Continental Drift, Fossil Evidence & Seafloor Spreading Lecture

Vocabulary flashcards summarizing the main terms and concepts related to Wegener’s Continental Drift, fossil and rock evidence, and the later theory of sea-floor spreading.

Alfred Wegener

German meteorologist who proposed the Continental Drift Theory in the early 20th century.

Continental Drift Theory

Idea that Earth’s continents were once joined as a single landmass and have slowly moved apart over geologic time.

Pangaea

Name Wegener gave to the ancient supercontinent containing all present-day continents.

Continental Jigsaw Puzzle

Observation that the coastlines of continents, such as South America and Africa, fit together like puzzle pieces.

Glossopteris

Extinct seed fern; its fossils on multiple southern continents support their former connection.

Mesosaurus

Freshwater reptile fossil found in Brazil and South Africa, indicating the continents were once joined.

Lystrosaurus

Triassic herbivorous reptile; fossils in Africa, India, and Antarctica provide drift evidence.

Cynognathus

Mammal-like reptile the size of a wolf; fossils on South America and Africa back Wegener’s theory.

Fossil

Preserved remains or traces of ancient organisms, such as bones, shells, or leaves.

Laurasia

Northern landmass formed when Pangaea split, including North America, Europe, and Asia.

Gondwana

Southern landmass from Pangaea’s breakup, comprising South America, Africa, India, Antarctica, and Australia.

Matching Rock Layers

Identical rock types and ages found on now-separated continental margins, indicating earlier continuity.

Appalachian Mountains

Mountain belt in eastern North America that lines up with Europe’s Caledonian range when continents are reassembled.

Caledonian Mountains

Mountain range in northern Europe that matches the Appalachians, supporting continental linkage.

Glacial Striations

Scratches carved by ancient glaciers; identical patterns across southern continents imply a shared polar past.

Coal Deposits

Thick layers of ancient plant matter; their presence in polar regions indicates those areas were once tropical.

Carboniferous Period

Geologic interval (≈360–290 Ma) when extensive swamp forests produced much of Earth’s coal.

Sea-Floor Spreading

Process by which new oceanic crust forms at mid-ocean ridges and moves outward, explaining continental motion.

Mid-Ocean Ridge

Underwater mountain chain where magma rises, cools, and creates new sea floor.

Divergent Plate Boundary

Tectonic boundary where two lithospheric plates move apart, such as at a spreading center.

Spreading Center

Zone along a mid-ocean ridge where magma erupts and pushes plates apart.

Subduction Zone

Region where old, dense oceanic crust sinks into the mantle, balancing sea-floor creation.

Harry Hess

American geologist who proposed sea-floor spreading in the 1960s, providing a mechanism for drift.

Sonar

Sound-wave technology used in the 1950s–60s to map the rugged ocean floor.

Transform Fault

Fracture where two tectonic plates slide past one another, offsetting sections of ridges.

Ridge Axis

Central line of a mid-ocean ridge where the youngest oceanic crust forms.

Oceanic Crust

Basaltic rock layer forming Earth’s ocean floors.

Lithospheric Mantle

Rigid uppermost mantle attached to the crust, together making up tectonic plates.

Moho

Boundary between Earth’s crust and mantle, known as the Mohorovičić discontinuity.

Isostasy

Concept describing the gravitational balance of Earth’s lithosphere floating atop the asthenosphere.