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4th Grade PSI The History of Planet Earth
Slide 2 / 107 The History of Planet Earth
· The Structure of Earth
Click on the topic to go to that section
· Rock Layers · Fossils and Relative Time · Rock Formations and Earth Forces · Earth's Visible Features · Patterns of Earth's Features · Tectonic Plates
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SLIDE 2 The Structure of Earth
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Slide 4 / 107 The Structure of Earth
When you look at the world around you, have you ever asked How did the Earth get to be the way it is today?
Slide 5 / 107 The Structure of Earth
The things that we see today on the surface of the Earth exist for many reasons, and they can teach us many things. The structures we can see on the surface and things underneath the surface tell us about the Earth's history.
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SLIDE 3 The Structure of Earth
Working with your table, come up with a list of structures on Earth that you think might tell some of the story of Earth's past.
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The things we see on the surface of Earth today have gotten to be that way over many, many years. The surface of Earth - what we see with our eyes - is the
- utermost layer of Earth and is called the crust.
Even though the crust is the outer layer, there are still parts of the crust that are too deep for us to see.
crust
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Earth has other layers underneath the crust. These are called the mantle and the core.
mantle core
But when we talk about the history of Earth, it is the crust - the outer layer - that can tell us the most. Why do we rely on the crust to tell us the story and not the mantle or the core?
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SLIDE 4
The Structure of Earth
Most of the crust is made up of rock. Much of this rock is sedimentary rock. Sedimentary rocks are one of the main reasons why the crust tells us so much about Earth's history.
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1 Can the things we see on Earth's surface can tell us about Earth's history? Yes No
Answer
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2 Is it possible Earth's surface has gotten to be the way it is within the past 50 years? Yes No
Answer
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SLIDE 5
3 The outer layer of Earth is called the: A skin B mantle C crust D core
Answer
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4 We can see all of Earth's crust with our eyes. Yes No
Answer
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5 Which layer of Earth tells us the most about Earth's history? A the core B the mantle C the outside D the crust
Answer
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SLIDE 6 Rock Layers
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Slide 16 / 107 Rock Layers
Sedimentary rock, which makes up much of Earth's crust, is made from sediment. Sediment is broken down pieces of rock and other solid material that settles to the bottom of a liquid. sediment Sediment is often dirt and rock particles that settle at the bottom
- f bodies of water, but it also
refers to any solid material that settles at the bottom of a liquid, such as these particles in this glass of water.
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Sedimentary rock is formed over many years. Where on Earth might we see evidence of layering? How could that have happened? Can you brainstorm any ways sedimentary rock could come to be? Remember our definition of sediment.
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SLIDE 7 Rock Layers
So here's how it happens: Sediments are deposited (usually by water). Sediments build up in layers - a process called sedimentation. Sediments are compacted as the weight of the sediments on top squash the sediments at the bottom. Sediments are cemented by crystals of salt that are left after the water has been squeezed out of the rocks.
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deposition sedimentation compaction cementation deposition sedimentation compaction cementation
txstate.edu
Rock Layers Slide 20 / 107 Rock Layers
Sedimentary rocks provide a history of the evolution of Earth, especially within the past billion years. When sediments are deposited and compacted to form sedimentary rock, sediments are accumulated in beds one on top of another - in layers. This means that when cut deep into the crust, below the surface we can see with our eyes, we find layers of different rocks that have formed over a long period of time.
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SLIDE 8 Rock Layers
Which layer of rock in this diagram do you think is the youngest? Which is the oldest? Label the top and bottom layers and then move the boxes to reveal the answers.
move for answer move for answer
This is called the Law of Superposition.
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Geologists study ancient sedimentary rocks to determine what environment they formed in. Determining ancient environments is very important to understand the history of Earth. It helps geologists understand how Earth's surface has changed over time. One way to study this is to compare the sedimentary structures in ancient rocks with sedimentary structures in modern environments.
