Chapter 3 Study Guide

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Chapter 3 STUDY GUIDE

For use with textbook pages 55–58.

Earth-Sun Relationships Chapter 3, Section 1

Terms to Know

weather The condition of the atmosphere in one place and time (page 55)

climate The weather patterns an area experiences over a long period of time (page 55)

axis An imaginary line running through the planet’s center from north to south (page 56)

temperature The measure of how hot or cold a place is (page 56)

revolution Trip around the sun (page 56)

equinox A day when the daylight and night- time hours are equal in length (page 57)

solstice A day with the longest or shortest period of daylight in a year (page 57)

greenhouse effect The trapping of heat from the sun by the atmosphere that prevents all the heat from escaping into space (page 58) global warming A general rise in global temperatures (page 58)

Introduction (page 55) The relationship between the earth and the sun influences all of life on Earth. Scientists study changes in this relationship.

1.          What does the relationship between the earth and the sun influence?

Climate and Weather (page 55) Weather is the condition of the atmosphere in one place at a particular time. Climate is the pattern of weather that an area experiences over a long period of time. The most important influence on the climate of an area is the earth’s position in relation to the sun. The sun’s heat and light do not reach all parts of the earth at the same time or with the same strength.

2.          What is the difference between weather and climate?

Earth’s Tilt and Rotation (page 56) The earth’s axis is an imaginary line running from the North Pole to the South Pole through the earth’s center. The earth is tilted on the axis at an angle of 231⁄2 ̊. Because of the tilt, different places on Earth receive direct sunlight at various times of year. The angle of the tilt affects the temperature—or how hot or cold a place is. Areas that get a large amount of direct sunlight have warmer temperatures than places that receive little direct sunlight.

Earth rotates on its axis, making one complete rotation every 24 hours. The part of the earth that faces the sun has light. The side facing away from the sun has darkness.

3.          How do tilt and rotation affect Earth?

Earth’s Revolution (page 56) The earth travels in an orbit around the sun. It takes 365 days—one year—to complete one revolution, or trip around the sun. The revolution of the earth and its tilt cause changes in the angle and amount of sunlight that reach different places. These changes cause seasons. The length of daylight and the daily temperatures change as the seasons change. On about March 21 and September 23 each year, the sun’s rays fall directly on the Equator. This event is known as an equinox because there are equal daylight and nighttime hours.

4.          What causes seasons on Earth?

The Tropics of Cancer and Capricorn (page 56) The Tropic of Cancer at 231⁄2 ̊N is the northernmost point on Earth to receive the direct rays of the sun. The direct rays reach the Tropic of Cancer on about June 21. This day is known as the summer solstice because it is the longest day of sunlight in the Northern Hemisphere. It is the beginning of summer there.

The Tropic of Capricorn at 231⁄2 ̊S is the southernmost point on Earth to receive the direct rays of the sun. The direct rays reach the Tropic of Capricorn on about December 22. This is known as the winter solstice because it is the shortest day of sunlight in the Northern Hemisphere. It is the beginning of winter there.

5.          What causes the beginning of summer and of winter in the Northern Hemisphere?

The Poles (page 57) The amount of sunlight at the poles changes greatly throughout the year.

When one Pole is tilted toward the sun, it receives continuous sunlight for six months. At the same time, the other Pole is tilted away from the sun and receives no sunlight at all for six months.

6.          Why does one Pole receive sunlight when the other Pole receives no sunlight at all?

The Greenhouse Effect (page 58) The earth’s atmosphere acts as a screen for the sun’s radiation. When rays from the sun reach the atmosphere, some of them are reflected back into space, but some of them pass through to the earth’s surface. The radiation that reaches the surface is then reflected back into the atmosphere. On its way back out through the atmosphere, some of the radiation passes into space, and some of it gets reflected back to earth again. This process is known as the greenhouse effect, because it traps heat the same way a greenhouse does.

The part of the atmosphere that traps the heat from the earth is made up of carbon dioxide (CO2) and water vapor. In recent years the burning of fossil fuels has caused the amount of CO2 in the atmosphere to rise rapidly. An increase in CO2 levels causes the atmosphere to trap more heat. This in turn causes a general rise in global temperatures, or global warming. Global warming can cause ice caps and glaciers to melt and cause a rise in sea levels.

