N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
EARTH SYSTEMS
In this 8th grade unit the student will describe interactions among solar, weather,
and ocean systems. Students will also relate the role of oceans to climate changes.
The Earth is a set of closely related systems that work together in such a way that
the Earth is continually changing its dynamics. Some of the most important
systems on Earth are the atmosphere (air), the hydrosphere (water), the
biosphere (life), and the geosphere (land). The Sun provides the power for most of
the processes found on earth. This unit will concentrate on how the sun is a
powerful source of energy that drives the weather and climate on Earth. As a
result, it would be appropriate at this time to review the concepts of radiation,
conduction and convection from the unit on heat. This unit will also cover the ocean
as a system that is interrelated to weather and climate.
Weather & Climate
The 6th grade student learned about the different layers of the atmosphere and
that all weather occurs in the layer nearest the Earth, called the troposphere.
They were introduced to weather fronts. The 8th grade student should learn
radiant energy is responsible for creating different climates across the planet.
While weather changes from day to day, climate is a region’s general pattern of
weather over a long period of time. Because the intensity of the sun is less at the
poles, these areas have the coldest climates. The equator receives the most direct
sunlight, creating the warmest climates.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
The study and research of weather is known as meteorology. The three main
factors affecting weather are wind, water, and temperature. It is important to
know that cold air and water are denser so they sink and warm air and water are
less dense so they rise, creating a convection current. Meteorologists use many
things to help them determine the weather. Balloons carrying weather instruments
are launched and humidity, pressure, and temperature are measured. Buoys that
float in different areas of the oceans can measure wind speed, air temperature, air
pressure, and water temperature. Planes carrying high tech equipment can fly over
areas and detect weather conditions. Radar instruments and weather satellites are
used to collect weather information. (National Geographic, Johnson, 2003).
As students study weather, it is necessary for them to review interpretation of
weather maps, first introduced in 6th grade. Students should be familiar with
basic symbols used on maps, should practice using keys to interpret the maps and
be able to make simple predictions (forecasts) about what is occurring on the map.
Students studying weather maps will need to understand that air mass movement is
not simply a result of differences in density and temperature. The curvature and
rotation of the Earth also contribute to weather patterns. As hot, equatorial air
masses move north and south toward less dense, cooler air, they follow the curved,
spherical shape of the Earth. This is known as the Coriolis effect.
Deflection patterns
that result from the
Coriolis Effect
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
Weather changes as a result of moving air masses. An air mass is a large body of
air with a particular temperature and humidity content. The area in which two
separate air masses meet is known as a front. There are several different types
of fronts.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
Climate is an area’s general pattern of weather over a long period of time. Climate
does not change as quickly as weather, but it does change. During the last ice age
one third of the planet was covered in ice. Millions of years ago the climate was
much warmer. How do scientists know this? They use clues from the past. Some
of these clues are core samples drilled from the bottom of the ocean, on land and
in ice. Tree rings can help us learn about past climates. Scientists rely on many
tools do study weather and climate. The science of weather and climate is quite
young. Daily weather records do not exist if you go back farther than a few
hundred years, and they were certainly not as advanced as the ones that are
recorded now because of all the technology that is available for use.
The World’s Oceans
The oceans have an important place in the Earth’s Systems. Oceans cover
approximately three-fourths of the surface of the earth. Waves are generated
which shape beaches, move sediment to build coastal landforms, and in some places
cause severe coastal erosion. Evaporation from the ocean surface is the main
source of moisture for precipitation on the continents as well as over the oceans.
Some of this precipitation feeds continental glaciers, which in some places return
their water directly back to the oceans. Atmospheric gases also reside in solution
in the ocean. A substantial percentage of human generated carbon dioxide
becomes dissolved in the oceans rather than remaining in the atmosphere. This
lessens the potential impact of burning of fossil fuels on global climate; however, in
another sense, it just postpones dealing with the problem. The ocean basins, as
well as the continental margins adjacent to them, are the domain of plate
tectonics, whereby new ocean floor is created and consumed. Weathering of
bedrock on the continents supplies the oceans with both particulate sediment and
dissolved salts (American Geological Institute, IES, Smith, Sourthard & Mably,
2002).
