World Geography
The Physical World
ESSENTIAL QUESTION
Why do we study Earth and its physical systems?
LESSON 1
Earth and the Sun’s Energy
LESSON 2
Water on Earth
LESSON 3
The Land
LESSON 4
Weather and Climate
LESSON 5
World Climates
LESSON 6
Environments and Biomes
LESSON 7
Natural Resources
1
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World Geography
LESSON 1
Earth and the Sun’s Energy
The Big Idea
Earth’s movement and the sun’s energy interact to create day and night, temperature changes, and the
seasons.
Main Ideas
•
•
Earth’s movement affects the amount of energy we receive from the sun.
Earth’s seasons are caused by the planet’s tilt.
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World Geography
Lesson 1
Earth’s Movement
Main Idea 1
Earth’s movement affects the amount of energy we receive from the sun.
• All life on Earth requires solar energy, or energy from the sun, to survive.
• The amount of solar energy places on Earth receive changes constantly.
• Earth’s rotation, revolution, tilt, and latitude all affect the amount of solar energy a place
receives.
3
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World Geography
Lesson 1
Main Idea 1
(continued)
Rotation
Revolution
•
Earth spins on its axis—an imaginary line
that runs through the center of the planet
around which it turns.
•
Earth follows an orbit, or path, around the
sun.
•
Orbit is not a perfect circle
•
It takes Earth 24 hours to make one
rotation, or complete spin on its axis.
•
It takes Earth 365¼ days to complete one
revolution, or trip around the sun.
•
As Earth spins, different parts of the
planet face the sun, thus causing the
changes from day to night.
•
Our calendar year is based on the time it
takes Earth to complete its orbit.
4
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World Geography
Lesson 1
Main Idea 1
(continued)
Tilt and Latitude
Tilt
Latitude
•
Earth’s axis is tilted at an angle of 23½
degrees from vertical.
•
Latitude is the distance north or south of
Earth’s equator.
•
At any give time of year, some places on
Earth tilt toward the sun, and others tilt
away.
•
Low-latitude areas, those nearest the
equator, receive direct rays from the sun
all year.
•
Places tilting toward the sun receive more
solar energy and have warmer
temperatures than those that tilt away.
•
High-latitude areas, those farther from
the equator, receive indirect rays from the
sun and have colder temperatures.
5
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World Geography
Lesson 1
The Seasons
Main Idea 2
Earth’s seasons are caused by the planet’s tilt.
• Seasons are periods during the year that are known for a particular type of weather.
• Many places experience four seasons—winter, spring, summer, and fall.
• In some parts of the world, seasons are based on the amount of rainfall.
6
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World Geography
Lesson 1
Main Idea 2
(continued)
Winter and Summer
Spring and Fall
Rainfall and Seasons
•
Earth tilts away from the
sun in winter and toward
the sun in summer.
•
•
•
Because of the Earth’s tilt,
the Northern and
Southern hemispheres
experience opposite
seasons.
In the tropics, regions
close to the equator,
seasons are marked by
rainfall rather than
temperature.
•
At certain times of year,
winds bring either dry or
moist air to the tropics,
creating wet and dry
seasons.
•
In spring, as part of Earth
begins to tilt toward the
sun, solar energy
increases, temperatures
rise, and days grow
longer.
In fall, the opposite
occurs, and solar energy
decreases, temperatures
fall, and days grow
shorter.
7
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World Geography
LESSON 2
Water on Earth
The Big Idea
Water is a dominant feature on Earth’s surface and is essential for life.
Main Ideas
•
•
•
Salt water and freshwater make up Earth’s water supply.
In the water cycle, water circulates from Earth’s surface to the atmosphere and back again.
Water plays an important role in people’s lives.
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World Geography
Lesson 2
Earth’s Water Supply
Main Idea 1
Salt water and freshwater make up Earth’s water supply.
•
Water covers some two-thirds of the planet.
Salt Water
•
About 97 percent of the Earth’s water
•
Unsafe to drink because of high levels of salt
•
In general, found in Earth’s oceans, which cover some 71 percent of the planet’s surface
•
Also found in some of Earth’s lakes
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World Geography
Lesson 2
Main Idea 1
(continued)
Freshwater
•
Water without salt, or freshwater, makes up only 3 percent of our water supply.
