Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 17 Chapter 17 The Oceans
Jan 02, 2016
Classroom presentations to accompany
Understanding Earth, 3rd edition
prepared by
Peter Copeland and William Dupré
University of Houston
Chapter 17Chapter 17The Oceans
The OceansThe Oceans
Steve Terrill/Stock Market
Fig. 17.1
Sandy Beach, North Carolina Barrier Island
Peter Kresan
Boulder Beach, Massachusetts
Fig. 17.2Raymond Siever
Wave height depends on:
• Wind velocity
• Wind duration
• Distance over which wind blows
Wave-generated Orbital WavesWave-generated Orbital Waves
Fig. 17.3
Wave characteristics
• Length (L): distance between crests
• Height (H) : vertical distance between crest and trough
• Period (T): time for successive waves to pass a fixed point
Velocity (V) of waves
V = L/T
Waves in shallow water
• Wave height Increases
• Wave length decreases
• Velocity decreases
• Period doesn’t change
Surf zone
Zone between where the waves break to point furthest up the shore where the waves wash up
Changes in Waves as they Approach the Beach
Fig. 17.4
Wave refraction
• Bending of wave crests as they approach the beach at a non-normal angle
• Caused by the change in velocity of waves as a function of water depth
Fig. 17.6
Wave Refraction
Waves Bending as they Approach the Beach
Fig. 17.5John S. Shelton
Fig. 17.7
Refraction at
Headlands and Bays
Fig. 17.8
Longshore Drift
Sediment transport near shore, parallel to the beach
• Longshore drift: sediment carried by swash and backwash along the beach
• Longshore currents: currents parallel to the beach within the surf zone
Tides
Twice daily rise and fall of the sea caused
by the gravitational attraction between
• earth and moon (lunar tides)
• earth and sun (solar tides)
Lunar Tidal Bulges
Fig. 17.9
Interaction between lunar and solar tides during the lunar month
causes:• Neap tides: when two tidal components
are out-of-phase, hence lower than usual, and
• Spring tides: when two tidal components are in-phase, hence higher than usual.
Earth-Moon-Sun Alignment and Neap-spring Tides
Fig. 17.10
Spring tides Neap tides
Fig. 17.11
Exposed tidal flats
Mont-Saint-MichelFrance
Thierry Prat/Sygma
Terrace Exposed at Low Tide
Fig. 17.12James Valentine
Major parts of beaches
• Offshore: from where the waves begin to feel bottom to the surf zone
• Foreshore: includes the surf zone, tidal flats, and swash zone
• Backshore: from beyond the swash zone to the highest level of the beach
Major Parts of a Beach
Fig. 17.13
Sand budget
The inputs and outputs of sediment by
erosion and sedimentation.
Fig. 17.14
Sand Budget of a Beach
Preventing beach erosion
• Structural approaches (e.g., groins): typically cause increased erosion downcurrent of structure
• Non-structural approaches (e.g., beach nourishment, land use planning): expensive, but don’t cause erosion in new areas
Groin: Built to Prevent Updrift Erosion Causes
Downdrift Erosion
Deposition
Erosion
Phillip Plissin/Explorer
Beach Nourishment, New Jersey
U.S. Corps of Engineers, New York District
Factors determining rates of erosion or deposition
• Uplift
• Subsidence
• Rock type
• Sea-level changes
• Wave heights
• Tidal range
Fig. 17.15
Sea Stacks
Kevin Schafer
Fig. 17.16
Wave-cut TerraceExposed at Low Tide
John S. Shelton
Fig. 17.17
Southern Tip of Cape Cod
Steve Durwell/The Image Bank
Fig. 17.19
Past 160 Years of Shoreline Change, Southern Cape Cod
Partially Developed Barrier Island
Fig. 17.18
Gulf of Mexico
LagoonMainland Florida
Barrier Island
Richard A. Davis, Jr
Uplifted Coastal Terrace
Fig. 17.20John S. Shelton
Mapping the seafloor
• Satellite measurements
• Echo sounding profiles
• Side-scan sonar
• Manned and unmanned submersibles
From Gravity Anomaly to Seafloor Topography
D.T. Sandwell & W.H.F. Smith/Scripps Institute of Oceanography
Fig. 17.22
Congo Submarine Canyon
Echo sounding profile
Fig. 17.23
Loiki Seamount
Imaged Using
Side-scan Sonar
Ocean mapping Development center, University of Rhode Island
Fig. 17.21
The Benthic Explorer Unmanned Submersible
T. Kleindinst/Woods Hole Oceanographic Institute
Fig. 17.24
Topographic Profile of the North Atlantic Ocean
Atlantic bathymetric features
• Continental shelf
• Continental slope
• Continental rise
• Abyssal plains
• Seamounts
• Mid-ocean ridge
Pacific bathymetric features
• Continental shelf
• Continental slope
• Trench
• Abyssal plains
• Seamounts
• Mid-ocean rise
Fig. 17.25
Continental shelf
Continental slope
Continental rise
Praxton & Haxby, 1996
From the Continental Rise to the Mid-Atlantic Ridge
Fig. 17.26
Fig. 17.27
Topography of the North Atlantic Ocean
Detail from H.C. Berannrket, based on Heezen & Tharp
Topographic Profile of the Western Pacific Ocean
Fig. 17.28
Fig. 17.29
Atlantic Passive Margin Off New England
Turbidity Current
• Flow of muddy water down a slope
• Forms deposits known as turbidites
Turbidity Currents
Fig. 17.30
Fig. 17.31a
Fig. 17.31b
Sandfall at the
Head of a Submarine
Canyon
U.S. Navy
“Black smoker” from the East Pacific Rise
D.B. Foster/Woods Hole Oceanographic Institute
Fig. 17.32
Central Rift Valley of the Mid-Atlantic Ridge
Fig. 17.32Macdonald & Fox, 1990
Some of the Maldive
Islands in the Pacific
Fig. 17.33
Atoll
Fringing Reef
Guido Alberto Rosi/The Image Bank
Fig. 17.34
Evolution of a Coral Reef
Types of marine sediment
• Terrigenous material eroded from the continents
• Biochemically precipitated shells of marine organisms
• Abiotic chemical precipitates
Fig. 17.35
Oceanic Ooze
Scripps Institute of Oceanography,University of California, San Diego
Carbonate Compensation Depth
Fig. 17.36
Depth below which carbonate material dissolves in seawater