Module 9- Oceans and Beaches
Oceans and Beaches
How do oceans shape our lives?
Image Credit: FreeDigitalPhotos.net
Distribution of Water on Earth
• 97% of all water on Earth is salt water.
• Only 3% is freshwater, including icebergs, lakes, rivers, and
groundwater.
• Water covers 71% of Earth’s surface.
• The major oceans in the world are the Pacific (51.6%); the Atlantic
(23.6%);Indian (21.2%); Southern and Arctic along with the other
seas of the world make up the remaining 3.6% of water on Earth.
Image Credit: Nasa.gov
Properties of Ocean Water
• Ocean water is a mixture of gases and solids dissolved in pure
water.
• There are 85 elements found to exist in ocean water.
• Salinity describes the amount of dissolved salts in ocean water. It is
expressed in parts per thousand, with the average being 35 parts
per thousand.
• The most abundant salt is sodium chloride, NaCl. A liter of
seawater will contain about 2.5 teaspoons of this common salt.
Image Credit: Photolib.noaa.gov
The most abundant gases in ocean water are nitrogen,
carbon dioxide and oxygen. The amount of dissolved gases is
affected by two things:
1. Depth – the greater supply of gases at the ocean’s
surface is due to the penetration of sunlight. This
allows photosynthesis to take place which ensures a
large supply of oxygen.
Image Credit: Photolib.noaa.gov
2. Temperature of ocean water – warm water holds less dissolved gas
than cold water. This means that denser cold water sinks, carrying
oxygen to deep areas of the oceans while allowing animals to live
there.
• The warmest layer of the ocean is the surface zone where water is
mixed by waves and currents.
• The thermocline is the zone below the surface where rapid
temperature change occurs.
• The coldest layer is the deep zone with temperatures of around 5
degrees Celsius.
Image Credit: PhotoLib.noaa.gov
Motions of the Ocean
• Waves are the movement of energy through a body of
water.
• Most waves are formed by winds blowing over the surface
of the ocean.
• This transmits energy to the water, forcing it to ripple. Wind
causes waves!
Image Credit: PhotoLib.noaa.gov
The size of a wave depends on three things:
1. The strength of the wind.
2. The distance the wind blows (called the fetch).
3. The length of the gust (duration).
Waves are divided into several parts.
• Crest – the highest point of the wave.
• Through – the valley between two waves.
• Wavelength – the horizontal distance between the crests or
troughs of two consecutive waves.
• Wave height – a vertical distance between a wave’s crest and
the next trough.
• Wave period – measures the size of the wave in time.
Ocean waves caused by earthquakes are
called tsunamis.
Water below the surface moves in streams called
currents.
These currents are caused by two factors:
 wind patterns and
 water density.
Image Credit: srh.noaa.gov
Surface currents are caused by wind patterns and
usually have a depth of several hundred meters.
These currents affect climate and weather patterns by
warming or cooling the air above the water.
Surface currents affect weather.
Image Credit: sos.noaa.gov
The Gulf Stream is known as a long-distance
current that carries warm water from the
southern tip of Florida along the eastern
coast of the US.
Image Credit: oceanservice.noaa.gov
Currents in the Northern Hemisphere move clockwise
(currents correspond to the wind circulation in each
hemisphere), while currents in the Southern Hemisphere
move counterclockwise.
Image Credit: mynasadata.larc.nasa.gov
Surface currents that travel over short distances are called shortdistance currents.
These currents are usually found at shorelines.
Currents moving parallel to the shore are called longshore
currents.
As these currents move they carry large amounts of sand
creating sand bars.
A rip current occurs when a current cuts an opening in a sand
bar and the currents return to the ocean in a powerful, narrow
flow (a type of undertow).
Deep currents are movements of water deep under the surface
of the oceans and are caused mainly by differences in water
densities.
The density (heaviness of the water) is affected by temperature
and salinity.
Cold water is more dense than warm water.
The saltier the water, the more dense.
Image Credit: sos.noaa.gov
Deep currents usually flow in opposite directions from
surface currents.
 The movement of deep ocean currents to the surface is called
upwelling.
 This occurs when deep cold currents are forced upward by the
ocean floor bring nutrient rich foodstuffs to the surface.