•
Much of Earth’s freshwater is locked in glaciers, large areas of slow moving ice, and in the
ice of the Arctic and Antarctic regions.
•
Surface water is water that is found in Earth’s streams, rivers, and lakes.
– Less than one percent of Earth’s water supply
– Streams, rivers, and lakes are common sources.
•
Precipitation is water that falls to Earth’s surface as rain, snow, sleet, or hail.
– Streams form when precipitation collects in a narrow channel and flows toward the
ocean.
•
Most available freshwater is groundwater, water found below Earth’s surface.
– Some naturally bubbles from the ground to the surface as a spring.
– Most obtained by digging wells
10
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World Geography
Lesson 2
The Water Cycle
Main Idea 2
In the water cycle, water circulates from Earth’s surface to the atmosphere and back again.
• Water is the only substance on Earth that occurs naturally as a solid, a liquid, and a gas, or
water vapor.
• The water cycle is the movement of water from Earth’s surface to the atmosphere and
back; it is driven by the sun’s energy.
– Evaporation—water turns from liquid to gas.
– Condensation—the rising gas cools and condenses, or changes from a vapor into tiny
liquid droplets, to form clouds.
– Precipitation—if the droplets in clouds become heavy enough, they fall back to Earth as
rain, snow, sleet, or hail.
– Runoff—excess water that isn’t absorbed as groundwater flows over land and collects in
streams, rivers, and oceans.
• The water cycle is constantly repeating, allowing us to maintain a fairly constant supply of
water on Earth.
11
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World Geography
Lesson 2
Water and People
Main Idea 3
Water plays an important role in people’s lives.
Water Problems
Water’s Benefits
•
Lack of available freshwater, which can be
caused by droughts or overuse
•
Provides us with food to eat
•
Important source of energy
•
Water shortages lead to problems
including crop failures, food shortages,
girls not going to school, and conflict.
•
Provides us with recreation, including
swimming, fishing, surfing, and sailing
•
Contaminated, or polluted, water can
harm humans, plants, and animals.
•
Some communities work together to manage
freshwater supplies.
•
Flooding can damage property and
threaten lives.
•
Water can also create sinkholes.
12
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World Geography
LESSON 3
The Land
The Big Idea
Processes below and on Earth’s surface shape the planet’s physical features.
Main Ideas
•
•
•
•
Earth’s surface is covered by many different landforms.
Forces below Earth’s surface build up our landforms.
Forces on the planet’s surface shape Earth’s landforms.
Landforms influence people’s lives and culture.
13
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World Geography
Lesson 3
Landforms
Main Idea 1
Earth’s surface is covered by many different landforms.
• Landforms, or shapes on the planet’s surface, make up the landscapes that surround us.
• Earth’s surface is covered with landforms of many different shapes and sizes.
– Mountains, land that rises higher than 2,000 feet
– Valleys, areas of low land located between mountains or hills
– Plains, stretches of mostly flat land
– Islands, areas of land completely surrounded by water
– Peninsulas, land surrounded by water on three sides
• Scholars study how landforms are made and how they affect human activity.
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World Geography
Lesson 3
Forces below Earth’s Surface
Main Idea 2
Forces below Earth’s surface build up our landforms.
Earth’s Plates
•
•
•
The planet’s continents, or large landmasses, are part of Earth’s crust—the solid outer
layer of the planet.
The theory of plate tectonics suggests that Earth’s surface is divided into a dozen or so
slow-moving plates, or pieces of Earth’s crust.
Energy deep inside the planet puts pressure on the crust and forces the plates to shift.
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World Geography
Lesson 3
Main Idea 2
(continued)
The Movement of Continents
•
The idea that continents have traveled great distances over millions of years is known as
continental drift.
•
The theory, developed by Alfred Wegener, states that the continents were once united in a
single supercontinent and over time, slowly separated and moved to their present
positions.
•
Earth’s continents are still moving.
•
As plates collide, separate, and slide, they shape Earth’s landforms.
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World Geography
Lesson 3
Main Idea 2
(continued)
Plates Collide
Plates Separate
Plates Slide
•
•
As plates move apart,
gaps between plates allow
magma to rise to Earth’s
crust.
