7th Grade Science
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3: Earth Science
Chapter 15: Organization of the Environment
Section 1: The Natural Environment
Section 2: How Ecosystems Change
Chapter 16: Climate
Section 1: What is Climate?
Section 2: Climates of the World
Section 3: Changes in Climate
Chapter 24: Earth, Sun, and Moon
Section 1: Days and Seasons on Earth
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Earth Science
Unit 3: Earth Science
Chapter 17: The Earth’s Ecosystems
Section 1: Land Ecosystems
Section 2: Marine Ecosystems
Section 3: Freshwater Ecosystems
Chapter 6: Energy Resources
Section 1: Natural Resources
Section 2: Fossil Fuels
Section 3: Alternative Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Earth Science
Unit 3: Earth Science
Chapter 21: Earthquakes
Section 1: What are Earthquakes?
Section 2: Earthquake Measurement
Chapter 22: Volcanoes
Section 1: Volcanic Eruptions
Section 2: Volcanoes’ Effects on Earth
Section 3: What Causes Volcanoes?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Earth Science
Organization of the Environment
What Do You Think?
How do you think our
environment is organized?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
An environment is made up of 2 parts.
1. Biotic- All of the organisms and the matter they
produce such as dead leaves and molten skin.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
An environment is made up of 2 parts.
2. Abiotic- All of the physical things-water, sunlight,
rocks- that affect organisms living in a certain
area.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
The environment is organized into 5 levels.
1. Organism
2. Population
3. Community
4. Ecosystem
5. Biosphere
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
Organism
• This level contains the individual species of a
particular organism.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
Population
• Populations are groups of individuals of the
same species that live together in the same area
at the same time.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
Communities
• Communities are made up of all of the
populations of different species that live and
interact in an area.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
Ecosystems
• Ecosystems are made up of a community of
organisms and its abiotic environment.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
Biosphere
• A biosphere contains the whole area of the Earth
where life exists, including its abiotic factors.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Let’s Review!
- 1Give 2 examples of biotic and abiotic factors
in your science room.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Answer
• Biotic- students, plants, textbooks
• Abiotic- floors, air, metal desks
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Let’s Review!
-2What do you think would happen to the
other organisms in a small lake if all of the
plants got a fungus and died?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Answer
• Many of the organisms depend directly or
indirectly on the plants for food. Without
the plants, these other organisms would
probably die or move into other areas.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
• Natureworks: Habitat
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 1
Organization of the Environment
What Do You Think?
Why could fire be good for a
forest?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
How Ecosystems Change
• Ecological succession is defined as the changes
an ecosystem goes through as it develops or
regrows.
• There are 2 types of ecological succession.
1. Primary succession
2. Secondary succession
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
Primary Succession
• Primary succession occurs in an area where
there were no living things.
• No soil is present during primary succession.
• Over a very long time, many organisms live and
die on the rocks. This eventually breaks the
rocks down.
• The rock is slowly changed into soil, and a
community of organisms eventually develops.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
Secondary Succession
• This succession occurs in an area where an
earlier community was disturbed by fire,
landslides, floods, or plowing for crops.
• Soil is present at the beginning, so the time for
secondary succession is shorter than primary
succession.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
• Ecological succession helps an ecosystem stay
balanced because it allows the ecosystem to
slowly recover from disturbances.
• Without succession, the disturbed ecosystem
would not recover after a natural disaster, and
would not reach equilibrium again.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Let’s Review
-1-
How does ecological succession maintain
equilibrium in an ecosystem?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Answer
• Ecological succession maintains
equilibrium be allowing an ecosystem to
slowly recover from disturbances.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
• Websites to see:
Natureworks: Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Organization of the Environment
1.
2.
3.
4.
5.
Identify the following examples as either
primary succession or secondary succession:
A rock face exposed by a scraping glacier.
A new shoreline in Hawaii created after a lava
flow.
A once forested area cleared by a tornado.
An island appearing from the activity of an
undersea volcano.
The lawn of an abandoned farmhouse.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 15 : Section 2
Climate
What Do You Think?
Why do we have different
seasons each year?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Climate
Seasons
• In most places around the
US, the year has four
seasons.
• Winter is cooler where we
live, but this is not the
case in all places.
• For example, areas near
the equator have around
the same temperature
and same amount of
daylight hours all year.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Climate
• This happens because of the Earth is tilted
on its own axis at a 23.5° angle.
• The tilt of the Earth affects how much solar
energy an area receives as it moves
around the sun. This also affects how long
our days are.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Climate
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Climate
Click below to see about the change of
seasons on Earth.
