Weathering, Erosion, Deposition, Landscapes


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Weathering, Erosion, Deposition, Landscapes

  1. 1. Unit #10:Weathering, Erosion, Deposition
  2. 2. Why do rocks weather? rocks below the surface are protected from the exposure to wind, water and biological processes once uplifted and exposed rocks begin to weather
  3. 3. Weathering  the breakdown of rock due to physical or chemical changes
  4. 4. Physical Weathering  changes the size and/or shape of a rock, without changing the rock’s chemical composition Example: breaking a rock into smaller pieces  harder minerals are more resistant to physical weathering
  5. 5. Types of Physical Weathering: Frost action  alternating temperatures above and below 0°C, allow water to melt and freeze, causing expansion of the cracks Biological Factors  roots of plants can grow within cracks in the rocks and increase the crack size, leading to crumbling of the rock Abrasion  collisions between particles caused by wind, moving ice and gravity, these particles act like sandpaper of the rocks
  6. 6. Chemical Weathering  changes in the chemical composition of rock, thereby forming new substances. Example: rusting of iron rich mineral
  7. 7. Chemical Weathering  chemical weather requires heat and water  some minerals are more resistant to chemical weathering, such as quartz  slightly acid water can cause significant weathering of limestone forming caves  emissions of atmospheric pollutants such as oxides of sulfur and nitrogen can cause rain to be acid and increase chemical erosion carbonic, nitric, and sulfuric acid are able to change hard limestone into a soft residue
  8. 8. How do soils form?Soil --> mixture of weathered rock and organic remains that usually cover bedrock Develop through:  physical weathering  chemical weathering  organic activity
  9. 9. Nature of soils dependent upon: rocks from which it weathered local climate amount of organic activity (plants and animals)
  10. 10. Soils Horizons --> distinct layers of soil created by different amounts of organic and inorganic material
  11. 11. Thickness of Soil horizons  young/immature soils do not show distinct horizons  mature soils show distinct A, B, and C horizons  arid climates have thin soils  humid climates have thick soils  steep sloping areas have thin soils gentle sloping areas have thick soils
  12. 12. Escarpments in an aridclimate
  13. 13. --> Soils must be conserved from windand water erosion--> it takes between 100 and 400 yearsfor one centimeter of topsoil to form--> Conservation methods include: Contour farming Terracing Increase vegetation cover Wind blocks
  14. 14. Types of Soils Residual soils --> form directly above the parent bedrock, thinner Transported soil --> form from sediments that has been moved into that area
  15. 15. How are weathered MaterialTransported? Sediments --> rocks that have been broken into fragment, regardless of their size
  16. 16. Erosion--> the transporting of sediments awayfrom their place of origin and thedepositing of them elsewhereForce behind erosion: gravity Example: rock falling from a cliff Water moving down slope
  17. 17. Erosion by Water Watering is the primary agent of erosion on the Earth’s surface  each year streams and rivers carry millions of tons of sediments downstream and into the oceans
  18. 18. Transportation of sediments by water: 1) Solution --> smallest particles dissolved in the water, can’t be filtered 2) Suspension --> large particles, not dissolved, can be filtered 3) bouncing and rolling --> largest particles will travel along the bottom of the stream channel
  19. 19.  Faster moving water carry largerparticles and small particles Slower moving water carry smallparticles, only
  20. 20. The Velocityof Streams.  controlled by the slope of the landscape and the volume of water  Stream gradient increases, water velocity increases Increase volume of water will also increase velocity
  21. 21. Discharge --> volume of water that is traveling in a stream Increases with velocity and volume
  22. 22. Speed of waterEquilibrium exists betweenthe force of gravity and thefriction created by thechannel In a straight stream,water will flow the fastestin the middle of thechannel, less friction
  23. 23. Meandering Stream •--> curvingstream path Erosion on theoutside of theturn, velocity isfastest Deposition onthe inside of theturn, velocity is
  24. 24. --> Gentlevalleys, likeMilford, will havemeanderingstream, morehorizontalerosion--> Steepvalleys, likeravine behindthe school, hasstraighterstreams, morevertical erosion
