2152 Definitions
.docx
School
Western University**We aren't endorsed by this school
Course
GEOGRAPH 2152G
Subject
Geology
Date
Dec 19, 2024
Pages
5
Uploaded by ChancellorBeaverPerson1072
Lecture 6 - Earthquakes:Epicenter: Center of quakeFocus: rocks first ruptureSeismographs: Measure and compare earthquake magnitudeRichter Scale: Strength of wave 100 km from epicenter Moment Magnitude Scale: Earthquake scale that measures the area of rock ruptured along a fault, the distance of movement along the fault, and the elasticity of the rock at the focusModified Mercalli Scale: Qualitative earthquake measuring scaleBlind Faults: Faults below Earth’s surfaceStrike Slip Faults: Horizontal displacementDip-slip faults: vertical displacement, include reverse, thrust, and normal faults. Composed of footwall (feet level) and hanging-wall (lanterns go here).Reverse Faults: The hanging-wall has moved up relative to the footwall and is inclined at an angle above 45 degrees. Thrust Fault: These are like reverse faults except the angle is 45 degrees or less. Normal Fault: The hanging-wall has moved down relative to the footwall.Fault Activity: Active if movement during last 11,600 years, potentially active past 2.6 million years, inactive if no movement in last last 2.6 million yearsTectonic Creep: The extremely slow movement of rock along a fracture caused by stress. Seismic Waves: Waves from fault ruptureBody Waves: P and S wavesP Waves: They move fast with a push-pull motion and can travel through solids or liquids. Appear first on seismograms. S Waves: They move slow, in an up-and-down motion and can only travel through solids.Surface Waves: Seismic waves that form when P Waves and S Waves reach earth’s surface and then move along it. Slowest and responsible for damage near the epicenter. Triangulation: Epicentre location finder using 3 stations.Focus Depth: Greater depth = Less shaking at surfaceDirection of Rupture: Waves are stronger along fault’s direction.Local Soil and Rock Type: Homogenous crust = spreads more.Amplification: An increase in ground motion during an earthquake. Alluvial: Material deposited by water that slows p and s waves.Earthquake Cycle: A hypothesis that explains successive earthquakes on a fault over time. Foreshock: A small to moderate earthquake that occurs shortly before and in the same general area as the mainshock.Mainshock: The largest earthquake in a series of associated earthquakes.Aftershocks: They are small to a moderate earthquake that occurs shortly after and in the samegeneral area as the mainshock. They occur after the largest ones. Calculated based on aftershocks on the first day divided by the given day.Plate Boundary Earthquakes: Earthquakes that occur on faults which separate plates. Include strike-slip, thrust, and normal earthquakes.Strike-Slip Earthquakes: Transform faults slide horizontally past each other.Thrust Earthquake: Separate converging plates aka subduction earthquakes. These are the strongest and can produce tsunamis
Normal Fault Earthquakes: Faults with divergent plate boundaries, usually in the oceanIntraplate Earthquakes: An earthquake on a fault in the interior of a continent, far from a plate boundary. Lack of preparedness can be dangerousRecurrence Interval: time between successive eventsFault Scarps: A linear escarpment at Earth’s surface formed by a movement along a fault duringan earthquake.Liquefaction: The transformation of water-saturated sediment from solid to liquid during an earthquake. Earthquake Natural Service Functions: Pathways for downward flow of surface water, channel groundwater to springs, Mineral resources exposedEarthquake Precursors: Small rupture patterns and frequency, land level change, seismic fault gaps, physical and chemical changes in groundwater from rock expansionLecture 7 - Volcanoes:Magma: Found deep within the crust and upper mantle.Lava: Found flowing from an erupting volcano.Silica: Oxygen + Silicon. Found in magma. More silica means more viscous, cooler, and more gases which are more explosive. Ranked low to high: basalt, andesite, dacite, rhyoliteViscosity: Liquid's Resistance to flow.Shield Volcanoes: Largest, Basaltic, contain tephraTephra: Fragmented material blown out during eruption.Pyroclastic Deposits: Accumulations of tephra.Pyroclastic Rock: Compacted pyroclastic deposits. Composite Volcanoes: Cone shaped Stratovolcanoes. Stronger but less frequent than shield.Volcanic Domes: Highly viscous rhyolite, form around ventsCinder Cone Volcanoes: Smallest oval-shaped with a crater at the topMaars: A circular volcanic crater produced by an explosion and filled with water. ”Mars has holes, it also once had water”Ice-Contact Volcanoes: Eruption beneath or along glaciersJokulhaups: Floods from Ice-Contact VolcanoesCrater: A depression formed by the explosion of a volcano top. They can be up to 2 km in diameter.Volcanic Vent: An opening on the surface through which lava and pyroclastic debris erupt. Most are circular but elongated cracks are called fissuresCaldera: A circular to oval depression formed during the collapse of a volcano. “Caldera-Collapse”. Very deadly, 25 km in diameter.Geyser: Underground chambers that boil water and release stream/water.Super Volcanoes: Cause super eruptions.Large in volume and with great pressure. Ash spread could kill millions and destroy health and agriculture. Ash reflects solar radiation causing cooling. Pahoehoe basaltic lava: Low viscosity, travel far, high temp., smooth texture when hardenedAa basaltic lava: High viscosity, low temp, travel slow, blocky texture when hardenedLateral Blast: An eruption directed away from a volcano where materials are blown parallel to the surface.
