Earth's Layers Three Types of Rocks Early Life on Earth / Fossils - - PDF document

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6th Grade

Earth's Materials and Systems Part 1: The History of Planet Earth

2015-08-27 www.njctl.org

Slide 3 / 75 Table of Contents: The History

• f Planet Earth

· Earth's Layers · Three Types of Rocks · Rock Strata · Early Life on Earth / Fossils

Click on the topic to go to that section

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Earth's Layers

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• f Contents

Slide 5 / 75 Review

Earth is a "terrestrial" or rocky

• planet. This means that it is made

up of rocks and minerals. The rocks and minerals that now make up our Earth were once just small chunks revolving around our

• sun. Over billions of years, they

combined to form the planet we live

• n today.

What are the other rocky planets in our solar system?

Slide 6 / 75 The Makeup of Earth

As Earth grew larger, its gravity increased. Pressure beneath Earth's surface caused changes to the Earth's makeup. Distinct layers began to form. Do you remember any of the names of the layers? Brainstorm with your table.

Slide 7 / 75 The Layers of Earth

Our Earth is divided into four major layers: Crust Mantle Outer Core Inner Core

Slide 8 / 75 Earth's Crust

Think of the crust of Earth as the crust of a pizza pie. The crust is the outermost layer of Earth, just like the crust above is the outermost layer of the pizza!

Slide 9 / 75 Earth's Crust

This section is very thin compared to

• ther layers of Earth (between 5 and

25 miles thick) and it is very hard and rigid. The crust is composed of plates that slide around on top of the section below it. This portion is called the lithosphere . There are 2 parts to the crust. One is the land. What is the other part?

Slide 10 / 75 Earth's Mantle

The next layer down is the mantle. This is the largest layer - about 1,800 miles thick! The mantle is made up of incredibly hot, semisolid rock (basically think of rock in a form sort of like pudding). This layer makes up about 2/3 of Earth's mass.

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1 Which best describes the lithosphere? A The part of the atmosphere which we breathe. B The layer of Earth that makes up the greatest mass. C A layer of Earth that is made of a jello-like substance. D The plates of Earth that slide around the surface.

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2 What is true of the mantle? A It is the thickest layer of Earth. B It is the top layer of Earth. C It is entirely made of liquid. D It is the least massive portion of Earth.

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3 The mantle is composed of Earth's land and oceans. True False

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4 Choose the correct order of Earth's layers from outermost to most inner. A mantle, crust, inner core, outer core B inner core, outer core, crust, mantle C inner core, outer core, mantle, crust D crust, mantle, outer core, inner core

Slide 15 / 75 Earth's Outer Core

The Outer Core is so hot that it is entirely

• liquid. It is the only liquid layer of Earth.

It is made up of mainly nickel and iron. To give you an idea of how hot it is, nickel becomes a liquid at 2,650 degrees F and iron melts at 2,800 degrees F! What temperature does ice melt at?

Slide 16 / 75 Earth's Inner Core

At the very center of Earth, you will find the Inner Core. Like the Outer Core, this layer is also extremely hot and is made of nickel and iron. Although the temperature is higher, the nickel and iron here are in solid form because of the intense pressure that this layer experiences.

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5 What separates the Inner and Outer Core? A The Inner Core is made of liquid; the Outer Core is solid. B The Outer Core is hotter than the Inner Core. C The Inner Core is solid; the Outer Core is liquid. D The Outer Core is under more pressure than the Inner Core.

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6 Which is the oldest layer of Earth? A crust B mantle C outer core D inner core

Slide 19 / 75 Size of Earth's Layers Slide 20 / 75

Three Types

• f Rocks

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Slide 21 / 75 Formation of Rocks

The layers of Earth are constantly moving and changing due to intense heat and pressure. The energy of this heat and pressure results in the formation of rocks. But what exactly is a rock ? With your table, come up with some characteristics

• f rocks.

Slide 22 / 75 Three Types of Rocks

How a rock forms depends on what type of rock it is. There are three types of rocks: Sedimentary Metamorphic Igneous Click on the rock type to see an example.

Slide 23 / 75 How Do Rocks Form?

The three types of rocks on the previous page each form in different ways. The animation on the next slide will introduce you to the process behind the transformation of rocks from

• ne type to another - a

process known as the rock cycle . Answer the questions on the accompanying worksheet while watching the animation.

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7 Which of the following is not a type of rock? A Metamorphic B Glacier C Igneous D Sedimentary

Slide 26 / 75 Sedimentary Rock

"Sediments" are small fragments of rock. To form Sedimentary rock, these fragments combine together. These rocks are typically multi-colored with many different textures.

