Earth's Internal Discontinuities and Ancient Supercontinents

A set of vocabulary flashcards covering Earth’s internal discontinuities, seismic waves, ancient supercontinents, and tectonic plates based on the lecture notes.

Discontinuities

Boundaries inside the Earth where seismic waves change speed or direction, indicating changes in composition, density, or state of matter (solid/liquid) and helping study internal structure without digging.

Mohorovičić Discontinuity (Moho)

Boundary between the crust and the mantle.

Conrad Discontinuity

Boundary between the upper crust and lower crust.

Gutenberg Discontinuity

Boundary between the mantle and the outer core.

Lehmann Discontinuity

Boundary between the outer core and inner core.

Repetti Discontinuity

Boundary between the upper mantle and lower mantle, around 700 km depth.

Seismic Waves

Vibrations caused by earthquakes or explosions that travel through Earth and change speed/direction based on material properties.

P-Waves (Primary Waves)

Fastest seismic waves that move through solids and liquids.

S-Waves (Secondary Waves)

Slower seismic waves that move only through solids.

Outer Core

Liquid layer beneath the mantle; S-waves do not propagate through it.

Inner Core

Solid sphere at Earth's center.

Pangaea

The most recent supercontinent (~300 million years ago) that later split into Laurasia and Gondwana.

Laurasia

Northern part of the former Pangaea that formed after its breakup.

Gondwana

Southern part of the former Pangaea that formed after its breakup.

Rodinia

Older supercontinent that existed around 1.1 billion years ago.

Columbia (Nuna)

Even older supercontinent, roughly 1.8–1.5 billion years ago.

Vaalbara

Believed to be the first supercontinent, about 3.6 billion years old.

Breakup of Pangaea

began about 200 million years ago, forming Laurasia and Gondwana which drifted into today’s continents.

Major Tectonic Plates

Large lithospheric plates: Pacific, North American, South American, African, Eurasian, Antarctic, and Indo-Australian.

Pacific Plate

Huge plate beneath the Pacific Ocean; interacts with many other plates to drive earthquakes and volcanism.

North American Plate

Plate covering North America and parts of the Atlantic and surrounding regions.

South American Plate

Plate covering South America and parts of the Atlantic and Pacific margins.

African Plate

Plate covering Africa and parts of the Atlantic Ocean and Indian Ocean margins.

Eurasian Plate

Plate covering Europe and most of Asia.

Antarctic Plate

Plate covering Antarctica and surrounding ocean basins.

Indo-Australian Plate

Major plate often split into Indian and Australian plates, covering parts of the Indian Ocean, Australia, and surrounding regions.

Minor Tectonic Plates

Smaller plates that interact at plate boundaries: defined in this group as Philippine Sea, Nazca, Cocos, Caribbean, Scotia, Arabian, and Juan de Fuca.

Philippine Sea Plate

Minor plate beneath the western Pacific Ocean.

Nazca Plate

Minor plate off western South America; subducts beneath the South American Plate.

Cocos Plate

Minor plate off the western coast of Central America; subducts under North and South America.

Caribbean Plate

Minor plate under the Caribbean region.

Scotia Plate

Small plate off the southern tip of South America.

Arabian Plate

Minor plate covering the Arabian Peninsula.

Juan de Fuca Plate

Small plate off the Pacific Northwest of North America; subducts beneath the North American Plate.

Plate Tectonics (concept)

Theory that Earth’s lithosphere is divided into plates that move over the asthenosphere, causing earthquakes, volcanism, and continental movement.