Plate Tectonics and Earth's Layers

Vocabulary flashcards reviewing Earth's layers, theories of crustal movement, types of crust, plate boundary classifications, and major/minor tectonic plates.

Crust

The outermost layer of the Earth.

Lithosphere

Composed of the Earth's crust and the rigid upper mantle; broken into pieces called tectonic plates.

Asthenosphere

The semi-fluid layer in the upper mantle located directly below the lithosphere.

Convection Currents

Thermal currents occurring in the asthenosphere that drive the movement of Earth's tectonic plates.

Continental Drift Theory

Proposed by Alfred Wegener, stating that all continents were once joined in a single massive supercontinent called Pangaea before breaking apart.

Panthalassa

The vast global ocean that surrounded the supercontinent Pangaea.

Laurasia

The Northern Hemisphere landmass formed when Pangaea split into two primary landmasses.

Gondwana

The Southern Hemisphere landmass formed when Pangaea split into two primary landmasses.

Plate Tectonics Theory

States that Earth's lithosphere is divided into rigid plates that move across the asthenosphere due to convection currents in the mantle.

Oceanic Crust

Crust composed primarily of dense igneous rock called basalt.

Continental Crust

Less dense, thicker crust primarily composed of granite.

Divergent Boundaries

Plate boundaries where plates move away from each other, creating new crust.

East African Rift Valley

An example of a divergent continental boundary formed when two continental plates pull apart.

Mid-Atlantic Ridge

A divergent oceanic boundary formed between the North American Plate and Eurasian Plate in the northern section, or the South American Plate and African Plate in the southern section.

Convergent Boundaries

Plate boundaries where plates move toward each other, destroying or buckling crust.

Subduction

The process where a denser plate is forced downward beneath a less dense plate into the mantle.

Continental-Continental Convergence

A convergent boundary sub-type that creates massive continental mountain ranges, such as the Himalayas formed by the collision of the Eurasian Plate and Indo-Australian Plate.

Volcanic Island Arc

A chain of volcanic islands created alongside a deep-sea trench at an oceanic-oceanic convergent boundary.

Mariana Trench

The deepest part of the ocean, formed at an oceanic-oceanic convergent boundary by the Pacific Plate subducting.

Oceanic-Continental Convergence

A convergent boundary sub-type that creates deep-sea trenches and continental volcanic mountain arcs like the Cascades in the Western USA.

Transform Boundaries

Plate boundaries where plates slide horizontally past one another, frequently causing high earthquake activity without creating or destroying crust.

San Andreas Fault

A geologic feature caused by transform boundaries located between the Pacific Plate and North American Plate.

Major Tectonic Plates

Primary large plates of the lithosphere, including the Eurasian Plate, African Plate, Pacific Plate, North American Plate, South American Plate, Antarctic Plate, and Indo-Australian Plate.

Minor Tectonic Plates

Smaller lithospheric plates such as the Arabian Plate, Cocos Plate, Juan de Fuca Plate, and Philippine Plate.

Divergent continental

Formed when two continental plates pull apart (e.g., East African Rift Valley).

Divergent oceanic

Formed when two oceanic plates pull apart through seafloor spreading (e.g Mid-Atlantic Ridge North American Plate and Eurasian Plate (Northern section) or South American Plate and African Plate)

oceanic-oceanic convergent

• Creates a deep-sea trench and a chain of volcanic islands known as an island arc.

  • Example: The Mariana Trench (deepest part of the ocean, formed by the Pacific Plate subducting).