1Chapter 17: Glaciated CoastsGlaciers: formation, movement, typesPleistocene Glaciation:Effects on Coastlines:Examples: Cape Cod, LIGlaciersLocated on most continentsOccur as narrow ribbons of flowing ice in high mountain regions Occur as thick ice sheets covering vast continental areasOccupy 10% of continental landmass (30% during last ice age)Glacier FormationLarge mass of ice that flows internallyAntarctica (oldest glacier active 8mya)Climate permits more snow accumulation during cooler months than ablates (ice wasting) during warmer monthsGlacier FormationSnow – ice – glacial ice: through expulsion of air, compaction, melting and re-crystallization Glacial ice: forms at ~50 m depth, blue in colorGlacier MovementPlastic Flow: internal deformation or movementBasal Slip: sliding along the bedrock of the entire glacierTypes and Distribution of GlaciersAlpine or Valley Glaciers: formed in mountainous regions where winter are long and summer are short and coolflow down old river valleys2Types and Distribution of GlaciersIce Sheets or Continental Glaciers:several km thick, cover vast land areasGreenland (3km thick), 80% of the islandAntarctic Ice Sheet (4.2 km thick)Ross and Filchner Ice ShelvesPleistocene GlaciationPleistocene Epoch (1.65 mya)Ice Ages extended 2.2-2.4 myaMore recent: ice age periods 100,000 yrPlate Tectonics: control on ice ages300 myaLand mass must be high latitudes for extensive ice sheets to formMilankovitch Cycles: control on recent glacial periodsThe Late Pleistocene:Wisconsin Ice Age70-90,000 ya18,000 maximum extent10,000 ya rapid sea level riseHolocene6,000 barrier islandsGlacial Effects on CoastlinesWaxing and waning of ice sheets = various coastal landforms (fjords, moraines, bays etc.)Erosion: ice wedging, plucking (material freezes to glacier), abrasion (striations)Ice sheets: tend to reduce relief along rocky coastsDepositional Features:end or terminal moraines outwash plainsdrumlins3Drumlins (Depositional bedform features)15-50 m, .2-2 kmExample Coastlines & MorphologyTerminal Moraine: Long IslandShoreline Retreat During The Flandrian Transgression -50 m -40 m -30 m-20 m-10 m0 mTerminal Moraine & Outwash PlainBluff Coastlines4 2 mGravel, sandGravelSandBarrier IslandCliff or Bluff CoastSouth Shore Bluffs reach elevations > 80 ft (24 m) North Shore Bluffs 33 to 100 ft (10 to 30 m) in elevation, indented by deep bays that form good harbors for small crafts. North Shore Bluffs > 100 ftSouth Shore Bluffs 80 ftBluff Erosion Processes•Direct Precipitation•Surface Runoff•Groundwater Seepage•Surface Erosion•Mass Wasting Along Hardpan (clay layers)5•Wave Undercutting of Bluff Toe•Overloading near the edge of the BluffErosion PreventionIMPROVING SURFACE DRAINAGE•Eliminate drainage over the edge of the bluff and down the face•Reduce impermeable surfacesIMPROVING SUBSURFACE DRAINAGE•French Drainage System6Toe Armoring (Revetment)Slope Reduction Angles < 45oare stableFilter Box TerracingVegetation-low shrubs and grasses, no