Read My Notes : ): February 2009

Earth Science- Chapter 8

Water Cycle- aka hydrologic cycle- cycle of how water is recycled.

Earth’s surface is divided in 3 categories:
1. Salt water- found in the oceans. Salt water makes up 97% of our water supply.
2. Fresh water- found in the form of ice (called glaciers) near the poles. Fresh water makes up 2% of earth’s water.
3. Surface and ground water- rivers, wells, etc. Surface and ground water make up 1% of earth’s water.

There’s a limited supply of water on earth’s surface, therefore our water supply is constantly being recycled. Water starts off by the ocean. It evaporates into the atmosphere and rains back down to the land.

Water cycle-
Water enters the atmosphere in 2 different ways:
1. Evaporation- liquid water turns into gas.
2. Transpiration- plants release water vapor into the atmosphere.
(Sometimes, combined as evapotranspiration.) These processes occur because of solar energy.

71% of earth’s surface is covered with oceans. Most water gets there through evaporation.
1. Water starts in the ocean.
2. It evaporates.
3. The water vapor condenses and forms rain.
4. The water will be returned to earth through the process of precipitation.
5. The precipitation will infiltrate into the earth and become ground water.

Infiltration-
Less than 1% of water that returns to the ground infiltrates into the earth as ground water. Ground water is mostly fresh water, and usually in liquid form. There are 2 basic reasons we need ground water:
1. Plants need it to grow.
2. It is a source of energy for our homes, agriculture and industry.

Ground water zones- distinct zones that ground water occupies after it infiltrates the soil. When ground water begins to infiltrate into the soil, the gravity pulls it down into the zone of saturation, which is located directly above bedrock- hard stone within the earth that the water can’t penetrate. Above the zone of saturation is a water table and above the water table is the zone of aeration- area that has space between particles and is full of air.

What is the water table? The boundary between the zone of aeration and the zone of saturation. It is really considered to be the uppermost layer of the zone of saturation.
The water table is full of water. What’s the use of the water table? If you dig a well, the well must reach the water table. If you remove the water quicker than it can refill itself, the entire level of the water table will sink down. When the water table falls below the level of the well, the well is dry. What do you do if a well is dry?
1. Drill a deeper well- the deeper the well, the more probable that it’ll be able to fill with water.
2. Use less water.

What affects the storage and movement of ground water? Soil and rock found near the surface is a big factor in how much water can enter into the earth. Why is this? Water can only infiltrate the ground where there are openings. Theses openings between the soil and rocks are called pore spaces. The water is going to be able to pass these pore spaces. If there is a lot of space, a lot of water can go through. If there’s a little space, only a little water can go through.

Most substances are porous, meaning water can enter into the empty spaces in this substance.

We measure the porosity of a substance- the amount of pore space is in a material. The porosity of a substance determines how much water of air this sample of rock can hold. Large porosity- a lot of water or air, small porosity- a little water or air.

What makes a substance more or less porous? Porosity depends on:
1. Shape of the particles.
2. How are they packed together.
3. Mixture of size of the particles.

The most porous sort of object:
1. Round particles.
2. Well sorted particles- all the same size.
3. Not closely packed together.

Material that’s not so porous (because the small particles slide in between the big particles like puzzle pieces):
1. Closely packed together.
2. Flat, angular particles.
3. Mixture of sizes.

Particle sizes don’t affect porosity even if an object is naturally porous. If you add any cement sort of material, it’s no longer porous.

Permeability- ability of soil to transmit water. The rate of permeability- how fast water can pass through soil. It depends on:
1. Size of the pores.
2. How are the pores connected.

High permeability- water can pass through quickly- has to have large pores and well connected pores (ex. sand).

Low permeability- small pores and pores are not well connected (ex. clay). Water moves through it very slowly and the water keeps sticking to particles along the side and doesn’t allow water to pass through.

Relationship between porosity and permeability- just because something has high porosity, it doesn’t necessarily have high permeability and vice versa.