Slide 27 / 75 Igneous Rock

"Igneous" has the same root word as "ignite." What does ignite mean? These rocks are typically dark, very shiny, and made up of crystals. Igneous rocks form when magma, which we can think of as "liquid fire," cools down.

Slide 28 / 75 Types of Igneous Rock

"Intrusive" igneous rock is still inside Earth. There are two types of igneous rock. "Extrusive" igneous rock has exited Earth.

Slide 29 / 75 Metamorphosis

A "Metamorphosis" is when something changes into something new. You have learned about a few organisms which undergo metamorphosis in your science classes over the years. At your table, talk for a few minutes about the 2 organisms below and the metamorphosis they undergo during their lives.

Slide 30 / 75 Metamorphic Rock

These rocks are typically made up of layers that formed as the rock was squashed under pressure. Just like the frog, metamorphic rock is formed when another one type

• f rock changes into a new type of rock.

Metamorphic rock forms when another type of rock changes its chemical makeup because

• f heat and pressure.

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8 Which type of rock is made up of pieces

• f other

rocks? A Metamorphic B Extrusive Igneous C Intrusive Igneous D Sedimentary

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9 Which type of rock is formed of magma below the surface of Earth? A Metamorphic B Extrusive Igneous C Intrusive Igneous D Sedimentary

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10 Which type of rock is formed when other rocks undergo a transformation due to heat or pressure? A Metamorphic B Extrusive Igneous C Intrusive Igneous D Sedimentary

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11 Which type of rock is formed from magma cooling on Earth's surface? A Metamorphic B Extrusive Igneous C Intrusive Igneous D Sedimentary

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12 This is an example of ________ rock. A Sedimentary B Igneous C Metamorphic

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13 This is an example of ________ rock. A Sedimentary B Igneous C Metamorphic

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14 This is an example of ________ rock. A Sedimentary B Igneous C Metamorphic

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15 This is an example of ________ rock. A Sedimentary B Igneous C Metamorphic

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Early Life on Earth / Fossils

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Slide 40 / 75 The Age of Earth

Scientists estimate that the Earth formed around 4.6 billion years ago. We can learn about the history of Earth by studying rocks and fossils.

Slide 41 / 75 First Life on Earth

There is evidence within the rocks on Earth that suggests that life first appeared on Earth about 3.6 billion years ago. The image above is of stromatolites , the oldest fossils on record. They provide us with evidence of very simple life forms like bacteria as long as 3.5 billion years ago.

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bacteria

Prokaryotes

The first cells that existed on Earth were closely related to

• prokaryotes. These are cells that do not have a nucleus.

Most prokaryotes are single-celled organisms. Why were the first

• rganisms on Earth

very simple? What is a more common name for prokaryotes? Move the image once you come up with an idea.

Slide 43 / 75 Prokaryotes

Very specific conditions were needed for these living organisms to form. Organic chemicals (chemicals that include carbon) as well as some sort of heat were needed to form these cells.

Slide 44 / 75 Photosynthetic Organisms

Food was scarce on the early Earth. Why do you think this was? What do most organisms that we know of today eat? Come up with a theory at your table.

Slide 45 / 75 Photosynthetic Organisms

Food was scarce on the early Earth because there were only a few

• rganisms to begin with! Some prokaryotes developed

the ability to create their own food by converting sunlight, carbon dioxide, and water into sugar and oxygen. The creation of oxygen through this process led the way for more complex organisms, like animals, to evolve.

Slide 46 / 75 How Do Scientists Reconstruct the Past?

Scientists can estimate what life was like billions of years ago thanks to the discovery of fossils. What is a fossil?

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Fossils are typically found in Sedimentary Rock

How Do Scientists Reconstruct the Past?

A fossil is the preserved remains of an organism which is found in rock formations. In what type of rock do you think fossils usually can be found ? Think about how rocks are formed. The answer is under the photo to the right

Slide 48 / 75 How Do Scientists Reconstruct the Past?

Photo : Thomas Bresson Fossilized Seaweed

The first fossils that hint at the existence of complex organisms are roughly 1.8 billion years old. The first algae appeared about 1.2 billion years ago.

Slide 49 / 75 How Do Scientists Reconstruct the Past?

How can scientists come up with the ages on the previous slide? It is difficult for scientists to figure out the age of the actual fossils, so instead they find the age of the sedimentary rock in which the fossil was found. The different colored layers in the picture above would help scientists estimate the age of fossils.

Slide 50 / 75 Activity - Fossil Layers

Most fossils can be found in layers of sedimentary rock. Some can also be found in metamorphic rock, but they would be distorted due to heat and pressure. In this activity, you will create your

• wn "sedimentary rock" full of fossils

and then examine the affect that pressure has on them.

