Velocity Calculation

The rate of crustal movement calculated using age-distance data from the Hawaiian-Emperor chain, showing steady plate movement over a stationary volcanic source at approximately $8.6 \pm 0.02\,\text{cm/yr}$ (or $8.7\,\text{cm/yr}$).

Ocean Floor Age Distribution

The age pattern of oceanic crust showing that ocean floor rocks are geologically young ($<208\,\text{Ma}$), youngest directly along mid-ocean ridges, and symmetrically distributed on opposite sides of the ridges.

Continental Rock Age Distribution

The age pattern of continental crust consisting of rocks up to $4.0\,\text{Ga}$ old, displaying an asymmetrical age distribution that is significantly older and fundamentally different from oceanic crust.

Continental Jigsaw Fit

The complementary alignment of continental coastlines, such as South America and Africa, which fit together like puzzle pieces with minor areas of overlap and gap.

Glossopteris

An extinct fossil plant species distributed across South America, Africa, India, Antarctica, and Australia, providing fossil evidence that supports the former union of these continents.

Mesosaurus

An extinct fossil reptile found in matching coastal regions of South America and Africa, serving as fossil evidence for continental drift.

Continental Glacial Evidence

The distribution of contemporary glacial striations and ice flow indicators across South America, Africa, India, Australia, and Antarctica that form a coherent polar ice sheet when the continents are reassembled into Pangea.