Fcat 2.0 science reviewmrs.bloch – coral gables prep

EARTH SCIENCE

SC.7.E.6.2 Identify the patterns within the rock cycle and relate them to surface events(weathering and erosion) and subsurface events (plate tectonics and mountain building).

SC.7.E.6.2 Identify the patterns within the rock cycle and relate them to surface events(weathering and erosion) and subsurface events (plate tectonics and mountain building).

SC.7.E.6.6 Identify the impact that humans have had on Earth, such as deforestation, urbanization, desertification, erosion, air and water quality, changing the flow of water.

SC.6.E.6.1 Describe and give examples of ways in which Earth’s surface is built up and torn down by physical and chemical weathering, erosion, and deposition.

SC.6.E.6.2 Recognize that there are a variety of different landforms on Earth’s surface such as coastlines, dunes, rivers, mountains, glaciers, deltas, and lakes, and relate these landforms as they apply to Florida.

Three main groups of rock

Rock How was it formed

Igneous RockIgneous rock forms from cooling magma or lava. The magma hardens underground to form rock. The lava erupts and hardens to form rock on Earth’s surface.

Sedimentary Rock Most sedimentary rock forms when small particles of rocks or organic remains are pressed and cemented together. Sedimentary rock forms in layers that are buried below the surface.

Metamorphic rockMetamorphic rock forms when a rock is changed by heat, pressure, or chemical reactions. Most metamorphic rock forms deep underground.

Classifying Rocks pg. 113

Figure 2Rock Origins

Rocks are classified by the way they formed.

Metamorphic Rock Igneous Rock Sedimentary Rock

ORIGIN OF IGNEOUS ROCK

Igneous rock may form on or beneath Earth’s surface.

Extrusive rock is igneous rock formed from lava that erupted onto Earth’s surface.

• Basalt is the most common extrusive rock.

Igneous rock that formed when magma hardened beneath the surface of Earth is called intrusive rock.

• The most abundant type of intrusive rock in continental crust is granite.

What are Metamorphic Rocks? – When great heat and pressure are

applied to rock, the rock can change both its

and its

Any rock that forms from another rock as a result of changes in heat or

pressure (or both heat and pressure) is a.METAMORPHIC ROCK.

How Do Sedimentary Rocks Form? Sediment is small, solid pieces of material that come from rocks or

living things.

Sedimentary rocks form when sediment is deposited by water and wind.

Most sedimentary rocks are formed through a sequence of processes:

1. weathering

2. erosion

3. deposition

4. compaction

5. cementation.

How Do Sedimentary Rocks Form? Rock on Earth’s surface is constantly broken up by weathering—the effects of freezing and thawing, plant roots, acid, and other forces on rock.

After the rock is broken up, the fragments are carried away as a result of erosion—the process by which running water, wind, or ice carry away bits of broken-up rock.

Deposition is the process by which sediment settles out of the water or wind carrying it.

The process that presses sediments together is compaction.

Cementation is the process in which dissolved minerals crystallize and glue particles of sediment together.

SC.6.E.6.1 Describe and give examples of ways in which Earth’s surface is built up and torn down by physical and chemical weathering, erosion, and deposition.

What Processes Wear Down and Build Up Earth’s Surface? Weathering is the process that breaks down rock

and other substances.

Erosion is the process by which natural forces move weathered rock and soil from one place to another.

What are agents or erosion??

Gravity, moving water, glaciers, waves, and windThe material that gets carried away by erosion is sediment.

What makes up sediment??pieces of rock or soil, or the remains of plants and animals

What Processes Wear Down and Build Up Earth’s Surface? Deposition occurs where the agents of erosion deposit, or lay down, sediment. Deposition changes the shape of the land.

Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface.

Erosion and deposition are at work everywhere on Earth. As a mountains wears down in one place, new landform builds up in other places! The cycle of erosion and deposition is never-ending.

Mechanical WeatheringActions of animals

Freezing and thawing,

Plant growth Release of pressure Abrasion

Animals burrow in the ground-moles, gophers, prairie dogs and some insects. Loosen the soil and break soil apart

Water seeps into cracks in rocks and freezes and expands. The ice forces the rock apart. Wedges of ice in rocks widen and deepen cracks in the process called frost wedging.

