Environmental Geology Exam 2
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121 terms
Terms | Definitions |
|---|---|
 Aftershocks | Smaller quakes produced after a major quake caused by rocks shifting to new positions |
| Body Waves | Seismic waves that travel through the Earth's interior |
| Creep | Slow, more or less continuous movement occurring on faults due to ongoing tectonic deformation. |
| Earthquake | Occurs when movement along a fault zone results in a sudden release of built-up strain energy in the lithosphere. |
| Earthquake Cycle | The concept that there is a periodic quality about the occurrence of major earthquakes on a given fault zone, with repeated cycles of stress buildup, rupture, and relaxation of stress through smaller aftershocks |
| Elastic Rebound | The sudden return of elastically deformed rock to its original shape |
| Epicenter | The point on the Earth's surface directly above the focus of an earthquake |
| Fault | A crack in the earth's crust resulting from the displacement of one side with respect to the other |
| Focus | The location within Earth along a fault at which the first motion of an earthquake occurs |
| Intensity of an Earthquake | Measurement of the damaging effects of an earthquake at a particular location. |
| Liquefaction | The process by which an earthquakes violent movement suddenly turns loose soil into liquid mud |
| Magnitude | A measure of the amount of ground displacement or shaking associated with the earthquake |
| Modified Mercalli Scale | A12 point scale developed to evaluate earthquake intensity based on the amount of damage to various structures. The higher the number, the more damage. |
| Moment Magnitude | Amore precise measure of earthquake magnitude than the Richter scale, which is derived from the amount of displacement that occurs along a fault zone and estimates the energy released by an earthquake |
| Precursor Phenomena | Phenomena that precedes an earthquake, volcanic eruptions or other natural events, which may be used to predict upcoming events |
| P Waves | A type of seismic wave that compresses and expands the ground |
| Richter Magnitude Scale | A scale that is used to compare the strength of the earthquakes based upon the amount of energy released |
| Seismic Gap | An area along a fault where there has not been any earthquake activity for a long period of time |
| Seismic Waves | Vibrations that travel through Earth carrying the energy released during an earthquake |
| Seismograph | A measuring instrument for detecting and measuring the intensity and direction and duration of movements of the ground (as an earthquake) |
| S Waves | A type of seismic wave that moves the ground up and down or side to side |
| Surface Waves | Travel along the earth's surface and are the slowest and largest of the seismic waves and cause most of the destruction during an earthquake |
| Tsunami | seismic sea wave that begins over an earthquake focus and can be highly destructive when it crashes on shore |
| Areas in the USA at earthquake risk | Southern Alaska, western states, the midwest along the New Madrid fault zones, and sections of the east coast |
| Earthquake Prediction Techniques | Recognizing seismic gaps and by studying precursor phenomena and earthquake cycles. |
| What type of body wave travels faster? | P waves |
| Earthquake Hazards | Ground shaking, landslides, liquefaction, Tsunamis, flooding and fires. |
| Locating the Epicenter | P waves arrive at a seismograph first, with S waves following close behind. P-S waves=distance from epicenter. The farther away an earthquake is, the greater the time between the arrival of the P and S waves. The radius of each circle is the distance from the seismograph to the epicenter |
| Earthquake Locations | Generally occur in linear belts on plate boundaries |
| Divergent Plate Boundaries | Tectonic plates spreading apart, new crust being formed (ex. mid-ocean ridges, rift valleys). Produce shallow earthquakes |
| Convergent Plate Boundaries | Two plates colliding and creating either a mountain range (2 continental) or a subduction zone (2 oceanic), or trench (oceanic and continental) |
| Reverse Fault | A type of fault where the hanging wall slides upward; caused by compression in the crust. Associated with mountain building |
| Continent-Continent Convergent Boundaries | Shallow Earthquakes associated with tall mountains with intense compression. Ex. Seismic zones from Himalayas, Afghanistan, Iran and Turkey |
| Transform Plate Boundaries | Two plates slide horizontally, cause shallow earthquakes. Ex. San Andres Fault |
