GEOG 1114 1st Edition Lecture 31 Outline of Last Lecture Review of chapters 13 15 Outline of Current Lecture Review of chapters 16 17 Current Lecture Lecture 15 Ch 16 Fluvial Landforms The work of running water as one of the most important external process shaping the landscape Erosion transportation and deposition of material Latin Fluvious meaning river Process involving running water both overland flow and stream flow Effective as an agent of erosion and deposition Contributes more to shaping landforms than all other external agents Smooth s irregularities carves sediments Unchanneled downslope movement of water overland flow Channeled movement of water stream flow Organization of streams into basins and network Stream Order Hierarchy in order within a drainage network Smaller streams join larger ones Feed into successfully larger streams down slope Larger numbers are longer in length and watershed order Smaller drainage basins feed into larger basins Patterns of drainage networks These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Drainage patterns Each basin has a unique pattern which is related to the geology and relief of the area Dendritic tree like pattern with random merging of streams most common Trellis forms in areas of hard and soft bedrock in close contact Ride the valley province of Appalachians and Ouachita Mountains Shape modified by structure of bedrock Radial Develop around an elevated central point volcano Pikes Peak Centripetal Streams converge into a uniform basin Annular Forms in areas of hard and soft domes or basins Flow follows soft bedrock and is confined by hard bedrock Down cutting creates a v shaped valley or enriched stream Deranged develop from a disruption of a pre existing drainage pattern No coherent pattern Fault line San Andreas Fault Glaciation Canadian Shield Energy of streams as a function of slope gradient volume friction Amounts of erosion and types of landform that develop are largely a result of Stream Energy Energy Forces Potential Energy Increases in slope increases potential energy influences stream discharge Kinetic Energy Energy of Motion of stream flow Velocity Laminar Slow Turbulent Fast Gravity Assists Flow enhances velocity Friction Nature of sides and bottom of channel Smooth faster velocity less friction Rough retards the velocity more friction Two Factors of Stream Energy Influence how much erosion and deposition will occur Stream Discharge Volume of water Carried Changes in response to PPTN Stream Velocity How fast it is moving Effected by stream gradient and friction Streams As Geomorphic Agents Stream energy affects how much erosion will take place and how much material is transported and deposited to downstream locations Erosion picking up material deepening of valleys canyon development Once channeled erosion is greatly Transport moving of sediments influenced by discharge and velocity Dissolved load fine particles dissolved in water Suspended load particles carried in suspension Bed load heavy particles rock and boulders bounced a rolled along the bottom Deposition deposition of sediments Stream Rejuvenation Fluvial landforms Floodplains Wide low laying areas around a river River Terraces When elevation is changed due to tectonic uplift there is an increase in gradient The river is rejuvenated has more energy and begins to down cut creating a new flood plain of deposition The abandoned flood plain above the new stream channel is called a river terrace Levees low banks that suffice to keep the stream in its channel during normal flow Bluffs or Escarpment as rivers cut deeper through sediments they can leave behind bluffs or escarpments steep slopes at the outer edge of a floodplain Alluvial Fan fluvial Landform in Arid Regions Fan Shaped landform that develops when a high velocity streams carrying large bed loads discharges the load into a broad flat valley floor Fan shaped sediments often develop from a mountain canyon Delta fluvial Landform in Humid Regions Similar process high velocity stream discharges its load in broad slower moving body of water Mississippi Delta Lecture 16 Ch 17 Landforms of Arid Lands Aeolian Landforms wind Wind as a Geomorphic Agent Abrasion Deflation blowouts Requirements Wind 10mph Lack of Vegetation Aeolian Landforms Loess Deposits Wind deposited salt lack horizontal stratification great vertical durability 10 of Earth covered in Loess Sand Dunes Semi arid to desert dunescapes Lack of vegetation Lack of pptn Types Barchan A individual dunes migrating across landscape crescent shaped Transverse C crescent shaped but entire landscape made of these dunes Seifs B long narrow that are parallel Coastal Dunes D Ocean waves deposit sand on beaches Propionate onshore winds move sands inland Rock Arches or Pinnacles Develop when wind slowly erodes sedimentary rock outcrops leaving behind a pinnacle type structure and arches Natural bridge formation Pillar formation Deserts specialized environment reflecting the interrelationships between many factors Mechanical weathering Thin soil thin or absent exposing bedrock Abundance of sand allows water to infiltrate transport and shape the sands PPTN can be brief but intense flash floods DESERT STREAMS CHANNELS EPHEMERAL INTERMITTENET STREAM BEDS Wind shifts sands Landforms Ergs seas of sand Large area covered with and in dune formation from wind Sahara Namibia Arabian deserts Reg Stony desert Erg Sea of sand Reg Surface covered with coarse gravel pebbles or boulders Desertification Expanding of desert conditions due to land degradation and water removal human activity Climate Change Prevalent in Africa Middle East Australia Chile and Peru India Mexico Estimates of 8 100 square miles are decertified each year Affects on human population growth and agricultural Landforms of Differential Physical and Chemical Weathering of Sedimentary Rocks Easily erodible shale evolves into lowlands or dissected slopes and is carried away as bedload slowly eroding sandstone often forms ledges and cliffs Shale Mechanically weak easily fragmented into thin flakes Chemically weathers into impermeable clay soils easily cut by stream channels Most erodible of all rock types Evolves into lowlands dissected slopes at the base if high hills or found in valley floor where it s carried away as bed load Sandstone Either weak or strong depending on the type of material Typically hard in