Plant roots enter cracks in rocks. As roots grow, they force the cracks apart. Even small plant root can pry apart cracked roots

Erosion removes material from the surface of a mass of rock pressure, pressure on the rock is reduced. The released of pressure causes the outside of the rock to crack and flake off like the layers of onion.

Abrasion refers to the wearing away of rock by rock particles carried by water, ice, wind, or gravity.

Agents of Chemical WeatheringOxygen- Carbon Dioxide- Living organisms- Acid rain-

the oxygen gas in air combines with iron in the presence of water in a process called oxidation. The product of oxidation is rust. Rust makes rock soft and crumbly.

Another gas found in the air, that causes chemical weathering when it dissolves in water. The result is a weak acid called carbonic acid. C. A. easily weathers some kinds of rocks, such as marble and limestone.

as plants roots grow, they produce weak acids that slowly dissolve rock around the roots. Lichens- plantlike organisms that grow on rocks- also produce weak acids.

Rainwater is naturally acidic. Burning coal, oil and gas for energy can pollute the air with sulfur, carbon, and nitrogen compounds. These compounds react with water vapor in clouds, making acids that are stronger than normal rainwater. These acids mix with raindrops and fall as acid rain. Acid rain causes rapid chemical weathering of rock.

How Fast Does Weathering Occur? The most important factors that determine the rate at which weathering occurs are the type of rock and climate. •Some rocks weather more easily because they are permeable. Permeable means that a material is full of tiny, connected air spaces that allow water to seep through it.

•Climate refers to the average weather conditions in an area. •(wet or dry / cold or hot)

•Both mechanical & physical weathering occur faster in wet climates.•Rainfall= chemical changes & freezing and thawing•Human activities= more acid rain & an increase rate of weathering.

What process do you know that breaks up rocks?

Weathering

What are the agents or natural forces that weather rocks?

Water, living things, oxygen, carbon dioxide,

changing temperature

What forces on Earth have you observed picking up or moving rocks, sand, or mud?

Floodwaters, gravity, strong winds, and people

Weathering

Water Agent(force that causes change) of Erosion•How can water be an agent of erosion?

By flowing over Earth’s surface.

•In what ways does this water flow? As a sheet, in rills, in gullies, and in streams.

•What factors determine the amount of runoff in an area?

Amount of rain, vegetation, type of soil, shape of the land, how the land is used.

Factors and Processes that Shape Earth’s Surface•How do people shape Earth’s surface?

They dig sediment and rocks from one place and dump them at another place.Water also picks up sediment at one place and deposits it at another.

Which factor/process do you think moves more sediment, people or water?

Water moves much more sediment than people.

What Land Features Are Formed by Water Erosion? Through erosion, a river creates

valleys, waterfalls, flood plains, meanders, and oxbow lakes.

• The flat, wide area of land along a river is a flood plain.

• A meander is a looplike bend in the course of a river.

• An oxbow lake is a meander that has been cut off from the river.

• Waterfalls form where a river meets an area of rock that is very hard and erodes slowly.

What Land Features Are Formed by Deposition ?Deposition creates landforms

such as alluvial fans and deltas.

Sediment deposited where a river flows into an ocean or lake builds up a landform called a delta.

An alluvial fan is a wide, sloping deposit of sediment formed where a stream leaves a mountain range. It is shaped like a fan.

Groundwater Erosion pg. 126 Groundwater is the term geologists use for underground

water.

. Groundwater can cause erosion via chemical weathering.

• Rain water is acidic Atmosphere = water+ carbon dioxide= carbonic acidic (weak acid)

• Carbonic acid breaks down limestone- the limestone is carried away in the water. Gradually, little by little, this process hollows out the rock forming caves/caverns.

How Do Waves Cause Erosion and Deposition? Where do waves get their energy from??Waves contain energy and are formed by winds.

When wind contacts waves= transfers some energy to the waves.

How do waves shape the land? Waves shape the coast through erosion by

breaking down rock and moving sand and other sediment.

Deposits by Waves Deposition occurs when waves slow down,

causing the water to drop its sediment.

Waves shape a coast when they deposit sediment, forming coastal features such as

beaches, barrier beaches, sandbars, and spits. (B, BB, S, S)

A beach is an area of wave-washed sediment along a coast. The sediment deposited on beaches is usually sand. Most sand comes from rivers that carry eroded particles of rock to the ocean.