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6 The most important characteristic of a sediment is: A that it settles to the bottom of a liquid B that it floats in liquid C its color D that it is small
Answer
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SLIDE 9
7 Order the following steps from first to last in the process of sedimentary rock formation (enter all 4 letters on your responder in the correct order): A compaction B deposition C cementation D sedimentation
Answer
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8 Sedimentary rocks form in layers. Yes No
Answer
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9 The Law of Superposition says: A rock layers that are closer to the surface are old B old and new rocks are found in the same place C rock layers get older as you go further down D rock layers that are deep down are the most recent
Answer
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SLIDE 10 10 Geologists study ancient rocks to learn about: A people B environments C sediments D cementation
Answer
Slide 28 / 107 LAB: Rock Layers
In this lab, we will look more at how sedimentary rocks form, focusing on the questions: How are different sediments deposited differently? How do sedimentary rocks form?
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Fossils and Relative Time
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SLIDE 11 Fossils and Relative Time
Sedimentary rocks not only contain sediments such as dirt, sand, and pebbles, but also fossils - preserved remains of plants or animals. Fossils come in many forms. They can be bones, tracks, plants, or bodies of animals, among other things.
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Rocks of the same age contain the same, or very similar, fossils. So, for example, very recently formed rocks may have a lot of these fossils, and in rocks from an even older time period, there may be lots of these fossils, but none of the types found in the more recent rock. while in rocks from an older time period there may be none of those fossils, but many of these fossils,
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So if fossils of this organism are found in these three places, then the rocks they were found in are all the same age.
Fossils and Relative Time
When the same kind of fossils are found in rocks in different places - for example, fossils of an organism that no longer exists - we know that the rocks are the same age. How?
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SLIDE 12 Fossils and Relative Time
This means that the age of a rock can be determined by the fossils that are found in it. A rock can also be compared to other rocks by the fossils the rocks contain. The types of fossils in the rocks being compared will show which rock is older than the other.
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very long time ago long time ago recent
When we compare fossils, we can form a general timeline of
- rganisms that existed throughout history!
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The kinds of fossils found in rocks from different time periods change because animals and plants change through time. These patterns of fossils exist globally. But in certain places, fossils are also found in different rock layers because the environment of that particular place changed throughout history.
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SLIDE 13 Fossils and Relative Time
For example, imagine that a long time ago there was a lake, and many fish and shell fossils were left in that rock. Many years later, something happened in that area and the rocks from that later time had many plant fossils, but no fish or shell fossils. What do you think scientists would be able to tell happened in that place based on what they learned from the fossils? Come up with an idea in your group you can share with the rest of the class.
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Fossils can tell us many things about the the history of:
- r the entire planet.
- ne place,
- ne region,
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11 Fossils are: (choose all that apply) A found in sedimemtary rocks B living organisms C able to help determine how old rocks are D preserved remains of plants and animals
Answer
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SLIDE 14 12 Is it possible to tell if one rock is older or younger than another rock by looking at their fossils? Yes No
Answer
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13 Rocks of the same age contain very different fossils. Yes No
Answer
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14 Why do rocks from different time periods have different kinds of fossils? (discuss as a class, do not answer with responders)
Students type their answers here
Answer
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SLIDE 15 ACTIVITY: Sediment Fossil Surprise
In this activity we will explore how fossils are deposited in rock layers. We will make our own models to better understand how fossils work and what they tell us. We will focus on the question: How are fossils deposited in sediment layers?
Slide 43 / 107 ACTIVITY: Relative Age with Edible Rocks
In this activity we will closely examine the inside of edible rocks to learn about their "sediments" relative age based on patterns of their deposition. We will focus on the question: How is relative age dating used when observing rock layers?
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Rock Formations and Earth Forces
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SLIDE 16 Rock Formations and Earth Forces
Sometimes rock layers are disturbed by different Earth forces. This means that the pattern we typically see in rocks - of older rocks being farther underground and newer rocks being closer to the surface - can sometimes be mixed up, with rock layers existing in different
- formations. What do you think might cause this?
