Hazards and Plate Tectonics - Video Notes

A vocabulary set of terms related to hazards, geologic cycles, plate tectonics, rock and water cycles, designed for quick review.

Hazards

Potential sources of harm that may affect people or the environment; not yet realized.

Disaster

A hazard event that causes significant damage or disruption beyond a community's capacity to cope.

Catastrophe

A large-scale disaster with widespread, long-lasting impacts.

Risk

The probability of harm from a hazard, combining likelihood and consequences; includes acceptable risk concepts.

Magnitude

The energy released by a hazard or the size of the event.

Frequency

How often a hazard event occurs within a given time period.

Magnitude-Frequency Concept

Hazard impact depends on both magnitude and frequency; large events are less frequent.

Internal forces

Forces generated inside the Earth (e.g., tectonic activity) that can drive hazards.

External forces

Forces acting on Earth’s surface from above (e.g., weathering, erosion) that can cause hazards.

Gravitational attraction

The force of gravity influencing hazard processes like landslides and tides.

Geologic Cycle

The set of physical and chemical processes that create and modify rocks and surface materials over Earth’s history.

Tectonic Cycle

The cycle of creation, movement, and destruction of tectonic plates, driven by Earth’s internal energy.

Plate tectonics

Theory that Earth’s lithosphere is divided into moving plates (oceanic and continental crust) driven by mantle convection.

Oceanic crust

Thinner, more dense crust under oceans, mainly basalt.

Continental crust

Thicker, less dense crust forming the continents, mainly granitic.

Lithosphere

Rigid outer shell including crust and upper mantle, broken into tectonic plates.

Asthenosphere

Ductile layer beneath the lithosphere that enables plate motion.

Mantle

Layer between the crust and core where convection drives plate tectonics.

Inner core

Solid iron-nickel sphere at Earth’s center.

Outer core

Liquid iron-nickel layer surrounding the inner core; generates Earth’s magnetic field.

Plate boundaries

Edges where tectonic plates interact: divergent, convergent, or transform.

Divergent boundary

Plates move apart; new crust forms at mid-ocean ridges.

Convergent boundary

Plates move toward each other; subduction or collision occurs.

Transform boundary

Plates slide horizontally past one another along transform faults.

Subduction

One plate sinks beneath another at a convergent boundary; forms trenches and volcanic activity.

Trench

Deep ocean depression formed at subduction zones.

Mid-ocean ridge

Undersea mountain chain where seafloor spreading creates new crust at divergent boundaries.

Slab pull

Gravitational pull of sinking subducting slabs that helps drive plate motion.

Ridge push

Buoyant forces at elevated ridges that help push plates apart.

Hot spots

Volcanic activity away from plate boundaries caused by mantle plumes (e.g., Hawaii).

Rock Cycle

Interrelated processes that produce and transform three rock types: igneous, sedimentary, metamorphic.

Igneous rock

Rock formed by crystallization of molten rock.

Sedimentary rock

Rock formed by lithification of deposited sediments.

Metamorphic rock

Rock transformed by heat, pressure, and fluids.

Weathering

Breakdown of rocks at the surface by physical and chemical processes.

Erosion

Removal and transport of weathered material by wind, water, or ice.

Deposition

Laying down of sediment in new locations.

Lithification

Compression and cementation of sediments into rock.

Melting

Process of turning rock into molten material.

Hydrologic cycle

Movement of water through the atmosphere, oceans, and land driven by solar energy.