Earth’s Structure and Processes Eighth Grade Science PACT Review of Standards

Earth’s Structure and Earth’s Structure and ProcessesProcesses

Eighth Grade ScienceEighth Grade Science

PACT Review of StandardsPACT Review of Standards

How would you summarize the three layers of the How would you summarize the three layers of the Earth on the basis of position, density, and Earth on the basis of position, density, and

composition?composition?

LayerLayer PositionPosition DensityDensity CompositionComposition

CrustCrust Outermost layer; Outermost layer; thinnest under the thinnest under the ocean, thickest ocean, thickest under continents; under continents; crust & top of crust & top of mantle called the mantle called the lithospherelithosphere

Least dense layer Least dense layer overall; oceanic overall; oceanic crust = dense crust = dense basalt, continental basalt, continental crust = less dense crust = less dense granite granite

Solid rock Solid rock

MantleMantle Middle layer, Middle layer, thickest layer; top thickest layer; top portion called the portion called the asthenosphereasthenosphere

Density increases Density increases with depth because with depth because of increasing of increasing pressure pressure

Hot softened rock; Hot softened rock; contains iron and contains iron and

magnesiummagnesium

CoreCore Inner layer; consists Inner layer; consists of two parts – outer of two parts – outer core and inner corecore and inner core

Heaviest material; Heaviest material; most dense layer most dense layer

Mostly iron and Mostly iron and nickel; outer core – nickel; outer core – slow flowing liquid, slow flowing liquid,

inner core - solidinner core - solid

The Earth's LayersThe Earth's Layers

How do scientists use seismic waves to How do scientists use seismic waves to determine the internal structure of determine the internal structure of

Earth?Earth? Earthquakes produce three types of waves Earthquakes produce three types of waves

with different behaviors as they travel with different behaviors as they travel through materials. through materials.

Primary (P) wavesPrimary (P) waves Move out from the Move out from the earthquake focus, the point where the earthquake focus, the point where the energy is released; they travel the fastest energy is released; they travel the fastest of the three waves; they move through of the three waves; they move through solid and liquid layers of Earth; they push solid and liquid layers of Earth; they push and pull rock creating a back-and-forth and pull rock creating a back-and-forth motion in the direction the wave is moving.motion in the direction the wave is moving.


Earth?Earth? Secondary (S) wavesSecondary (S) waves Move out from Move out from

the earthquake focus; they move slower the earthquake focus; they move slower than primary waves; they can only move than primary waves; they can only move through solid rock; they move at right through solid rock; they move at right angles to primary waves causing rocks to angles to primary waves causing rocks to move up and down and side to side.move up and down and side to side.

Surface wavesSurface waves Form when P and S waves Form when P and S waves reach the surface; they can cause the reach the surface; they can cause the ground to shake making rock sway from ground to shake making rock sway from side to side and roll like an ocean wave.side to side and roll like an ocean wave.


Earth?Earth? Scientists use the principle that the speed Scientists use the principle that the speed

and direction of a seismic wave depends and direction of a seismic wave depends on the material it travels through. on the material it travels through.

Because of the behavior of these different Because of the behavior of these different waves, scientists have indirect evidence waves, scientists have indirect evidence for the solid inner core and liquid outer for the solid inner core and liquid outer core of Earth; because earthquake waves core of Earth; because earthquake waves travel faster through the mantle than travel faster through the mantle than through the crust, scientists know that the through the crust, scientists know that the mantle is denser.mantle is denser.


Earth?Earth?The movement of materials in the The movement of materials in the

outer core of Earth is inferred to be outer core of Earth is inferred to be the cause of Earth’s magnetic field. the cause of Earth’s magnetic field. A compass needle will align with the A compass needle will align with the lines of force of Earth’s magnetic lines of force of Earth’s magnetic field. Iron and nickel are metals that field. Iron and nickel are metals that easily magnetize, and are inferred to easily magnetize, and are inferred to be the metals in Earth’s core. be the metals in Earth’s core.

Which method is best for studying the composition of Earth’s core?

A. Drill holes to the center of Earth to take samples. B. Study rocks eroded by rivers. C. Study earthquake waves. D. Take samples in a cave.

