Plate Tectonics, Continental Drift, and Sea-Floor Spreading

Comprehensive vocabulary flashcards covering continental drift timelines, plate tectonic boundaries, seafloor spreading, and scientific evidence.

Laurasia

The northern continent created along with Gondwana after the breakup of Pangea 200 million years ago during the Triassic period.

Gondwana

The southern continent formed alongside Laurasia after the initial breakup of Pangea.

Tethys Sea

The sea created between Laurasia and Gondwana following the breakup of Pangea.

Pangea

A single giant supercontinent created 250 million years ago during the Permian period of the Paleozoic era.

Fanerozoic Eras

The three geological eras in order: Paleozoic, Mesozoic, and Cenozoic.

Mesozoic Periods

The three periods of the Mesozoic era in order: Triassic, Jurassic, and Cretaceous.

Mesozoic Era

The geological era during which dinosaurs lived on Earth.

Plate Boundary Types

The three ways tectonic plates interact: divergent boundaries (a), convergent boundaries (b), and transform boundaries (c).

Lithosphere

Earth's strong, rigid outer shell, approximately 200 km thick, consisting of the crust and a layer in the outermost part of the mantle.

Plate Tectonics Theory

The unifying geological theory stating that pieces of Earth's lithosphere are in constant, slow motion, combining continental drift and seafloor spreading.

Divergent Boundary

A plate boundary where tectonic plates move apart from each other.

Convergent Boundary

A plate boundary where tectonic plates come together or move toward each other.

Transform Boundary

A plate boundary where tectonic plates slide or slip past one another.

Faults

Breaks in Earth's lithosphere where rocks have slipped past each other.

Tectonic Plates

Separate sections of Earth's lithosphere that move slowly at rates from 1 to 12 centimetres a year.

Rift Valley

A deep valley on land that forms along a divergent boundary where pieces of crust diverge.

Subduction

The process by which ocean floor sinks beneath a deep-ocean trench and back into the mantle when a denser plate sinks under a less dense plate.

Convection Currents

Circulating currents in the mantle that provide the driving force behind the movement of lithospheric plates.

Mid-Ocean Ridges

The longest chain of mountains in the world, forming along cracks in the oceanic crust where molten material erupts.

Sonar

A device developed in the mid-1900s that bounces sound waves off underwater objects and records echoes to map mid-ocean ridges.

Sea-Floor Spreading

The process in which molten material erupts at a mid-ocean ridge, cools into solid rock, and continually adds new material to the ocean floor while pushing older rock aside.

Pillow-shaped Rocks

Strange rocks formed in the central valley of mid-ocean ridges that can only form when molten material hardens quickly after erupting underwater.

Deep-Ocean Trenches

Deep underwater canyons where part of the ocean floor sinks back into the mantle through subduction over tens of millions of years.

Pacific Ocean

An ocean that is shrinking because its many deep-ocean trenches swallow more ocean crust than its mid-ocean ridge produces.

Atlantic Ocean

An ocean that is expanding as its floor spreads, carrying the attached continental crust on its edges outward.

Hypothesis

In scientific reasoning, a construct created before any applicable research has been conducted.

Scientific Theory

A principle supported by evidence, formed as an attempt to explain phenomena that have already been substantiated by data.

Geographical Evidence

The first evidence for continental drift, showing that joining the continental shelves of different continents fits them together perfectly into Pangea.

Paleontological Evidence

The second evidence for continental drift, based on finding identical fossils of non-flying, non-swimming organisms across separated continents.

Geological Evidence

The third evidence given by Wegener, showing that rocks and geological structures in North Europe and North America share the same age and composition.

Climatic Evidence

The fourth evidence given by Wegener, based on parallel glacial striations and tillites in current tropical regions like South America and South Africa.

Tillites

Angulated sediments left behind by glaciers, proving past cold glacial climates in regions that now experience tropical climates.