Bedrock is an example of something whose porosity and permeability don’t match up. Pieces of stone are close together and have no pores. It gets a fracture down the middle. The bedrock will now have a high rate of permeability because of the well-connected fracture.

Runoff- when the amount that it rains outside is so great that the ground can’t absorb it, the water will run off the surface usually into streams or rivers.

3 times a runoff will occur:
1. When there’s so much water, the soil becomes saturated and no more water can infiltrate.
2. The gradient of the soil is very steep.
3. The temperature of the soil is below 0°C- soil is frozen and infiltration is impossible.

Capillarity- the ability of soil to draw water upward through tiny spaces between soil particles. The water is moving against gravity. How? There’s an attraction between the water droplets and the surface of the soil particles.

Capillarity will happen most often with small soil particles. Why? Because small particles have more surface area.

Water this happens to is called capillary water. It is drawn up above the water table and into the zone of aeration and it becomes available for plants to use.

Streams and rivers-
Where do they get their water from? Runoff- after precipitation, the streams get water from overland flow (aka runoff). There are 2 different scenarios:
1. Moist climate- streams will generally get water from runoff. If there is any dry period of no rain, water will be drawn out from the ground. Water from the water table and zone of saturation will seep into the stream. This is aka perennial stream.
2. Dry climate- doesn’t rain so much- no rain= dry stream. The only place the stream gets water from is rainwater and runoff from the rainwater. When the streams are full, the stream will give water to the water table- replenish the ground water.

Rainfall- right after it rains, the streams don’t automatically fill with water. In order for the stream to get full, you need runoff.

From the time it rains the most (aka maximum precipitation) until the time that the stream fills up with water (aka maximum stream discharge), there’s a space of time called time lag. The longer the runoff, the longer the time lag will be. There are 4 factors of time lag:
1. Size of the stream-
a. Large stream- has a long runoff and it responds slowly to the rainfall because the runoff has to flow over a great distance of land.
b. Small stream- will respond quickly to precipitation.
2. Precipitation- snow causes a stream to respond more slowly to precipitation because before it starts runoff, the snow has to melt.
3. Gradient- how steep the land is. The steeper the slope, the quicker the runoff.
4. Area of the rainfall-
a. Mountainous area with streams and rocks will have the quickest runoff.
b. Urban area with paved roads and sidewalks will have a pretty quick runoff because it’s smooth.
c. Area with vegetation- a lot of trees, shrubs and other plants that prevent water from flowing, therefore there will be a slow runoff.

Watersheds/ drainage basin- an area in which all streams and rivers of 1 area empty into 1 large body of water. A river and its natural tributaries make up 1 watershed. Several small watersheds can eventually flow into 1 larger watershed.

How is a watershed created? By natural divides of high land that don’t allow the water to pass.

The pollution of a river and its tributaries will be contained within its own watershed.

Heat-
Heat is a form of energy. Why is heat considered a source of energy? Because it can make things work.

There are 3 ways for heat energy to travel:
1. Convection- heat flows by way of density currents within a fluid (liquid/gas). Examples of convection:
a. Wind convection currents- bringing warm air from the equator to the poles.
b. Ocean currents- oceans transfer heat through convection.
2. Conduction- heat transfers through a solid. When a warm substance meets a cold substance, heat is transferred through the process of conduction. When the vibrational energy of the molecules in the warm object are transferred by contact to the cooler substance, that is conduction.
What’s a conductor of heat? An object through which conduction can occur. Some objects conduct better than other objects, for example metal gets hot to the touch.
3. Radiation- the flow of the energy through space or transparent materials. An example of radiation is the electro-magnetic rays of the sun that reach us- they travel through space through the process of radiation. These electro-magnetic rays are our primary source of energy:
a. Heat rays that come to us through radiation can’t be seen, but can be felt.
b. Light waves- can’t be felt.
c. Radioactive rays- can’t be felt and can’t be seen. They’re the most dangerous rays of the sun.