• NASA: Earth's Seasons
• Enchanted Learning: Earth's Seasons
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Let’s Review
-1Describe how the tilt of the Earth affects the
amount of daylight hours in the Northern
Hemisphere.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Answer
• As the Earth revolves around the sun, the
tilt of the Earth’s axis causes the Northern
Hemisphere to receive different amount of
sun, depending on the time of year.
• During the winter, when the Northern
Hemisphere is tilted away from the sun,
there are fewer daylight hours.
• In the summer, there are more daylight
hours.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Let’s Review!
-2How would season’s be different if the Earth
did not tilt on its axis?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Answer
• If the Earth did not tilt on its own axis,
there would be no seasons at all.
• The same amount of solar radiation would
reach both hemispheres year-round.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 1
Climate
What Do You Think?
Can polar bears live in Texas?
Why or why not?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Climate
• A Biome us a large region characterized by
a specific type of climate and the plants and
animals that live there.
• Climate is the average weather conditions
in an area over a long period of time.
• Different biomes support different
organisms based on their climate.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Climate
• Tropical Rain Forest
Temperature
25°C to 28°C
(77°F to 82°F)
© Fall 2005, Pflugerville ISD, 7th Grade
Rainfall
200 cm or
more each
year
Soil
thin and
nutrient
poor
Unit 3 : Chapter 16 : Section 2
Climate
• Tropical Deserts
Temperature
16°C to 50°C
(61°F to 120°F)
© Fall 2005, Pflugerville ISD, 7th Grade
Rainfall
0-25 cm per
year
Soil
poor in
organic
matter
Unit 3 : Chapter 16 : Section 2
Climate
• Tropical Savannas
Temperature
Rainfall
27°C to 32°C (80°F around 100 cm
to 90°F)
per year
© Fall 2005, Pflugerville ISD, 7th Grade
Soil
generally
nutrient
poor
Unit 3 : Chapter 16 : Section 2
Climate
• Temperate Deciduous Forest
Temperature
0°C to 28°C
(32°F to 82°F)
© Fall 2005, Pflugerville ISD, 7th Grade
Rainfall
Soil
76-250 cm per
year
very fertile,
organically
rich
Unit 3 : Chapter 16 : Section 2
Climate
• Temperate Grassland
Temperature
Rainfall
Soil
-6°C to 26°C (21°F
to 78°F)
38-76cm per
year
most fertile of
all biomes
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Climate
• Chaparrals
Temperature
Rainfall
Soil
11°C to 26°C (51°F
to 78°F)
48-56 cm per
year
rocky, nutrient
poor
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Climate
• Temperate Deserts
Temperature
Rainfall
1°C to 50°C (34°F
to 120°F)
0-25 cm per
year
© Fall 2005, Pflugerville ISD, 7th Grade
Soil
poor in
organic
matter
Unit 3 : Chapter 16 : Section 2
Climate
• Tundra
Temperature
Rainfall
Soil
-27°C to 5°C
(-17°F to 41°F)
0-25 cm per
year
frozen
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Climate
• Taiga
Temperature
-10°C to 15°C
(14°F to 59°F)
© Fall 2005, Pflugerville ISD, 7th Grade
Rainfall
Soil
0-25 cm per
year
frozen
Unit 3 : Chapter 16 : Section 2
Climate
• Plants that require a lot of water must live
in climates with a lot of precipitation (rain).
• Animals that require the sun to keep them
warm must live in a biome that has higher
temperatures.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Let’s Review
-1What kinds of plants and animals would live
in a tropical desert?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Answer
• The organisms that would live in a tropical
desert must be adapted to hot, dry
conditions.
• Cactuses, and lizards would be examples.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Let’s Review!
-2Describe how different biomes support
different varieties of organisms.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Answer
• Cold, wet biomes support animals and
plants that can survive in cold, wet
conditions.
• Warm, dry biomes support animals that
can survive in warm, dry conditions.
• The same applies for cold and dry biomes,
and warm and wet biomes.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 2
Climate
What Do You Think?
What is global warming, and how
does it affect us?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
• The greenhouse effect is the Earth’s
natural heating process in which gases in
the atmosphere trap thermal energy.
• Global warming is a rise in the average
temperatures that can result from an
increase in the greenhouse effect.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
Global Warming
• Our Earth acts just like a plant greenhouse.
• It allows the sunlight to come in, but the glass (or
atmosphere) keeps the thermal energy (heat)
from escaping.