How Does Wind Cause Erosion and Deposition? Wind shapes the land by erosion=Deflation

How is it that can wind erode the land?Wind can be a powerful force in shaping the land

in areas where there are few plants to hold the soil in place.

Wind causes erosion mainly by deflation.

Geologists define deflation as the process by which wind removes surface materials.

Desert Pavement and Desert LandformsIn deserts, deflation can sometimes create an area of

rock fragments called desert pavement.

•There, wind has blown away the smaller sediment leaving behind rocky material.

•Abrasion by wind-carried sand can polish rock, but it causes relatively little erosion.

How are most of the desert landforms formed?Geologists think that most desert landforms

are the result of weathering and water erosion.

6th Grade Benchmarks

SC.6.E.7.2 Investigate and apply how the cycling of water between the atmosphere and hydrosphere has an effect of weather patterns and climate.

SC.6.E.7.3 Describe how global patterns such as the jet stream and ocean currents influence local weather in measurable terms such as temperature, air pressure, wind direction and speed, and humidity and precipitation.

SC.6.E.7.4 Differentiate and show interactions among the geosphere, cryosphere, atmosphere, and biosphere.

SC.6.E.7.6 Differentiate between weather and climate.

SC.6.E.7.9 Describe how the composition and structure of the atmosphere protects life and insulates the planet.

How Do Clouds Form? Clouds form when water vapor in the air condenses to

form liquid water or ice crystals.

Two conditions are required for condensation: 1. cooling of the air

2. the presence of particles in the air.

The Role of Cooling When air cools water vapor in it condenses into tiny droplets of water.

The temperature at which condensation begins is called the dew point.

The Role of Particles

• Before water vapor can condense and form clouds, it must have a surface on which to condense.

• These surfaces are small particles of dust, smoke, and salt crystals.

• Liquid water that condenses from the air onto a cooler

surface is called dew.

• Ice deposited on a surface that is below freezing is called

frost.

What Are the Common Types of Precipitation?Any form of water that falls from clouds and reaches Earth’s surface is precipitation.

Common types of precipitation include:

rain, sleet, freezing rain, snow, and hail.

RainPrevailing winds move air masses (water vapor)

Rain is the most common. (They come in different sizes!!!)

• Drops of water are called rain if they are at least 0.5 millimeters in diameter. (L)

• Smaller drops of water are called drizzle (M)

• Even smaller ones are called mist. (S)

Freezing PrecipitationThere are four types of freezing precipitation:

• SnowHail

freezing rainFreezing rain is rain that freezes when it hits a cold surface.

When clouds are colder, water vapor can convert directly

into ice crystals, forming snow.

SC.6.E.7.4 Differentiate and show interactions among the geosphere, cryosphere, atmosphere, and biosphere.

The Earth system has five main spheres:

The sun is a major source of energy for Earth processes, the sun can be considered part of the Earth system as well.

SC.6.E.7.6 Differentiate between weather and climate.

Climate refers to the average, year-after-year weather patterns in a given area.

temperature

• Scientists classify climates by their

precipitation.

Climate areas have distinct: vegetation, or plant growth

Climate Vs.

Climate is the typical weather pattern in an area over a long

period of time.

Weather

Weather refers to the conditions of Earth’s atmosphere at a particular time and place.

What is the Composition of Earth’s Atmosphere? SC.6.E.7.9 Describe how the composition and structure of the atmosphere protects life and insulates the planet.Weather is the condition of Earth’s atmosphere at a

particular time and place. Earth’s atmosphere is the envelope of gases that

surrounds the planet. Earth’s atmosphere consists of:

oNitrogen, Oxygen, Carbon dioxide, Water vaporo other gases (trace gases)o particles of liquids and solids

Gases in the Atmosphere Nitrogen

• The most abundant gas in the atmosphere is nitrogen.

• It makes up a little more than three fourths (3/4)of the air we breathe.

Oxygen

• Is the second most abundant gas, makes up about 21 percent of the volume.

• Plants and animals take oxygen from air and use it to release the energy in food.

• Oxygen is also necessary for fire to burn.

Oxygen and nitrogen make up 99 percent of dry air.

Carbon dioxide

• Makes up much less than 1 percent of the atmosphere, but it is essential to life.

• Plants must have carbon dioxide to produce food.

Argon (trace gases)

• The other one percent is mostly argon, plus other gases in amounts so small that they are described as trace gases.

