Geology and Earth Processes: Faults, Folds, Seismic Waves, and Climate

Stress

Force applied to rocks (compression, tension, or shear).

Strain

The deformation or change in shape that results from stress.

Elastic deformation

Temporary deformation of rocks.

Plastic (ductile) deformation

Permanent bending of rocks.

Brittle deformation

Breaking of rocks.

Normal Fault

Tensional stress; crust pulled apart; hanging wall moves down (e.g., Basin & Range Province).

Reverse/Thrust Fault

Compressional stress; hanging wall moves up (e.g., Himalayas).

Strike-Slip Fault

Shear stress; horizontal movement (e.g., San Andreas Fault).

Anticline

Upward-arching fold; oldest rocks at core.

Syncline

Downward-arching fold; youngest rocks at core.

Monocline

Single bend in otherwise horizontal layers.

Strike

Compass direction of a horizontal line on a rock layer.

Dip

Angle between horizontal surface and the tilted layer.

Seismic Waves

Waves of energy caused by the sudden release of strain along faults.

P-waves (primary)

Fastest seismic waves, compressional, move through solids & liquids.

S-waves (secondary)

Slower seismic waves, shear motion, only through solids.

Magnitude

Energy released during an earthquake (measured by Richter or Moment Magnitude).

Intensity

Damage and human perception of an earthquake (measured by Modified Mercalli Scale).

Mass Wasting

Down-slope movement of rock or soil under gravity.

Water Cycle

Continuous movement of water via evaporation, condensation, precipitation, infiltration, runoff, and transpiration.

Discharge (Q)

Calculated as width × depth × velocity of a stream.

Groundwater

Water stored in aquifers (permeable rock).

Surface Currents

Driven by global wind belts; modified by Coriolis effect and continental boundaries to form gyres.

Deep Currents (Thermohaline)

Driven by temperature and salinity differences; cold, salty water sinks near poles.

Global conveyor belt circulation

Forms global circulation driven by thermohaline currents.

Thermocline

Rapid temperature decrease with depth.

Pycnocline

Rapid density increase with depth.

Mixed layer

Warm, well-mixed upper ocean.

Deserts Formation

Occur where evaporation > precipitation (< 25 cm rain/year).

Deserts Processes

Mechanical weathering dominates; wind erosion (deflation, abrasion) and flash flooding shape landforms.

Landforms in Deserts

Dunes, alluvial fans, playas, mesas, and buttes.

Glaciers Formation

Form where snow accumulation > melting over years.

Glaciers Distribution

Found at high latitudes or altitudes.

Glaciers Processes

Plastic flow within ice and basal sliding over the ground.

Glacial Erosion

Plucking, abrasion → U-shaped valleys, cirques, aretes, horns.

Glacial Deposition

Moraines, drumlins, eskers, till, outwash plains.

Global Effects of Glaciers

Sea-level change: ice melt → rise; ice growth → fall.

Ice-albedo feedback

Ice reflects sunlight; melting decreases reflection, causing further warming.

Weather vs. Climate

Weather: short-term atmospheric conditions; Climate: long-term averages and patterns.

Atmospheric Composition

78% N₂, 21% O₂, <1% CO₂, H₂O, Ar, etc.

Atmospheric Layers

Troposphere (weather), Stratosphere (ozone), Mesosphere, Thermosphere.

Weather Processes

Solar heating → convection cells.

Coriolis effect

Influences wind belts and storm rotation.

Fronts

Boundaries between air masses; cold fronts cause storms, warm fronts bring gradual rain.

Carbon Cycle

CO₂ exchanges between atmosphere, biosphere, ocean, lithosphere, and mantle via photosynthesis, respiration, volcanism, and fossil fuel burning.

Chemical Weathering Feedback

More CO₂ → higher temperatures → faster weathering → CO₂ removal → cooling (negative feedback).

Greenhouse Effect

Greenhouse gases (CO₂, CH₄, H₂O, N₂O) trap heat by absorbing outgoing infrared radiation.

Evidence of Anthropogenic Change

Rising global temperatures, melting glaciers, sea-level rise, more extreme weather, CO₂ records (Keeling Curve).

Past Climate Change

Reconstructed from ice cores, sediment, tree rings, isotopes.

Faint Young Sun paradox

Early Sun dimmer, yet Earth warm—likely due to higher greenhouse gas concentrations.

Adaptation

Adjusting to impacts (flood defenses, drought-resistant crops).

Mitigation

Reducing emissions (renewable energy, carbon capture, reforestation).