• This makes our Earth warmer, just like a plant
greenhouse.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
Global Warming
• Most scientists believe that the rise in global
temperatures is due to an increase in carbon
dioxide, a greenhouse gas, as a result of human
activity.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
Global Warming
• Increased amounts of carbon dioxide in the air is
caused by the burning of fossil fuels (oil, coal,
and gasoline).
• Deforestation, or the process of clearing forests,
also adds carbon dioxide to the air.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
Global Warming
• There are many theories as to what will happen
if we continue to increase the greenhouse
gases.
1. The ice caps could melt, and flooding could
occur.
2. Areas that receive little rain, like deserts,
might receive less because of increased
evaporation.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
Volcanic Eruptions
• Many natural factors can affect global
warming. Volcanic eruptions can influence
climate.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
• A volcanic eruption would send large
amounts of dust, smoke, and ash particles
into the atmosphere.
• The dust, smoke, and ash particles act as
a shield.
• They would block out so much of the sun’s
rays that the Earth would cool.
• This could affect the balance of the gases
in the atmosphere.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Let’s Review!
-1Explain how the greenhouse effect warms
the Earth.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Answer
• Greenhouse gases allow sunlight to pass
through the atmosphere, where it is
absorbed by the Earth’s surface as heat.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Let’s Review!
-2What impact could a volcanic eruption have
on the Earth?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Answer
• A large volcanic eruption could send
enormous amounts of dust and ash into
the atmosphere. These materials will
block the sun’s rays and make the Earth
cooler.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Climate
• Websites to Visit
Ozone Facts
Climate Changes
Global Warming
Volcanic Effects on Global Warming
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 16 : Section 3
Earth, Sun, and Moon
What Do You Think?
What causes daylight and night?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 24 : Section 1
Earth, Sun, and Moon
• Revolution is the motion of a body as it
orbits another body in space.
- It takes 1 year, or 365 ¼ days for the Earth to
revolve around the sun.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 24 : Section 1
Earth, Sun, and Moon
• Rotation is the spin of an object in space.
- The Earth rotates once on its own axis in 23
hours and 56 minutes.
- The Earth’s rotation is a direct cause of day
and night.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 24 : Section 1
Earth, Sun, and Moon
• See Chapter 16, Section 1 for how the tilt
and movement of the Earth causes
changes in seasons and the length of the
day.
Click here to return to the information on
Seasons.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 24 : Section 1
Earth, Sun, and Moon
• Earth, Sun, and Moon Demo
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 24 : Section 1
The Earth’s Ecosystems
What Do You Think?
What are the main differences
between a desert and a rain
forest?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• We learned in Chapter 16 that different
climates of biomes support a variety of
organisms.
• There are 4 main ecosystems that support
different types of plants and animals.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
Forests
• Forest ecosystems develop in places where the
temperatures are mild and there is plenty of rain.
• The 3 main types of forest ecosystems are
temperate deciduous forests, coniferous forests,
and tropical rain forests.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Temperate Deciduous Forest
Go.hrw.com
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Coniferous Forest (Taiga)
© Fall 2005, Pflugerville ISD, 7th Grade
Go.hrw.com
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Tropical Rain Forest
© Fall 2005, Pflugerville ISD, 7th Grade
Go.hrw.com
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
Grasslands
• Grasslands are areas where grasses are the
main plants.
• They are found between forests and deserts.
• Most grasslands are flat or have gently rolling
hills.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Temperate Grasslands
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Tropical Savanna
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
Deserts
• Deserts are areas that are very dry and usually
very hot.
• Organisms have developed special ways to live
in a hot, dry climate.
• What is an example of a plant adaptation in the
desert?
• What is an example of an animal adaptation in
the desert?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
•Deserts
© Fall 2005, Pflugerville ISD, 7th Grade
Go.hrw.com
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
Tundra
• Areas with very cold temperatures and little
rainfall are called tundra ecosystems.
• It is so cold here that trees don’t even grow!
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Arctic Tundra
- The ground remains frozen almost all of the
time.
- This frozen layer is called permafrost.
- The layer of soil above the permafrost is too
shallow for plants with deep roots.
- Grasses and shrubs live here.
- Animals that feed on grasses and shrubs, such
as the musk oxen, wolves, and caribou live here.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Alpine Tundra
- This is very similar to the artic tundra, but it’s
found at the tops of tall mountains.
- Trees are not able to grow here.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
• Natureworks: Land Ecosystems
• Enchanted Learning: Land Biomes
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 1
The Earth’s Ecosystems
What Do You Think?
