GEO 104 EXAM 1 (Chapters 1-3)

Flashcards covering introductory natural hazard concepts, Earth's internal structure, plate tectonics, and earthquake principles.

Natural Hazard

A natural process or event that is a potential threat to human life or property.

Disaster

A hazardous event occurring over a limited time in a defined area that meets at least one criterion: 10 or more people killed, 100 or more people affected, a state of emergency declared, or international assistance requested.

Catastrophe

A massive disaster requiring a significant amount of money or time to recover, typically necessitating outside assistance.

Internal Processes

Forces originating from within the Earth, driven by Earth's internal energy and mostly resulting from plate tectonics, such as volcanoes and earthquakes.

External Processes

Forces originating at or near Earth's surface, driven by solar energy (atmospheric effects and the water cycle) or gravitational effects (landslides and downslope movement of water and sediment).

Processes

Physical, chemical, and biological ways in which events affect the Earth's surface.

Natural Service Functions

The multi-benefit processes and conditions provided by natural ecosystems that sustain and fulfill human life.

Prediction

Specifying the exact date, time, and magnitude of a future hazardous event.

Forecast

Determining a range of probability or percentage chance for a hazardous event to occur within a time window or region.

Risk

The product of event likelihood and potential consequences, defined by the formula: $\text{Risk} = (\text{probability of event}) \times (\text{consequences})$.

Inner Core

The solid innermost layer of Earth, greater than 1,200 km (~750 mi) thick, characterized by high temperature and pressure, composed of 90 percent iron by weight along with sulfur, oxygen, and nickel.

Outer Core

The liquid layer of Earth surrounding the inner core, greater than 2,200 km (1,370 mi) thick, with an average density of $10.7\,\text{g/cm}^3$.

Mantle

The solid (partly molten) layer of Earth ~2,900 km (1,800 mi) thick, composed of iron- and magnesium-rich silicate rocks with an average density of ~$4.5\,\text{g/cm}^3$.

Crust

The outer rock layer of Earth with variable thickness (~25 to 70 km) and an average density of ~$3.0\,\text{g/cm}^3$.

Moho Discontinuity

The boundary separating lighter crustal rocks from denser mantle rocks beneath.

Lithosphere

The cool, strong, and rigid elastic shell of Earth (20 to 400 km thick) consisting of the crust and outermost rigid mantle that bends or breaks under stress.

Asthenosphere

The hot, weak, and plastic layer of the upper mantle capable of slow flow and permanent, irreversible shape changes under stress without breaking.

Seismology

The branch of science studying earthquakes and seismic wave travel paths, providing most knowledge of Earth's internal structure.

Paleomagnetism

The study of rock remnant magnetism used to reveal the history and orientation of Earth's magnetic field.

Curie Point

The specific temperature below which cooling iron-bearing minerals preserve the orientation of Earth's magnetic field.

Mid-Atlantic Ridge

A 10,000-mile-long mountain chain and rift valley running down the middle of the ocean floor.

Triple Junction

A location on Earth's surface where three tectonic plates border one another.

Hot Spots

Volcanic centers where hot material rises up from the deep mantle or core-mantle boundary through overlying plates, creating volcanic island chains or seamounts.

Seamounts

Submarine volcanoes or worn-down underwater mountains formed over hot spots.

Compressional Stress

Squeezing stress acting on rocks, typical of convergent plate boundaries.

Tensional Stress

Pulling-apart stress acting on rocks, typical of divergent plate boundaries.

Shear Stress

Stress causing rocks to slide past one another horizontally, typical of transform boundaries.

Footwall

The block of rock located below an inclined fault plane, named after where miners placed their feet.

Hanging-wall

The block of rock located above an inclined fault plane, named after where miners hung their lanterns.

Elastic Rebound Theory

The theory explaining that continuous motion deforms rocks elastically along a fault until stress exceeds rock strength, releasing stored energy as seismic waves.

P Waves

Primary or compressional body waves that travel fastest through Earth and can pass through both solids and liquids.

S Waves

Secondary or shear body waves that travel slower than P waves and can propagate through solids, but not liquids.

Surface Waves

Seismic waves constrained to travel along Earth's surface from the epicenter, causing complex ground motion.

Triangulation Method

A mathematical method using earthquake recordings from three or more seismic stations to pinpoint the epicenter.

Moment Magnitude

An earthquake magnitude scale based on the total amount of energy released by an earthquake.

Richter Magnitude

An earthquake magnitude scale calculated from the maximum amplitude of S waves recorded on a seismograph.

Modified Mercalli Intensity Scale

A qualitative scale (ranging from I to XII) used to describe earthquake intensity based on damage to structures and human perceptions of shaking.

Seismic Gap

A quiet section along an active fault line where no major earthquakes have occurred for a long time relative to adjacent sections.

Slab Pull

A plate tectonic mechanism resulting from the sinking of cold, dense oceanic lithosphere into the lower-density asthenosphere.

Ridge Push

A gravity-driven mechanism at mid-ocean ridges that pushes oceanic lithosphere toward subduction zones.