Viewed from space, the most striking feature of our planet is the water.
In both liquid and frozen form, it covers 75% of the Earth’s surface.
It fills the sky with clouds. Water is practically everywhere on Earth, from inside the planet's rocky crust to inside the cells of the human body.
71% of the planet's surface is covered by ocean and it is because of this that the Earth is sometimes called "
the water planet".
The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again.
The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.).
Plants also lose water to the air (this is called transpiration).
The water vapor eventually condenses, forming tiny droplets in clouds.
When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea).
Some of the underground water is trapped between rocks or clay layers this is called groundwater.
But most of the water flows downhill as runoff (above ground or underground), eventually returning to the seas as slightly salty water.
Topics covered in this snack-sized chapter:
Sun rays gives power to this cycle.
Sun energy push water to rise in the form of water vapors and then again in the form of rain it falls back to earth.
Water drops on land, river or ocean then sun energy once again evaporates the water, thus completing the cycle.
Some rain water soaks through the ground while some evaporates into gases.
The rain water which doesn’t go either of these run over the ground and ends up in lakes, storms, and oceans and is called Run off.
The amounts of rain and for how long it rains are two factors that affect run off.
Light rain for long time may result in soaking of water, while heavy rains over a short period result in run off.
Surface runoff is the water flow that occurs when the soil is infiltrated to full capacity and excess water from rain, melt water, or other sources flows over the land.
Infiltration (hydrology) — Infiltration is the process by which water on the ground surface enters the soil. Infiltration is governed by two forces, gravity, and capillary
Sewer — Sewers transport wastewater from buildings to treatment facilities. Storm sewers (also storm drains) are large pipes that transport storm water
Erosion — Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water or ice, by downward or down-slope movement.
Water that soaks into the ground and collects in the pores of the soil is called ground water.
Scientist estimate that 14% of fresh water of earth exists as ground water.
Soil and rocks are permeable because the pore spaces are connected and water can pass through them.
Rock and soil that don’t have large connected pores are called impermeable and water can’t pass through them.
The oceans are important source of food, energy and minerals for many organisms.
The energy source like coal and oil are found beneath the ocean’s surface.
1/3 of salt is taken from oceans salt water.
They are also the medium of transport for goods.
When earth was first formed, its surface was mostly volcano and cooled volcano rocks.
When these rocks erupted, lots of water vapors were formed.
These water vapors gathered and condensed into oceans.
Contain gases like Oxygen, carbon dioxide and nitrogen.
Today’s average is 3.5% of ocean water is salt.
The oceans contain many dissolved salts along with elements like calcium, magnesium, and sodium.
An Ocean current is a mass movement, or work flow of ocean water.
They are like rivers in oceans.
Tides are the rise and fall of sea level.
They are created by giant waves that are produced by gravitational pull of the sun.
Water level moves out at low tides and rise again at high tide.
Oceans react to the pull between the earth and moon.
Two bulges of water always form when the moon rotates around the earth.
These bulges cause high tides where the moon is closest to the earth,
The areas of the earth that the moon is not over at that time experience low tides.
When the sun, moon and earth are all lined up it cause more gravitational pull and create the spring tides.
It makes higher tides higher and lower tides lower.
When the sun, moon and earth are at right angles to each other they cause neap tides.
It gives lower high tides and higher low tides.