•
•
Lava, magma that
reaches the Earth’s
surface, emerges from the
gap.
As plates pass by each
other, they sometimes
grind together, producing
earthquakes, sudden,
violent movements of
Earth’s crust.
•
Earthquakes often take
place along faults, or
breaks in Earth’s crust
where movement occurs.
•
•
Two ocean plates: one
pushes under the other,
creating ocean trenches,
or deep valleys in ocean
floor
Ocean and continental
plate: ocean plate drops
beneath continental plate,
forcing land above to
crumple and form
mountain range
Two continental plates:
land pushes up to form
mountains
•
As lava cools, it builds a
mid-ocean range, or
underwater mountain,
that can rise above the
surface of the ocean to
form islands.
17
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World Geography
Lesson 3
Processes on Earth’s Surface
Main Idea 3
Forces on the planet’s surface shape Earth’s landforms.
• Weather, water, and other forces change Earth’s landforms by wearing them away or
reshaping them.
Weathering
•
•
•
•
Weathering is the process by which rock is broken down into smaller pieces called
sediment.
Heating and cooling can cause rocks to crack.
Expansion of water as it freezes can cause cracks to expand.
Roots of trees can pry rocks apart.
Erosion
•
•
Erosion is the movement of sediment from one location to another.
Can wear away or build up landforms
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World Geography
Lesson 3
Main Idea 3
(continued)
Wind Erosion
Glacial Erosion
Water Erosion
•
•
Glaciers, or large, slowmoving sheets of ice,
erode the land by carving
valleys and mountain
peaks.
•
Waves can wear away
shorelines.
•
Flowing water can cut
through rock, forming
canyons.
Crush rock into sediment
and move it great
distances
•
Water can carry and deposit
sediment in new locations.
•
In a process called alluvial
deposition, floodplains are
created when rivers flood
their banks and deposit
sediment.
•
Sediment carried by a river
all the way to the sea creates
a delta.
Winds lift sediment into air
and carry it across great
distances.
•
On beaches and in deserts,
deposits can form dunes.
•
Blowing sand can wear
down rock.
•
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World Geography
Lesson 3
Landforms Influence Life
Main Idea 4
Landforms influence people’s lives and culture.
• Landforms can influence where people settle.
• Landforms often influence what jobs are available in a region.
• Landforms can affect language by isolating people from outside influence.
• People sometimes change landforms to suit their needs.
• People have created canals, terraces in mountains, and dams.
20
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World Geography
LESSON 4
Weather and Climate
The Big Idea
The sun, location, wind, water, and mountains affect weather and climate.
Main Ideas
•
•
•
•
While weather is short term, climate is a region’s average weather over a long period.
The amount of sun at a given location is affected by Earth’s tilt, movement, and shape.
Wind and water move heat around Earth, affecting how warm or wet a place is.
Mountains influence temperature and precipitation.
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World Geography
Lesson 4
Understanding Weather and Climate
Main Idea 1
While weather is short term, climate is a region’s average weather over a long period.
• Weather is the short-term changes in the air for a given place and time.
– Temperature and precipitation from hour to hour or day to day
• Climate is a region’s average weather conditions over a long period.
– The expected weather for a place based on data and experience
22
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World Geography
Lesson 4
Sun and Location
Main Idea 2
The amount of sun at a given location is affected by Earth’s tilt, movement, and shape.
Tilt
•
The part of the Earth
tilted toward the sun
receives more solar
energy than the part tilted
away from the sun.
Movement
Shape
•
•
Earth’s spherical shape
means that the sun’s rays
directly strike the equator,
but only somewhat strike
the poles.
•
The farther from the
equator, or the higher the
latitude, the colder the
climate.
As Earth revolves around
the sun, the part of Earth
that is tilted toward the
sun changes during the
year, thus creating the
seasons.
23
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World Geography
Lesson 4
Wind and Water
Main Idea 3
Wind and water move heat around Earth, affecting how warm or wet a place is.
• Air and water warmed by the sun are constantly on the move, making different areas of
Earth warmer or cooler.
Global Winds
•
•
•
•
•
•
•
•
•
Wind, or the sideways movement of air, blows in great streams around the planet.
