The study of 'Continental Drift' suggests that the Earth's outer crust is divided into large chunks called "plates" which are always moving. As the continents slowly drifted apart, basins were formed. Over time, these basins filled with water and created our oceans.
The Continental shelf is the gradual sloping landform that lies below the shallow water. These shelves form a rim around the continent.
At some point the continental shelf drops suddenly. This steep slope leads down toward the bottom of the ocean floor.
The ocean floor is not flat. It is land and is as varied as the ground we live on.
Mountain Ranges: as magma erupts through the ocean floor, long chains
of mountain form. The longest chain is the Mid-Atlantic Ridge, located in the
Atlantic Ocean. Valleys in the ridge form deep canyons between mountains.
Seamounts: when a volcano erupts, isolated mountains called seamounts are formed
as the molten lava cools in the ocean water.
Guyots: as waves erode the tops of seamounts, they leave flat-topped mountains
Islands: some volcanoes or seamounts rise up from the ocean water and form islands.
Trenches: deep trenches form in between plates, when one plate is pushed under
another. The deepest of all trenches is located in the Pacific Ocean. It is hundreds of metres deeper than Mount Everest is tall.
Abyssal Plains: are the large, relatively flat areas of the ocean floor.
Waves are caused by the wind blowing over the surface of the ocean. The size of the waves depends on the speed of the wind. A boat moves along because of ocean currents, not as a result of the waves. Waves cause boats to bob up and down.
Waves can have very noticeable effects on the coastline. They gradually wear away at
Another movement of water is called ocean currents. Currents can be compared to rivers travelling along the surface of oceans and deeper waters. Ocean currents are affected by the wind, continental shape, the temperature and density of the ocean water and of course the earth's rotation (spin).
Tides occur everyday as the water level of the oceans increases and decreases. When the water covers
more land, it is high tide. When the water recedes it is at low tide.
All tides occur as a result of the pull of gravity by the sun and moon. click here
Rivers and Lakes
Rain is the raw material of rivers, streams and lakes. It is estimated that approxiamtely 30% of the rain that falls on land finds its way into rivers. Rivers, because of their ability to erode are one of the main things that shape our landscape. Most rivers have their sources in hills and mountains which are areas of high rainfall. (Orographic Rainfall) Rivers and lakes are important for things such as agriculture, fishing, tourism, recreation, industry, drinking Water etc.
formation of rivers, parts of a river - click here
formation of the Great Lakes - movie (flash) - click here
Water and Climate
Oceans, seas, lakes do affect the climate of of our world.
Proximity to Water
Large bodies of water affect the climate of a place. Coastal areas are cooler in summer and warmer in winter than inland areas. They usually receive more rainfall as well. The centre land area of continents generally have a greater range of temperatures. In the summer, temperatures can be very hot and dry and winters maybe very cold. Example: Toronto, Ont. - cold in winter, hot in summer; Vancouver, BC - mild in winter, warm in summer
Ocean Currents - see map
Warm Currents will cause the air above the water to be warmer than normal. The Gulf stream is warm thus when it travels across to Britain it causes the air there to be warm. If currents are cold then air passing over them will also be cold. If this air blows onto a city then consequently the city's temperature will drop because of this current.
Winds that blow from a warm body of water often bring warm temperatures and rain to the coast and dry weather to inland areas. Winds that blow from a cool body of water bring cooler temperatures and very often a desert-like area will be found along the coast.
Do the Great Lakes affect our weather?
On shore breeze - cools warm summer temperatures
Temperatures are usually cooler down by the lake
Often on shore breezes result in an increase in the precipitation -
(more rain in the warmer months and more snow in the winter months)
Something to think about: Scientists have found that the atmosphere is changing which may result in changes in the global climate. Increased CO from industry and energy production (burning of coal, oil and gas and from deforestation) and increased methane gas (livestock, wetlands and rice paddies) trap surface heat. This trapped heat "Greenhouse affect" will alter global climate. Because there is a relationship between climate and the hydrologic cycle, changing the climate would change the water cycle. HOW? Perhaps more dry spells causing droughts or increased rainfall causing floods. This would ultimately affect water supply and possibly water quality.
Should we practice water conservation? How do we manage water? What is being done about cleaning up the Great Lakes? Should we export our fresh water?