Oceans Control the Water Cycle notes and study guides

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Oceans Control the Water Cycle notes and study guides

Ch. 11 NOTES
Oceans Control the Water Cycle

11.1 Ocean Basins

Oceans formed over 1.5 billion years from the runoff of the continents
2/3 earth’s surface covered by oceans
5 major oceans are: Pacific, Atlantic, Indian, Antarctic (Southern), and Arctic
Basin- low points on the earth’s surface = oceans
Oceans make life possible, control temperatures, create weather patterns, source of water for precipitation.

The Origin of Ocean Water

Planet formed 4.5 billion years ago ball of molten rock, started to cool but heat released from within, by volcanoes
Water vapour released into the atmosphere
Water from ice on comets coming to earth

Features of the Ocean Floor

Ocean floor is not flat but have many features like: mountain ranges, valleys, flat plains, canyons, and volcanoes
The features are larger than on land
Ocean floor has two distinct parts:

Ocean basin- middle part
Continental margins- edges

Ocean Basins

Forces change the ocean floor (storm water erode coral reefs)
Greatest force = plate tectonics

Solid rock plates floating over a molten layer

Two types of tectonic plates

Oceanic- those that lie under the ocean
Continental – those under continents

When plates are pushed apart magma rises to the surface = mid ocean ridge, the largest being the mid Atlantic Ridge
This ridge has been pushing Europe and America apart
Move 2.5 cm per year
Plates also move toward each other = subduction

Ocean plate-ocean plate - islands
Ocean- continent = ocean under continent = trench formed and mountains (volcanic)
Continent – continent – mountains formed in the middle of the continent

Area between trenches and mid-ocean ridges = abyssal plains
Occasional peak = sea mount = inactive volcano

Continental Margins

Made up of the continental shelf and the continental slope

Shelf = flat area that extends from the shoreline
Slope = steep area that drops off to the ocean floor
Rise = where sediments have been deposited at the end of a submarine canyon

Sediments are carried to the ocean in rivers and streams and build up on the slope, when they become too great the slope collapses creating a turbidity current = underwater landslide
Turbidity currents create the gentle slope of the continental rise
Some currents are so powerful they carve out submarine canyons
Sediments are also created from the remains of living animals

11.2 Ocean Currents

Large amount of ocean water that moves, almost like a river in a particular and unchanging direction
More than twenty major currents
Move: dissolved minerals, solar energy, O2, CO2, as well as animals and plankton (microscopic plants and animals)
Largest = Antarctic Circumpolar Current
Two types:

Surface – up to 200m deep
Deep water – more than 200m deep

Surface currents are affected by wind, Earth’s spin, shape of continents
Deep currents are affected by temperature and salinity of the water
Waves and tides also move the ocean

What Makes Surface Currents Move?

The Effect of Wind

Air masses move from one area to another because of temp. differences (Fig. 11.11)
Energy is transferred to the water molecules, causing the water to move
Wind direction and speed directly related to surface currents

The Effect of Spin

Earth spins from west to east
As winds and currents move they get redirected by this effect
= Coriolis effect = clockwise in North and counter-clockwise in South

The Effect of Continent Shape

Continents act as natural barriers that affect current movement

What Makes Deep Currents Move?

Water Temperature

Temperature affects density colder = more dense
Cold water sinks and moves along the bottom = density current

Three layers of ocean water:

Surface – warmest, keeps mixing, constant temp
Thermocline – temp. drops rapidly, also occur in lakes
Deep water – 2 degrees above freezing

Water Salinity

High salinity means the water is more dense
To increase salinity – evaporation and freezing
To decrease salinity – fresh water from rivers and ice melting
Saltiest, coldest, densest water is found at the poles
It sinks and only surfaces after 500-2000 years
Upwelling is the rising of the water from the deep and it brings nutrients to the surface = food for plankton
Upwelling occurs along the coast lines of N and S America

Ocean Waves and Their Effect of Shaping the Land

Waves are produced from surface winds
Size of wave depends on:

Speed of wind
Time the wind is over the water
Size of area wind passes over

Swells = large waves that form in the open ocean
When swells reach the shallow water they become breakers
Tsunami –created by an under water earthquake
Waves erode the coastline – how quickly depends on:

Force of the waves
Type of rock
Sand carried in the water

Waves behave depending on the shape of the coastline
Headlands = sections of coastline that extend into the ocean and are composed of harder rock
Receive most force of wave can create sea stacks
Bays = indented areas in the coastline

Tides

Is the daily cycle of rising and falling ocean
Caused by the gravitational attraction between the Earth and the Moon
Gravitational effects depend on the distance between two bodies so because the moon and the Earth are close they attract strongly
Moon pulls on the water to give a high tide on one side of the earth and the low tide would be on the other side
There are two high tides and two low tides on earth each day
Figure 11.23
Tidal range = difference between the high and low tide height
Shape of coast line affects how high the tide gets
Sun can also add to the affect and twice a month the create a lower low and a higher high = spring tides
Less extreme tides = neap tides Figure 11.24

11.3 Oceans and Climates

Heat capacity = measure of time for a material to heat up or cool down
Water has a high heat capacity
Evaporation to precipitation: this exchange produces weather
Weather can be described in terms of:

Temperature
Wind speed and direction
Air pressure
Moisture

Weather monitored for a long time for an area = climate

How Oceans Effect Weather

Oceans, atmosphere, and weather all influence each other
Convection is responsible for the transfer of heat to the atmosphere from the oceans
Mass of warm air = thermal
When thermals reach the higher atmosphere they cool and sink
El Nino = warm ocean waters that appear off the S.A. coast
When these currents stay for a few months = unusual weather patterns
La Nina = colder than normal waters = opposite weather effects

The Moderating Effect of Oceans on Climate

Ocean temp affects climate of coastal areas
Heat capacity of the water is higher compared to the land mass
Ex. Vancouver compared to the Fernie
Mild climate at the coast = moderator = no extreme temperatures
Coastal mountains block this air mass from moving into the interior
Rain shadow is formed
Five main climate zones in BC:

Coast Mountains and Islands
Interior Plateau
Eastern mountain Ranges
Northern and Central Plateau
Northeast Plains

Source : http://fc2.sd23.bc.ca/~jreed/FOV1-00087E5F/FOV1-00087E9C/FOV1-00088012/Chapter%2011%20completed%20notes.doc

Web site link to visit: http://fc2.sd23.bc.ca/~jreed/

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