Energy absorption-
Some surfaces on earth absorb heat better than others. The sun’s rays shine on the earth and they have to be absorbed.
1. A lot of absorption-
a. Dark color
b. Rough surface- any surface that absorbs energy well will also radiate the energy very quickly.
2. Poor absorption (heats up slowly and radiates the heat quickly)-
a. Light color
b. Smooth surface

The reason one object will absorb better is because it has a low specific heat- the amount of energy needed to become hot. It needs less energy to become hot.

Something that absorbs well radiates well, and vice versa- land heats up and cools off quickly. Water heats up and cools off slowly.

Insolation- the sun’s electro-magnetic rays that reach the earth.

The intensity of insolation depends on:
1. The angle of insolation- the measure of how high the sun is in the sky. We measure the horizon up to the sun’s position in the sky. There are 2 cycles to the angle of insolation:
a. Daily cycle- depending on how high the sun is in the sky, that’s how great the angle of insolation is. When the sun rises, there’s a small angle of insolation. As the day progresses, the sun gets higher in the sky and the angle of insolation is increasing. The sun has the greatest angle of insolation at noon. The greater the angle of insolation, the greater the intensity of insolation. Depending on how high the sun is in the sky, that’s how hot it is going to be outside. As the day moves on, the sun begins to get lower in the sky and the angle of insolation and the intensity of insolation both decrease and it’s going to get cooler outside.
Why is it that when the angle of insolation increases, the intensity of insolation also decreases? When the sun is directly overhead, the rays are concentrated over a smaller area, causing there to be a greater intensity of sunlight. When the sun is at a lower angle of insolation, its rays are spread out over a larger area and there’s less intensity of insolation.
b. Seasonal cycle- in the northern hemisphere, the winter solstice has the lowest angle of insolation. Because there’s the lowest angle of insolation, it’s the coldest. In the summer, there’s the largest angle of insolation and it’s the hottest.

Vertical ray- only certain parts of the earth receive vertical rays. The sun strikes the earth’s surface at a 90˚ angle. This is the greatest angle of insolation that it’s possible to receive. You can only receive this angle of insolation if you are located between 23 ½ ˚ S and 23 ½ ˚ N, and even there you’ll only get it sometimes.
The N and S poles receive the lowest angles of insolation- 66 ½ ˚ - 90˚.
2. The duration of insolation- the length of time from sunrise to sunset. When will the intensity of insolation be the greatest?
a. Greatest duration of insolation- longest time between sunrise and sunset.
b. Greatest angle of insolation- as the duration of insolation and the angle of insolation increase, the intensity of insolation will also increase.
In the northern hemisphere, the greatest duration of insolation is in the summer. The duration of insolation depends on the latitude and the season. The further N you go, the duration of insolation will be greater in the summer and less in the winter.
3. The surface that the insolation is going to strike- depending on what surface the insolation strikes, that will determine how much energy is going to be absorbed. Solar energy is radiated onto this earth. 43% of this energy is visible light rays and the surface of earth absorbs it. The UV rays (high energy radiation) that are givin off are absorbed by the gases in the atmosphere, such as the ozone. This is about 25%. The third type of energy- infrared rays (heat)- are absorbed by water vapor and carbon dioxide in the lower atmosphere.

Different waves come to earth through the process of radiation. Once the surface absorbs the energy from the sun, it sometimes radiates the waves back into the atmosphere. This energy is called terrestrial radiation- energy that was radiated by the earth. Terrestrial radiation radiates infrared waves into the atmosphere. These heat waves are absorbed by the water vapor and carbon dioxide in the atmosphere. About 9% of terrestrial radiation is lost to outer space. 91% is absorbed by the atmosphere and we receive that heat.