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Earth forces can disturb the Law of Superposition. Some Earth forces include earthquakes, rivers, and erosion.
Slide 47 / 107 Rock Formations and Earth Forces
EARTHQUAKES Patterns in rock formations can show where earthquakes - shaking caused by the movement of rock under Earth's surface - occurred and layers are no longer aligned.
fault line
Rock layers impacted by an earthquake will often show distinct change at the fault line where the earthquake occurred.
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SLIDE 17 Rock Formations and Earth Forces
RIVERS Rivers are strong forces that can impact rocks. Often times rivers will cut through rocks, leaving rock layers exposed. Rivers may also deposit new sediment in the middle of old rock layers.
Slide 49 / 107 Rock Formations and Earth Forces
EROSION Different forces such as rain, wind, flowing water, and living animals can make rocks erode, or wear down. This erosion wears down rocks and creates new patterns in rock layers.
eroded rock layers
Slide 50 / 107 Rock Formations and Earth Forces
Often the cause of Earth forces that disrupt rock patterns is plate tectonics, the movement of plates that make up Earth's crust.
crust
Remember, we said the crust is not a solid layer on the outside
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SLIDE 18 Rock Formations and Earth Forces
geology.er.usgs.gov
You can see the plates here with a map of the continents underneath. These plates move slowly and interact at their boundaries. It is broken into sections called plates.
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Tectonic plates fit closely together along their boundaries.
mantle
The plates are many miles thick. They bump and rub agains each other, while pulling apart, and pushing together. The plates float on top of Earth's mantle which is made up of liquid rock.
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So in a cross-section under Earth's surface, the layers of rock that make up the crust are floating on top of the thick mantle of liquid rock.
Earth's surface mantle crust Earth's surface mantle crust
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SLIDE 19
Rock Formations and Earth Forces
Earthquakes are one example of Earth forces caused by tectonic plate movement. Earthquakes occur when the plates interact - typically when they are pushing together or sliding past each other - and, as we saw, they disturb rock layers. Earthquakes often leave visible marks on Earth's surface, but especially leave visible marks on rock layers.
Slide 55 / 107 Rock Formations and Earth Forces
Tectonic plates can also cause rock layers to bend and fold.
Slide 56 / 107 Rock Formations and Earth Forces
When Earth forces disturb typical rock formations, it can be trickier to understand what has happened in Earth's history. But using fossils and other clues can help scientists understand rocks and their ages even in these cases when the layers are mixed up and not in straight lines.
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SLIDE 20 Rock Formations and Earth Forces
recent
youngest very old
For instance, if these fossils were found in these layers, we could figure out which layers were oldest and youngest even though the layers are diagonal.
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15 If Earth forces have impacted rocks in an area, will younger rocks still always be located on top of
Yes No
Answer
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16 Earth forces can cause rock layers to: (choose all that apply) A disappear B fold up C unalign D swap
Answer
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SLIDE 21 17 What may have happened to these rocks? (discuss as a group, not a responder question)
Students type their answers here
Answer
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18 The crust is a solid layer on the outside of Earth. Yes No
Answer
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19 The crust is broken into pieces called: A continents B regions C plates D shells
Answer
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SLIDE 22 20 Tectonic plates: (choose all the apply) A never move B interact at their boundaries C can cause earthquakes D are very thin
Answer
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Tectonic Plates
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Slide 65 / 107 Tectonic Plates
The crust is divided into two types: oceanic and continental.
geology.er.usgs.gov
If you look closely at this map of tectonic plates, you can see that parts of the plates are covered with water and parts are covered with land.
