Geology Final Exam Study Guide - Vocabulary

Tectonics and Surface Relief

• Earthquakes are usually shallow; deep earthquakes mostly occur in subduction zones.
• Faulting causes earthquakes, but not all faulting results in earthquakes.

Earthquake Intensity and Magnitude

• Earthquake intensity is more relevant than magnitude for daily life.
• Earthquake magnitude is directly linked to the energy released.
• An increase of 1 in magnitude represents a 32-fold increase in energy release.
• For the same earthquake, intensity can be small even when magnitude is large.
• Aftershocks happen along the same faulting zone as the main shock, but their magnitude isn't necessarily smaller.
• Magnitude: A numerical measure of earthquake size, determined from seismic records and related to energy released.
• Only large earthquakes (M > 7) can cause landslides and tsunamis.
• Predicting the exact time, location, and magnitude of future earthquakes isn't currently possible.
• On average, less than one M > 4 earthquake happens every year.
• Earthquake warning systems are based on the propagation speed difference between P and S waves.

Motion on the Earth's Surface

• Motion on the Earth's surface can lead to earthquakes and surface relief (e.g., mountain ranges and basins).

Surface Relief: Isostasy

• Most common mountain elevations are 0.5 km above sea level and 4.5 km below sea level.
• Isostasy determines elevation.
• Isostasy: Equal standing.
• Principle of Isostasy: Adjacent blocks of crust are equal in terms of pressure beneath them, even if at different elevations.
• Pressure at the base of the block = pressure in the water at the same depth.
• Continental and oceanic crust have different densities.
• Continents are higher than oceanic crust because continental crust is thicker and less dense than oceanic crust.
• Isostasy relates to surface geologic processes: mass mountain root move to shallower depth AND mass development of deeper mountain root.

Tectonic Shortening and Stretching

• Formation of rift and thick mountain root.
• Horizontal compressional forces dominate. Compression causes shortening and thickening of the crust.

Gravitational Collapse

• Gravitational forces dominate. Gravitational collapse results in stretching and thinning of crust.
• Smaller planets have a higher limit on how high a mountain can rise.

Craton

• Interior region of a continent, stable for more than 500 million years.
• Low elevation (<0.5 km above sea level).
• Exposes ancient Precambrian rocks or relatively thin Phanerozoic sedimentary rocks covering older Precambrian rocks.

Dynamic Topography

• Surface elevation affected by mantle convection.
• Plume push-up the continent, subduction drag-down the continent.
• Surface relief and sea-level changes when average surface temperature changes; increasing the amount of seawater results in larger area covered by ocean.

Origin of Water

Water Cycle (Hydrologic Cycle)

• Evapotranspiration and precipitation are processes by which water moves from land surface to the atmosphere.
• Rainfall, snowmelt, and infiltrated groundwater re-emerge at the surface where the water table intersects stream channels.

Distribution of Earth's Water

• Seas, freshwater rivers, glaciers.
• Precious water: The small fraction of Earth's water that is accessible and usable for life.
• Emphasizes the scarcity and value of usable water, especially in the face of climate change, population growth, pollution, overuse, and depletion.

Work of Streams

• Erode, transport, and deposit materials.

Stream Erosion

• Removal of blocks from the bed of a stream channel.
• Quarrying (Plucking):
  • Process of lifting and removing large chunks of rock from the bed or banks of a stream.
  • Fast-moving water enters cracks in rocks, loosens them, and pulls blocks free.
  • Most effective in high-energy streams with strong currents and fractured bedrock.
• Abrasion:
  • Grinding or swirling action of sediment and rock fragments carried by the stream scraping against the channel bed and walls.
  • The rotating motion of swirling pebbles acts like a drill to create potholes.
  • Bed and banks of bedrock are bombarded by particles carried by the flow.
• Corrosion (Chemical Weathering):
  • The dissolving of rock by chemical reactions with the water.
  • Rock is gradually dissolved by the flowing water.
  • Mostly takes place when streams passing through limestone rocks are made of calcium carbonate CaCO3.

Stream Transport

• Dissolved load, suspended load, bedload.
• Dissolved Load:
  • Ions and minerals dissolved in the water.
  • Invisible.
  • Carried in solution.
  • Result of chemical weathering.
• Suspended Load:
  • Fine particles like silt and clay.
  • Makes water look muddy, especially during floods.
• Bedload:
  • Large grains that cannot be picked up but still are able to be moved.
  • They roll, bounce, and slide along the bottom.
  • Only move when current is strong enough.
• Settling Velocity:
  • Determines when and where particles are deposited.
  • Fine particles like clay have low settling velocity; stay in suspension longer.
  • Coarse particles like gravel settle quickly when stream velocity drops.
  • Dependent on particle size, density, water viscosity, and shape of particle. Larger, heavier, and rounder particles settle faster.