At any givin latitude, land and water will have different temperatures. Why is that?
1. Water has a higher specific heat than land.
2. When there’s a low angle of insolation, water is going to reflect the energy back into the atmosphere, but the land will absorb that energy.
3. Solar energy will penetrate the water deeply because it’s transparent.
4. The convection currents of the ocean carry the heat throughout the hydrosphere and the heat gets spread throughout the ocean.

Every amount of insolation that we receive is spread over a greater area in the ocean than land.

Example of the effect of ocean currents on the world- El Nino Southern Oscillation (ENSO). What is this? In the Pacific Ocean, along the coast of S America, the ocean water is cold. It’s full of oxygen and nutrients. The fish have plenty to eat. There is good fishing there, so the people benefit too. It’s an ideal situation. How is this water so well supplies? Where does this water come from? Upwelling of water. Ocean currents bring water to S America. Some years, there is less upwelling of water- the cold water isn’t being brought to the coast of S America. Instead, there’s warm water, which isn’t as productive. The effects are poor fishing, less nutrients in the water, the warm water evaporates, which leads to more rainfall in the area and less rainfall and a draught in the W Pacific. It causes unusual weather patterns.

Reflection of insolation-
When light is reflected or when light bounces off a surface, less light is absorbed and vice versa. Some surfaces are good absorbers and some surfaces are good reflectors:
1. Ice and snow reflect. They absorb very little, so they’re bad absorbers and good reflectors.
2. Calm surface water reflects when there’s a low angle of insolation. When there’s a high angle of insolation, the water does absorb.
3. Black roads absorb 90% of solar energy.
4. The N and S poles- receive the same total duration of insolation as the rest of the world- 6 months of light and 6 months of dark, so why don’t the poles warm up?
a. Because there’s so much snow and ice at these areas, that most of the solar energy is reflected back into the atmosphere.
b. The sun is always low in the sky in the poles- when there’s a low angle of insolation, most of the sunlight is reflected.
c. When there is a low angle of insolation, the sunlight is very spread out and the sun is not as strong. This results in cold weather.

In the atmosphere, there’s dust, pollen and pollution- all these particles in the atmosphere scatter the sun’s solar energy, so the intensity of insolation is reduced. (When the air is polluted, it’s colder.)

Terrestrial radiation-
Once earth has absorbed the energy, the energy is then reflected back into the atmosphere. When the energy is absorbed, it’s absorbed as visible light. When the energy is radiated, it’s reflected as infrared rays (longer than visible rays).

What happens to the rays that are reflected? They are absorbed as carbon dioxide and water vapor in the atmosphere. The process of heat being absorbed as carbon dioxide and water vapor is the greenhouse effect. In a greenhouse, the walls are made of glass and there are plants inside. The visible light rays from the sun pass through the walls and strike the plants inside. These plants reflect this energy back as infrared rays, but the walls reflect the heat back, resulting in extreme heat in the greenhouse.

The same thing happens in our atmosphere. Visible light rays are reflected as heat and the heat is absorbed by the carbon dioxide and water vapor in the atmospheres. This keeps our atmosphere warm enough to be lived in- there’s the right amount of carbon dioxide in our atmosphere. Venus has too much carbon dioxide, so it’s very hot.

Global warming-
If there’s too much gas or carbon dioxide in the atmosphere, then too much heat will be absorbed and there will be global warming.

Effects of global warming:
1. Ice caps and glaciers will melt.
2. There will be too much water in the oceans. The sea level will rise and flood coastal cities.

Why will global warming occur? If there are too many gases in the atmosphere. Why are there too many gases in the atmosphere?
1. We burn fossil fuels, which create carbon dioxide.
2. We cut down forests, which prevents the carbon dioxide from being taken in by the plants.
3. Methane (gas) is increasing. How does it increase? If we use too much gas and from the decay of organic matters.

Insolation temperature lag-
There’s a space of time between when we receive the most sunlight and the highest temperature. Why does this happen? Because the insolation is being absorbed by the earth and then radiated back into the atmosphere as heat. This heat energy is what raises earth’s temperature.

