Geology Video: Rocks, Energy, and Plate Tectonics (Chapter 1-9 Highlights)

Vocabulary flashcards covering key terms from the lecture on rocks (igneous, sedimentary, metamorphic), energy sources (geothermal vs solar), and plate tectonics (lithosphere/asthenosphere, convection, plate boundaries, and related processes).

Sedimentary rock

Rock formed from the accumulation and lithification of sediments; often contains fossils.

Igneous rock

Rocks formed by cooling and crystallization of molten rock; can be plutonic (intrusive) or volcanic (extrusive).

Metamorphic rock

Rock altered by high heat and pressure, usually from existing rocks, without melting.

Magma

Molten rock beneath the Earth's surface.

Lava

Magma that erupts onto the surface.

Plutonic rocks

Intrusive igneous rocks that crystallize underground; e.g., granite.

Volcanic rocks

Extrusive igneous rocks that crystallize from lava at the surface; e.g., basalt.

Granite

Common plutonic rock; light-colored; forms continental crust.

Basalt

Dark, fine-grained volcanic rock common in oceanic crust.

Fossil

Preserved remains or traces found in sedimentary rocks.

Bedrock

Hard rock forming the solid foundation; igneous or metamorphic; underlying surface.

Rock cycle

Concept that any rock type can transform into another given time through weathering, burial, metamorphism, melting and crystallization.

Lithosphere

Rigid outer shell of the Earth comprising crust and upper mantle; broken into plates that move.

Asthenosphere

Weak, ductile mantle layer beneath the lithosphere that allows plate motion.

Convection

Heat-driven movement of a fluid (liquid or gas) due to density differences. Hotter, less dense material rises, while cooler, denser material sinks, creating a continuous circulatory motion. In Earth's mantle, this process \"mantle convection\" drives the movement of tectonic plates, playing a crucial role in phenomena like seafloor spreading and

Continental drift

Wegener's idea that continents move; supported by fossil and fit evidence; precursor to plate tectonics. Jigsaw-puzzle fit: The striking resemblance of continental coastlines, particularly South America and Africa.

• Fossil evidence: The distribution of identical fossil species (e.g., Mesosaurus, Glossopteris flora) across widely separated continents.

• Rock type and mountain ranges: The presence of similar rock formations and ancient mountain chains that align when continents are reassembled (e.g., Appalachians and Caledonian Mountains).

• Paleoclimatic evidence: Records of ancient climates, such as glacial deposits found in present-day tropical regions, suggesting these areas were once at polar latitudes.

Pangaea

Hypothetical supercontinent that existed about 200–300 million years ago.

Seafloor spreading

A fundamental process in plate tectonics where new oceanic lithosphere is formed at mid-ocean ridges and then moves away from the ridge. This occurs as magma wells up from the Earth's mantle, intrudes into the rift valley along the ridge axis, and solidifies to create new oceanic crust. As this new crust forms, it pushes the older crust horizontally away from the ridge. Key evidence includes:

• The symmetrical magnetic striping patterns parallel to the ridges.

• The youngest rocks and highest heat flow are found at the ridge crest, with rocks progressively getting older and colder farther away from the ridge.

This process is a primary mechanism driving the movement of tectonic plates at divergent boundaries and is responsible for the continuous creation and renewal of the ocean floor.

Mid-ocean ridge

Undersea mountain belt where new ocean floor forms; rocks near ridge are youngest.

Subduction zone

Region where one plate sinks beneath another into the mantle; associated with trenches and volcanism. This process is a fundamental aspect of plate tectonics, driven largely by \"slab pull\" (the weight of the subducting plate pulling the rest of the plate along) and playing a crucial role in recycling oceanic crust back into the mantle.

Deep-sea trench

A long, narrow, and often V-shaped depression in the ocean floor, representing the deepest parts of the Earth's oceans. Blank form at convergent plate boundaries, specifically where one oceanic tectonic plate is forced to subduct beneath another oceanic or continental plate. They mark the initial point where the denser oceanic lithosphere begins its descent into the Earth's mantle.

• Role in Plate Tectonics: They are crucial sites for the recycling of oceanic crust back into the mantle, a fundamental part of the Earth's rock cycle and plate tectonic processes.

Hotspot

Localized volcanic region not at a plate boundary, formed by mantle plumes; creates volcanic chains as plates move over it.

Slab pull

Gravity-driven force pulling a subducting plate into the mantle; a major driver of plate motion.

