Evolution of Continental Drift and Plate Tectonics

Vocabulary flashcards covering key terms, people, evidence, and processes related to the evolution of Continental Drift, Seafloor Spreading, and Plate Tectonics theories.

Contraction Theory

Early idea that Earth cooled and wrinkled, forming mountains; proposed by Eduard Suess.

Eduard Suess

Austrian geologist who proposed the Contraction Theory.

Continental Drift Theory

Alfred Wegener’s hypothesis that continents were once joined in Pangaea and have since moved apart.

Alfred Wegener

German meteorologist who proposed Continental Drift in 1912 and wrote “The Origin of Continents and Oceans.”

Pangaea

Supercontinent meaning “all-lands” that existed about 300 Ma before breaking apart.

Panthalassa

Vast global ocean that surrounded Pangaea.

Laurasia

Northern landmass formed from Pangaea; source of North America and Eurasia (except India).

Gondwana

Southern landmass from Pangaea; included South America, Africa, Australia, India, and Antarctica.

Continental Fit

Geometric matching of continental coastlines, e.g., South America and Africa, supporting drift.

Glossopteris

Extinct seed-fern whose fossils on multiple southern continents support Continental Drift.

Mesosaurus

Fresh-water reptile fossil found in South America & Africa, evidence for Continental Drift.

Lystrosaurus

Triassic herbivorous reptile whose fossils on Africa, India, Antarctica support drift.

Cynognathus

Triassic mammal-like reptile found in South America & Africa, backing drift theory.

Paleoclimatic Evidence

Signs such as ancient glaciations and coal in Antarctica indicating continents changed latitude.

Seafloor Spreading Hypothesis

Harry Hess and Robert Dietz’s proposal that new ocean crust forms at mid-ocean ridges and moves outward.

Harry Hess

Princeton petrologist who co-developed Seafloor Spreading Hypothesis.

Robert Dietz

US oceanographer who independently advanced Seafloor Spreading ideas.

Mid-Ocean Ridge

Submarine mountain chain where new oceanic crust forms via divergent boundaries; ~20 % of ocean floor.

Paleomagnetic Stripes

Symmetric patterns of magnetic reversals in basalt recording seafloor spreading.

Magnetic Reversal

Periodic switch of Earth’s magnetic polarity, recorded by cooling oceanic basalt.

Transform Fault

Strike-slip fracture offsetting mid-ocean ridges; common on seafloor.

Abyssal Plain

Extensive, flat region of deep-ocean floor.

Black Smoker

Hydrothermal vent emitting dark, mineral-rich fluids on the ocean floor.

Oceanic Trench

Long, narrow, deep depression where oceanic plates subduct.

Seamount

Submarine mountain rising from the ocean floor but not reaching sea level.

Guyot

Flat-topped seamount eroded below sea level.

Plate Tectonics Theory

Unifying geological theory that the lithosphere is divided into moving plates driven by mantle processes.

Lithosphere

Rigid outer shell of Earth composed of crust and uppermost mantle, broken into plates.

Major Tectonic Plates

Seven largest plates: Pacific, North American, South American, African, Eurasian, Australian-Indian, Antarctic.

Mantle Plume

Upwelling column of hot mantle rock creating volcanic hotspots.

Hotspot

Stationary surface expression of a mantle plume, e.g., Hawaii; tracks plate movement.

Deep Sea Drilling Project

Research program that recovered ocean-floor cores showing seafloor age increasing away from ridges.

Layer-Cake Convection

Mantle convection model with separate upper and lower cells divided by transition zone.

Whole-Mantle Convection

Model where subducting slabs sink through entire mantle, stirring it as a single layer.

Ridge-Push

Gravitational force that drives plates from elevated mid-ocean ridges toward trenches.

Slab-Pull

Force exerted by sinking, dense, cold oceanic lithosphere at subduction zones, pulling the plate along.

Divergent Plate Boundary

Region where plates move apart and new lithosphere is created, typically at mid-ocean ridges.

Subduction Zone

Convergent boundary where one plate dives beneath another into the mantle.

Tectonic Evidence – Hotspot Track

Age progression of volcanoes (e.g., Hawaiian–Emperor chain) showing plate motion over a fixed hotspot.

Unifying Theory of Geology

Status of Plate Tectonics because it integrates Continental Drift, Seafloor Spreading, and diverse geologic phenomena.