Seismic WavesSeismic WavesHow Are Earthquakes Studied?How Are Earthquakes Studied?

How can you locate the How can you locate the epicenter of an earthquake?epicenter of an earthquake?

Seismic waves can be measured and recorded by Seismic waves can be measured and recorded by a a seismographseismograph. .

The vibration record, call a The vibration record, call a seismogramseismogram, looks like , looks like jagged lines on paper. jagged lines on paper.

The time between the arrival of the P and S The time between the arrival of the P and S waves is measured to determine the distance waves is measured to determine the distance between the recording seismograph and the between the recording seismograph and the earthquake epicenter.earthquake epicenter.

To make the inference as to the location of the To make the inference as to the location of the epicenter, the records from three seismograph epicenter, the records from three seismograph stations to plot circles on a map. This stations to plot circles on a map. This triangulationtriangulation will identify the epicenter where the will identify the epicenter where the three circles intersect.three circles intersect.

How are all rocks linked by the How are all rocks linked by the rock cycle?rock cycle?

There are three large classifications There are three large classifications of rocks – igneous, metamorphic, and of rocks – igneous, metamorphic, and sedimentary. sedimentary.

Each type of rock is formed Each type of rock is formed differently and can change from one differently and can change from one type to another over time.type to another over time.


Igneous:Igneous:Forms when molten rock cools and hardens.Forms when molten rock cools and hardens. If cooling takes place slowly beneath If cooling takes place slowly beneath

Earths surface, the igneous rock is called Earths surface, the igneous rock is called intrusive, and the mineral crystals that form intrusive, and the mineral crystals that form are large. are large.

If the cooling takes place rapidly on Earths If the cooling takes place rapidly on Earths surface, the igneous rock is called extrusive surface, the igneous rock is called extrusive and the mineral crystals are small and and the mineral crystals are small and glassy. glassy.


Metamorphic:Metamorphic: Forms when rocks buried deep inside Earth are Forms when rocks buried deep inside Earth are

changed into different kinds of rocks by great changed into different kinds of rocks by great heat and pressure – they are heated, heat and pressure – they are heated, squeezed, folded or chemically changed by squeezed, folded or chemically changed by contact with hot fluids. contact with hot fluids.

When minerals within a metamorphic rock are When minerals within a metamorphic rock are lined-up forming layered bands, it is called lined-up forming layered bands, it is called foliation. foliation.

Some metamorphic rocks are foliated (banded) Some metamorphic rocks are foliated (banded) and others are non-foliated (no bands)and others are non-foliated (no bands)


Sedimentary:Sedimentary:Forms from the compaction and/or Forms from the compaction and/or

cementation of rock or organic cementation of rock or organic fragments called sediments. fragments called sediments.

They can also form from the chemical They can also form from the chemical depositing of materials that were once depositing of materials that were once dissolved in water.dissolved in water.


The rock cycle is an ongoing process. The rock cycle is an ongoing process. A series of natural processes that A series of natural processes that

slowly change rocks from one kind to slowly change rocks from one kind to another: (1) igneous, (2) another: (1) igneous, (2) sedimentary, and (3) metamorphic.sedimentary, and (3) metamorphic.

Rock OnRock On

How are the properties of How are the properties of minerals, ores, and fossil fuels minerals, ores, and fossil fuels

useful to us?useful to us? Earth resources have properties that make Earth resources have properties that make

them important and useful. them important and useful. The two types of properties are:The two types of properties are:

Physical propertiesPhysical propertiesHardnessHardnessLusterLusterColorColorTextureTextureThe way the mineral splitsThe way the mineral splitsDensityDensity

Chemical propertiesChemical propertiesThe ability to burn The ability to burn The reactivity to acidsThe reactivity to acids

How are the properties of How are the properties of minerals, ores, and fossil fuels minerals, ores, and fossil fuels

useful to us?useful to us? Three common Earth resources that have Three common Earth resources that have

importance based on their properties are:importance based on their properties are: MineralsMinerals

Natural, solid materials found on Earth that are Natural, solid materials found on Earth that are the building blocks of rock; each has a certain the building blocks of rock; each has a certain chemical makeup and set of properties. chemical makeup and set of properties.