What is the difference between
marine and freshwater
ecosystems?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
Marine Ecosystems
• Marine ecosystems are in the oceans of
the world. They contain a wide variety of
plant and animal species.
• There are 4 main parts, or zones, in the
ocean. Each zone has different plants and
animals.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
Part 1: The Intertidal Zone
• The intertidal zone is the place where the ocean
meets the land.
• Animals and plants that live here must adapt to
the tide moving in and out each day.
• The animals and plants must be able to live in
and out of water.
• Most of the animals have shells that protect
them from drying out. Other animals bury
themselves in the sand for protection.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
Part 2: The Neritic Zone
• As you keep walking into the ocean you reach
the neritic zone.
• This area is warm and sunny.
• Water in this area is less than 200 m deep.
• Most animals and plants live in this zone.
• The large amount of sunlight makes it possible
for a lot of plankton to grow. The plankton feeds
many fish, which provide food for birds and
marine mammals.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
Part 3: The Oceanic Zone
•
•
•
This zone is past the continental shelf where
the ocean floor drops sharply.
Since there is not much sunlight, animals must
get their energy from food that has drifted
down from the surface.
Many of the larger mammals that live in the
neritic zone also live in the upper parts of the
oceanic zone. There is a lot of space to swim
in this area.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
Part 4: The Benthic Zone
• This zone is the ocean floor. (From 200m-6000m
deep)
• Very unusual organisms live here. Some get their
food from chemicals found near thermal vents.
• A thermal vent is a place in the ocean floor where
heat and chemicals escape from a crack in the
Earth’s crust.
• There is no sunlight here, so plants cannot
produce food.
• This area is extremely cold, except in areas near
thermal vents.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
Let’s Review!
-1Describe how different marine
environments support different varieties of
organisms.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
Answer
• Different marine environments provide
different combinations of light, salt
concentration, temperature, and nutrients.
These different combinations provide a
variety of conditions, each of which
supports organisms adapted to those
conditions.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
Let’s Review!
-2Determine which areas of the ocean each of
the following animals would live in:
1. Dolphins
2. Starfish
3. Tube worms
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
Answers
1. Dolphins live in the neritic zone, or the
upper part of the oceanic zone.
2. Starfish live in the intertidal zone.
3. Tube worms live near hot water vents in
the benthic zone called black smokers.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
•
•
•
•
•
Natureworks:
Natureworks:
Natureworks:
Natureworks:
Natureworks:
© Fall 2005, Pflugerville ISD, 7th Grade
Marine Ecosystems
Estuaries
Intertidal Zone
Oceanic Zone
Benthic Zone
Unit 3 : Chapter 17 : Section 2
The Earth’s Ecosystems
What Do You Think?
Name as many freshwater
ecosystems as you can.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
Freshwater Ecosystems
• Freshwater Ecosystems include all of the plant
and animals, along with the abiotic factors, that
are in fresh (no salt) water.
• They are usually separated on how fast the
water is moving.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
• Moving Water Ecosystems
– Include brooks, streams, and rivers
• Fast Moving Water- many streams and
some rivers have water that moves fast.
1. This type of water is full of life.
2. Organisms that live here need ways
to keep from being washed away.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
• Moving Water Ecosystems cont…
• Slow Moving Water- eventually rivers grow
wider and slower
1. Many insects live in the slow moving
rivers and marshes.
2. They eventually empty into a lake or an
ocean.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
Still Waters
• Include ponds and lakes.
• These still water ecosystems are divided into 3
parts:
– Littoral Zone
– Open-Water Zone
– Deep-Water Zone
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
Littoral Zone
• This zone is closest to the edge of the land.
• Many plants an animals live here.
• Examples of plants include cattails and water
lilies.
• Animals include frogs, snakes, and various types
of fish.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
Open Water Zone
• This zone extends from the littoral zone across
the top of the open water.
• The open water zone only goes as deep as the
light can reach.
• This zone is home to bass, lake trout, blue gills,
and many plankton.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
Deep Water Zone
• This is an area below the open water zone.
• No light reaches here.
• Catfish, carp, bacteria, fungi, and worms feed on
pieces of dead organisms that fall from above.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
Wetlands
• A wetland is an area of land where the water
level is near or above the surface of the ground
for most of the year.
• Wetlands have a variety of plants and animals.
• They also play an important role in flood control.
During heavy rains, or spring snow melt,
wetlands soak up large amounts of water that
replenish the underground water supplies.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
• There are 2 types of wetlands:
1. A marsh is a treeless wetland.
• They are often found in shallow waters
along the shores of lakes, ponds, rivers,
and streams.