  25. 25. Erosion By Wind --> pick up loose rock materials such as sand, silt and clay and carry them away --> occurs in arid climates with little vegetation --> erosion of clay and silt (smallest) particles leaving behind only larger particles called: desert pavement --> can also erode by abrasion --> similar to sandpaper rubbing against a rock creating angular, but smooth sediments called: ventifacts
  26. 26. Erosion by Ice--> when the snow during the winter does not melt during the summer and begins to accumulate year after year --> Ice can get up to a mile thick --> Ice will start to move down slope under its own weight --> Glaciers will trap all sizes of sediments within the ice, creating a massive piece of sandpaper that will scour the valley it travels through
  27. 27. Evidence of Glaciation--> Glaciers will deepen and widen preexisting valley to give them a characteristic U-shape. --> Stream cut through valleys with vertical erosion to create a V-shape Unsorted deposits --> deposition of sediments of all sizes in one area Striations --> scratches in the bedrock caused by the rough undersurface of the parallel grooves that align with the glaciers movement --> In NYS these striation run from NW to SE, indicating that the last glacial advancement came from Canada
  28. 28. Four Periods of continental glaciation inthe past two million years in NYS due to glaciation, NYS is coveredwith thick transported soilsThe last glacial advancement was theWisconsin glacier approximately 11,500years ago
  29. 29. o Created U-shaped valleyso Rounded mountain topso Polished bedrock with striationso Unsorted sedimentso Long Island and Cape Codo Finger lakeso Thick transported soilsLarge miscellaneous boulders called: Glacialerratic
  30. 30. What is depositions? Deposition --> when an agent of erosion deposits, or lays down, particles and fragments of earth materials  also called sedimentation  most deposition occurs in water
  31. 31. Factors that affect deposition Rate of deposition is dependent upon factors such as:  Size  Shape  Density  Speed of the transporting material
  32. 32. Particle Size: --> Inverse relationship  large a particles settle first, while small particles settle last  particles in solution or suspension may stay suspended indefinitely
  33. 33. Particle Shape:--> flat, angular and irregularly shapedparticles settle more slowly thansmooth, rounded particle
  34. 34. Particle Density--> denser particles settle faster--> less dense particles settle moreslowly
  35. 35. Settling Rate and Settling Time--> Inverse relationship --> faster rate indicates less settling time --> slower rate indicates more settling time
  36. 36. Time Settling Time of Particles Mass (g) (Size) Settling Rate of Particles (meters/sec.) Rate Mass (g)(Size)
  37. 37. Sorting of Sediments--> velocity of transporting materialplays a major role in determining whendeposition of particles will occur--> initiated by a reduction in velocity
  38. 38. Stream is moving at a velocity of 500 cm/sec it is carrying all sized particles. Slow down, drop sediment load Clay Pebbles Silt Sand
  39. 39. Horizontal sorting  sorting with largest, densest and roundest first and then farther out the smallest, least dense and flattest particles farther out (horizontal arrangement)
  40. 40. Vertical sorting (graded bedding)particles are deposited inlayers with the largest,densest and roundestparticles on the bottom andthen the smallest, leastdense and flattest particleson top Example: dropping amix of particles into water(can be repetitive)
  41. 41. Deposition by streams:Sandbars  shallow area in a stream due to low water velocity o frequently dredged to keep the stream deep Delta  deposits created when a stream enters a larger body of water o land around the mouth of the Mississippi is a delta, New Orleans, Mississippi delta is thousands of square miles
  42. 42. Deposition by Wind generally sorted by size and located in arid climates wind leaves behind larger sediments creating
  43. 43. Sand dunes  hills of wind blown deposits
  44. 44. Deposition by Gravity gravity pulls sediments toward the Earth’s center, they are not sorted when deposited by gravity, angular
  45. 45. Deposition by Glaciers Adult person  deposition occurs when the glacier melts leaving behind eroded sediments  unconsolidated and unsorted Glacial erratic  large rocks that have been transported by glacial ice
  46. 46. Two types of Glacial sediments: 1) unsorted sediments  deposited directly by the glacier 2) sorted sediments  deposited by the moving melt water of the glacier
