Geol Lab

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Geol Lab
2010-04-19 02:26:55
geology lab

Topographic maps, earthquakes, groundwater, stream processes, and glacier terms
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  1. What are Earthquakes?
    • The shaking or trembling caused by the sudden release of energy in the Earth's rock. Usually associated with faulting or breaking of rocks.
    • Continuing adjustment of position results in aftershocks.
  2. What is Elastic Rebound Theory?
    • Explains how energy is stored in rocks:
    • Rocks bend until the strength of the rock is exceeded
    • Rupture occurs and the rocks quickly rebound to an undeformed shape
    • Energy is released in waves that radiate outward from the fault
  3. Focus
    The point within Earth where faulting begins; also called hypocenter
  4. Hypocenter
  5. Epicenter
    The point directly above the focus on the surface
  6. Where do Earthquakes occur and how often?
    • 80% of all earthquakes occur in the circum-Pacific belt
    • most of these result from convergent margin activity
    • more than 150,000 quakes strong enough to be felt are recorded each year
  7. Economic and Social Impacts of Earthquakes (4)
    • Building collapse
    • Fire
    • Tsunami
    • Ground Failure
  8. What are Seismic Waves?
    Response of material to the arrival of energy fronts released by rupture
  9. What are the two Body waves?
    P and S waves
  10. P-waves (4)
    • Primary waves
    • Fastest waves; travel through solids, liquids and gases; compressional waves
  11. Compressional Waves?
    material movement is in the same direction as wave movement; P-waves
  12. S waves (3)
    • Secondary waves
    • slower than P waves; travel though solids only; shear waves
  13. Shear waves?
    move material perpendicular to wave movement; S-waves
  14. What are the two surface waves?
    R and L waves
  15. Surface waves?
    travel just below or along the ground's surface; slower than body waves, rolling and side-to-side movement; especially damaging to buildings
  16. Relative Motion?
    Reaction of P-wave to dilation and compression detected at seismic stations
  17. Dilation?
    pulling rocks apart (first movement down on a seismograph)
  18. Compression?
    squeezing rocks together (first movement up on a seismograph)
  19. How is an Earthquake's epicenter located?
    • By seismic wave behavior:
    • P waves arrive first, then S waves, then L and R
    • Average speed for all these waves is known
    • After an earthquake, the difference in arrival time at a seismograph station can be used to calculate the distance from the seismograph to the epicenter
  20. Time-distance Graph
    showing the average travel times for P and S waves. The farther away a seismograph is from the focus of an earthquake, the longer the interval between the arrivals of the P and S waves
  21. What is need to locate the epicenter?
    Three seismograph stations
  22. How are the size and strength of an earthquake measured?
    by intensity and magnitude
  23. Intensity?
    subjective measure of the kind of damage done and people's reaction to it
  24. Mercalli scale
  25. Richter scale
  26. What are the destructive effects of earthquakes?
    ground shaking
  27. Ground Shaking?
    amplitude, duration, and damage increases in poorly consolidated rocks
  28. Can Earthquakes be predicted?
    by Earthquake precursors
  29. Earthquake precursors?
    changes in elevation or tilting of land surface, fluctuations in groundwater levels, magnetic field, electrical resistance of the ground; seismic dilatancy model; seismic gaps
  30. What is a glacier?
    the existence of year-round ice in the landscape
  31. What are the two broad types of glaciers?
    Continental and alpine
  32. How do glaciers form?
    glaciers form whenever snowfall exceeds snowmelt year after year. The snow accumulates incrementally, pressure increases, and it is changed into never and then ice by this pressure.
  33. Cirque
    a semicirculr or amphitheater-shaped bedrock feature created as glaciers scour back into the mountain. This is where the snow and ice forming the glacier first accumulates; it is the "headwaters" of a glacier.
  34. Arete
    Steep-sided, sharp-edged, bedrock ridge formed by two glaciers eroding away on opposite sides of the ridge.
  35. What are the two ice sheets that exist today?
    Greenland and Antarctica
  36. Topographic map
    • 1.a graphical representation of the three dimensional shape of the earth's surface
    • 2. a reduced, simplified, categorized/classified, symbolized and annotated representation of the earth's surface which has been projected on a horizontal plane
  37. Latitudes
    a family of lines drawn on the globe parallel to the equator
  38. Longitudes
    circles drawn on the globe that pass through the two poles
  39. Projection
    the process of constructing a map, the transferring of the meridians and parallel to a flat sheet of paper
  40. Map scale
    a means of showing the relationship between the size of an object or feature indicated on a map and the actual size of the object on the ground.
