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Facts about the quake 8.8 on the Richter Scale Occurred at the boundary between the Nazca and the South American Plate ( The two plates are converging at a rate of 80 millimeters a year, with the Nazca plate moving down and eastward under the South American plate.)

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location

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Magnitude of the Quake The Quake that hit Haiti was a 7 on the Richter Scale, yet the one that hit Chile was an 8.8. Scientists say that the Chilean quake was 500 times stronger. How did they come up with this figure?

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Differences in the quakes Haiti 2010 Chile 2010 7.0 on the Richter scale Focus was 8 miles Happened in Capital City Death toll 200,000 Buildings not built to code 37 mile after shock fault line zone Strike Slip Fault 8.8 on the Richter Scale Focus was 22 miles Major cities farther away Death toll Strict seismic building code enforced 375 mile after shock fault line zone Dip Slip Fault at a subduction zone

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The Chile quake caused a massive uplift of the sea floor, triggered tsunami waves that race across the ocean at up to 550 miles per hour the speed of a jet plane. When the waves approach a coast, they slow down to about 20 to 30 miles an hour. They are now at their most dangerous: As all their energy gets compressed into much less depth, the waves can dramatically increase in height.

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Tsunami damage in Pelluhue, Chile

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Review of why Tsunamis are so Dangerous

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Ch 16 Running Water

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The Hydrologic Cycle

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Percent of Fresh vs. Salt Water What percent of earths water is salt water? What percent is fresh water ?

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Water on Earth 97 % is Ocean Salt water 3% is Fresh Water of the 3 % - 2.15% is in glaciers and 0.62 % is Ground water The rest is in the atmosphere, in lakes 0.009% streams -.0001%

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Characteristics of running water Sheet flow running of long thin sheets across the ground Infiltration capacity is how much water can run on the surface without sinking into the ground.

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Factors Affecting the Infiltration Capacity: Duration and intensity of rainfall Prior wetted conditions of the soil The soil texture The slope of the land The nature of vegetative cover

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Rills Tiny channels begin to form and carry water to a stream Streams turn into rivers Rivers carry water to the ocean Streams in Geology means channelized flow of any kind from a small brook to a roaring river.

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Carrying Capacity Competency The Amount that a stream is able to carry. Most streams are not at capacity The maximum size of a particle that a river can carry, based on its velocity. Competence increase as a square of its velocity

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Running Water Streamflow Two types of flow determined primarily by velocity Laminar flow Turbulent flow Factors that determine velocity Gradient or slope Channel characteristics including shape, size, and roughness

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Laminar Flow vs. Turbulent Flow- Laminar Flow Turbulent Flow When fluid flows in parallel layers or horizontal layer Fluid flow in which the fluid undergoes irregular fluctuations, or mixing. The speed of the fluid at a point is continuously undergoing changes in magnitude and direction, which results in swirling and eddying as the bulk of the fluid moves in a specific direction

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Laminar vs. turbulent The type of flow is related to the type of sediment a stream can carry. Rivers with turbulent flow carry larger sediment. There is a fine layer at the bottom of each stream that is a laminar flow which is protective of the particles that lay there.

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Running Water Streamflow Factors that determine velocity Discharge the volume of water moving past a given point in a certain amount of time Changes from upstream to downstream Profiles Cross sectional view of a stream Viewed from the head (headwaters or source) to the mouth of a stream

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Cross-Section of a Stream

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Running Water Factors that increase as you go downstream Velocity Discharge Channel Size

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Running Water Changes from upstream to Downstream Factors that decrease downstream Gradient-Steep to Shallow Channel Roughness the rougher the base level the more resistance to flow

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Base Level The lowest point to which a stream can erode Ultimate (exterior) (sea level) Local or temporary (interior)-never reaches the ocean Readjustment of base level is caused by changing conditions or stream activities Raising the base level causes deposition Lowering the base level cause erosion

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Base Level A streams main job is to get to its base level Whether that is the ocean like it is for exterior streams Or a lake, valley, or basin as it is for interior streams. This is a cycle as described by Davies in the early 1900s

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The Mississippi is external

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The Streams and Rivers in the Wasatch front are local or interior

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Deltas

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Alluvial Fans - Bajadas formed by internal streams