Prevailing winds are winds that blow in the same direction over large areas of Earth.
Cold air is heavier than warm air.
When air cools, it gets heavier and sinks and when air warms, it gets lighter and rises.
As warm air rises, cooler air moves in to take its place, creating wind.
The rising, sinking, and flowing of air creates Earth’s prevailing wind patterns.
At the equator, hot air rises and flows toward the poles. At the poles, cold air sinks and
flows toward the equator.
Earth’s rotation causes prevailing winds to curve east or west.
Prevailing winds can make a region warmer or colder and drier or wetter.
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World Geography
Lesson 4
Main Idea 3
(continued)
Ocean Currents
•
Ocean currents—large streams of surface seawater driven by winds—move heat around
Earth.
•
Currents carry warm or cool water to different areas.
•
Water’s temperature affects air temperature near it.
•
The Gulf Stream and North Atlantic Drift are important ocean currents that warm Europe.
Large Bodies of Water
•
Large bodies of water, such as an ocean or sea, also affect climate.
•
Water heats and cools more slowly than land does.
•
Large bodies of water make the temperature of the land nearby milder.
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World Geography
Lesson 4
Main Idea 3
(continued)
Wind, Water, and Storms
•
The place where two air masses of different temperatures or moisture content meet is a
front.
•
Fronts can produce rain, snow, thunderstorms, and blizzards.
•
Thunderstorms produce rain, lightning, and thunder and are most common in spring and
summer in the United States.
•
Blizzards produce strong winds and large amounts of snow and occur mostly in winter.
•
Tornadoes are small, rapidly twisting funnels of air that touch the ground and can be
destructive and deadly.
•
Hurricanes and typhoons are large, rotating storms that form over tropical waters in the
ocean.
•
The Atlantic Ocean has hurricanes and the Pacific Ocean has typhoons.
•
These largest and most destructive storms produce drenching rains, strong winds, and
storm surges.
26
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World Geography
Lesson 4
Mountains
Main Idea 4
Mountains influence temperature and precipitation.
• Mountains can influence an area’s climate by affecting both temperature and precipitation.
• Temperature decreases with elevation, the height on Earth’s surface above sea level.
• Mountains also create wet and dry areas.
– Air blowing against mountains is forced to rise.
– As the air rises, it cools and precipitation falls.
– This effect produces a rain shadow, a dry area on the mountainside facing away from
the direction of the wind.
27
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World Geography
LESSON 5
World Climates
The Big Idea
Earth’s five major climate zones are identified by temperature, precipitation, and plant life.
Main Ideas
•
•
•
•
Geographers use temperature, precipitation, and plant life to identify climate zones.
Tropical climates are wet and warm, while dry climates receive little or no rain.
Temperate climates have the most seasonal change.
Polar climates are cold and dry, while highland climates change with elevation.
28
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World Geography
Lesson 5
Major Climate Zones
Main Idea 1
Geographers use temperature, precipitation, and plant life to identify climate zones.
• Earth is divided into five general climate zones.
– Tropical—occur near the equator, in low latitudes
– Temperate—occur about halfway between the equator and the poles, in the middle
latitudes
– Polar—occur near the poles, in the high latitudes
– Dry—occur at many different latitudes
– Highland—occur at many different latitudes
• Geographers divide some climate zones into more specific climate regions.
29
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World Geography
Lesson 5
Tropical and Dry Climates
Main Idea 2
Tropical climates are wet and warm, while dry climates receive little or no rain.
Tropical Climates
•
The tropics extend from the Tropic of Cancer to the Tropic of Capricorn.
30
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World Geography
Lesson 5
Main Idea 2
(continued)
Humid Tropical Climate
Tropical Savanna Climate
•
At the equator
•
North and south away from the equator
•
Warm, muggy and rainy year-round
•
•
Temperatures average 80F.
Long, hot, dry season followed by short
periods of rain
•
Rainfall ranges from 70 to 450 inches.
•
Temperatures are hot in the summer,
cooler in the winter.
•
Some areas have monsoons, seasonal
winds that bring either dry or moist air.