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SLIDE 23 Tectonic Plates
OCEANIC CRUST Where do you think oceanic crust is found? It is made of dense rocks such as basalt. This means that
Oceanic crust is about 4 miles thick.
mantle
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CONTINENTAL CRUST Where do you think continental crust is found? It is made of less dense rocks such as granite. This means continental crust is light. Its thickness varies between 6 to 47 miles. Continental crust is almost always much older than oceanic crust.
continental crust mantle
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There are three types of tectonic plate boundaries: convergent, divergent, and transform.
geografas.eu
If you look closely at this map of tectonic plate movement, you can see arrows showing that different plates move in different directions relative to each
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SLIDE 24
Tectonic Plates
CONVERGENT BOUNDARIES At convergent boundaries, plates collide with one another. At convergent boundaries, continental crust is created and oceanic crust is destroyed as it subducts, melts, and becomes magma. The collision causes the edge of one or both plates to buckle, or causes one plate to move underneath the other, a process known as subduction.
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DIVERGENT BOUNDARIES At divergent boundaries, plates separate. At divergent boundaries, oceanic crust is created. Here, geysers spurt super-heated water, and magma, or molten rock, rises from the mantle and solidifies to form new crust.
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TRANSFORM BOUNDARIES At transform boundaries, plates slide past one another. Here, earthquakes tend to occur when plates move and rub against one another. New crust is neither created or destroyed at transform boundaries.
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SLIDE 25 Tectonic Plates
USGS.gov
Here is a diagram of the three types of plate boundaries.
(The lithosphere and asthenosphere are parts of the mantle. The asthenophere is made of molten rock.)
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Can you find the 3 different types of plate boundaries on this diagram?
geografas.eu
Slide 74 / 107 Tectonic Plates
On this diagram each type of boundary is shown in a different color.
Did you correctly identify some of these boundaries in the last diagram?
http://johomaps.com/world/worldtecton.html
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SLIDE 26 21 The two types of crust are ______________ and ______________ . (not a responder question)
Students type their answers here
Answer
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22 Oceanic crust is heavier than continental crust. True False
Answer
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23 When tectonic pates move apart, it is called a: A divergent boundary B transform boundary C convergent boundary D subducting boundary
Answer
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SLIDE 27 24 This shows a _____________ boundary. A divergent boundary B transform boundary C convergent boundary D subducting boundary
Answer
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Earth's Visible Features
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Slide 80 / 107 Earth's Visible Features
Some rock layers indicate Earth forces that happened a long time ago, but there are also many features on Earth's surface that are visible signs of Earth forces today. This is because tectonic plates are still moving. These visible features include mountain ranges, ocean trenches, mid-ocean ridges, rift valleys, and volcanoes, all existing due to the movement of tectonic plates.
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SLIDE 28 Earth's Visible Features
MOUNTAIN RANGES Where plates collide or push together, mountain ranges form. You can see that as the plates push together, the top layer of rock crunches up to form mountains. Sometimes one plate moves under the other plate - subducts - and the other plate pushes upwards. Sometimes both top layers are pushed upwards.
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quake.eas.gatech.edu
Earth's Visible Features
MOUNTAIN RANGES When a oceanic and continental plate converge, the oceanic plate subducts and the continental crust crunches up, forming a mountain range. Where two continental plates converge, they are likely to bothbuckle, or crunch up, forming a mountain range.
Slide 83 / 107 Earth's Visible Features
MOUNTAIN RANGES The Himalayas, shown here, are an example of this.
shanahan2.pbworks.com
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SLIDE 29 trench
Earth's Visible Features
OCEAN TRENCHES Where oceanic plates converge and one plate subducts underneath the other,
- cean trenches are formed.
Trenches mark the position at which the flexed, subducting crust begins to descend under the crust it is colliding with. Oceanic trenches typically extend 1.9 to 2.5 miles below the level of the surrounding
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magma
Earth's Visible Features
MID-OCEAN RIDGES Where oceanic plates diverge, mid-ocean ridges are formed. Hot magma from Earth’s mantle bubbles to the surface where plates diverge. This magma is then cooled by seawater and forms new crust. The newest oceanic crust is located near the center of the ridge. Over time, new oceanic crust pushes older crust farther away.