2. A swamp is a wetland where trees and vines
grow.
• Swamps occur in low lying areas and
beside slow moving rivers.
• Most swamps are flooded only part of the
year, depending on rainfall.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
Let’s Review!
-1Compare and contrast the littoral zone with
the open-water zone of a lake.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
Answer
Littoral
Open Water
•Edge of lake
•Both have light
•In the middle of a
lake or pond
•Large number of
plants and animals
•Both contain
fish
•Home to larger
fish
•Both are in still
water
•Contains many
plankton
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
Let’s Review!
-2How are a swamp and a marsh different?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
Answer
• A marsh is a wetland with trees, and a
swamp is a wetland without trees.
• Because they lack trees, marshes support
plants and animals that thrive in sunlight.
• Since swamps have trees, they provide a
better environment for organisms that can
live in shade.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
The Earth’s Ecosystems
• Natureworks: Freshwater Ecosystems
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 17 : Section 3
Energy Resources
What Do You Think?
Why is recycling so important?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
Earth’s Resources
• The Earth provides almost everything needed
for life!
• A natural resource is any natural substance,
organism, or energy form that living things use.
• We use natural resources to help make our lives
easier.
• What would be a natural resource that you are
using right now that makes your life easier?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
There are 2 types of Natural
Resources.
1. Renewable Resources
2. Nonrenewable Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
Renewable Resources
• A renewable resource is a natural resource that
can be used and replaced over a short period of
time.
• Examples include trees and freshwater.
• Humans often use renewable resources more
quickly than they can be replaced.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
Nonrenewable Resources
• A nonrenewable resource is a natural resource
that cannot be replaced, or can only be replaced
over thousands or millions of years.
• The amount available on Earth is fixed, once
they are used up, they are gone forever.
• Examples are coal, oil, and natural gas.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
1.
2.
3.
4.
5.
Label the following as renewable or
nonrenewable resources:
Trees
Gasoline
Petroleum
Water
Sunlight
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
How can natural resources be
conserved?
• use them only when we have to.
• recycle (newpapers, cans, plastic)
• carpool / ride your bike instead of driving.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Let’s Review!
-1List 2 ways humans use natural resources.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Answer
• Lumber from trees for paper
• Gasoline for cars, lawnmowers, etc…
• Sun, wind, and water to create energy
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Let’s Review!
-1What is the difference between renewable
and nonrenewable resources?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Answer
• Renewable resources can be replaced
over a relatively short period of time.
• Nonrenewable resources cannot be
replaced pr can only be replaced over
thousands or millions of years.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 1
Energy Resources
What Do You Think?
Why do you think the term fossil
fuels has the word fossil in it?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
• Energy resources are natural resources
that humans use to produce energy.
• Fossil fuels are defined as nonrenewable
energy resources that form in the Earth’s
crust over millions of years.
• Fossil fuels form from the buried remains
of once-living organisms.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Fossil Fuels
• Fossil fuels release energy when they are
burned.
• We rely on fossil fuels to provide us the
energy we need for many modern
conveniences.
• Fossil fuels can be solids, liquids, or
gases.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Liquid Fossil Fuels
• Composed of things such as gasoline, jet
fuel, kerosene, diesel fuel, and oil.
• Petroleum, also known as crude oil, is a
mixture of oily compounds.
• Petroleum is separated in a refinery.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Solid Fossil Fuels
• Humans most use coal.
• Coal is a source of energy formed underground
from buried, decomposed plant materials.
• Coal used to be the leading source of energy in
the US, but it has been replaced by things that
create less pollution and are more affordable.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Gaseous Fossil Fuels
• Gaseous fossil fuels are also called natural gas.
• Natural gases are often used for heating and
generating electrical energy.
• Examples of natural gases include methane,
butane (camp stoves), and propane (outdoor
grills).
• The use of vehicles powered by natural gases is
increasing. Why?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
• There are many problems
associated with using fossil fuels.
1. When coal is burned, sulfur dioxide is
produced. When mixed with air, sulfur dioxide
causes acid precipitation. This harms wildlife,
plants, buildings, and statues.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Fossil Fuel Problems continued….
2. The mining of coal can also cause
environmental problems. Strip mining removes
soil which plants need for growth, and some
animals need for shelter.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Fossil Fuel Problems continued….
3. Transporting petroleum can also cause
environmental problems. In 1989, Exxon
Valdez had a tanker spill 257,000 barrels
of crude oil into the ocean off the coast of
Alaska. Thousand of plants and animals
were killed by the oil.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
Fossil Fuel Problems continued….