•
Can support savannas—areas of tall
grasses and scattered trees and shrubs
•
Can support lush tropical rain forests that
host a great diversity of plant and animal
life
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World Geography
Lesson 5
Main Idea 2
(continued)
Dry Climates
Desert Climate
Steppe Climate
•
Earth’s hottest and driest climate
•
•
Receive less than 10 inches of rain a year
Semidry grasslands or prairies—called
steppes
•
Temperatures can reach as high as 130°F.
•
Often border deserts
•
Only very hardy plants and animals can
live in these conditions.
•
Receive slightly more rain than deserts
•
Short grasses are the most common
plants, but shrubs and trees grow along
streams and rivers.
32
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World Geography
Lesson 5
Temperate Climates
Main Idea 3
Temperate climates have the most seasonal change.
• Mild and tend to have four seasons
– Warm or hot summers
– Cool or cold winters
• Occur in the middle latitudes, the regions halfway between the equator and the poles
33
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World Geography
Lesson 5
Main Idea 3
(continued)
Mediterranean Climate
Humid Subtropical Climate
•
Named for the region around the
Mediterranean Sea
•
Occurs along east coasts near the tropics
•
Summers are hot and muggy.
•
Sunny, pleasant climate occurring mainly
in coastal areas
•
Winters are mild.
•
Summers are hot, dry, and sunny.
•
Storms occur year-round.
•
Winters are mild and somewhat wet.
•
Mixed forests with deciduous and
coniferous trees
•
Plants are mostly shrubs and short trees.
34
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World Geography
Lesson 5
Main Idea 3
(continued)
Marine West Coast Climate
Humid Continental Climate
•
Occurs on west coasts where winds carry
moisture in from the seas
•
Occurs closer to the poles, in the uppermiddle latitudes
•
Mild temperatures year-round
•
Four distinct seasons
•
Winters are foggy, cloud, and rainy.
•
Supports grasslands and forests.
•
Summers can be warm and sunny.
•
Evergreens thrive.
35
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World Geography
Lesson 5
Polar and Highland Climates
Main Idea 4
Polar climates are cold and dry, while highland climates change with elevation.
Subarctic Climate
Tundra Climate
•
Occurs mainly in Northern Hemisphere
south of Arctic Ocean
•
Coastal areas along the Arctic Ocean
•
Long, bitterly cold winters
•
Winters are long and bitterly cold;
summers short and cool
•
Only mosses, lichens, and small shrubs grow
•
Below freezing half the year
•
In some parts is permafrost, or permanently
frozen layers of soil
•
Support evergreen forests called taiga
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World Geography
Lesson 5
Main Idea 4
(continued)
Ice Cap Climate
Highland Climate
•
North and South poles
•
Found on mountains
•
Temperatures lower than -120°F reported
•
Includes several climates in one
•
Snow and ice remain year-round, but little
precipitation
•
As you go up a mountain, temperatures
drop and plant life grows sparser.
•
No vegetation
37
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World Geography
LESSON 6
Environments and Biomes
The Big Idea
Plants, animals, and the environment, including soil, interact with and affect one another.
Main Ideas
•
•
The environment and life are interconnected and exist in a fragile balance.
Soils play an important role in the environment.
38
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World Geography
Lesson 6
The Environment and Life
Main Idea 1
The environment and life are interconnected and exist in a fragile balance.
•
Plants and animals live where they are suited to the environment, or surroundings.
Limits on Life
•
Factors such as temperature, rainfall, and soil conditions limit options of where plants and
animals can live.
•
All plants and animals are adapted to specific environments.
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World Geography
Lesson 6
Main Idea 1
(continued)
Connections in Nature
•
An ecosystem is a group of plants and animals that depend on each other and the
environment in which they live for survival.
•
Ecosystems can be any size and can occur wherever air, water, and soil support life.
•
A biome is larger than an ecosystem. It may be several ecosystems.
•
An entire tropical rain forest is a biome.
•
Each part of the ecosystem fills a certain role.
•
Plants and animals depend on each other and the sun for food.
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World Geography
Lesson 6
Main Idea 6
(continued)
Changes to Environments
•
Ecosystems exist in a fragile balance; a small change to one part can affect the whole
system.
•
People can affect ecosystems in many ways.
•
Some actions can destroy a habitat—the place where a plant or animal lives.