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Temporary Base Levels Lake being filled by sediment Water falls continually being eroded

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Niagara

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William Daviss Theory of Rejuvenation Mountain Streams are in the juvenile stage Mass wasting High velocity in streams Large boulders Low level of suspended load in the water V shaped Valleys Downward Cutting by Streams into bedrock

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Davis Mature stage of stream rejuvenation Erosion begins to go latteral instead of straight down into the bedrock Meandering streams

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Changes from upstream to downstream The longitudinal profile of a stream

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Old age-Oxbow lakes

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Uplifting causes rejuvenation 10,000,o00 the Colorado River was uplifted and the process started all over again

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Where in the river is the velocity of the water flow the greatest? Is it in the mountain zone or in the valley?

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Answer the valley Why? The velocity must be higher to accommodate the upper flow or it would back up The turbulence of the mountain portion is higher creating more turbulent flow and less laminar flow Rivers upstream sometimes even go backwards

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Kayaker in an eddy

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Drainage Basins The land area that contributes water to a river system

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The Great Salt Lake Desert Basin Vast desert area of over 18,000 square miles expanding south, west and north of The Great Salt Lake. Bonneville salt flats are part of this basin Streams in this basin have very little flow except for snowmelt and runoff months of April July. Lower basin gets about < 5 inches Higher areas such as mountains get > 50 inches Maximum elevation = 13,000 ft Minimum elevation = 4, 190 ft

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Mystery of the levels of the basin around the Great Salt Lake Sometimes we have a large amount of winter and summer precipitation but the river remains low, why? Get together with a group and if you can explain why you get 20 pts to use towards the next 2 quizzes!

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Equilibrium of a River System River systems function as a unified whole (if one part is altered, it affects the whole river) Major Variables to consider Discharge Gradient Base level Sediment Load Volume Channel Shape

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A graded stream is: A hypothetical stream where equilibrium has been established All parts mentioned on the previous slide are in balance so that no erosion or sedimentation has occurred.

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How would each of the following get changed and put out of equilibrium? Discharge Gradient Base level sediment load Volume Channel shape Discuss this with someone and then we will share answers.

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The following can affect a graded stream: Faulting causing waterfalls, fissures, Mass wasting slides etc. Human construction projects like dams, channels, hydrologic power plants, irrigation. Floods extra sediment deposit

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Examples of River dis-equilibrium The Aswan Dam of the Nile Floods deposited silt flooding and fertilizing The dam was built to provide hydroelectric power and irrigation in 1970 BUT. The dam destroyed the equilibrium of the river physical and biological balance in the delta was destroyed marine currents and wave erosion ate away at the delta front receding several meters per year marine life that ate sediment deposits perished and killed off the sardines, mackerel, clams, and crustacean industry Farm lands have to be artificially fertilized The lack of sediment increased the velocity of the river and it has ruined many bridges and dams formerly built Many other problems have arisen

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Aswan Dam and Nasser Lake

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Urbanization Roads, parking lots and structures disrupt the hydrologic cycle. Water does not percolate into the ground water at the same rate There are less areas dedicated to releasing water vapor by plants through evapotranspiration

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Basic Processes of Stream Erosion 1. Removal of the Regolith 2. Downcutting of Stream Channels by abrasion 3. Headward erosion

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1. Removal of the Regolith Regolith rock debris produced by weathering

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2.Downcutting of Stream Channels From gullies to canyons Abrasion by sand, cobbles, and boulders moving along a channel floor Sediment acts like sand paper Falls rapids

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Down Cutting Slot Canyons

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Potholes happens during down-cutting Rotational movement of sediment creates holes

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3- Headward Erosion Erosion headward = upstream or upslope Increase the length of the valley until it reaches the divide Velocity and erosive power increases beyond the slower sheet of the surrounding ungullied slopes Additional volume and velocity of the channel water erode the head of a valley

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The hoodoos at Bryce Canyon are a result of unique headward erosion

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Headward erosion of the fault scarp by the Paria River and its tributaries has produced the spectacular scenery of the Paria Amphitheater

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End of Ch 16 Reminder no class March 22 (Monday after spring break) Unit Test on Streams, Running Water and Mass Wasting on March 31 (Wednesday) Turn in all late work before the test