Scientists divide Earth’s atmosphere into 4 main layers.

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere 1. Ionosphere

2. Exosphere

The layers are classified according to changes in temperature.

The troposphere• the lowest layer of Earth’s atmosphere. • Tropo- means “turning” or “changing.” • The layer of the atmosphere in which Earth’s weather occurs. • About 12 kilometers thick, it is the thinnest and most dense layer. • It contains almost all the mass of the atmosphere.

The Stratosphere • extends from the top of the troposphere to about 50 kilometers

above Earth’s surface.• Strato- means “layer” or “spread out.” • The 2nd layer of the atmosphere and contains the ozone layer. • The lower stratosphere is cold, about –60°C. The upper

stratosphere is warmer because the ozone layer absorbs energy from the sun.

The Mesosphere• The 3rd layer ,Above the stratosphere.• Meso- means “middle.” • extends from about 50–80 km above Earth’s surface. • Temperatures approach –90°C.• The layer of the atmosphere that protects Earth’s surface from being hit by

most meteoroids.

The Thermosphere• The outermost layer of Earth’s atmosphere. • extends from 80 km above Earth’s surface outward into space with no definite

outer limit.• It has two layers

• The lower layer, the ionosphere, extends from about 80–400 km above Earth’s surface.

• The outer layer, the exosphere, extends from about 400 km outward for thousands of km.

Mesosphere & Thermosphere

SC.7.E.6.1 Describe the layers of the solid Earth, including the lithosphere, the hot convecting mantle, and the dense metallic liquid and solid cores.

SC.7.E.6.4 Explain and give examples of how physical evidence supports scientific theories that Earth has evolved over geologic time due to natural processes.

SC.7.E.6.3 Identify current methods for measuring the age of the Earth and its parts, including the law of superposition and radioactive dating.

SC.7.E.6.5 Explore the scientific theory of plate tectonics by describing how the movement of Earth’s crustal plates causes both slow and rapid changes in Earth’s surface, including volcanic eruptions, earthquakes, and mountain building.

SC.7.E.6.7 Recognize that heat flow and movement of material within Earth causes earthquakes, and volcanic eruptions, and creates mountains and ocean basins.

SC.7.E.6.1 Describe the layers of the solid Earth, including the lithosphere, the hot Convecting mantle, and the dense metallic liquid and solid cores.

What Are The Features of Earth’s Crust, Mantle, and Core? Pg. 100The three main layers of Earth are the crust, the mantle, and the core. These layers vary greatly in size, composition, temperature, and pressure.

Pressure results from a force pressing on an area.

The Deeper Down Inside Earth, The Greater the Pressure !

The Deeper Down Inside Earth, The greater The Temperature!

Earth’s Crust pg. 101Earth’s crust is the layer of rock that forms Earth’s outer skin. The crust is a layer of solid rock that includes both dry land and the ocean floor. The overall composition of oceanic crust is much like basalt, a dark rock that has fine grains. Overall the composition of continental crust is much like granite, a rock that usually is a light color and has coarse grains. The oceanic crust (5 miles thick) is thinner than the continental crust (25 miles thick)

Earth’s Mantle pg. 102The solid material of the mantle is a layer of hot rock. Earth’s mantle is made of rock that is very hot, but solid. Scientists divide the mantle into layers based on the physical characteristics of those layers. Overall, the mantle is nearly 3,000 kilometers thick.

Geologists often group the crust and uppermost mantle into a single layer called the lithosphere. The soft layer just beneath the lithosphere is called the asthenosphere. Beneath is a layer called the mesosphereWhich is hot but more rigid.

Earth’s Core pg. 103

The core is made mostly of the metals iron and nickel.

It consists of 2 parts— 1. a liquid outer core- The outer core is a layer of molten metal surrounding the inner core.

2. a solid inner core- The inner core is a dense ball of solid

metal.

SC.7.E.6.7 Recognize that heat flow and movement of material within Earth causes earthquakes, and volcanic eruptions, and creates mountains and ocean basins.

How is Heat Transferred? Heat is constantly being transferred inside Earth and all around Earth’s surface.

The movement of energy from a warmer object to a cooler object is called heat transfer. There are three types of heat transfer: radiation, convection, and conduction.