  41. What are the three scale types?
    Fractional, graphical, verbal
  42. Contour lines
    a contour line is an imaginary line on the surface of the earth connecting points of equal elevation
  43. contour interval (C.I.)
    the difference in elevation between any two adjacent contour lines
  44. Topographic profile
    a diagram that shows the change in elevation of the land surface along any given line
  45. Groundwater
    the water which is contained within the saturated zone beneath the Earth's surface
  46. Hydrologic cycle
    a process by which water is transported from one part of the Earth to another.
  47. Zone of Aeration
    comprised of water and air filled spaces
  48. Evapotranspiration
    a process by which water is returned to the atmosphere by the transpiration of living plants.
  49. Zone of Saturation
    every pore space is completely saturated/filled with water.
  50. Water Table
    upper surface of the saturated zone which divides the saturated zone from the unsaturated zone.
  51. Aquifer
    an underground unit of soil/rock/sediment that can yield a significant quantity of groundwater
  52. Permeability
    the capacity of rock/unconsolidated material to transmit a liquid
  53. Porosity
    measure of the volume of pore space per volume of rock/sediment
  54. Confined aquifers
    aquifers which are bound above and below by a confining layer.
  55. Confining layer
    layer of sediment/rock which has a lower permeability than the aquifer that is confines
  56. Aquitards
    confining layers
  57. Unconfined aquifer
    does not have a confining later above it
  58. Water table aquifers
    unconfined aquifer
  59. Potentiometric surface
    when a well is excavated the level to which the water rises within the well
  60. Flowing well or spring
    when the potentiometric surface is above the surface of the ground
  61. Point source
    pollution which has a single identifiable source of pollution
  62. Non-point source
    pollution that may come from a variety of sources and has no apparent source
  63. Velocity
    the times is takes a given particle of water to traverse a given distance in a stream
  64. Laminar
    all water molecules travel along similar parallel paths
  65. Turbulent
    individual water particles take irregular paths
  66. Discharge
    • the amount of water flowing in a stream, which is the volume of water passing any point in a given time interval
    • Area x Average Velocity
  67. Load
    the rock particles and dissolved ions carried by the stream
  68. Suspended Load
    particles that are carried along with the water in the main part of the streams
  69. Bed load
    coarser and denser particles that remain on the bed of the stream most of the time but move by a process of saltation (jumping) by a result of collisions between particles, and turbulent eddies
  70. Dissolved load
    ions that have been introduced into the water by chemical weathering of rocks. this load is invisible because the ions are dissolved in the water.
  71. Stream
    characterized by water flowing in a channel of some sort
  72. Fluvial
    relates to stream
  73. Watershed
    the area of land that contributes water to stream; drainage basin
  74. headwaters
    the upstream part of a stream near its origin
  75. mouth
    the downstream end of a stream where it empties into another stream or body of water
  76. Tributary
    a smaller stream that joins a larger, mainstem stream
  77. Mainstem stream
    a larger stream that is joined by smaller tributaries
  78. gradient
    the steepness of the slope of the stream bed, generally steeper near headwaters and becoming gentler towards the mouth.
  79. Step-pool
    pools are deep and smooth. steps are formed by water running over a shallow rocky area (a bar) and down into a pool. Due to high gradient channels with rocky sediments.
  80. Pool-riffle
    riffles are shallow and turbulent of water flows over a bar
  81. channel bed
    the bottom of the stream channel
  82. Channel banks
    the sides of the stream channel
  83. Point bars
    gently sloping sediment deposited on the inside of the bend.
  84. thalweg
    the deepest part of the stream channel
  85. Erosion
    the movement of sediment from its source to another location
  86. Bank full width
    the width of a stream channel when the water just fills the channel but does not overlap the banks
  87. Floodplain
    The level are near a stream channel constructed by stream overflow during flood events.