Factors Affecting Climate Chapter 3, Section 2

For use with textbook pages 59–64.

Terms to Know

prevailing wind Global wind that blows in a fairly constant pattern (page 62)

Coriolis Effect The effect of the earth’s rotation on prevailing winds and currents (page 62) doldrums A narrow band of windless area at the Equator (page 62)

current A stream of water moving through a body of water in a certain direction (page 62)

El Niño A periodic reversal of the pattern of ocean currents and water temperatures in the mid-Pacific region (page 63) windward The side of a mountain range facing the wind (page 64)

leeward The side of a mountain range that does not face the wind (page 64)

rain shadow The dry area found on the lee- ward side of a mountain range (page 64)

Climate Factors

Introduction (page 59) Latitude, wind and water patterns, and landforms combine with the earth- sun relationship to influence world climates.

Latitude and Climate (page 59) The climate follows general patterns within each latitude zone. There are three latitude zones:

Chapter 3, Section 2

A.  Low latitudes- between the Tropic of Cancer and the Tropic of Capricorn, receive direct rays of the sun year-round. Low latitudes have warm to hot climates.

B.  High latitudes are at the earth’s north and south polar areas—north of the Arctic Circle and south of the Antarctic Circle.  When either pole is tilted toward the sun, it receives continuous indirect sunlight for about six months.  At the same time the opposite polar region is tilted away from the sun and receives continuous darkness. High latitudes have cool to very cold climates.

C.  Mid-latitudes are located between the Tropic of Cancer and the Arctic Circle in the Northern Hemisphere and between the Tropic of Capricorn and the Antarctic Circle in the Southern Hemisphere. The mid-latitudes generally have temperate climates with more dramatic seasonal weather changes than high or low latitudes.

Elevation and Climate (page 61) The earth’s atmosphere becomes thinner as altitude increases. Thinner air keeps less heat, so temperatures are generally cooler at higher elevations.

Wind and Ocean Currents (page 61) Winds distribute the sun’s heat around the earth. Global winds blow in fairly constant patterns called prevailing winds. The earth’s rotation causes winds to blow diagonally from the Equator. This is known as the Coriolis Effect. Low latitude winds are called trade winds, because they were travelled on by ships involved in trade. Mid-latitude winds are called Westerlies because they blow from the west. High latitude winds are called polar easterlies because they push cold air from east to west toward the mid-latitudes. At the Equator there is a narrow band of generally windless area called the doldrums.

Cold and warm streams of water, called currents, move through the oceans. The Coriolis Effect causes ocean currents to move in clockwise circles in the Northern Hemisphere and counterclockwise circles in the Southern Hemisphere. Ocean currents bring cold water from the polar areas toward the Equator. The water warms as it moves through the Tropics and forms warm ocean currents. Cold ocean currents cool the lands they pass. Warm ocean currents warm the lands they pass.

The water cycle also affects weather. Water vapor forms in the atmosphere from evaporated surface water. As colder temperatures cool the rising air, the vapor forms clouds. Further cooling causes rain to fall, which can lower the temperature on warm days.

Climate is affected by recurring events, such as El Niño. This is a periodic reversal of the pattern of ocean currents and water temperatures in the mid-Pacific region. El Niño influences climates throughout the world. In an El Niño year, precipitation increases along the coasts of North and South America, increasing the risk of floods. In Southeast Asia and Australia, El Niño causes droughts and sometimes forest fires.

Landforms and Climate (page 63) The presence of landforms such as continents can affect climate. Large bodies of water are slower to heat than land, so water temperatures change less than land temperatures. As a result, coastal lands experience less changeable weather than inland areas.

Mountains can also affect climate. Winds that blow over an ocean are pushed upward when they meet a mountain range. The rising air cools, and precipitation is released on the mountain’s windward side—the side of facing the wind. After the precipitation is released, winds get much warmer and drier as they go down the opposite, or leeward, side of mountains. The hot, dry air on the leeward side is known as a rain shadow.

World Climate Patterns Chapter 3, Section 3

For use with textbook pages 65–69.

