GEOG 1114 1st Edition Lecture 31Outline of Last Lecture Review of chapters 13-15Outline of Current Lecture Review of chapters 16-17Current Lecture Lecture 15 Ch. 16 - Fluvial LandformsThe work of running water as one of the most important external process shaping the landscape :Erosion, transportation, and deposition of materialLatin – 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 flowOrganization of streams into basins and networkStream 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 networksThese 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 bedrockRadial – Develop around an elevated central point (volcano, Pikes Peak)Centripetal – Streams converge into a uniform basinAnnular – 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 EnergyEnergy ForcesPotential Energy Increases in slope increases potential energy –influences stream dischargeKinetic Energy Energy of Motion of stream flow – VelocityLaminar: SlowTurbulent: FastGravity Assists Flow – enhances velocityFriction Nature of sides and bottom of channelSmooth: faster velocity (less friction)Rough: retards the velocity (more friction)Two Factors of Stream Energy – Influence how much erosion and deposition will occurStream Discharge – Volume of water Carried; Changes in response to PPTN.Stream Velocity - How fast it is moving. Effected by stream gradient and frictionStreams As Geomorphic AgentsStream 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 waterSuspended load – particles carried in suspensionBed load - heavy particles (rock and boulders) bounced a rolled along the bottom.Deposition: deposition of sediments Stream RejuvenationFluvial 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 floodplainAlluvial 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 LandsAeolian Landforms - wind Wind as a Geomorphic Agent AbrasionDeflation (blowouts)RequirementsWind > 10mphLack of VegetationAeolian LandformsLoess Deposits: Wind deposited salt, lack horizontal stratification, great vertical durability, 10% of Earth covered in LoessSand Dunes: Semi arid to desert dunescapesLack of vegetationLack of pptn Types:Barchan – (A) individual dunes migrating across landscape, crescent shaped. Transverse – (C) crescent shaped, but entire landscape made of these dunesSeifs – (B) long narrow that are parallelCoastal 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 formationDeserts – specialized environment reflecting the interrelationships between many factorsMechanical weatheringThin soil – thin or absent, exposing bedrockAbundance of sand – allows water to infiltrate, transport and shape the sands.PPTN – can be brief but intense; flash floodsDESERT STREAMS CHANNELS; EPHEMERAL (INTERMITTENET) STREAM BEDSWind – shifts sandsLandforms: Ergs: seas of sand, Large area covered with and in dune formation from wind. Sahara, Namibia – Arabian deserts. Reg: Stony desertErg Sea of sandReg Surface covered with coarse gravel, pebbles, or bouldersDesertificationExpanding 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 agriculturalLandforms of Differential Physical and Chemical Weathering of Sedimentary RocksEasily erodible shale evolves into lowlands or dissected slopes and is carried away as bedload slowly eroding sandstone often forms ledges and cliffsShale: -Mechanically weak, easily fragmented into thin flakes-Chemically weathers into impermeable clay soils – easily