Ocean water movements
Waves
• Energy traveling along the interface
between ocean and atmosphere
• Derive their energy and motion from wind
• Parts
• Crest
• Trough
The components and motion of a non-breaking wave
Wavelength (λ)
Amplitude
(H)
Depth
(D)
The components and motion of a non-breaking wave
Wavelength (λ)
Amplitude
(H)
Depth
(D)
Period (T): time for one wave to pass
The components and motion of a non-breaking wave
Wavelength (λ)
Amplitude
(H)
Depth
(D)
Period (T): time for one wave to pass
1
Frequency (f): number of waves per time =
T
The components and motion of a non-breaking wave
Wavelength (λ)
Amplitude
(H)
Depth
(D)
Period (T): time for one wave to pass
1
Frequency (f): number of waves per time =
T
λ -or- λxf
Velocity (c): wavelength/period =
T
Waves
Wave velocity depends upon water depth:
If water depth > wave depth it is a deep-water wave
Cdeep = √ g λ / 2 π
Waves
Wave velocity depends upon water depth:
If water depth < 1/20 wave depth it is a shallow-water wave
Cshallow = √ g D
Waves
Steepness of a wave is height/length:
h
λ
When steepness exceeds 1/7, wave breaks
Ocean breakers, whitecaps
Waves
Driving force of waves is wind
Wind speed
Length of time the wind blows
Fetch – the distance over which wind blows
Height, Length, and Period
Changes that occur when a wave moves onto
shore
Wave interference
Beaches and shoreline processes
Beaches are composed of whatever
material is available
Usually sand
Beaches and shoreline processes
Beaches are composed of whatever
material is available
Usually sand
Material in constant motion
Beaches and shoreline processes
Beaches are composed of whatever
material is available
Usually sand
Material in constant motion
Wave erosion
Caused by energy of impacting waves
Beaches and shoreline processes
Beaches are composed of whatever
material is available
Usually sand
Material in constant motion
Wave erosion
Caused by energy of impacting waves
Weathers rock material
Beaches and shoreline processes
Beaches are composed of whatever
material is available
Usually sand
Material in constant motion
Wave erosion
Caused by energy of impacting waves
Weathers rock material
Transports and distributes sediment
Beaches and shoreline processes
Wave refraction
Bending of waves due to shallow water near shore
Beaches and shoreline processes
Wave refraction
Bending of waves due to shallow water near shore
Waves arrive almost parallel to shore
Beaches and shoreline processes
Longshore Current
“River” that moves parallel to shore
Bounded by shoreline, breakers
Beaches and shoreline processes
Longshore transport
Sand/sediment moved by longshore current
Beaches and shoreline processes
Wave refraction
Sediment is transported/distributed along coastline
Wave erosion straightens an irregular shoreline
Wave refraction along an
irregular coastline
Truncated headlands along
irregular coastline
Sea arch
Sea arch
Sea stack
Wave-cut platform
Wave-cut platform
Wave-cut platform
Wave-cut
platform
Wave-cut platform
Wave-cut platform
Marine Terraces
Spit
Baymouth bar
Tombolo
Tombolo
Coastal dunes
Form where constructive waves encourage the net
deposition of sand
Coastal dunes
Offshore winds predominate, pushing sand beyond
wave action
Coastal dunes
Dunes become “anchored” by physical
obstructions and by plant growth
Dunes and Barrier Islands
Barrier Islands
• East and gulf coasts of the U.S.
• Submergent coastlines
• Represent reworked dunes, sand from river
deltas and accumulated beach deposits
• May be anchored by coarser deposits
beneath
Barrier Islands
East and gulf coasts of the U.S.
(Submergent coastlines)
Long Island, NY
Mississippi-Alabama coast
Barrier Islands
Represent reworked dunes, sand from
river deltas and accumulated beach
deposits
Long Island, NY
Mississippi-Alabama coast
Barrier Islands
May be anchored by coarser deposits
beneath
Long Island, NY
Mississippi-Alabama coast
Shorelines
Advance and
Retreat as Sea
Level Rises
and Falls
Present
Coastline
Shorelines
Advance and
Retreat as Sea
Level Rises
and Falls
Present
Coastline
Coastal
Plain
Continental
Shelf
Shorelines
Advance and
Retreat as Sea
Level Rises
and Falls
Present
Coastline
Coastal
Plain
Coastline
18,000
Years ago
Continental
Shelf
Shorelines
Advance and
Retreat as Sea
Level Rises
and Falls
Coastline
During Maximum
Ice Melt
Present
Coastline
Coastal
Plain
Coastline
18,000
Years ago
Continental
Shelf
Estuary:
submerged river
valley
Aerial view of a spit and baymouth bar
along the Massachusetts coastline
Stabilizing the shore
Structures that effect the shoreline
•
•
•
•
Groins
Breakwaters
Seawalls
Jetties
Groins - built at a right angle to the beach;
designed to trap sand
Breakwater - built offshore and parallel to the coast
to protect boats from breaking waves
Seawalls - Armor the coast against the
force of breaking waves
Isle of Wight, U.K.
Jetties – barriers to protect the mouth of a river
from filling with sediment
Humboldt Bay, N CA
Carlsbad CA
Beach nourishment, Miami FL
After
Before
Miami Beach after beach nourishment