  47. 47. New York and The Ice Ages  NYS’ climate has changed over the last 2 million years causing 4 different ice ages  Accumulation of snow and ice creates a glacier that will then begin to move to lower elevations due to its own weight  When the climate warms again, glaciers melt, releasing tremendous amounts of water causing even more erosion
  48. 48. Types of Glaciers: 1) Alpine glaciers (valley glaciers)  occur in mountain regions 2) Continental glaciers (ice sheets)  large glaciers that start in colder regions and move down slope  this type of glacier produced most of NYS glacial features
  49. 49. Evidence of Glaciation in NYSU-shaped valleys
  50. 50. Evidence of Glaciation in NYS glacial polish, rounded hills: bedrock that has been smoothed by the scouring action of the ice and collected sedimentsstriations grooves and scratches in the bedrock, indicate the direction of flowdrumlins  small rounded mounds created when a glacier goes over hills of unconsolidated sediments
  51. 51. Evidence of Glaciation in NYS moraines  unconsolidated, unsorted sediments that were pushed forward by the glacier as it advanced o form Long Island and Cape Cod o created the valley head moraine, which allowed for the formation of the Finger Lakes  outwash plan  area of sorted sediments created by glacial melt water
  52. 52. The Oceans and Costal Processes  Earth is 71% covered by seawater  Average depth 3 miles  Most sediments from land will be eroded to the oceans Edges of the oceans are places of rapid change caused by the action of waves and longshore currents.
  53. 53. Waveswater does not move forward with thewaves, but circulate transferring energy
  54. 54.  movement of waves and longshorecurrents create many typical featuresalong the shorelinehumans love to live near the ocean, butthe rapid rate of erosion causedestruction of property
  55. 55.  humans build structures to reduce thedamage created by waveso breakwaters – shelter harbors, boatsjetties – build to keep sand from erodingaway from the beach
  56. 56. What is a Landscape? Landscape  a region on Earth’s surface in which physical features, such as hills, valleys and streams are related by a common origin Topography  general shape of the landscape
  57. 57.  landscape features aredetermined by: o climate o bedrock o geologic structures o human activities
  58. 58. Landscape regions: Mountains  greatest relief, often igneous and metamorphic or nonhorizontal sedimentary rocks Example: Rockies, Adirondacks, Alps, Himalayas
  59. 59. Landscape regions: Plateau  relatively flat or rolling uplands, underlain by flat sedimentary bedrock Example: Milford area, Grand Canyon
  60. 60. Landscape regions: Plains  little topographic relief, flat low elevation Example: Florida & Midwest
  61. 61. The Influence of Climate  humid areas have more rounded landscapes arid areas have more sharp angles and steeper slopes to the landscape
  62. 62. Moisture is important to therate of chemical weathering  causing more rounded landscapes  thicker soils  promotes plant growth
  63. 63. Arid environments produce:  greater amounts of physical weathering  thin soils  deserts have the most rapid stream erosion after a rainfall
  64. 64. Landscapes of the United States abrupt changes in landscape is a result of change in the bedrock
  65. 65. How do geologic Factorsinfluence the landscape?  within the same climate landscape regions can develop very differently  hard minerals create rocks that are very resistant to weathering and erosion o creating cliffs or escarpments near regions of less resistant rock streams also follow areas of weaker, softer rock
  66. 66. Landscapes affect drainage patterns
  67. 67. Landscapes of New York State St. Lawrence/ Champlain Lowlands  plains areas, predominantly layers of sedimentary rocks
  68. 68. Appalachian Uplands (Allegheny Plateau)  largest landscape region in NYS o underlain by flat layers of sedimentary rocks o landscape have been uplifted 1000 of meters, which were later eroded by streams (dissected plateau) Finger lakes have been eroded out of this landscape
  69. 69. Erie-Ontario Lowlands  areas south of these lakes o created by sediments left by glacial meltwater great soils for agricultural purposes
  70. 70. Adirondack Highlands o only true mountain landscape in NYS o uplifted ancient metamorphic and igneous rocks creating a dome o very hard and resistant to weathering NYS highest mountain: Mount Marcy (5240 feet)
  71. 71. Landscape vs. Age Streams will continue to erode an area to produce a wide flat valley and many meanders in the stream