Stream Channels

• Bedrock channels: Streams cutting into solid rock near headwaters.
• Alluvial channels: Bed and banks are composed largely of unconsolidated sediment (alluvium) that was previously deposited in the valley.
• Meandering channels: A single main channel that has various loops and curves down its path.
• Braided channels: A series of small channels that are interwoven into a larger one.

Formation of Meandering Channels

• In flat or sloping land, rivers start to wander back and forth, creating meanders (big looping bends).
• Water moves slower on the inside, causing deposition dropping off sediments over time.
• This erosion and deposition makes the bends more pronounced.

Formation of Oxbow Lake

• As a meander gets tighter, the river might cut through the narrow neck, creating a new path.
• The old loop gets cut off from the main river, curved cresent shaped lake next to the river

Depositional Landforms

• Delta, natural levees, alluvial fan.

Delta

• Forms where sediment-laden streams enter the relatively still waters of a lake, an inland sea, or the ocean.
• Triangle-shaped landform made of sediment deposited where a river meets a standing body of water like an ocean or a lake.
• As a river slows down at its mouth, it drops its load of sediment.

Natural Levees

• Some rivers occupy valleys with broad floodplains and build natural levees that parallel their channels on both banks.
• Raised banks along the sides of a river made naturally by sediment deposition.
• When a river overflows, it loses energy, dropping heavier sediments right by the channel first, building up ridges over time.

Alluvial Fans

• Typically develop where a high-gradient stream leaves a narrow valley in mountainous terrain and comes out suddenly onto a broad flat plain or valley floor.
• Fan-shaped deposits of sediment that form at the base of mountains where a river suddenly slows down on flatter land.
• When fast-flowing mountain streams reach a valley floor, they lose energy and spread out, dropping their sediments quickly.

Flood and Flood Control

• Flood Types: Regional floods, flash floods, ice jam floods, dam failure floods.

Flood Types

• Regional Floods:
  • Seasonal rapid melting of snow and heavy rain.
  • Happens slowly over large areas after long periods of heavy rain and snowmelt.
• Flash Floods:
  • Often occur with little warning and are potentially deadly.
  • Involve rapid rises in water levels and can have devastating flow velocities.
• Ice Jam Floods:
  • Happen when floating ice blocks a river, causing water to back up and flood.
  • Associated with northward-flowing rivers in the Northern Hemisphere.
• Dam Failure Floods:
  • Happen when a dam breaks, sending a huge rush of water downstream.
  • Can result in a flash flood.

100-Year Flood

• The chance of a flood of that magnitude happening in any given year is 1/100 = 1 \%.
• A 100-year flood is worse than a 50-year flood; a 5-year flood is bad but not that bad.
• 50-year floods don't necessarily occur at 50-year intervals.
  *

Flood Control Methods

• Artificial Levees: Manmade embankments built along rivers to keep water inside the channel.
• Flood Control Dams: Hold back and release water slowly to prevent big floods.
• Channelization: Straightening and deepening rivers to make water flow faster and reduce overflow.
• Floodplain Management: Planning land use wisely, like keeping parks or open land near rivers, to reduce damage when flooding happens.

Shorelines and Ocean Waves

• The coastal zone is not a stable platform; shorelines constantly change due to wave action.
• Shoreline: The line that marks contact between the land and sea.
• Unstable shoreline, fast erosion, and powerful ocean waves.
• Particle motion is circular for ocean waves (similar to seismic Rayleigh waves).
• Waves in deep water are unaffected by water depth.
• When waves approach shallower water, they feel the bottom and begin to slow.
• Faster water at the top of the wave catches up, and the wave grows.
• When a wave becomes too steep, it eventually collapses and breaks.
• Velocity decreases, and wave height increases.

Wave Erosion

• Breaking waves exert great force, which is even greater during storms.
• Erosion is common, caused by wave impact and pressure.
• The grinding action of water and rock fragments erodes and weathers rock at the shoreline fastest.

Rip Currents

• Flow in the opposite direction of breaking waves.
• Concentrated movement of backwash that moves along the surface instead of along the bottom as normal.
• Extremely dangerous.