4. Burning petroleum causes an
environmental problem called smog.
Smog is a fog produced by the reaction of
sunlight and air pollutants. It is a big
problem in bigger cities such as Los
Angeles and Houston.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
How do we help fossil fuel problems?
1.
2.
3.
4.
5.
Carpooling
Riding your bike
Walking
Ride the bus
Use alternative energy resources
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Let’s Review!
-1Name 3 problems with fossil fuels.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Answer
1. Oil spills
2. Loss of soil from strip mining coal.
3. Production of smog.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 2
Energy Resources
What Do You Think?
What is an alternative energy
resource?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Alternative Energy Resources
•
Alternative energy resources are needed to slow
the use fossil fuels.
•
They include:
1. Nuclear energy
2. Solar energy
3. Wind energy
© Fall 2005, Pflugerville ISD, 7th Grade
4. Hydroelectric energy
5. Plant energy
6. Geothermal energy
Unit 3 : Chapter 6 : Section 3
Energy Resources
Nuclear Energy
• Nuclear energy is an alternative source of
energy that comes from the nuclei of atoms.
• Fission is a process in which the nuclei of
radioactive atoms are split and energy is
released.
• The energy from fission is used to produce
steam to run electric generators in a power
plant.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Nuclear Energy continued…
• Fusion is the joining of two or more nuclei with
small masses to form a larger, more massive
nuclei. This process releases energy.
• So far, fusion reactions have only taken place in
laboratory experiments.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Pros and Cons of Using Nuclear Energy
Pros
Cons
No air pollution
Radioactive wastes are
produced.
More concentrated source
of energy than fossil fuels.
Storage sites are hard to
find.
Can be cheaper than
obtaining fossil fuels.
High temperatures are
required for fusion. No
materials can withstand the
temperatures required.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Solar Energy
• Solar energy is energy from the sun.
• The sun is an inexhaustable resource because it
cannot be used up. The Earth always receives
solar energy.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Pros and Cons of using Solar Energy
Pros
Cons
No air pollution
Very expensive to produce solar
cells.
Solar cells are dependable,
quiet, and can last for
years with no
maintenance.
Running electrical wires required
to use solar cells is difficult and
costly.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Wind Energy
• Wind is created indirectly by solar energy
through the uneven heating of air.
• Wind energy is the energy captured in wind.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Pros and Cons of Using Wind Energy
Pros
Cons
No air pollution
Wind energy is
inexhaustable along as
solar energy is present.
The land that has the wind
turbines on them can also
be used for farming.
© Fall 2005, Pflugerville ISD, 7th Grade
Wind turbines are costly.
The wind does not blow strong
and steady in most places in
the US, so wind energy is only
beneficial in places with a lot of
wind, such as California.
Unit 3 : Chapter 6 : Section 3
Energy Resources
Hydroelectric Energy
• Electrical energy generated by falling water is
called hyrdoelectric energy.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Pros and Cons of Using Hydroelectric Energy
Pros
Little pollution is produced.
Inexpensive to produce.
Water can be renewed
because of the water
cycle.
© Fall 2005, Pflugerville ISD, 7th Grade
Cons
Can only be produced where
large amounts of falling
water can be harnessed.
Building the dams for
hydroelectric power plants
destroys forests and wildlife
habitats.
Unit 3 : Chapter 6 : Section 3
Energy Resources
Plant Energy
• Plants are similar to solar collectors because
they store energy from the sun for later use in
their leaves, wood, and stems.
• An organic matter that contains stored energy is
called biomass.
• Most countries use animal dung or wood to heat
their homes and cook their food.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Plant Energy
• Biomass can also be changed into liquid fuel.
Plants that contain sugar or starch can be used
to produce ethanol. Ethanol can be burned, or
mixed with gasoline to make a fuel mixture
called gasohol.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Pros and Cons of Using Biomass for Energy
Pros
Can be used in countries
that are poor, and do not
have access to fossil
fuels.
Always renewable.
© Fall 2005, Pflugerville ISD, 7th Grade
Cons
Produces a lot of air
pollution when burned.
Requires a lot of biomass
to make a small amount
of fuel.
Unit 3 : Chapter 6 : Section 3
Energy Resources
Geothermal Energy
• Geothermal energy is the energy resulting from
the heating of the Earth’s crust.
• In some areas, rainwater enters porous rock
near a source of magma. Magma heats up
water that is below the surface of the Earth.
• This water turns into steam, and it escapes
through natural vents called geysers.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Pros and Cons of Using Geothermal
Energy
Pros
Geothermal energy is
renewable.
