Landform Geography - PowerPoint PPT Presentation

1 / 31
About This Presentation
Title:

Landform Geography

Description:

Title: Slide 1 Author: Lawrence McGlinn Last modified by: COAS Created Date: 12/28/2006 2:09:16 AM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

Number of Views:88
Avg rating:3.0/5.0
Slides: 32
Provided by: LawrenceM151
Learn more at: https://www.westga.edu
Category:

less

Transcript and Presenter's Notes

Title: Landform Geography


1
Landform Geography
Coastal Processes and Landforms
2
Coastal Processes and Landforms
  • Oceans and Seas
  • Nature of Coastlines Intersection of Earths
    Spheres
  • Coastal Landforms
  • Human Impacts on Coastlines

3
Oceans and Seas
  • Oceans largest bodies of water Pacific,
    Atlantic, Indian, Southern, and Arctic
  • Seas next largest water bodies Black,
    Mediterranean, Barents, etc.
  • Gulf next largest, usu. opens to larger water
    body Mexico, Alaska, Guinea, etc.
  • Bay smaller still Fundy, Biscay, etc.

4
Oceans and Seas
5
Water as Solvent
  • Salinity concentration of dissolved solids in
    seawater global seawater salinity 34-37 parts
    per thousand ()
  • Brine water with gt35 salinity
  • Brackish water - lt35 salinity

6
Shaping the Coastline
  • Key to shaping coastline is movement of water
  • Eustatic Change - changes in water level in ocean
    due to tectonic uplift or hydro cycle variation
  • Land above sea level forms river valleys that
    extend to sea level when sea level rises,
    valley floods, as with Chesapeake Bay or Delaware
    Bay
  • Ria river valley flooded by rising sea level
  • Fjord glacial valley flooded by rising sea
    level

7
Eustatic Sea Level Changes
8
North American Coastline Through Time
Lowest sea levels occurred during glaciations
when water was tied up in glaciers (130k 19k
bp) highest sea levels in interglacial periods
(120k bp)
9
Tides
  • Regular, predictable oscillations of sea level
    due to gravitation of moon (56) Sun (44)
  • High tide on side of Earth facing moon and on
    side away from moon ellipsoid shape
  • Long, narrow bays usually have highest tides up
    to 16 meters in Bay of Fundy in eastern Canada

10
(No Transcript)
11
Waves
  • Oscillations in water due to force of friction
    from wind blowing across its surface
  • Waves travel horizontally, but most movement of
    water is vertical, up-and-down
  • Near coast seafloor slopes upward wave base
    intersects ocean floor wave pushes water up as
    it slows waves pile up from behind - wave
    height exceeds 7X wavelength, and forms a breaker
  • Only horizontal movement of water from breaker to
    beach, called surf erosional agent

12
Wave Compression
13
Tsunami
  • Caused by undersea earthquakes with vertical
    displacement, volcanic eruptions, or landslides
  • Vertical displacement of water causes fast wave
    with long wavelength no harm at sea, but
    massive as it hits coastline
  • March 2011 Pacific plate subducts under North
    American plate which snaps upward massive
    tsunami hits Indian Ocean

14
2011 Japan Earthquake
15
Littoral Processes
  • Transport deposition of sediment in shore zone
  • Longshore current forms when wave hits beach at
    oblique angle water deflects downwind, parallel
    to beach
  • Longshore drift process of longshore current
    eroding carrying sediment down shore
  • Beach drift zig-zag motion of sediment down
    beach due to swash backwash
  • Littoral Drift longshore beach drift together

16
Littoral Drift
17
Coastal LandformsErosional Coastlines
  • Breaking waves have great power to erode
  • Headland promontory that juts into ocean or sea
    made of resistant rock
  • Waves slow pivot around headlands erosive
    power of waves concentrated on headland
  • Retrogradation retreat of coastline due to
    erosion
  • Wave-Cut Bluff basic erosional landform of
    coastlines near-vertical cliff at waters edge

18
Coastal Erosional Landforms
19
Depositional Coastlines
  • Progradation process of coastline extending
    outward into water through deposition
  • Beach dynamic transition from sea to land
  • Offshore under water, where waves break
  • Foreshore rise fall of tides
  • Offshore Bar between offshore foreshore
  • Beach Ridge at high water line
  • Backshore flat, only covered in storms

20
Beach Cross Section
21
Spits and Baymouth Bars
  • Longshore current carries sediment down beach
  • Current slows upon reaching bay sand deposited
    as a Spit extending out into bay current in bay
    turns spit toward land in hook shape
  • Baymouth Bar spit extends across bay, isolating
    it from ocean bay now called Lagoon
  • Tombolo longshore currents from 2 directions
    meet sand extends out to island or sea stack

22
Depositional Landforms
23
Barrier Islands
  • Elongated bars of sand that form parallel to
    shore
  • Likely formed from sand deposited on cont. shelf
    during last glaciation waves wind shaped sand
  • Lagoons w/mudflats form behind barrier islands
  • Mudflats develop into vegetated salt marsh

24
Coral Reefs
  • Coral polyps excrete external skeletons of
    calcium carbonate (limestone) Coral Reefs
  • New reefs form on top of old, dead reefs
  • 30º N - 25º S latitude, water warmer than 20º C
  • 3 settings
  • Fringing reef on shallows around island
  • Barrier reef line of coral parallel to shore
  • Atoll semicircular reef around degraded
    volcanic island

25
Development of Atoll
26
Global Distribution of Coral Reefs
27
Human Impacts on Coastlines
  • 37 of world pop. live lt60 mi. from shore (2
    billion) 50 within 120 miles of shore
  • In US, 53 of pop. live near coastline
  • Coastal Engineering Purposes
  • Protecting shore property from hazards
  • Stabilizing nourishing beaches
  • Maintaining traffic trade into ports

28
Mitigating Coastal Hazards
  • Raise buildings on stilts so waves roll
    underneath
  • Sea wall vertical, concrete wall to absorb
    energy of waves
  • Revetment slope covered with large rocks
    (rip-rap) to absorb energy of waves
  • These work locally, but they aggravate erosion up
    and down shore from wall due to wave refraction

29
Beach Nourishment
  • Bringing sand to beaches that have eroded over
    336M spent in Florida since 1960s
  • How?
  • Trucking in sand from remote location
  • Limit loss of sand through groins low walls
    built at right angles to beach intercept
    longshore drift
  • Jetties stone or concrete structures to keep
    channel open, keep sand to side

30
Sea Wall
31
Groins and Jetties
Write a Comment
User Comments (0)
About PowerShow.com