Hurricanes

• The ultimate coastal hazard; the greatest storms on Earth and among the most destructive natural disasters.
• Called typhoons in the western Pacific and cyclones in the Indian Ocean.
• Physical Nature of Hurricanes:
  • Low-pressure center with a steep pressure gradient.
  • They carry tropical moisture, moving from the edges toward the center.
  • Pressure decreases toward the center.
• Hurricane Formation:
  • Late summer and early fall due to water temperature.
  • Between 5 and 20 degrees of latitude due to both water temperature and the Coriolis effect.
• The Coriolis effect results in a spiraling motion, clockwise in the Southern Hemisphere and counterclockwise in the Northern Hemisphere. Points near the equator are moving faster than near the poles.
• Hurricanes DO NOT develop within 5 degrees of the equator because the Coriolis effect is too weak; spiraling motion cannot form.

Hurricane Destruction

• The amount of damage depends on: size and population density of the affected area, the shape of the ocean bottom near the shore, and the strength of the storm.
• Saffir-Simpson Hurricane Scale.
• Storm Surge: The most devastating damage in the coastal zone, especially in low-lying coastal areas.
• In the Northern Hemisphere, the surge is more intense on the right side of the storm's movement, as this side has stronger winds because of the storm's counterclockwise rotation.
• A dome of water 65-80 km wide that sweeps across the coast near the point where the eye makes landfall.

Hurricane Monitoring & Forecasting

• Track forecasts are predicted paths of hurricanes.
• Speeds of the storm, hot towers.
• Track forecasts, storm speed (how fast it moves), and wind speed (how fast winds inside the storms are).
• Hot towers are very tall, warm cloud formations inside the hurricane, signaling that the storm is strengthening.
• Forecasts are pretty accurate now.

Water Flowing Underground

• Groundwater is the easiest accessible, but largest reservoir of freshwater is on freshwateris 2.5 of total global water.
• Glaciersmelted groundwater represents the largest reservoir of freshwater that is readily available to humans; ice glaciers are the largest but not accessible in general.
• Primary Use of Groundwater: Irrigation.
• Water conservation efforts and increased efficiencies help reduce groundwater extraction.
  • Water Conservation Examples: Fixing leaks, limiting irrigation directly save water.
  • Increased Efficiencies Examples: More efficient irrigation systems, water-saving appliances using less water to get the same results.
• San Juan Chama Drinking Water Project New Mexico

Groundwater and Water Table

• Zone of Saturation (Phreatic Zone): Water that is not held as soil moisture percolates downward until it reaches a zone where all the open space is refilled with water.
• Water in the zone of saturation is called groundwater.
• The upper limit of the zone of saturation is the water table.
• The area above the water table is called the unsaturated zone (vadose zone): pore spaces contain both air and water.
• Saturated Zone: Area underground where all the pores and spaces are completely filled with water.
• Unsaturated Zone: Area above the saturated zone where pores contain both air and water.
• Water Table: The boundary between the saturated and unsaturated zones. It rises or falls depending on rainfall, usage, and season.

Variations in the Water Table

• Seasonal Changes: Rises during wet seasons (rain, snowmelt) and falls during dry seasons (drought).
• Spatial Distribution: Higher in low areas and lower in elevated areas.
• Human Usage: Overpumping groundwater lowers the table and can cause wells to dry up or cause land to sink (subsidence).

Monitoring and Mapping Water Table

• The water table coincides with the water level in observation wells.
• Observation Wells: Special wells used to measure and monitor the depth of the water table.
• Data collected helps map underground levels over time.

Interactions Between Groundwater and Streams

• Streamwater is the surface runoff from rainfall, snowmelt, Infiltratedground water that reemerges at the surface where the water table intersects stream Channels.
• Gaining Stream: Receives water from groundwater system.
• Losing Stream (Connected): Provides water to the groundwater system.
• Losing Stream (Disconnected): Losing streams re separated from the groundwater system by the unsaturated zone a bulgemayform in the watertable.
• Discharge: Water that leaves.
• Recharge: Water added.
• Artificial Recharge:The practice of using injection wells or infiltration onds to assist ground water recharge heavy pumping induced cone of depression can change groundwater.

Groundwater Storage and Movement

• Porosity: The amount of empty space (pores) in a rock or sediment where water can be stored.
• Higher porosity is linked to higher permeability.
• Permeability: How easily water can flow through a rock or sediment.
• The linkage between the pores is more important.
• Aquifers: Rocks or sediments with high porosity and high permeability are good at storing and transmitting water (e.g., sandstone, gravel).
• Aquitards: Rocks or sediments with low permeability block or slow water movement (e.g., clay, unfractured shale).

Measuring Groundwater Movement

• Darcy's Law represents hydraulics crossfiction regreas of conductivity: Q = KA \frac{h1 - h2}{L}
  • Q = Discharge: the actual volume of water that flows through an aquifer in a specified time.
  • Hydraulic gradient difference in water table height over distance like the slope that pushes water
  • Hydraulic conductivity how easily water moves through a material
  • Cross-section area size of the area water moves through

Wells, Artesian Systems, and Water Tables

Wells

• Wells: Holebored into the zone of saturation. Common method for removing groundwater.
• Perched Water Table: Small localized water table above the main one, often on a layer of impermeable rock.