© Fall 2005, Pflugerville ISD, 7th Grade
Cons
Can only be used in places on the Earth
where magma and rainwater are
avaliable in the same place.
Unit 3 : Chapter 6 : Section 3
Let’s Review!
-1How could human activities affect
inexhaustable resources?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Answer
• Although inexhaustable resources, such
as sunlight, cannot be used up, the
amount available to a specific area can be
affected.
• The amount of solar energy in an area can
be affected by air pollution from using
other energy resources.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Let’s Review!
-1Explain why the use of gasohol could help to
reduce the problems associated with the
use of fossil fuels.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Answer
• The use of gasohol would reduce the total
amount of gasoline used. As the amount
of gasoline used decreases, the problems
with fossils fuels will also be reduced.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Energy Resources
Websites to Visit!
• Energy Facts
• Fossil Fuels
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 6 : Section 3
Earthquakes
What Do You Think?
Where do earthquakes happen,
and what causes them?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Earthquakes
Where do Earthquakes happen?
• Most earthquakes happen near boundaries
between tectonic plates.
• Tectonic plates are giant pieces of Earth’s thin,
outermost layer.
• Tectonic plates move around on a layer of softer
rock beneath.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Earthquakes
Where do Earthquakes happen?
• Because of tectonic plate movements, the
Earth’s crust breaks in some places.
• A fault is a break in the Earth’s crust along which
blocks of the crust slide past each other.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Earthquakes
What causes Earthquakes?
• As the tectonic plates push against each other a
huge amount of potential energy is built up.
• Potential energy is energy that an object has
because of its position or shape.
• Potential energy does not cause the Earth to
move. It is energy built up along the fault.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Earthquakes
What causes Earthquakes?
• When the rocks of the earth shift (along a fault
line), this potential energy changes to kinetic
energy and the earth shakes.
• Kinetic energy is the energy of motion.
• An earthquake is the kinetic energy that is finally
released after enough pressure builds up along
a fault.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Let’s Review!
-1Explain how potential and kinetic energy act
on rock to cause earthquakes.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Answer
• Most earthquakes occur because tectonic
forces cause potential energy to build up
in the rocks along a fault.
• When the stress becomes too great, the
rocks shift and kinetic energy is released,
causing an earthquake.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 1
Earthquakes
What Do You Think?
Explain how earthquakes are
detected.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 2
Earthquakes
How are Earthquakes detected?
• Seismologists use a device called a
seismograph to detect seismic waves.
• The focus is the place on earth where the
earthquake originates.
• The epicenter is the place on earth directly
above the focus.
• The epicenter from several stations help
determine where an earthquake began.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 2
Earthquakes
How strong are Earthquakes?
•The Richter scale
measures the
strength of an
earthquake.
•As magnitude
increases, the
amount of energy
released by the
earthquake
increases.
© Fall 2005, Pflugerville ISD, 7th Grade
Magnitude
Effects
2
Detected by a
seismograph
3
Felt at epicenter
4
Felt by most in area
5
Damage at epicenter
6
Widespread damage
7
Great, widespread
damage.
Unit 3 : Chapter 21 : Section 2
Let’s Review!
-1Predict the impact of an earthquake with a
magnitude of 5.0.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 2
Answer
• If an earthquake with a magnitude of 5.0
happened in a small town, some buildings
would be damaged, but only a few people
would be hurt.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 2
Earthquakes
Websites to visit
• Earthquake Seisomgraph
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Section 2
Pre-AP Extension
Earthquakes
3 Causes of Earthquakes
Transform
plate
Convergent
plate
Plates slip back Moderate,
and forth
shallow
earthquake
Plates come
Strong, deep
together
earthquake
Divergent
plate
Plates pull apart Weak, shallow
earthquake
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Pre-AP
Pre-AP Extension
Earthquakes
How do Earthquakes travel?
• Seismic waves are waves of energy
that travel through the earth away
from the earthquake in all directions.
• 2 types of seismic waves
1. Body Waves
2. Surface Waves
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Pre-AP
Pre-AP Extension
Earthquakes
Body Waves
• P (primary) waves
- move rock particles back and forth by
first squeezing and then stretching the
rock.
- first waves to arrive
- travel through solids, liquids, and
gases
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Pre-AP
Pre-AP Extension
Earthquakes
Body Waves continued…
• S (shear) waves
-these waves move back and forth like a flag
waving in the wind
-1/2 as fast as p waves
-only travel through solids
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Pre-AP
Pre-AP Extension
Earthquakes
Surface Waves
• Surface Waves are seismic waves that move the
ground up and down.