OresOres Minerals that are mined because they contain Minerals that are mined because they contain

useful metals or nonmetals.useful metals or nonmetals. Fossil FuelsFossil Fuels

Natural fuels that come from the remains of Natural fuels that come from the remains of living things; fuels give off energy when they living things; fuels give off energy when they are burned.are burned.

How does the theory of plate tectonics How does the theory of plate tectonics explain changes in landforms over explain changes in landforms over

time?time? The theory of plate tectonics explains why The theory of plate tectonics explains why

and how large sections of Earth’s crust, and how large sections of Earth’s crust, called called lithospheric plates,lithospheric plates, move. move.

Motion of the Lithospheric PlatesMotion of the Lithospheric Plates Plates float on the lower part of the mantle. Plates float on the lower part of the mantle. Convection currents deep inside Earth can Convection currents deep inside Earth can

cause the asthenosphere to flow slowly cause the asthenosphere to flow slowly carrying with it the plates of the lithosphere. carrying with it the plates of the lithosphere.

This movement of plates changes the sizes, This movement of plates changes the sizes, shapes, and positions of Earth’s continents and shapes, and positions of Earth’s continents and oceans.oceans.


time?time? Divergent boundaryDivergent boundary

Where two plates are moving apart Where two plates are moving apart Most located along mid-ocean ridge (sea-floor Most located along mid-ocean ridge (sea-floor

spreading); spreading); New crust forms because magma pushes up and New crust forms because magma pushes up and

hardens between separating plates.hardens between separating plates. Convergent boundaryConvergent boundary

Where two plates come together and collide; Where two plates come together and collide; Activity depends upon the types of crust that meet; Activity depends upon the types of crust that meet; Oceanic plate slides under less dense continental plate Oceanic plate slides under less dense continental plate

or another oceanic plate – or another oceanic plate – subduction zonesubduction zone, some crust , some crust is destroyed;is destroyed;

Two continental plates converge, both plates buckle and Two continental plates converge, both plates buckle and push up into mountain rangespush up into mountain ranges


time?time?

Transform boundaryTransform boundaryWhere two plates slide past each otherWhere two plates slide past each otherCrust is neither created nor destroyed;Crust is neither created nor destroyed;Earthquakes occur frequently along this Earthquakes occur frequently along this

type of boundary.type of boundary.


time?time? Changes in Landform areas over Geologic TimeChanges in Landform areas over Geologic Time Plates move at very slow rates – from about one to ten Plates move at very slow rates – from about one to ten

centimeters per year;centimeters per year; At one time in geologic history the continents were joined At one time in geologic history the continents were joined

together in one large landmass that was called Pangaea. together in one large landmass that was called Pangaea. As the plates continued to move and split apart, oceans As the plates continued to move and split apart, oceans

were formed, landmasses collided and split apart until the were formed, landmasses collided and split apart until the Earth’s landmasses came to be in the positions they are Earth’s landmasses came to be in the positions they are now;now;

Evidence of these landmass collisions and splits comes Evidence of these landmass collisions and splits comes from fossils, landform shape, features, and rock structures, from fossils, landform shape, features, and rock structures, and climate change;and climate change;

Landmass changes can occur at hot spots within Landmass changes can occur at hot spots within lithospheric plates;lithospheric plates;

Earth’s landmasses will continue to move and change Earth’s landmasses will continue to move and change during the geologic time of the future.during the geologic time of the future.

What effect do volcanic eruptions and What effect do volcanic eruptions and mountain-building forces have on mountain-building forces have on

landforms?landforms?The landforms of Earth can be The landforms of Earth can be

changed by volcanic eruptions and changed by volcanic eruptions and mountain-building forces. mountain-building forces.


landforms?landforms?Volcanic EruptionsVolcanic Eruptions:: Volcanic eruptions are constructive in that they add Volcanic eruptions are constructive in that they add

new rock to existing land and form new islands.new rock to existing land and form new islands. Magma from the mantle rises to Earth’s surface and Magma from the mantle rises to Earth’s surface and

flows out an opening called a vent.flows out an opening called a vent. Magma that reaches Earth’s surface is known as Magma that reaches Earth’s surface is known as

lava.lava. The vent as well as the mountain that forms around The vent as well as the mountain that forms around

it from cooled lava, ash, cinders, and rock is called a it from cooled lava, ash, cinders, and rock is called a volcano.volcano.