When learning about all of these processes, students should be reminded that the
sun is the driving force behind ocean systems. The 2006 TAKS Study Guide states
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
that students should know there are 2 important ways in which solar – ocean
interactions affect the climate on land:
1. Land heats up faster than water because land has a lower specific heat.
This in turn causes the air over the land to heat more quickly than the air
over the ocean water. The warm air rises, starting a convection current that
pulls air toward land from the ocean. This pattern is seen on all the
continents on Earth. This keeps air over the land from getting too hot. It
also brings moist ocean air inland.
2. Warm air holds more water vapor than cold air. When warm, moist air is
cooled, clouds form and can produce precipitation. This warm air can be
cooled by rising into the colder upper atmosphere, by moving over cold ocean
or lake water, or by mixing with colder air.
Movement of water in the ocean is known as a current. Currents that occur at or
near the surface of the water are called surface currents. Their direction of
travel is affected by winds and the Coriolis effect. They may then change
direction as they are deflected by the continents. Deep ocean currents occur far
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
below the surface of the water. Direction of travel for deep currents is affected
by many factors, including temperature, density, and salinity differences.
The climate surrounding oceans varies around the world. One of the most
important effects on an ocean’s environment is its location on the Earth. If a
person looks at a map of the world and locates England and then follows it across
the Atlantic Ocean to North America, one would see that Nova Scotia has a much
colder climate than England does. For many years this puzzled experts until an
understanding of surface ocean currents was obtained. A major ocean current
that originates in the Gulf of Mexico is called the Gulf Stream, and it is a warm
current. As the scientists follow the path of this ocean current they discovered
that it went all the way to the British Isles. Therefore, England has a warmer
climate than Nova Scotia because of warm and cold ocean surface currents.
El Nino is a term given to a condition where the earth‘s warm and cool ocean
surface waters in the Pacific Ocean change locations. Warmer surface areas
become cooler, and cooler surface areas become warmer. El Nino affects the
surface waters and the surface currents. It changes the interaction between the
ocean and the atmosphere, which, in turn, changes global weather patterns. This
phenomenon occurs about every 2-12 years. In addition, El Nino usually brings
unusual and severe conditions to different areas around the world. Severe
droughts, unusually large floods and mudslides have been known to occur during an
El Nino year.
Another important condition of Earth’s oceans is the tides. Students have not
learned about tides since the 4th grade. A tide is a daily change in the level of
ocean water, caused by the gravitational pull of the sun and moon. The moon has
the greatest affect on the tides because it is much closer to the Earth than the
sun is. The moon pulls on the side of the Earth it is facing. This causes the water
on this part of Earth to bulge towards the moon. The water also bulges on the side
of the Earth directly opposite because of Earth’s rotation. This bulge is high tide.
When the bulge occurs, it pulls water away from the areas not facing the moon.
These bodies of water will be at low tide. High and low tides occur twice daily.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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N o r t h E a st I n d ep en d e nt S c h o o l D i st ric t
8th Grade Science
Unit 7
Earth Systems
Spring 2006
Low Tide
High Tide
High Tide
Low Tide
Gravitational pull
of the moon
When the Sun, Earth and moon are lined up during new and full moon phases, the
gravitational pull on the Earth is increased. This creates even higher tides, known
as spring tides. When the Sun, Earth and moon are aligned perpendicular to one
another during first and third quarter moon phases, the gravitational pull on the
Earth is decreased. This is because the gravitational forces of the moon and sun
are working against one another, causing minimal low tides, known as neap tides.
Clarifying statements are intended to deepen teachers’ understanding of science concepts and serve as a guide for
instructional design. They are not intended to serve as student instructional materials.
This publication is the property of North East Independent School District. Duplication in whole or in part, outside of NEISD, is
prohibited without express written permission from NEISD.
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