Ridge push

Ridge push is a gravitational force acting at divergent plate boundaries, specifically at mid-ocean ridges. As new oceanic lithosphere forms at the ridge crest, it is hot, less dense, and stands at a higher elevation than the surrounding older ocean floor. As this newly formed lithosphere moves away from the ridge, it cools, increases in density, and thickens, slowly subsiding.

This continuous cooling and sinking of the lithosphere, combined with the slight topographic slope (gravitational potential energy) away from the elevated ridge, cause gravity to exert a force that effectively 'pushes' the entire lithospheric plate away from the ridge axis. This gravitational sliding is one of the primary forces contributing to the movement of tectonic plates, working in conjunction with other forces like slab pull.

Plate boundary

The edge where two tectonic plates meet; sites of earthquakes, volcanoes, and mountain-building; includes divergent, convergent, transform.

Divergent boundary

Plates move apart; seafloor spreading occurs at mid-ocean ridges.

Convergent boundary

A plate boundary where two tectonic plates move toward each other. This interaction leads to the destruction of old crust or intense deformation, earthquakes, volcanoes, and mountain building.

Oceanic-Continental Convergence: Occurs when a denser oceanic plate collides with a less dense continental plate. The oceanic plate is typically forced to subduct (sink) beneath the continental plate, a process known as oceanic subduction. This often results in:

• Formation of deep-sea trenches where the subduction begins.

• Creation of a continental volcanic arc (e.g., the Andes Mountains) as magma generated from the melting of the subducting plate rises.

• Frequent and powerful earthquakes due to friction and stress between the plates.

• Oceanic-Oceanic Convergence: Happens when two oceanic plates collide. The denser of the two oceanic plates will subduct beneath the other. This process leads to:

  • Formation of deep-sea trenches.

  • Development of volcanic island arcs (e.g., the Mariana Islands, Japan) on the overriding plate, as magma rises to the surface.

  • Intense seismic activity, including deep earthquakes.

• Continental-Continental Convergence: Involves the collision of two continental plates. Since both continental plates are relatively buoyant and not easily subducted, neither plate descends significantly into the mantle. Instead, the crust is intensely compressed, folded, and faulted, resulting in:

  • Formation of massive mountain ranges (e.g., the Himalayas) with thick crust.

  • Frequent, often shallow to moderate-depth earthquakes.

  • Little to no volcanism, as there is no deep subduction to generate magma.

Transform boundary

A plate boundary where two tectonic plates slide horizontally past each other. Unlike divergent or convergent boundaries, there is little to no creation or destruction of lithosphere (crust) at transform boundaries. Instead, the primary geological activity is characterized by significant seismic events.

Key characteristics and associated phenomena include:

• Plate Movement: Plates move in a shearing motion, grinding alongside each other in opposite directions. This movement can be continuous but often occurs in sudden slips after stress builds up.

• Crustal Preservation: Because plates are sliding past each other laterally, new crust is not generated (as at divergent boundaries) nor is old crust consumed (as at subduction zones within convergent boundaries).

• Earthquakes: These boundaries are well-known for frequent and often powerful, shallow-focus earthquakes. The friction between the grinding plates causes immense stress to build up, which is then released in seismic waves.

• Lack of Volcanism and Major Mountain Building:

• Topographic Features: They often manifest as linear valleys, offset streams, or scarps where the land has been horizontally displaced.

• Examples: The most famous example is the San Andreas Fault in California, which marks where the Pacific Plate and the North American Plate slide past each other. Another significant example includes the numerous transform faults found along mid-ocean ridges, connecting segments of divergent boundaries.

Geothermal energy

Geothermal energy is heat energy originating from the Earth's interior, a continuous and immense internal heat source. It is primarily derived from two main mechanisms:

1. Primordial Heat: This is the residual heat left over from the Earth's formation approximately 4.5 billion years ago. During its accretion from dust and gas, gravitational compression and kinetic energy from impacts generated significant heat, much of which is still trapped within the Earth's core and mantle.

2. Radiogenic Heat: This heat is continuously generated by the radioactive decay of naturally occurring isotopes (such as uranium, thorium, and potassium present within the Earth's mantle and crust. The decay process releases thermal energy, contributing significantly to the Earth's internal heat budget.

This internal heat drives geological processes like plate tectonics, volcanism, and the formation of hot springs and geysers.

Primordial heat

Heat remaining from Earth's formation.

Radiometric dating

Technique using radioactive isotopes (e.g., uranium, thorium, potassium, rubidium) to determine rock ages; not carbon dating.

Solar energy

Energy from the Sun; drives weather and climate, not tectonics.

Plate tectonics

Theory that Earth's lithosphere is divided into moving plates driven by mantle convection; explains earthquakes, volcanoes, and mountain-building.