| Logarithmic Scale | When Richter scale increases by 1, displacement increases by 10 and the energy released increases by 30 |
| Loma Prieta, CA Earthquake | October 1989, magnitude of 7.1. Only 63 die because of massive crowd outside watching world series. Damage done to structures built on mud. |
| Mexico City Earthquake | September 1985. Magnitude of 8.1. 20,000 people died. Mexico city built on a drained lake bed with lots of soft sediments |
| Building Codes to withstand earthquakes | Reinforced masonry, rubber foundation pads, prestressed bracing rods |
| Gaining streams | Water flows from groundwater into a stream or lake. Common in humid areas |
| Losing streams | Water flows from a stream or lake into groundwater. Common in arid areas. |
| Perennial Streams | Streams that flow all year long. |
| Ephemeral/Intermittent streams | Streams that only flow during the wetter part of the year. |
| Stream Discharge | Cross-sectional area of river channel multiplied by velocity of water. |
| How to find stream discharge | Divide river into intervals and measure the water depth and velocity in the middle. Multiply width of each interval by depth/velocity. Add the discharge from all intervals together. |
| Stage | Elevation of water surface |
| Rating curve | Take discharge measurements when the river is at different stages and plot discharge vs. stage. |
| Hydrosphere | all the water on earth's surface |
| Steps of the hydrologic cycle | Evaporation, condensation, precipitation, transpiration, runoff, infiltration and percolation |
| Stream | Flowing water within a channel |
| Drainage basin | a region from which a stream draws water |
| Load | The total quantity of material that a stream transports by all methods (traction, saltation, suspended and dissolved) |
| Capacity | a measurement of the total load of material a stream can move |
| Gradient | The steepness of the stream channel |
| Base Level | The lowest elevation to which the stream can erode downward |
| Longitudinal profile | a sketch of a stream's elevation from source to mouth |
| Slow moving water | carries fine-grained sediments |
| Fast moving water | carries a wider range of grain sizes |
| Sorted | Sediments characterized by size and density |
| Delta | a large, fan-shaped pile of sediments in still waters created by a stream |
| Alluvial fan | fan shaped pile of sediment in a larger stream or a region between mountains and a plain formed by a small tributary system |
| Meander | a curve in a stream |
| Cut Bank | downstream and outside side of the meander, flows somewhat faster |
| Braided Stream | A stream or river that is composed of multiple channels that divide and rejoin around sediment bars |
| Floodplain | the flat area of a river valley next to the channel, which is built of deposited sediments and is covered with water when the river overflows its banks at flood stage. |
| Oxbows | When higher discharge, the stream may cut off the meanders to make a more direct flow |
| Hydrograph | a plot of stream discharge at a point over time |
| Crest | Maximum stage is reached |
| Upstream Flood | small, localized floods (sudden, locally intense rains and events such as dam failure) |
| Downstream Flood | a flood affecting a large area of drainage basin or a large stream system;typically caused by prolonged rain or rapid regional snow melt. |
| Restrictive Zoning | Flood hazard reduction: similar to strategies applicable to reducing damage from seismic and other geologic hazards |
| Retention Pond | Flood hazard reduction: A large basin designed to catch surface runoff to prevent its flow directly into a stream |
| Diversion Channel | Flood hazard reduction: Redirects water flow into areas next to the stream when the stage is raising |
| Levees | Raised banks along a stream channel that increase velocity, upstream risks and create false security to live by bodies of water likely to flood |
| Point bar | deposit of sediment build up by a river on the inside bend of a meander |
| Infiltration | water that is absorbed by the soil and funneled down to groundwater |
| flood | the rising of a body of water and its overflowing onto normally dry land |
| Bed Load | sediment that is carried by a stream along the bottom of its channel |
| Channelization | An engineering technique to straighten, widen, deepen, or otherwise modify a natural stream channel. |
| Recurrence Interval | how frequently a flood of 'x' severity occurs in average for that particular stream |
| Saltation | The leaping movement of sand or soil particles as they are transported in a fluid medium over an uneven surface |