The transfer of energy that is carried in rays like light is called radiation. Heat transfer by the movement of a fluid is called convection. Heat transfer between materials that are touching is called conduction.

How Does Convection Occur in Earth’s Mantle? Convection Currents

Density is a measure of how much mass there is in a given volume of a substance. The flow that transfers heat within a fluid is called a convection current.

Convection Currents pg. 108

-Heating and cooling of a fluid-Changes in the fluid’s density AND The force of gravityALL Combine to set convection currents in motion!

Inside Earth, large amounts of heat are transferred by convection currents within the core and mantle. Heat from the core and the mantle itself causes convection currents in the mantle.

Convection Currents in Earth Over millions of years, the great heat and pressure in the mantle

have caused solid mantle rock to warm and flow very slowly.

Many geologists think that plumes of mantle rock rise slowly from the bottom of the mantle toward the top.

The hot rock eventually cools and sinks back through the mantle.

Over and over, the cycle of rising and sinking takes place.

Convections currents like these have been moving inside Earth for more than four billion years!

SC.7.E.6.5 Explore the scientific theory of plate tectonics by describing how the movement of Earth’s crustal plates causes both slow and rapid changes in Earth’s surface, including volcanic eruptions, earthquakes, and mountain building.

What Was Wegener’s Hypothesis About the Continents?In 1910, a German scientist named Alfred Wegener became curious about why some continents look as though they could fit together.

Wegener’s hypothesis was:

that all the continents were once joined

together in a single landmass called

Pangea and have since drifted apart.

Wegener’s idea that the continents moved

over Earth’s surface became known as

continental drift.

Evidence #1 From Land Features pg. 173

Land features on the continents such as mountain ranges and coal fields provided Wegener with evidence for his hypothesis.

He pieced together maps of Africa and South America.

He noticed how the coal fields lined up.

He also noticed that coal fields in Europe and North America also match up.

Evidence #2 From Fossils pg.174Wegener also used fossils to

support his hypothesis for continental drift.

•A fossil is any trace of an ancient organism that has been preserved in rock.

•Plant fossils such as Glossopteris (fernlike plant) found in various continents Africa, South America, Australia, India, and

Antarctica.

•Freshwater reptiles such as Mesosaurus and Lystrosaurus found in places that are now separated by oceans (reptiles that could not swim long distances)

Evidence #3 From Climate pg. 175 Wegener also used evidence of climate

change to support his hypothesis.

As continents move towards the equator= climates warmer as they move towards the Poles= Colder.

As continents moves, they carry along fossils and rocks formed at all its previous locations.

Wegener’s Hypothesis Rejected

Wegener could not provide a satisfactory explanation for the force that pushes or pulls the continents. Because he could not identify the cause of continental drift, most geologists of his time rejected his idea.

What Are Mid-Ocean Ridges? Pg. 176

In certain places, the floor of the ocean appears to be stitched together like the seams of a baseball.

Scientists found that the seams formed mountain ranges that ran along the middle of some ocean floors. Scientists called these mountain ranges mid-ocean ridges.

Mid-ocean ridges form long chains of mountains that rise up from the ocean floor.

What Are Mid-Ocean Ridges? Pg. 177 & 178Sonar is a device that uses sound

waves to measure the distance to an object.

Scientist have used sonar to map mid-ocean ridges since the mid-1900’s. Pg.177

Mid-ocean ridges continually add new material to the ocean floor in a process called sea-floor spreading.

Sea-floor spreading adds more crust to the ocean floor. At the same time, older strips of rock move outward from either side of the ridge.

Figure 2. Sea-Floor Spreading pg. 178

Sea-Floor Spreading

Some mid-ocean ridges have a valley that runs along their center. Evidence shows that molten material erupts through this valley and then hardens to form the ocean floor.

What Happens at Deep-ocean Trenches? Pg. 180Does the ocean keep getting wider without stopping??No! Ocean floor eventually plunges into deep underwater canyons called deep-ocean trenches.

•At a deep-ocean trench, the oceanic crust bends downward.

In a process taking tens of millions of years, part of the ocean floor sinks back into the mantle at deep-ocean trenches.

The Process of Subduction pg. 180Explanation of ocean floor density Example:

washcloth + water(wet cloth)= washcloth’s density increases

Higher density of washcloth= washcloth heavier(denser)= sinks

Subduction and the Earth’s Oceans

The processes of subduction and sea-floor spreading can change the size and shape of the oceans.

