5. Tides
•A “bulge” in the world’s
oceans, caused by the
gravitational pull of the
moon and sun
Fg = G m1 m2
d2
6. Tides
• Tidal range—the difference
between high and low tide
• Affected by the shape of the
coastline and seafloor
• Spring tides—highest tides,
strong and quick
– Occur when sun, moon, and
Earth line up (the sea
“springs” up and back)
• Neap tides—lowest tides
– Sun and moon at right angles
with respect to Earth
– Neap = A low incline of bend
(when graphed)
8. Extreme High Tides
• The Bay of Fundy
• A 50’ (15m) tidal fluctuation
is common (x2)
•A tidal bore (several in. to
several ft. high) rushes miles
up the Petitcodiac River in
New Bruswick
14. Waves and Wave Dynamics
•Period—The time it takes two successive
waves (from crest to crest, or from trough to
trough) to pass a given point
•Fetch—The distance over which the wind
blows, creating waves
15. Waves and Wave Dynamics
•Factors affecting open ocean waves:
–Fetch
•The greater the distance over which the wind blows,
the larger the waves
–Wind strength
•The stronger the wind, the larger the waves
–Wind duration
•The longer the wind blows, the more waves will be
created
22. Erosional Environments
•If there is not enough sediment replacing what’s
being lost through wave erosion/longshore current,
erosion will occur, creating a rocky coastline
–Dammed or channelized streams
•sediment can’t get to the beach
•Erosive environments create distinctive landforms
–rocky headlands and pocket beaches, sea arches and
sea stacks, wave-cut cliffs, wave-cut platforms, wave-
built terraces, etc.
23. Wave Energy is Concentrated at
Headlands and Dissipated in Bays
29. The Holderness Coast is one of Europe's fastest eroding coastlines. The
average annual rate of erosion is around 2 metres per year. The main reason
for this is because the bedrock is made up of till. This material was deposited
by glaciers over 18,000 years ago.
47. “Any serious researcher would be hard-
pressed to find a marina, a sea wall, or any
other human structure along the shoreline that
does not pose some long-term deleterious
effects to both the natural and cultural
environments it attempts to protect.”
--Physical Geography: Earth’s Interconnected Systems
Angela Orr, 2007
Coastal Stabilization and
Human Impact
48. Coastal Stabilization and Human
Impact
•Damming and channelizing streams
–Causes a loss of sediment where streams empty into
the sea. Without sediment, the beach will erode
away.
•Groynes (groins)
•Seawalls
•Breakwaters and jetties
53