Chapter 3 STUDY GUIDE

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.

Chapter 2 STUDY GUIDE

For use with textbook pages 33–36.

Planet Earth

This section focuses on what humans know about the physical nature of our planet, Earth.

Chapter 2, Section 1

Terms to Know

hydrosphere The part of the earth made up of oceans, lakes, rivers, and other bodies of water (page 35) lithosphere The surface land areas of the earth’s crust, including continents and the ocean floor (page 35)

atmosphere The air that surrounds the earth (page 35)

biosphere The part of the earth where life exists (page 35)

continental shelf The part of a continent that extends underwater (page 36)

Earth’s Features

(page 33) Water, land, and air form the physical environment of the earth.

1.      What makes up the physical environment of the earth?

Our Solar System (page 33) Our solar system is made up of the sun and all the objects that revolve around it. The sun, the center of the solar system, is a ball of burning gases. The huge amount of matter contained in the sun creates a strong pull of gravity. This physical force keeps the earth and the other objects revolving around the sun.

Planets are the largest objects in the solar system, besides the sun. Each planet moves in its own orbit around the sun. There are nine known planets in our solar system:

A. Mercury, a hot, inner planet, is closest to the Sun.   B. Venus is a hot, inner planet. Mercury and Venus are the only planets without moons.   C.  Earth is an inner planet and the third from the sun. It is fifth in size among the planets. Earth is the only planet with liquid water at the surface and able to support varieties of life. D. Mars is a cold, barren desert.  It is an inner planet.   E.  Jupiter is an outer planet and the largest of all planets.   F.  Saturn is an outer planet with at least 18 moons.   G. Uranus is an outer planet.   H.  Neptune is an outer planet.   

I.  Pluto is an outer planet. It is the smallest planet and is a ball of ice and rock.

All the planets, except Pluto, are grouped into two types:

A.  Terrestrial planets have solid, rocky crusts.  Mercury, Venus, Earth, and Mars are terrestrial planets.

B.  Gas giant planets are larger, more gaseous, and less dense than terrestrial planets. Jupiter, Saturn, Uranus, and Neptune are gas giant planets.

STUDY GUIDE Chapter 2, Section 1

Besides planets, other objects that revolve around the sun include asteroids, comets, and meteoroids. Asteroids are small, oddly shaped, planet like objects. Comets are made up of icy, dusty particles and frozen gases. Meteoroids are large pieces of rock and iron.

Getting to Know Earth (page 35):  The surface of the earth is made up of water and land.  About 70 percent of Earth’s surface is water. The earth’s hydrosphere consists of bodies of water such as oceans, lakes, and rivers. About 30 percent of Earth’s surface is land, or lithosphere.  Earth’s atmosphere is a layer of gases that extends about 1,000 miles above the surface. The biosphere is the part of the earth where people, plants, and animals live.

The natural features of the earth’s surface are called landforms. Earth is made up of four major types of landforms: mountains, hills, plateaus, and plains. Landforms are found on the earth’s surface and underwater. The largest landforms on Earth are the seven continents. The continents are: Australia, Antarctica, Europe, Asia, North America, South America, and Africa. The continental shelf is the part of the continent that extends underwater.

The earth has great differences in the heights and depths of its surface. Mount Everest is its highest point at 29,035 feet above sea level. The shore of the Dead Sea is the earth’s lowest point at 1,349 feet below sea level.

(For use with textbook pages 37–43.)

Forces of Change

DRAWING FROM EXPERIENCE

In the last section you read about the features of Earth. This section focuses on the forces that change the surface of earth.

Chapter 2, Section 2

Terms to Know

mantle A thick layer of hot, dense rock beneath the earth’s crust (page 38)

continental drift The slow movement of continents across the earth (page 38)

magma Molten rock (page 38) plate tectonics The movement of great slabs of

rock that make up the earth’s crust (page 38)   

subduction:  A heavier sea plate diving under a lighter continental plate (page 39)

accretion Pieces of the earth’s crust coming together slowly as a sea plate slides under a continental plate (page 40)

spreading Sea plates pulling apart (page 40)

fold A bend in layers of rock (page 40)

fault A crack in the earth’s crust (page 40)

weathering The process that breaks down rocks into smaller pieces (page 42)

erosion The wearing away of the earth’s surface by wind, glaciers, and moving water (page 42) loess A fertile, yellow-gray soil deposited by wind and water (page 42)

glacier Large body of ice that slowly moves across the earth’s surface (page 42)

moraine Large piles of rocks and debris caused by melting and moving glaciers (page 42)

Internal Forces/ External Forces

Introduction (page 37) Scientists have evidence that the center of the earth is active with intense heat and pressure. Movements deep within the earth cause changes to the earth’s surface.

Earth’s Structure (page 37) The earth is made up of three layers:

A. The core is the center of the earth.  The inner core is solid, very hot, and under great pressure. It contains lead, iron and nickel.  The outer core is liquid. It is made up of melted iron and nickel.

B.      The mantle is a thick layer of hot, solid rock. It is made up of many elements.

C.     The crust is a rocky shell that forms the earth’s surface.  The crust is broken into several huge slabs of rock called plates.

Many scientists believe in continental drift. This is a theory that the continents were once joined and then slowly drifted apart. Many scientists also believe that the moving plates created the earth’s largest features— continents, oceans, and mountains. Plate movement is constant and very slow. As the plates move, they crash into each other, spread apart, or grind and slide past each other. The movements of plates are called plate tectonics. When the plates spread apart, magma, or melted rock, pushes up from the mantle.