 This produces rich fishing grounds in areas where upwelling
occurs. (Example – Peru, Chile)
Image Credit: oceanservice.noaa.gov
El Nino refers to a warm ocean current that
typically appears around Christmas time and
lasts for several months, but may persist into
May or June.
The warm current influences storm patterns
around the globe.
Image Credit: science.nasa.gov
Upwelling ceases to occur when winds die down.
Without the nutrient rich waters, many fish and sea
creatures die, devastating the fishing industry.
Without upwelling, the water becomes much warmer
changing weather patterns globally.
Image Credit: oceanservice.noaa.gov
Shoreline Formation
Shorelines are constantly changing landscapes due to
powerful waves constantly eroding rocks and depositing
sediments to reshape the land. The following are examples of
shoreline formations:
Image Credit: nps.gov
1. Sea Cliffs – steep faces of rocks
2. Caves – hollowed out portions of sea cliffs
Image Credit: celebrating200years.noaa.gov
3. Sea Stacks – columns of resistant rocks left
standing.
4. Sand Bars – an underwater ridge of sand
created by longshore currents .
Image Credit: srh.noaa.gov
Image Credit: photolib.noaa.gov
Beaches – waves deposit large amounts of rock particles to form our beaches.
• The backshore is the area of the shoreline above the high water or
high tide mark. This can contain cliffs or sand dunes or a berm (flat
upper beach).
• The foreshore is the area that is exposed at low tide. It may have a
beach scarp (vertical slope produced by wave erosion) and a low
tide terrace (broad flat area exposed at low tide).
• The offshore region extends from the low tide mark seaward
beyond the wave breaking zone. It has a shoreface (slope below the
low tide mark) and a longshore trough (a depression parallel to the
beach between the low tide mark and wave breaking zone).
Image CreditL ngs.noaa.gov
Barrier Islands – (nature’s way of straightening out the shore)
• Elongated bodies of sand bounded on either end
by inlets allowing salt and fresh water to flow into
and out of the estuary behind the island. (Example
– The Outer Banks)
Image Credit: learnnc.org
V. North Carolina’s Barrier Islands – The
Outer Banks
A. Barrier islands form in response to four
factors:
1. Levels beginning about 10,000 years ago.
The sea level was 300 to 400 feet below
its present level. The following is an
example of sea level creating barrier
islands.
a.
b.
c.
d.
A straight coast forms during lower sea
levels.
Rising sea levels flood valleys on land
and creates a sinuous coast.
Sand eroded from pre-existing ridges
forms spits (sandbar connected to a
curving shoreline).
The spits are breached by storms,
separating the islands from the
mainland.
2.
A large supply of sand – 15,000 years ago
the sea level was much lower, waves and
winds formed beach ridges (dunes) on the
coast of North Carolina. Sea levels rose
and broke through the dune forming a
lagoon, and the dune is now isolated as an
island.
3.
A gently sloping coastal plan – North Carolina’s
coast slopes at .2 feet per mile. The
underlying geology of North Carolina consists of
sediments dating of Quaternary age (1.8 million
years ago to present) with older sediments
buried underneath. The deposition of these
sediments created a gentle slope conducive to
forming barrier islands.
4.
Sufficient wave energy to move sand
occurred.
The Truth About Shorelines
• Beach erosion is an expected part of barrier island
evolution, especially as sea levels rise.
• Shoreline erosion is not a problem until someone
builds a structure by which to measure it.
• Shoreline erosion does not create problems for the
beach, it simply changes its position.
Image Credit: coastalmanagement.noaa.gov
Human activities such as building seawalls, dune construction,
building construction, channel dredging, reduce the beaches’
sand supply.
This increases the rate of shoreline retreat.
Shoreline engineering protects the interests of few people, who
are causing the erosion to begin with, and is a high cost to state
and federal governments.
Image Credit: coastalmanagement.noaa.gov
“You can have buildings, or you can have beaches; in
the long run you cannot have both.” The ultimate truth
is to avoid the hazards and evaluate the level of risk if
choosing to build on a barrier island or coastline.
Image Credit: sos.noaa.gov
The End 
Image Credit: FreeDigitalPhotos.net