Terms to Know

natural vegetation The plant life that grows in an area where the natural environment has not been changed by human activity (page 66) coniferous A type of tree with cones and needle-shaped leaves (page 68)

oasis An area of lush vegetation in the desert (page 67)

deciduous A type of tree with broad leaves that drop in autumn (page 65)

mixed forest A forest with both deciduous and coniferous trees (page 68)

chaparral Thickets of woody bushes and short trees (page 68)

prairie Inland grasslands (page 68) permafrost The frozen subsoil (page 68) hypothesis Scientific explanation (page 69)

smog A visible chemical haze that endangers people’s health (page 69)

Major Climates and Vegetation

Introduction (page 65) Ordinary climate patterns can be different from region to region, depending on the climate factors present.

Climate Regions (page 65) Geographers divide the earth into several climate regions. Each region has its own type of soil and natural vegetation, or plant life growing in an area that has not been changed by human activity. There are five major climate regions:

A. Tropical climates are found in or near the low latitudes.

1.  A tropical rain forest climate is hot and humid. It rains almost

everyday.  The vegetation grows thickly in layers.  Tall trees form a canopy over shorter trees and bushes.  Vines and shade-tolerant plants grow on the rain forest floor.

2.  A Tropical Savanna climate has dry winters and wet summers, with hot temperatures year-round. Fewer trees grow here than in rain forests. Coarse grass covers the ground.

B.  Dry climates are areas with little precipitation and temperatures that vary from hot during the day to cool at night.  There are two types of dry climates. 1.)       The desert climate has little vegetation, with some scrub and cactus. Some desert areas have underground springs to support an oasis. This is an area with abundant vegetation. 2.)     Steppe climate regions have grasslands with few trees.

C.  Mid-latitude climates include four temperate climate regions.

1.  Marine west coast climates have ocean winds that bring cool summers and damp winters.  Vegetation consists of coniferous and deciduous trees. Deciduous trees have wide leaves that change color and drop in autumn. Coniferous trees have cones and needle-like leaves. Marine west coast climates have mixed forests with both evergreen and deciduous trees.

2.  A Mediterranean climate is found near the Mediterranean Sea, in southern California, and in parts of southern Australia. Mediterranean climates have mild, rainy winters and hot, sunny summers.  The vegetation includes chaparral, which are woody bushes and short trees.

3.  Humid sub-tropical climates in the southeastern United States, South America, and Asia have short, mild winters and nearly year- round rain.  Vegetation includes mixed forests and inland grass- lands called prairies.

4.  A humid continental climate is found in the northern United States, southern Canada, Eastern Europe, and northeastern China. The further north in this climate, the longer and more severe are the snowy winters and the shorter and cooler are the summers. The vegetation is a mixture of deciduous and evergreen trees.

D. High latitude climates have freezing temperatures most of the year. There is little vegetation in the three high latitude climate regions.

1.  The subarctic is just south of the Arctic Circle.  Winters are long and very cold. Summers are short and cool. In many parts of the subarctic, only a thin layer of the surface soil thaws each summer. The permanently frozen subsoil below it is called permafrost. The vegetation is mostly coniferous evergreens.

2.  The tundra climates are closer to Polar regions and colder than subarctic.  Winter is dark and bitterly cold.  The constant sunlight in summer brings little heat.  The vegetation is limited to low bushes, short grasses, moss, and lichens.

3.  The ice cap climates are located in Antarctica and the interior of Greenland, where the temperature averages below freezing.  The surface in this region is always covered with snow and ice. Lichens are the only vegetation.

E.  High mountains, or highlands climates, are similar to high latitude climates because of the thinning atmosphere at high altitudes.  The higher the elevation, the cooler the temperature. Mixed forests are found at the base of mountain ranges. Higher up, meadows with small trees, shrubs, and wildflowers are on mountainsides.

Climate Changes (page 69) Climates change over time. For example, the earth has experienced four eras, known as ice ages, when glaciers covered large areas of the planet’s surface. These eras occurred during the last 1 to 2 million years. One hypothesis, or scientific explanation, for the ice ages is that the earth soaked up less solar energy because of changes in the earth’s orbit. Another hypothesis is that dust clouds from volcanic activity reflected sunlight back into space, cooling the atmosphere and lowering surface temperatures.

Human interaction with the environment also affects climate. The burning of fossil fuels releases gases that mix with water in the air. This forms acid that could destroy forests when it falls in rain and snow. The exhaust released from fossil fuels can also form smog. Smog is a visible chemical haze in the atmosphere that endangers people’s health. Building dams and changing the flow of rivers may cause areas of land to flood or dry out. These changes all will affect climate over time.