The ocean floor is renewed about every 200 million years.

An ocean surrounded by many trenches may shrink.

An ocean that contains more ridges than trenches will probably grow larger.

What is the Theory of Plate Tectonics? Pg. 182 Earth’s lithosphere, its solid outer shell, is like an eggshell

broken into pieces separated by cracks.

These pieces are called plates. Earth’s plates meet at boundaries.

There are 3 main types of Boundaries:

1. DIVERGENT BOUNDARIES

2. CONVERGENT BOUNDARIES

3. TRANSFORM BOUNDARIES

Divergent BoundariesPlates Move Away From Each Other or Divide.

Convergent BoundariesPlates Move Towards Each other or Come

together like people do at a conference.

Transform BoundariesPlates Slide Past Each Other. These

are also called Sliding Boundaries!

The Theory of Plate Tectonics pg. 183In the mid-1960s, geologists combined what they knew about sea-floor spreading, Earth’s plates, and plate motions into a single theory called plate tectonics.

The theory of plate tectonics states that Earth’s plates are in slow, constant motion, driven by convection currents in the mantle.

Mantle Convection and Plate Motions pg. 183Plate Motions Over Time

Earth’s plates move because they are the top part of the large convection currents in Earth’s mantle.

During subduction, gravity pulls denser plate edges downward, into the mantle.

Plates move very slowly—from about 1 to 12 centimeters per year.

Earth’s plates can carry ocean floor, continents, or continents and oceans together.

So the movement of Earth’s plates has greatly changed the location of Earth’s continents, landmasses, and oceans.

Volcanoes and Plate Boundaries pg.197 Volcanoes and Plate Boundaries

In general, volcanoes form a regular pattern on Earth. They occur in many great, long belts.

Volcanic belts form along the boundaries of Earth’s plates.

Volcanoes can occur where two plates pull apart, or diverge.

They can also occur where two plates push together, or converge.

The Ring of Fire is one major belt of volcanoes. It includes the many volcanoes that rim the Pacific Ocean.

Diverging & Converging Boundaries pg. 198

Volcanoes form along the mid-ocean ridges, where two plates move apart.

Along the rift valley, lava pours out of cracks in the ocean floor. This process gradually builds new mountains.

Volcanoes also form along diverging plate boundaries on land.

Example: Large Volcanoes found along the Great Rift Valley in East Africa.

Converging Boundaries pg. 198

Many volcanoes form near converging plate boundaries where two oceanic plates collide.

The resulting volcanoes sometimes create a string of islands called an island arc.

Example: Japan, New Zealand, Aleutians and the Caribbean islands.

Volcanoes also occur where an oceanic plate is subducted beneath a continental plate.

Example: Volcanoes of the Andes Mts. In South America.

3 Kinds of Stress in Earth’s Crust pg. 223As Earth’s plates move, they can bend or fold rock. Forces created by movement of the Earth’s plates are examples of stress. Stress adds energy to rock until the rock changes shape or breaks.

Three kinds of stress can occur in the Earth’s crust –

tension, compression, and shearing. All three work over millions of years to change the shape and

volume of rock.

Tension, compression, and shearing work over millions of years to change the shape and volume of rock

How Does Stress Change Earth’s Crust? Pg. 223

Stress can push, pull, or squeeze rock in Earth’s crust.

Three kinds of stress can occur in the crust.Tension -Tension is the stress force that pulls on the crust and thins the rock in the middle. It occurs where two plates pull apart.

Compression - Compression is the stress force that squeezes rock until it folds or breaks. It occurs where two plates come together and push against each other.

Shearing -Shearing is the stress force that pushes rock in two opposite directions. It occurs where two plates slip past each

other.

How Does Plate Movement Create New Landforms? Pg. 226 Over millions of years, the forces of plate movement can change

a flat plain into features such as anticlines and synclines, folded mountains, fault-block mountains, and plateaus.

What Are Seismic Waves? Pg. 231Plate movement increases the stress along a fault until the rock slips or breaks and an earthquake begins. An earthquake is the shaking and trembling that happens when rock under Earth’s surface moves. The focus is the place under Earth’s surface where rock starts to move. The point on the surface directly above the focus is called the epicenter.