| Suspended Load | the fine sediment carried within the body of flowing water |
| Flood Prediction | Design flood prevention structures and decide where the floodplain will be |
| Calculating Probability of a flood | N-year storm is 1/N% |
| Factors that influence flooding | Soil/rock type, topography, vegetation, soil conditions |
| How people influence flooding | Asphalt and concrete, vegetation is removed, storm sewers, buildings push water higher |
| Point Source | A specific source of pollution that can be identified, such as a pipe. |
| Non-Point Source | a widely spread source of pollution, such as road runoff, that is difficult to link to a specific point of origin |
| PCBs | synthetic chemicals containing chlorine that are used in the manufacture of plastics and other industrial products, become stored in the tissue of animals, and also persist in the environment |
| Aquifer | a body of rock or sediment that stores groundwater and allows the flow of groundwater |
| Aquitard | earth materials which do not allow the free movement of groundwater through it |
| Artesian System | a confined aquifer system in which ground water can rise above its aquifer under its own pressure |
| Cone of depression | lowered area of a water table produced by pumping water from a well |
| Confined Aquifer | A groundwater storage area trapped between two impermeable layers of rock. |
| Desalination | a process of removing salt from ocean water |
| Ground water | the part of the subsurface water that is in the zone of saturation, including underground streams. |
| hard water | water that contains salts (as calcium and magnesium ions) that limit the formation of lather with soap |
| Karst Topography | a type of landscape in rainy regions where there is limestone near the surface, characterized by caverns, sinkholes, and valleys |
| Permeability | The ability of a rock or sediment to let fluids pass through its open spaces, or pores. |
| Phreatic Zone | zone of saturation, is the area in an aquifer, below the water table, in which relatively all pores and fractures are saturated with water |
| Porosity | The percentage of the total volume of a rock or sediment that consists of open spaces. |
| Potentiometric Surface | The potential level to which water will rise above the water level in an aquifer in a well that penetrates a confined aquifer |
| Recharge | new water that enters the aquifer from the surface. Urbanization and the filling of wetlands can reduce this. |
| Saltwater Intrusion | Movement of salt water into freshwater aquifers in coastal and inland areas as groundwater is withdrawn faster than it is recharged by precipitation. |
| Sinkhole | a depression produced in a region where soluble rock has been removed by groundwater |
| Soil Moisture | Water contained in the aeration or unsaturated zone. |
| Unconfined Aquifer | aquifer in which there is no impermeable layer restricting the upper surface of the zone of saturation |
| Vadose Zone | subsurface zone in which rock openings are filled with air and water |
| Water Table | underground surface below which the ground is wholly saturated with water |
| Zone of aeration | upper region of groundwater between the water table and the earth's surface |
| Zone of saturation | The lower zone where water accumilates between small rock particles. |
| Aerobic decomposition | decomposition using or consuming oxygen |
| Anaerobic Decomposition | When oxygen is gone in the water and breakdown of matter is turned into noxious gases, including hydrogen sulfide, and methane. |
| Algal bloom | an immediate increase in the amount of algae and other producers that results from a large input of a limiting nutrient |
| Biochemical Oxygen Demand | Amount of oxygen required by aquatic bacteria to decompose a given load of organic waste;a measure of water pollution |
| Aeration | Restores oxygen depletion in lakes |
| Dredging | Removal of contaminated sediments laden with toxic compounds that are attached to the sediments |
| Eutrophication | Complete breakdown of excess organic matter that enriches water with plant nutrients (nitrates, phosphates and sulfates) plants such as algae thrive on these |
| Geochemical Cycle | Precipitation--> weathering-->ions dissolved in stream load-->minerals precipitate out and cycles continue |
| Oxygen Sag Curve | a graph of dissolved oxygen content as a function of distance from a waste source |
| Thermal Pollution | Release of excess heat or waste heat, generate by power from a product (cars) |
| Residence Time | How quickly a substance cycles through each reservoir |
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