Daily cycle of insolation-
Sunrise- the ground is cool and it begins to absorb radiation. It keeps absorbing until noon- max incoming radiation. Noon however, is not the hottest time of day because we’re absorbing more than we are reflecting. At mid afternoon, the incoming solar radiation is equal to the outgoing reflection- reach the highest temperature. At sunset, the ground is radiating more than it’s absorbing, so the ground is cool.

Climates- average local temperature.
Climate is effected by:
1. Latitude- distance from the equator. As your latitude increases, your temperature decreases.
a. The N and S poles have the coldest climates because they’re the furthest from the equator.
b. The equator area has the most tropical climate.
c. The mid-latitude area has a mid- latitude climate. In a mid-latitude climate, the seasons have great seasonal changes.
2. Altitude- elevation above sea level. As you increase in altitude, your temperature decreases because air cools as it rises.
3. Mountain ranges- chain of mountains. Near a mountain, there’s an ocean. The side of the mountain near the ocean is called the windward side. The other side of the mountain is called the leeward side. From the ocean comes warm, moist air. In order for the air to pass by the mountain, it has to rise above the mountain. When the warm air rises, it cools and condenses and precipitation occurs.
Adiabatic cooling- air that cools as it rises. After it rains, cool and dry air passes over the mountain.
Adiabatic heating- air that warms as it descends.
4. Oceans- there is less of a temperature change in oceans than land.
a. Convection currents- heat is spread throughout the ocean.
b. Energy penetrates deep into the ocean.
c. The ocean uses some of the energy for evaporation.
d. Water has a higher specific heat.
These factors make sure that the ocean never gets as hot or cold as the land.
Effects of the ocean on climate- the area near the ocean has a moderate climate- doesn’t change so much. Because it’s getting the breeze from the ocean, coastal climates have cooler temperatures in the summer and warmer weather in the winter. (There’s not such a big difference between summer and winter.)
5. Ocean currents- a stream of water that circulates through the ocean. A cold ocean current= cold air and warm ocean current= warm air.
Examples:
a. Warm ocean currents in Florida. Coming from the strait of Florida, this ocean current moves N into the Mid Atlantic Ocean and is now called the Mid Atlantic Drift aka the Gulf Stream.
b. England should be cold because it is at high latitude, but because of the warm ocean currents, it’s warmer than you would think.
c. N California is colder than you would imagine because of the cold Pacific Ocean currents.
6. Planetary wind belts- made up of the prevailing winds of each area.
Air that is sinking is high pressured, cold, dry air (usually). Air that is rising is low pressured, warm, moist air.
a. 0˚- equator there is low pressured, warm, moist air- humid climate and precipitation will occur.
b. 30˚ N/S- desert area- high pressured, dry, hot air. The air is heated by adiabatic heating- the air warms as it sinks.
c. 60˚ N/S- mid latitude area- low pressured, warm, moist air. There’s precipitation.
d. 90˚ N/S- poles- high pressured, dry, cold air.
7. Monsoons- when low pressure winds push high pressure winds back up N.
There is very heavy precipitation during the summer months. Monsoons are caused by in continental climate.
During the winter, N Asia is very cold and dry (high pressure system). This high pressure air travels to S Asia- in continental system- S is getting the cold air from the N. As the summer approaches, the ocean brings low pressure air into the continent. These low pressure winds cause the high pressure winds to reverse direction- the high pressure wind goes back up, pushed by the low pressure winds. The extreme difference between the high and low pressure winds causes monsoons.
8. Typical Storm tracks- based on the storm tracks, weather will occur following a certain pattern. For example, in the US, weather usually moves from the W to the E. Hurricanes move NW. When a hurricane arrives at the E coast, the storm and the hurricane will meet, and the weather patterns will push the hurricane back into the Atlantic Ocean.

Read My Notes : )

Wednesday, February 25, 2009

Earth Science - Chapter 8

Earth Science - Chapter 7, Continued

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