Most volcanoes occur along plate boundaries; an Most volcanoes occur along plate boundaries; an area in the Pacific Ocean where volcanoes are area in the Pacific Ocean where volcanoes are common is called the Ring of Fire. common is called the Ring of Fire.


landforms?landforms? Mountain-building forces:Mountain-building forces:

Forces or stresses (for example, tension and Forces or stresses (for example, tension and compression) on rocks in the lithosphere can cause compression) on rocks in the lithosphere can cause them to bend and stretch.them to bend and stretch.

This bending and stretching can produce mountain ranges.This bending and stretching can produce mountain ranges. If pressure is applied slowly, folded mountains form.If pressure is applied slowly, folded mountains form.

Forces or stresses (for example, tension, compression, Forces or stresses (for example, tension, compression, or shearing) great enough to cause rocks to break can or shearing) great enough to cause rocks to break can create faults; there are three types:create faults; there are three types:

Normal fault – caused by tension forcesNormal fault – caused by tension forces Reverse fault – caused by compression forcesReverse fault – caused by compression forces Strike-slip fault – caused by shearing forcesStrike-slip fault – caused by shearing forces If normal faults uplift a block of rock, a fault-block mountain If normal faults uplift a block of rock, a fault-block mountain

forms.forms.

A Science Odyssey: You Try It: Plate A Science Odyssey: You Try It: Plate TectonicsTectonics

What causes earthquakes?What causes earthquakes? That stress along faults can build up as blocks of That stress along faults can build up as blocks of

rock are pushed together; if the rock breaks, rock are pushed together; if the rock breaks, energy is released. energy is released.

The energy spreads outward in all directions as The energy spreads outward in all directions as vibrations called seismic waves.vibrations called seismic waves.

The The focusfocus of the earthquake is the point in the of the earthquake is the point in the crust, or mantle, where energy is released. crust, or mantle, where energy is released.

The The epicenterepicenter is the point on Earth’s surface is the point on Earth’s surface directly above the focus; energy that reaches the directly above the focus; energy that reaches the surface is greatest at this pointsurface is greatest at this point

When rocks on both sides of a fault are pushed When rocks on both sides of a fault are pushed together and pressure on the rocks increases, the together and pressure on the rocks increases, the pressure may become too great and the rocks pressure may become too great and the rocks break at a weak point.break at a weak point.

How can you identify the geologic How can you identify the geologic features of South Carolina on a map or features of South Carolina on a map or

photograph?photograph? Geologic features on Earth can be Geologic features on Earth can be

identified and visually modeled through identified and visually modeled through the use of aerial photography, satellite the use of aerial photography, satellite imagery, and topographic maps.imagery, and topographic maps.

ImageryImagery:: Highflying aircraft and satellites high above Highflying aircraft and satellites high above

Earth use sensors and cameras to gather Earth use sensors and cameras to gather information about Earth’s landforms and information about Earth’s landforms and resources. resources.

Computers create images from the data; Computers create images from the data; scientists identify specific features by the scientists identify specific features by the combination of colors and shapes that the combination of colors and shapes that the feature makes on the satellite image.feature makes on the satellite image.

How can you identify the geologic How can you identify the geologic features of South Carolina on a map or features of South Carolina on a map or

photograph?photograph?Topographic maps:Topographic maps:

These are maps that use symbols to portray These are maps that use symbols to portray the land as if viewed from above.the land as if viewed from above.

They provide information on elevation, They provide information on elevation, relief, and slope of the ground surface, as relief, and slope of the ground surface, as well as the location of roads, buildings, well as the location of roads, buildings, swamps, and other features, natural and swamps, and other features, natural and man-made.man-made.

Along with the scale and symbols, the Along with the scale and symbols, the contour lines and the contour interval are contour lines and the contour interval are critical to understanding the topographic critical to understanding the topographic map.map.

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Earth’s Structure and Processes Eighth Grade Science PACT Review of Standards