• These do not affect deep layers of the earth.
• Travel slower than body waves, but are more
destructive.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Pre-AP
Pre-AP Extension
Earthquakes
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 21 : Pre-AP
Volcanoes
What Do You Think?
How could potential and kinetic
energy relate to volcanoes?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
• A volcano is a mountain that forms when
molten rock, called magma, is forced to
the Earth’s surface.
• Magma is commonly a mixture of hot,
liquid rock, and solid mineral crystals
below the surface of the Earth.
• Lava is molten rock at or above the
surface of the Earth.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
Potential and Kinetic Energy in
Volcanoes
• Just like earthquakes, potential energy builds up at
tectonic plates where a volcano may occur.
• As the pressure from the magma builds up, the
potential energy is changed to kinetic energy as the
volcano erupts.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
Volcanoes as Systems
• A volcano is a system of vents, magma, and
rock.
• The system is in equilibrium when the force of
the magma pushing up equals the force of the
rock pushing down.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
Volcanoes as Systems
• When a volcano erupts, it is no longer in
equilibrium because the force of the magma is
greater than the downward force of the rocks.
• After the eruption, the system returns to
equilibrium, because the forces are equal again.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
Magma
• The composition of the magma determines how
explosive a volcanic eruption will be.
• Viscosity is a liquid’s resistance to flow.
• If magma has a high viscosity, it flows slow, like
honey.
• If magma has a low viscosity, it flows fast, like
water.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
• Magma with a high viscosity keeps water
vapor and other gases from escaping
easily. This can cause a huge buildup of
pressure, causing a very explosive
reaction.
• Magma with a low viscosity produces a
nonexplosive, less violent reaction.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Let’s Review!
-1Describe how a volcanic system changes
from a state of equilibrium to a state of
eruption and back.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Answer
• When in equilibrium, the force of the
magma pushing up equals the force of the
rocks pushing down.
• If more magma build up under the
volcano, the forces are no longer equal
and an eruption results.
• After the eruption, the forces of the rock
and the magma are once again in
equilibrium.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 1
Volcanoes
What Do You Think?
What impact could volcanoes
have on Earth?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 2
Volcanoes
Impacts of Volcanoes
• In the most violent eruptions, ash and gases are
blasted into the atmosphere.
• These blasts can blow down trees and even
nearby buildings.
• The volcanic ash can also stay in the
atmosphere, where it can block the sun for
weeks. This can dramatically affect crops.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 2
Let’s Review!
-1Explain why the ash from an eruption can be
catastrophic.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 2
Answer
• Volcanic ash is hazardous when it flows
downhill, which chokes and burns living
things, and when it smothers crops, it can
result in food shortages.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 2
Volcanoes
What Do You Think?
What methods do scientists use
to predict volcanoes?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Volcanoes
Predicting Volcanoes
• Scientists classify volcanoes based on their
eruption histories and on the likelihood that they
will erupt again.
– Extinct volcanoes are those that have not erupted in
recorded history, and probably never will again
– Dormant volcanoes are those that are not now
erupting, but have erupted at some time in recorded
history
– Active volcanoes are those that are now erupting or
that show signs of erupting soon.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Volcanoes
Predicting Volcanoes
• Small earthquakes, detected by a seismograph,
usually occur just before a volcanic eruption.
Scientists can predict if a volcano will occur
based on the small earthquake waves.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Volcanoes
Predicting Volcanoes
• The movement of magma can also cause
changes in a volcano’s slope.
• Scientists use a tiltmeter to measure small
changes in the angle of the volcano’s slope.
• The tiltmeter can help scientists to predict a
volcanic eruption based on the movement of the
magma below.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Volcanoes
Predicting Volcanoes
• Scientists measure changes in the ratios of
certain volcanic gases to help predict eruptions.
• If the ratios of certain gases change, the magma
is also changing, and a volcanic eruption could
be near.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Volcanoes
Predicting Volcanoes
• Using satellite images to predict volcanic
eruptions is a new technique used in science.
• Infrared satellite images can see changes in the
temperature of a certain area.
• If a volcano is getting hotter, the magma below is
probably rising.
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Volcanoes
Websites to visit
• Volcanoes
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Let’s Review!
-1What kind of technology do scientists use to
predict volcanic eruptions?
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3
Answer
• Seismographs
• Tiltmeters
• Infrared satellite images
© Fall 2005, Pflugerville ISD, 7th Grade
Unit 3 : Chapter 22 : Section 3