chapter 2. the greenhouse effect the earth’s atmosphere is compared to the glass walls and roof of...

Chapter 2

The Greenhouse Effect• The Earth’s atmosphere is compared

to the glass walls and roof of a greenhouse– Traps the sun’s warmth for

growing plants• Solar Radiation reaches the Earth’s

atmosphere• Some radiation reflects back into

space• Other radiation remains to warm the

Earth’s surface• Not all places on the Earth get the

same amount of heat from the sun– This depends on the relative

position of the sun and the Earth

Rotation

• The Earth rotates on an axis as it moves through space– The axis is an invisible line

through the center of the Earth from pole to pole

• The Earth completes one rotation in 24 hours

• The side that faces the sun it is daytime, and the side that is turned away from the sun is night

Revolution• The Earth also revolves around the sun in a orbit• The Earth completes one revolution every 365 ¼ days (one year)• To account for the ¼ a day, every 4 years we have an extra day,

known as Leap Year• The Earth’s position to the sun is tilted at a 23 ½ degree axis

– The Tropic of Cancer is at 23 ½ degrees North – The Tropic of Capricorn is at 23 ½ degrees South– These places receive the most direct sunlight

Solstices and Equinoxes

• Because of the Earth’s tilt, sunlight hits the surface differently at certain times of the year– As the Earth moves halfway around the sun, the

Northern and Southern Hemispheres tilt closer or farther from the sun

– These changes are marked by summer and winter solstices

• June 21 and December 21

• For the equinox, at noon the sun appears directly overhead at the Equator – March 21 and September 23

Influences on Climate

• The angle of the sun’s rays affect weather and climate in certain areas of the Earth

• Wind– Rising warm air creates areas of low pressure– Falling cool air causes areas of high pressure– Winds move from areas of high pressure into areas of

low pressure – The movement of winds distributes the sun’s heat

over the earth’s surface– If the earth were not moving, winds would blow in a

straight line, because the earth moves, the winds blow in different directions

Influences on Climate

• Currents– Ocean currents carry warm water from the tropics to

the poles– Other currents return cold water to the Equator

Influences on Climate

• Precipitation– Forms as air temperature changes– Warm, less-dense air absorbs more moisture than cool air– When the air cools, it cannot retain all of its water vapor, so the

excess water vapor condenses into a liquid– Tiny droplets of water gather together to form clouds– Precipitation occurs when more water collects in clouds than

they can hold– Precipitation is divided into three types: convectional,

orographic, and frontal

Influences on Climate• Convectional Precipitation

– Occurs when hot, humid air rises from the earth’s surface and cools. It then losses its ability to hold much water

– Common near the Equator and in the tropics– Produces nourishing rainfalls that feed lush, tropical

forests

Influences on Climate• Orographic Precipitation

– Sometimes warm, moist air is forced upward when passing over high landforms

– This is common on seacoasts where moist, ocean winds blow toward coastal mountains

– The warm winds cool as they rise up over the mountains– Clouds form and rain or snow falls– The air is cool and dry by the time it reaches the other side of

the mountains

Influences on Climate• Frontal Precipitation

– The most common kind of precipitation – Occurs when two fronts (or air masses) of different

temperatures meet– The warm air is forced upward by the heavier cool air– The rising warm air cools, and frontal precipitation

forms

Influences on Climate

• Nearby Bodies of Water– Bodies of water temperatures change much

more slowly then land temperatures – Because of this difference, large bodies of

water affect the surrounding climates– Winds blow over the water take on the water’s

temperature

Influences on Climate

• Elevation – Elevation has a dramatic effect on climate in highland

areas throughout the world– Air temperature decreases at a rate of 3.5 degrees for

every 1000 feet– Hikers must use caution because of this

Influences on Climate

• Nearby Landforms– All landforms affect climate

• Coastal mountains• Lakes• Forests• Tall buildings• Pavement – absorbs large amounts of solar energy

Plant Communities

• Plants usually don’t live alone. Most plants are in groups that depend on each other – Nourishment, shade, support

• A Plant community is a mix of interdependent plants that naturally grow in one place

• Similar environments tend to produce similar plant communities

Biomes and Vegetation Regions

• Biome describes a region in which the environment, plants, and animal life are suited to one another

• Regions are classified by their natural vegetation – or the typical plant life in areas where humans have not altered the landscape significantly