Chapter 16
Ocean current-mass of ocean
water that flows from one place
to another
 Surface currents
 movements of water that flow
horizontally in the upper part
of the ocean’s surface
 Upwelling
 rise of cold water from deeper
layers to replace warmer
surface water
 brings greater concentrations
of dissolved nutrients, such as
nitrates and phosphates, to the
ocean surface
 Density currents
 vertical currents of ocean
water that result from density
differences among water
masses
Waves
 Where do waves come
from?
 The energy from
strong winds
 Parts of a wave
 A –crest
 B –trough
 C –wavelength
 D –amplitude
Wave Period and Speed
 Wave period
 the time it takes for a
complete wave to pass
a given point
 Wave speed
 how fast the waves are
traveling
 Wavelength ÷ period
Factors that Affect the height,
length and period of a wave
 Speed of the wind
 Duration
 how long the wind will
blow
 Fetch
 the length of water
surface over which the
wind blows in a
constant direction
Breakers
 Spilling breakers
 over-steepened waves
that are unstable and
the top spills over.
Occur on flat beaches.
 Plunging breakers
 Hawaii (large splash)
Types of Waves
 Wind waves
 Tsunamis
 tidal waves formed by
movements on a fault
line
 Internal waves
 Occurs within the water
and not on the surface.
“dead water”
What are they and how do they work?
Tides
 What are Tides?
 changes in
elevation of the
ocean surface
 What causes
Tides?
 Gravitational
forces of the
moon and sun
Tidal Range
 Vertical distance
between the high and
low tides.
 Vary from place to
place and week to
week.
 Many factors (shape of
the coastline,
configuration of ocean
basins, and water
depth) influence tidal
ranges.
Spring
Tides
 Spring Tides
 Occur during the
new and full
moons
 All gravitational
forces are added
together
 Extreme high and
low tides
 High tidal range
Neap Tides
 Neap Tides
 During the 1st and
3rd quarters of the
Moon
 Gravitational
forces are offset
 Tidal range is the
smallest value
Tides
 Tides occur 50
minutes later due
to …
 Rotation pattern
of earth and moon.
 This is known as a
lunar day
Tidal Patterns
 Diurnal (daily)
 one high and one low tide
each lunar day. Occurs at
Pensacola, Fl. And the Gulf
coast.
 Semidiurnal (semi-daily)
 2 high and 2 low tides:
each high and low tides
are similar to the
preceding high and low.
Occurs in the Atlantic
coast
 Mixed
 2 high and 2 low tides each
day. Each high and low
tides are different from
each other. Occurs on the
west coast.
Coast, Beaches and Shores
 Beach
 accumulation of sediment
(sand and gravel) that
occupies a portion of the
shore. (moving)
 Coast
 where the land meets the
sea.
 “lands edge that boarders
the sea”
 Shore
 part of the coast in which
the outer limits of wave
action influences the land.
Forces that act on a shore
 Wave Impact
 changes the shape
 Abrasion
 most intense
 Wave refraction
 sediment
transportation
 Longshore transport
 works with refraction
Longshore Currents
 Longshore current
 caused by waves which
approach the shore at an
angle –move sand grains
along the beach
(responsible for the
beach erosion on the
barrier islands)
 Littoral drift
 the movement of sand
along the beach because
of longshore currents
Rip Currents
 Rip currents
 water current formed
when water moves to
the sea through a break
in an offshore bar.
Erosion Features
 Sea Arches
 form when two caves are
eroded and unite.
 Spit
 elongated ridge of sand
that projects from the
land into the mouth of a
bay and hooks.
Erosion Features
 Tombolo
 ridge of sand that
connects an island to the
mainland or another
island.
 Baymouth Bar
 sandbar that has
completely crossed a bay,
sealing it.
 Barrier island
 Narrow sandbars parallel
to, but separated from the
mainland.
Protective Structures
 Groin/Jetty
 structures that are at right
angles to the beach to trap
sand.
 Breakwater/Seawall
 structures built parallel to
the shoreline to protect
the coast from powerful
breakers.
 Bulkhead
 structure separating land
and water areas –reduces
erosion.
Beach Nourishment
 Addition of large
quantities of sand to the
beach system