Some of the energy released during

an earthquake travels through Earth

in the form of seismic waves. Seismic

waves travel out in every direction

from the focus.

SC.7.E.6.4 Explain and give examples of how physical evidence supports scientific theories that Earth has evolved over geologic time due to natural processes.

What are Fossils? Pg. 141Fossils are reserved remains or traces of living things.

FOSSILS FORM IN SEDIMENTARY ROCK!!

Most fossils form when living things die and are buried by sediment. The sediment slowly hardens into rock and preserves the shapes of the organisms.

Sediment is made up of rock particles or the remains of living things.

How a Fossil Forms: A fossil may form when sediment quickly covers an organism’s body.

What Do Fossils Show? Pg. 144

A paleontologist is a scientist who studies fossils.

The fossil record is the combined information about fossils collected by scientists throughout history.

It provides evidence about the history of life and past environments on Earth.

It also shows how different groups of organisms have changed over time.

The term evolution is used to identify the process of gradual change in living things over long periods.

A type of organism is extinct if it no longer exists and will never again live on Earth.

How Old Are Rock Layers? Pg. 146

Relative Age vs. Absolute Age

The Relative Age of a rock is its

age compared to the ages of other

rocks.

The Absolute Age (Numerical Age)

of a rock is the number of years that

have passed since the rock formed.

Rock Layers pg. 147The Law Of Superposition

Geologists use the law of superposition to determine the relative ages of sedimentary rock layers.

According to the law of superposition, in horizontal sedimentary rock layers the oldest layer is at the bottom.

Each higher layer is younger than the layers below it.

Half-LifeThe half-life of a radioactive element is the amount of time it takes for half of the radioactive atoms to decay. What pattern do you see in the graph?

What is Radioactive Dating? Pg. 154Radioactive elements in igneous rocks decay over time into other elements. This slowly changes the composition of the rock.

Geologists use radioactive dating to determine the absolute ages of rocks.

In radioactive dating, scientists first

determine the amount of a radioactive element in

a rock.

Then they compare that amount with the amount

of the stable element into which the radioactive

element decays.

They calculate the age of the rock using this

information and the half-life of the element.

How Do Scientists Determine Earth’s Age? Pg. 156

To determine Earth’s age, scientists use radioactive dating and evidence from rocks on Earth and the MOON!

Using radioactive dating, Earth rocks are estimated to be between 3.8 and 4.28 billion years old.

However, Earth rocks have changed over time due to the processes of plate tectonics and erosion.

Moon rocks, fortunately, have not changed over time due to the fact that moon has no atmosphere.

According to one theory, scientists infer that the moon formed when another object collided with Earth. Since the moon came from Earth, the moon is about the same age as Earth.

Radioactive dating estimates moon rocks to be 4.6 billion years old. Scientists estimate that Earth is about the same age.

What is the Geologic Time Scale? Pg. 159

The history of the Earth covers an enormous length of time. Scientists have developed new terms to identify long periods.

Because the time span of Earth’s

past is so great, geologists use the

geologic time scale to show Earth’s

history.

The geologic time scale is a record of

the geologic events and the evolution

of life forms as shown in the fossil record.

The Geologic Time Scale

In the geologic time scale, scientists have placed Earth’s rocks in order by relative age. Then they divided geologic time into parts, based on times in Earth’s history when there were major changes in life forms. The earliest part of the geologic time scale was named Precambrian Time. This part, which is by far the longest of the geologic time scale, ended 542 million years ago.

Geologic Time

Dividing Geologic Time pg. 161Scientists divided the time between Precambrian Time and the present into three long units of time called eras.

These are the Paleozoic Era, the Mesozoic Era, and the Cenozoic Era.

Moreover, scientists subdivided eras into units of geologic time called periods.

The Paleozoic Era is made up of six periods; the Mesozoic Era is made up of three periods; and the Cenozoic Era is made up three periods. The last of these, the Quaternary Period, continues to the present time.

How Has Earth Changed Over Geologic Time? Pg. 162

Scientists use the principle of uniformitarianism to help explain Earth’s past.

This principle states that geologic processes that operate today are the same ones that operated in the past.

Natural processes such as weathering, erosion, and plate tectonics have reshaped Earth’s surface. The distribution of land and water on Earth’s surface has changed over time.

Using fossils, evidence from rock layers, and radioactive dating, scientists can infer about events in Earth’s history.