Grade 12 Geography - Solid Earth and Geological Processes

A comprehensive set of vocabulary flashcards covering the theory of continental drift, plate tectonics, and internal vs. external geological forces as presented in the Grade 12 Geography Unit 1 notes.

Continental Drift Theory

A theory proposed by Alfred Wegener in 1912 suggesting that all continents were once joined in a single supercontinent called Pangaea.

Pangaea

The single supercontinent that existed millions of years ago before breaking apart into current continental positions.

Panthalassa

The vast ocean that surrounded the supercontinent Pangaea.

Laurasia

The northern landmass formed after the split of Pangaea, consisting of North America, Europe, and Asia.

Gondwanaland

The southern landmass formed after the split of Pangaea, consisting of South America, Africa, Antarctica, Australia, and the Indian subcontinent.

Mesosaurus

An extinct organism whose identical fossils were found in both Africa and South America, supporting the Continental Drift Theory.

Paleoclimatic Evidence

Evidence of past climates, such as glacial deposits in present-day tropical regions like Africa and India, used to support continental drift.

Plate Tectonics Theory

A theory stating that the Earth's lithosphere is divided into large and small plates that float and move on the semi-fluid asthenosphere.

Asthenosphere

The semi-fluid layer of the Earth upon which lithospheric plates float and move slowly.

Mantle convection currents

One of the driving mechanisms behind the movement of lithospheric plates.

African Plate

A tectonic plate covering the African continent and surrounding ocean floors, notable for the East African Rift Valley where the plate is splitting.

Eurasian Plate

One of the largest tectonic plates, which formed the Himalayas through its collision with the Indian Plate.

San Andreas Fault

A transform boundary between the North American Plate and the Pacific Plate known for frequent earthquakes.

Pacific Plate

The largest tectonic plate on Earth, mostly oceanic, and surrounded by the Ring of Fire.

Nazca Plate

An oceanic plate in the eastern Pacific that subducts beneath the South American Plate, forming the Andes Mountains.

Ring of Fire

An area with frequent earthquakes and active volcanoes located around the edges of the Pacific Plate.

Divergent Boundaries

Also called constructive boundaries; these occur where plates move apart, allowing magma to rise and create new crust.

Convergent Boundaries

Also called destructive boundaries; these occur where plates move toward each other, leading to subduction or mountain building.

Transform Boundaries

Also called conservative boundaries; these occur where plates slide past each other horizontally without creating or destroying crust.

Endogenic Forces

Internal forces originating from within the Earth, driven by geothermal energy such as heat from the core and radioactive decay.

Diastrophic Forces

Slow, long-term endogenic movements that deform the Earth's crust, including folding and faulting.

Folding

The bending of rock layers due to compressional forces, usually occurring at convergent plate boundaries.

Anticline

An upward arching fold where the oldest rocks are typically found at the center.

Syncline

A downward trough-like fold where the youngest rocks are found at the center.

Faulting

The fracturing and displacement of rock layers in the Earth’s crust when stress exceeds the rocks' ability to bend.

Rift Valley (Graben)

A long, narrow depression formed when a block of land sinks between two parallel faults due to tensional forces.

Block Mountain (Horst)

An uplifted block of land that stands higher than the surrounding area due to faulting.

Earthquake

Sudden shaking of the Earth's surface caused by the rapid release of energy, mainly along fault lines.

Focus (Hypocenter)

The specific point inside the Earth where an earthquake originates.

Epicenter

The point on the Earth's surface directly above the earthquake's focus.

Magma

Molten material located in the interior of the Earth.

Lava

Molten material that has reached the Earth’s surface through vents or fissures.

Lava Plateau

A landform formed by repeated outpourings of lava over large areas, such as the Ethiopian Highlands.

Exogenic Forces

External processes driven by solar energy and gravity that wear down, transport, and reshape landforms on the Earth's surface.

Weathering

The breakdown of rocks into smaller pieces at or near the Earth's surface without movement or transport.

Physical (Mechanical) Weathering

The breakdown of rocks into smaller pieces without changing their chemical composition, such as freeze-thaw action.

Chemical Weathering

The process where rocks are chemically altered or dissolved, common in warm and wet climates through oxidation or carbonation.

Biological Weathering

Weathering caused by living organisms, such as plant roots growing into cracks or animal activity.

Erosion

The removal and transportation of weathered materials from one place to another by agents like water, wind, or ice.

Abrasion

The scraping of rocks by materials being transported by natural agents.

Attrition

An erosional process where transported materials collide and break into smaller pieces.

Hydraulic action

The process where the force of moving water removes material from the Earth's surface.

Deposition

The settling or laying down of transported materials when the energy of the transporting agent decreases.

Delta

A depositional landform created where a river deposits sediments at its mouth, such as the Nile Delta.

Floodplain

A flat area formed by river deposits that accumulate during periods of flooding.