Slide 51 / 75 Fossil Excavation

As was mentioned in the section on the Types of Rocks, the older rocks will be further down within Earth. Fossilized organisms will be about the same age as the layer of rock they are found in. It is the job of a paleontologist to excavate, or dig up, these fossils and determine their ages.

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16 Fossils are usually found in _________ rock. A metamorphic B sedimentary C igneous

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17 Old fossils will be found ______ Earth than younger fossils. A deeper down in B on the surface of C anywhere on

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18 Scientists use _________ to determine the age of fossils. A chemistry B microscopes C rock layers

Slide 55 / 75 Activity - Cookie Excavation

The work of a paleontologist is very delicate and difficult. It requires a lot of patience and care. In this activity, you will practice these skills on different types of cookies. Can you excavate the chocolate chips from the cookies using only your paleontology tools?

Slide 56 / 75 Vertebrate Fossil Webquest

Now that the "fossils" have been excavated, how do they get from the site to the museum? Use the site above to track a vertebrate fossil!

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Rock Strata

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Slide 58 / 75 How Do We Determine a Fossil's Age?

In our last section, we learned that we can tell a fossil's age based on the rock it is found in. This provides us with a general range for the age of the fossil. The deeper it is within Earth, the older the fossil is.

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19 What kind of rock is featured on the previous page? A Sedimentary B Metamorphic C Igneous

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20 Which type(s) of rocks can contain fossils? A Sedimentary B Metamorphic C Igneous

Slide 61 / 75 Life on Earth

One goal of geology (the study of rocks) is to develop a timeline

• f Earth's past...

...and we can use this information to make connections between the first simple life forms to the diversity on Earth today.

Slide 62 / 75 Absolute Age

Scientists use various techniques to determine the age of rocks. Sometimes, scientists are able to determine the absolute age , or the exact age, of a rock or fossil. The absolute age of the petrified wood above is 2,500 years old.

Slide 63 / 75 How Do Scientists Determine Absolute Age?

Scientists use a technique called radiometric dating to determine absolute age. Radiometric dating compares the ratio of a radioactive element with the amount that has decayed in the rock or fossil.

Slide 64 / 75 Half Life

When it comes to relative age, scientists analyze the amount of certain radioactive elements within the object. They then use the "half life" of the element to determine the object's age. The half life is the period of time it takes for half of the substance to decay.

Slide 65 / 75 Carbon Dating

A radioactive version of the element Carbon is known as Carbon 14 because it has an atomic mass of 14 (rather than the usual 12). What is atomic mass? Carbon 14 has a half life

• f about 5,700 years.

Carbon 14 is found in every living thing.

Slide 66 / 75 Carbon Dating

This means that if there are 100 atoms of Carbon 14 in the tree when it was alive, there will be only 50 left after it has been dead for 5,700 years. So after one half life, the amount

• f Carbon 14 is cut in half .

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21 After two half lives, how much Carbon 14 would be left from the tree on the previous slide? (hint: what was Carbon-14's half life?)

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22 After one half life, what percentage of Carbon 14 remains? ______%

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23 After two half lives, what percentage of Carbon 14 remains? ______%

Slide 70 / 75 Carbon 14

In organisms that were once living, the amount of Carbon 14 will be cut in half every 5,700 years. Scientists use this information to determine how long an organism has been dead ... and therefore find out roughly how old it is!

Slide 71 / 75 Webquest - The Radioactive Dating Game

In this activity, you will learn about different types of radiometric dating , such as carbon dating. You will understand how decay and half life work to enable this dating. You will finish it up with a game that tests your ability to match the percentage of the dating element that remains to the age of the object!

Slide 72 / 75 Relative Age

When scientists cannot be exact, they try to determine an object's relative age. This is when they compare the age of an object or event to another object or event. Scientists can estimate the age of this volcano by looking at rocks and fossils found around its base. Why would they use the base of the volcano and not the top?

Slide 73 / 75 Index Fossils

What is an index fossil ? Click on the dinosaur below to uncover the definition! An index fossil is used to determine the age range of a rock layer. It is the fossil of an organism that existed only for a limited period of time. Since scientists know that the stegosaurus lived between 150 and 155 million years ago, any rock layer containing a stegosaurus fossil will be around that age as well.

Slide 74 / 75 Layers of Rock

When new rock is formed on the surface of Earth, it settles on top of what was there before it. The deeper you dig into Earth's surface, the farther back in time you will see.

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24 In the diagram below, in what layer would the oldest rocks be found? A B C

Layer 1 Layer 2 Layer 3

Permission Granted: FL Museum of Natural History