  88. Terraces
    abandoned floodplains and usually have a higher elevation that the present floodplains
  89. Dendritic drainage pattern
    resembles the branching of a tree, many tributaries flowing into the mainstream of the stream
  90. Rectangular drainage
    channels that form right angle bends
  91. Radical drainage
    channel flow outwards from the center, resembles the spokes of a wheel
  92. Centripetal drainage
    channels flow to a center point
  93. annular (radical) drainage
    streams form concentric rings connected by short radical channels
  94. Trellis drainage
    the mainstream is intersected by angular tributaries, resembles a vine
  95. Deranged drainage
    random pattern
  96. Flood hazards: normal stage
    when the water level of a river is below the river's banks
  97. Flood hazards: bankfull stage
    when the water level is even with the banks
  98. Flood hazards: flood stage
    when the water level exceeds the banks
  99. Relief
    difference in elevation
  100. Quadrangles
    rectangular sections of Earth's surface bound by lines of latitude and longtiude
  101. GN
    true north
  102. MN
    magnetic north
  103. Declination
    difference between MN and GN, is exact only for the year listed on the map
  104. Photovision
    how maps are updated through aerial photographs to discover changed in the landscape
  105. Stereo pair
    topographic maps are made from overlapping pairs of photos
  106. Index contour
    lines marked with numbers
  107. Contour interval
    the elevation
  108. benchmark
    a permanent marker, labeled as an X symbol on the map
  109. Gradient
    measure of the steepness of a slope
  110. regional relief
    the difference in elevation between the highest and lowest point a topo map
  111. Zones
    stripes of longitude having a width of 6 degrees
  112. Bearing
    compass direction
  113. Groundwater
    rain that soaks into the ground
  114. Surface water
    water in lakes and streams
  115. base flow
    melting snow
  116. Perennial streams
    flow continuously through the year
  117. intermittent stream
    flow only during certain times of the year
  118. alluvium
    where sediments are deposited
  119. drainage basin
    entire stream drainage system
  120. divides
    lines boundaries that separate stream drainage system
  121. uplands
    the small valleys in a drainage basin occur at it's highest elevation
  122. Head
    point of origin of stream
  123. Head-ward erosion
    process of form v-shaped erosion
  124. Mouth
    end of river valley
  125. hydraulic gradient
    the slope of the water surface
  126. karst
    a distinctive topography that indicates dissolution of underlying soluble rock
  127. Sink hole
    surface depression formed by the collapse of caves or other larger undergrounf void spaces
  128. Solution valleys
    valley-like depressions formed by a linear series of sink holes or collapse of the roof of a linear cave
  129. Springs
    places where water flows naturally from the ground
  130. disappearing streams
    streams that terminate abruptly by seeping into the ground
  131. stalactites
    icicle-like masses of chemical limestone that hang from ceillings
  132. Artesian wells
    water flows naturally from the top of the well
  133. Wastage
    winter accumulation of snow and ice exceeds the summer ablation
  134. Ablation
    the loss of snow and ice by melting and sublimation to gas
  135. Sublimation
    direct change from ice to water vapor, without melting
  136. snowflieds
    regions of permanent snow cover
  137. Zone of Accumulation
    as snow and ice collect they become compacted and highly recrystallized under their own weight
  138. Zone of Ablation
    ice melts or sublimes faster than new ice forms
  139. Snowline
    the boundary between the zone of accumulation and ablation
  140. terminus
    the bottom end of the glacier
  141. glacial retreat
    when a glacier melts, it appears to retreat up the valley from which it flowed
  142. Drift
    deposits of rocky gravel, sand, silt, and clay accumulate where there once was ice
  143. till
    drift that accumulates directly from the melting ice is unstratified
  144. Stratified drift
    drift that is transported by the melt water becomes sorted by size
  145. loess deposits
    wind-transported glacial material
  146. Valley glaciers
    long glaciers that flow down stream valleys in the mountains
  147. piedmont glaciers
    mergers of two or more valley glaciers at the foots of a mountain range
  148. ice sheet
    a vast, pancake-shaped ice mound that covers a large portion of a continent and flows independent of the topographic features beneath it
  149. bergschrund
    the upper end of the glacier is the large part that separates the flowing ice from the relatively immobile portion of the snowfield
  150. crevasses
    the other cracks or open fissures that form when the velocity of ice flow is variable
  151. transverse crevasses
    perpendicular to the flow direction
  152. longitudinal crevasses
    aligned with direction of flow