Internal Force of Change (page 39) There are six internal forces that change the surface of the earth:

A. Mountains can form when continental plates collide.  For example, the Himalaya ranges were formed when the Indian landmass rammed into Asia. Mountains can also be formed in a process known as subduction, where a sea plate dives beneath a continental plate.  The sea plate melts as it crashes into the mantle, and the resulting magma bursts through the crust to form volcanic mountains.

Chapter 2, Section 2

In another process known as accretion, pieces of the earth’s crust pile up slowly as a sea plate slides under the continental plate.  This accumulating debris causes continents to rise.

B.      Spreading is a process in which sea plates pull apart.  This causes deep cracks in the ocean floor, releasing magma, which hardens into undersea volcanic mountains or ridges.

C. Moving plates sometimes squeeze the earth’s surface, causing folds or bends in layers of rock.

D. Grinding or sliding plates create cracks in the earth’s crust called faults.

E.  Earthquakes are caused by sudden, violent movements in plates along a fault line.

F.      Volcanic eruptions can occur when one plate plunges beneath another. Magma often blasts through the surface of the earth as volcanoes.  Volcanic island chains can form from the molten rock.

External Force of Change (page 42) Wind and water change the earth’s surface:

A. Weathering is the process that breaks down rocks on the earth’s surface into smaller pieces.

B.      Erosion is the wearing away of the earth’s surface by wind, glaciers, and moving water. It can cause the loss of soil and lead to dust storms.  Wind erosion can also create deposits of mineral–rich soil called loess, a fertile, yellow-gray soil found in China.

Glaciers are large bodies of ice that slowly move across the earth’s surface, causing erosion.  As glaciers move, they pick up rocks and soil and carve grooves in the landscape.  When glaciers melt and withdraw, they leave behind large piles of rock and debris called moraines. Water erosion is mostly caused by fast-moving water in streams and rivers that wears away soil and rock.  The pounding waves of oceans cause erosion along coasts.

(For use with textbook pages 46–49.)

Earth’s Water

In the last section, you learned about the forces that change the earth’s surface. This section focuses on the earth’s water.

Chapter 2, Section 3

Terms to Know

water cycle The movement of water from the oceans to the air to the ground (page 47)

evaporation The changing of liquid water into gas or vapor (page 47)

condensation A process in which water vapor changes into liquid water (page 47)

precipitation Moisture that falls to the earth in the form of rain, snow, or sleet (page 47)

desalination The process of removing the salt from ocean water (page 48)

groundwater Fresh water which lies beneath the earth’s surface (page 49)

aquifer An underground rock layer saturated with water in the form of streams (page 49)

Earth’s Water:  Fresh Water/Salt Water

 (page 46) All living things need water to survive. Water on Earth comes in three forms:

A. The liquid form of water is in rivers, lakes, and oceans.   B.  The gas form of water is held in the atmosphere. It is sometimes called water vapor. C. The frozen form of water is in glaciers and ice sheets.

Where is the earth’s water found?

The Water Cycle (page 46) Almost all of the hydrosphere is salt water found in oceans, seas, and salt- water lakes. The rest is fresh water found in lakes, rivers, and springs.

The total amount of water on Earth does not generally change. The water cycle is the constant movement of water from the oceans, to the air, to the ground, and finally back to the oceans. The water cycle has four main stages:

A. Evaporation is the changing of liquid water into vapor, or gas.  The sun’s heat causes water vapor to rise from the oceans and other bodies of water into the atmosphere.

B.  Condensation is the stage in which warm air cools and some of the water vapor changes back into liquid water.  Tiny droplets of water come together to form clouds.

C.  Precipitation is rain, snow, or sleet, which falls from clouds that contain more water than they can hold.

D.  Surface runoff is formed from the precipitation as it falls to the ground.  This water collects in rivers, lakes, and oceans.

Chapter 2, Section 3

Bodies of Salt Water (page 47)

About 70 percent of the earth’s surface is water. Almost all of the earth’s water is salt water. There are four main kinds of bodies of salt water— oceans, seas, gulfs, and bays. Oceans make up about 97 percent of the earth’s water. There are four oceans—the Pacific, the Atlantic, the Indian, and the Arctic. The Pacific is the largest and covers more area than all the earth’s land combined. Seas, gulfs, and bays are much smaller than oceans. These bodies of water are partially enclosed by land.

The water found in oceans is too salty for drinking, farming, or manufacturing. A process is being developed, called desalination, or obtaining freshwater from oceans by removing the salt content.

Bodies of Freshwater (page 48) About 3 percent of Earth’s total water supply is freshwater. Most of this 3 percent is not available to use. More than 2 percent of Earth’s total water supply is frozen in glaciers and ice caps. About 0.5 percent is found beneath the earth’s surface. Lakes, streams, and rivers contain less than 1 percent of the earth’s water. This water is important to people because it meets their everyday needs. For this reason, most large urban areas began as settlements along the shores of lakes and rivers where people could have a constant supply of water.

Another source of freshwater is groundwater, which lies beneath the earth’s surface and supplies wells and springs. Groundwater comes from rain and melted snow that filter through the soil. It also comes from water seeping into the ground from lakes and rivers. In areas with little water, people sometimes depend on aquifers for their water supply. An aquifer is an underground porous rock layer often filled with water in the form of streams.