Artesian System

• Artesian System: Self-rising wells.
• Water is confined to an aquifer that is inclined so that one end can receive water.
• Aquitards both above and below an aquifer must be present to prevent the water from escaping confined aquifer.
• City water systems additional water is needed to pump the water up to reach the highest level of high rise.

Springs, Hot Springs, and Geysers

Springs

• Spring: a natural outflow of groundwater that occurs when the water table intersects the surface.

Hot Springs

• There is no university accepted definition of hot springs; frequently used definition is water in a hotspring is 6-9 ^\circ C warmer than he meananval air temperature for the locality where it occurs.
• Heat Source: Temperature increases with depth. When groundwater circulates to great depths, it becomes heated.
• If hot water rises rapidly to the surface, it may emerge as a hot spring.

Geysers

• Geysers: intermittent hot springs or fountains in which columns of water are ejected with great force at various intervals, often rising 30 to 60 meters (100-200 ft) into the air
• A geyser can form if the underground plumbing does not allow heat to be readily distributed by convection. Geysers erupt periodically.
• More hot springs and geysers are in the West part of the US because of more volcanic activities there.

Geyser Deposits

• Geyser Deposits: When groundwater from hot springs and geysers flows out at the surface material in solution is often precipitated producing an accumulation of chemical sediment rocky
• Geyserite (Siliceous Sinter): Water contains dissolved silica.
• Averting (Calcareous Tufa): Water contains dissolved calcium carbonate.
• Some hot spots contain sulfur, which gives a poor taste and odor.
• Not all natural spring water is tasty or even can be drinked.

Geologic Work of Groundwater

• Groundwater acts as a powerful agent of erosion and deposition.
• Groundwater dissolves rock (limestone in particular) and forms caverns and sinkholes and deposits minerals like calcium carbonate to form dripstone features.
• Cavern Formation: Occurs mainly in limestone but also gypsum and marble.
• Slightly acidic groundwater containing carbonic acid dissolves calcium carbonate in limestone, enlarging fractures and forming caverns.
• Stalactite: Hang from the ceiling of caves, form as mineral-rich water drips down and deposits calcite over time; may connect to form columns.
• Stalagmite: Grow up from the floor, forming from droplets falling from stalactites.

Karst Topography

• Karst Topography: Formed by the dissolution of soluble rocks, especially limestone.
  • High Water Table Level: Scattered sinkholes.
  • Intermediate Water Table Level: Large sink holessurface subsidence.
  • Low Water Table Level: Rock owers insoluble leftovers.
• Rock Towers: Isolated sleep limestone hills left behind as surrounding rock is dissolved away. Features include sinkholes collapsed or dissolved depressions caverns Underground voids formby groundwater erosion
  • Tower karst is the final landscape evolution of karst topography. Sink holes caverns collapsed Most soluble rocks are completely gone
  • Eaving a landscape close to the water able peppered with rock towers of less soluble materials

Icecores climate Change

Glacial icecores

• Glacial icecores from the greenland and Antarctic Icesheets air bubblestrapped in Ice cores proxyData isotopeanalysis isotope analysis howeachelement isotope will behave underdifferenttemperatures Oxygen isotopeconcentration is temperature dependent Fosillplantdata TreeRings widerringsindicategoodgrowingconditions narrowerrings indicateharshgrowing conditions

Climate change

• Natural causes of climate change greenhousegasses earthgetsmost energyfromthe sun mostradiation is absorbed by earth's surface and warms it MOST important and abundant greenhouse gas is WATERVAPOR responsible for 50 earth'sgreenhouse effect Water is the biggest contributor to Earth's greehouse effet because of its abundance most powerful greehouse gas is Florinated gasses Or is stillthe kingdueto very large emmision and long life time in the atmosphere
• Plate positions and Milankovitchcycles platepositions and Milankovitchcycleslong term largescale Milankovitch cycles is
  Eccentricity is gyrently highmeans warmtemp
• Cutting down forrest carbongoes into air farming produce lots of CO2 and methane enoughgreenhouse gasses to warm the planet
  Volcanic activity short term cooling and longterm warming.
• Bigeffect platepositions and Milankovitchcycleslong term largescale anything related tothesun has almost no effect on Earth's global climate 3.3evidence from Caciers Globalwarming does NOT mean every year you will feel warmer than lastyear Whatwedon'tknow howlong this transitionalphase will last
  Predictingfuture climate change is verydifficult findengineeringmethods tostore and absorbCO2