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RIFT VALLEYS Where continental plates diverge, rift valleys are formed. Rift valleys are often narrow, with steep sides and a flat floor. Rift valleys can lead to the creation of entirely new continents, or deepen valleys in existing ones.
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SLIDE 30 Earth's Visible Features
VOLCANOES Where tectonic plates push together, volcanoes - mountains that erupt with lava - often form. Where plates collide, pressure is built up in Earth. Magma - a mixture of gases and hot molten rock - builds up in the mantle and pushes up into rock layers. The magma opens cracks in weak spots in rocks, and eventually pushes all the way to the surface.
Slide 88 / 107 Earth's Visible Features
VOLCANOES When the magma erupts on Earth's surface, it is called lava. The place it erupts is the volcano.
lava magma volcano
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25 Mountain ranges form where tectonic plates diverge. Yes No
Answer
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SLIDE 31
26 Subduction is when: A two plates buckle up when they collide B a colliding plate goes under another C continental crust moves under oceanic crust D two plates diverge
Answer
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27 Mid-ocean ridges form where: A oceanic and continental crust converge B oceanic crust converges with oceanic crust C continental or oceanic plates diverge D oceanic crust diverges
Answer
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28 Which of the following are true of volcanoes: (choose all that apply) A they form where plates converge B they do not need magma to form C they erupt with lava D pressure in the earth helps to cause them
Answer
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SLIDE 32 ACTIVITY: Where Plates Meet
In this activity we will explore tectonic plate boundaries across the
- globe. We will focus on the question: What do we find on Earth’s
surface at tectonic plate boundaries?
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Patterns of Earth's Features
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Slide 95 / 107 Patterns of Earth's Features
The features we see on Earth, both visible and underground, occur in
- patterns. Think about what causes earthquakes and volcanoes.
geology.er.usgs.gov
Where do you think earthquakes and volcanoes are most likely to occur?
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SLIDE 33 Patterns of Earth's Features
Here is a map of earthquake locations over a 15 year period.
black = earthquakes close to the surface (0 - 70km) green = earthquakes a bit farther down (70 - 300km) red = earthquakes farther down in the crust (300 - 700km)
What do you notice?
http://oceanworld.tamu.edu
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If you place the map next to a map of the tectonic plates, you can see that earthquakes are most likely to occur along plate boundaries.
http://oceanworld.tamu.edu
geology.er.usgs.gov
This is because earthquakes are caused by plates interacting at their boundaries.
Slide 98 / 107 Patterns of Earth's Features
We know that volcanoes occur where plates are converging.
geografas.eu
From looking at this map, can you guess where volcanoes are located?
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SLIDE 34 Patterns of Earth's Features
Here is a map of volcano locations around the world. Are any of the volcanoes where you guessed they would be?
http://www.globalchange.umich.edu
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Similar to earthquakes, volcanoes are also found along plate boundaries. More specifically, volcanoes exist where plates converge.
http://www.globalchange.umich.edu geografas.eu
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Many volcanoes are found around the edges of the 5 main plates in the Pacific Ocean. This area is known as The Ring of Fire. Why is it called this?
http://www.globalchange.umich.edu
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SLIDE 35 Patterns of Earth's Features
A map of tectonic plates and their movements can help us predict and know many things about Earth's features.
geografas.eu
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29 Earthquakes occur in completely random locations that could never be predicted. True False
Answer
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30 Earthquakes are likely to occur: A anywhere B in random places C where plates diverge D around plate boundaries
Answer
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SLIDE 36 31 What is The Ring of Fire? (not a responder question)
Students type their answers here
Answer
Slide 106 / 107 ACTIVITY: Finding Plates by Mapping Quakes
In this activity we will map earthquakes across the globe and compare their locations to the location of plate boundaries. We will think more about the question: What can the location of earthquakes help us understand?
http://oceanworld.tamu.edu
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