•
Extreme changes in ecosystems can cause species to die out, or become extinct.
•
Many countries are working to balance people’s needs with the needs of the environment.
41
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World Geography
Lesson 1
Soil and the Environment
Main Idea 2
Soils play an important role in the environment.
• Soils help determine what plants will grow and how well.
• Fertile soils are rich in minerals and humus, decayed plant or animal matter.
– Support abundant life
• Soils can lose fertility in many ways.
– Erosion
– Planting the same crops over and over
• When soil becomes worn out, it cannot support as many plants.
– Can lead to desertification, the spread of desertlike conditions
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World Geography
LESSON 7
Natural Resources
The Big Idea
Earth’s natural resources have many valuable uses, and their availability affects people in many ways.
Main Ideas
•
•
•
•
Earth provides valuable resources for our use.
Energy resources provide fuel, heat, and electricity.
Mineral resources include metals, rocks, and salt.
Resources shape people’s lives and countries’ wealth.
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World Geography
Lesson 7
Earth’s Valuable Resources
Main Idea 1
Earth provides valuable resources for our use.
Using Natural Resources
Types of Natural Resources
Managing Natural Resources
•
A natural resource is any
material in nature that
people use and value.
•
Renewable resources are
resources Earth replaces
naturally.
•
•
Some are used as is.
•
•
Some are changed to
make something new.
Nonrenewable resources
are resources that cannot
be replaced; they will run
out one day.
People must manage
resources to ensure they
will be available in the
future.
•
Deforestation, the
clearing of trees, is a
result of lack of
management.
•
Reforestation, planting
trees to replace lost
forestland, prevents
resource loss.
44
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World Geography
Lesson 7
Energy Resources
Main Idea 2
Energy resources provide fuel, heat, and electricity.
Nonrenewable Energy Resources
Renewable Energy Resources
•
•
Will not run out
•
Generally better for the environment
•
Hydroelectric power—the production of
electricity from water power—is the main
alternative to fossil fuels.
Most energy we use comes from fossil
fuels, nonrenewable resources that
formed from the remains of ancient
plants and animals.
•
Coal—pollutes the air; used mainly to
create electricity at power plants
•
Petroleum, or oil—used to make fuels and
other products
•
Wind is used to power wind turbines that
create electricity.
•
Natural gas—cleanest-burning fossil fuel;
used mainly for heating and cooking
•
Solar power and geothermal energy—heat
from within Earth—can heat water or homes
and be turned into electricity
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World Geography
Lesson 7
Main Idea 2
(continued)
Nuclear Energy
•
Obtained by splitting atoms, small particles of matter
•
Uses the metal uranium, so some consider it a nonrenewable resource
•
Does not pollute the air
•
Produces dangerous wastes that must be stored for thousands of years before they are safe
•
Accidents at nuclear power plants have terrible effects.
•
Energy sources are not evenly spread across Earth, so different regions have different
resources.
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Copyright © by Houghton Mifflin Harcourt Publishing Company
World Geography
Lesson 7
Mineral Resources
Main Idea 3
Mineral resources include metals, rocks, and salt.
• Mineral resources include metals, salt, rocks, and gemstones.
• Minerals fulfill countless needs.
• Minerals are nonrenewable, and therefore need to be conserved.
• Recycling can make the supply of mineral resources last longer.
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Copyright © by Houghton Mifflin Harcourt Publishing Company
World Geography
Lesson 7
Resources and People
Main Idea 4
Resources shape people’s lives and countries’ wealth.
Resources and Daily Life
•
•
•
•
The natural resources available to people affect their lifestyles and needs.
People in areas with many natural resources sometimes have more choices on ways to
dress, eat, live, travel, and entertain themselves.
People in areas with fewer natural resources will likely have fewer choices and different
needs.
In areas where more than one group wants to use the same resources, conflicts can arise.
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Copyright © by Houghton Mifflin Harcourt Publishing Company
World Geography
Lesson 7
Main Idea 4
(continued)
Resources and Wealth
•
Availability of natural resources affects countries’ economies.
•
The many resources available in the United States have helped it become one of the
world’s wealthiest economies.
•
Countries with few natural resources often have weak economies.
•
Some countries have only one or two valuable resources but few others.
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