Pyroclastic Flow: An avalanche of ash, gas, and rock fragments that travels down the slopes of a volcano during an explosive eruption. Very fast and deadly. . Smog: A type of smog called Vog is produced that damages the respiratory system. Lots of sulfur dioxide. Lahar: Mudflow of saturated water moving downslopeVolcano Natural Service Functions: Internal heat produces gases that help form the atmosphere, source of renewable geothermal energy, and create new land.Lecture 8 - Technological Hazards and Space:Hybrid Disasters: One hazard that leads to a technological hazard.Risk: Infrastructure = probability of failure during lifetime of structure, transportation = probabilityof death or injury per km travelled, Industry = probability of death or injury per person per number of hours exposed.Radon: From the decay of uranium, inhaled becomes polonium and lodges in lungs to damage tissues. Very difficult to detect in living spaces. Basements are at high risk during winter due to reduced air circulation.Radiation: direct impact shows cancer or acute sickness, indirect causes genetic mutations. Exposed by mining of uranium and production of electricity using uranium in power plants.Nuclear Meltdown: Overheating that exceeds cooling systems and melts fuel rods allowing hot liquid to seep into soil. Oil Spills: Cause animals to be less buoyant and vulnerable to temperature changes in waterSolar System: Formed 4.6 billion years ago.Nebular Hypothesis: Supernova made an explosion in space that created a solar nebula, fragments came together to form the sun while others formed rocksSupernova: The explosion of a star that has reached the end of its life cycle.Galaxy: A cluster of billions of stars. Our solar system makes up a tiny portion of the milky way galaxy.Star: A hot glowing ball of gas that generates energy by converting hydrogen to helium.Bolide: An extraterrestrial body that originates in outer space. Contains rare Iridium elements. Asteroid: A rocky metallic material in space 10 m to 1000 km in diameter Metereroid: Similar in composition to an asteroid but only up to 10 m in diameterMeteor: A meteoroid that has entered Earth’s atmosphere.Meteorite: A meteor that strikes the Earth’s surface.Comet: These are distinguishable by a large glowing tail of gas and dust.Airburst: Bolide explosion in the skyEjecta Blanket: Rock fragments blown out of the crater upon impact.Breccia: Fragmented rock falling into impact crater sitesComplex Crater: Impact craters over 6 km in diameterMass Extinctions: 5 during last 550 million years with 6th occurring todayK-T Boundary Mass Extinction: Cooling caused by bolide impact killing dinosaurs and 70% of alllife.Chicxulub Crater: Crater of K-T boundary bolide.Lecture 9 - Snow Avalanches:
Snow Avalanches: A mass of snow many cubic meters in volume that separates from a snowpack and moves downslope. Only reserved for snow. Depends on steepness, snowpack stability, and weather. Consist of coherent blocks and ones that become wider going downslope.Point-Release Avalanche: The sliding snow that causes more failures in the adjacent snowpack causing the trough to widen.Slab Avalanche: It occurs when a snowpack fractures along a weak layer parallel to the surface.Most dangerous. Avalanche Potential: Dry powdery snow will be more likely to slide more alongside being above vegetation level, and above large boulders.Wind: Blowing snow can accumulate on the lee slope (downwind slope) of mountains.Hoar: Layers composed of hoar have less strength than the rest of the snowpack.Avalanche Motion: Fast and can climb opposing slopes. South-east side is the most likely side for avalanches to occur. Consist of start zone, Track, and run-out zone. Terrain Angles: Most occur between 25 to 60 degrees. Few at 25, little above 60. Orientation: Direction a slope faces. Facing the sun increases odds.Avalanche Natural Service Functions: Increase local plant and animal diversity by creating openareas from forested regions.Splitting wedges: Divert flow of snow from human structuresAvalanche Sheds: Shelter for roads and railways.Controlled Explosives: Minimize buildups.Compression Test: A vertical force is placed on the top of the snowpack to detect weak layers.Shovel Test: A column of snow is isolated and then a force is applied on the uphill slide.Rutschblock Test: A skier pushes and jumps on a column of snow to determine the cohesion of a snowpack.Avaluator: Chart designed for avalanche risk assessment.Avalanche Rescue: 90% within 15 min, 30% within 35 min, 0% within 2 hours.Avalanche Survival Aids; Include cord, transceiver, and dogs.Lecture 10 - Wildfires: Wildfire Elements: MUST have fuel, oxygen, and heat.Pre-ignition phase: Includes pre-heating where vegetation is hot and dry from nearby flames radiating heat. Combustion Phase: ignition that could be from a natural (lightning) or human cause. Not all ignitions result in a wildfire if vegetation is not dry.Flaming Combustion: The rapid, high temperature conversion of fuel into heat.Smoldering Combustion: Occurs in areas with ash and already burned material. Conduction: Transfer of heat by solid-to-solid contactRadiation: Transfer of heat in the form of invisible wavesConvection: Transfer of heat by movement of a liquid or gas. Radiation and convection is main source of heat transfer. Heated air becomes less dense and rises, new oxygen sustains combustion. Extinction Phase: Insufficient heat/fuel to sustain fire. Surface Fires: Travel slowly on the ground.
Crown Fires: Travel fast through forest canopy (trees).Wildfire effects: Hydrophobic soil causes erosion and runoff. Creates haze that harms ocular and respiratory systems.Natural Burn Policy: Allowing fires to naturally burn.Mountain Pine Beetles: An Insect infestation that destroys forests.Wildfire Natural Service Functions: Reduce Competition for sunlight and moisture, can release seeds and stimulate flowering.Pioneer vegetation: The first plant species to appear after a wildfireFire Regime: The potential for wildfire in an area.Fire Break: Area with no fuel a fire is steered too.Prescribed Burn: These are controlled fires that are purposely ignited to reduce fuel.