chapter earth: its characteristics and phenomena · let’s take a closer look at the lithosphere....

CHAPTER

5W H AT I S E A R T H ?

Earth: its characteristics and phenomena

Earth occupies a unique position in the solar system. It is just the right distance from the Sun; its surface is neither too hot nor too cold to support life. Its average temperature is 14ºC allowing water to exist in its liquid state. Liquid water is essential for creating and sustaining life as we know it.

Our planet is a sphere with a diameter of 12 760 km. Its mass is 6 x 1024 kg (that’s 6 followed by 24 zeroes). That said, Earth is not a perfect sphere. Its rapid rotation means that it bulges slightly at the equator and is slightly flattened at the poles.

Earth takes approximately 365 days to orbit the Sun. It also completes a rotation on its axis once every 24 hours. It is situated 150 million kilometres from the Sun. It has a surface area of 510 million square kilometres.

Earth’s position in the solar system, as well as the way it moves through space, causes a number of events that determine the rhythm of our lives: the changing seasons, the cycle of day and night, eclipses, etc.

Earth is one of eight planets in the solar system. It holds a special position within the solar system that allows it to sustain life.

In this chapter, you will look at Earth’s composition.Then, you will learn about Earth’s spheres and how they interact with each other.Finally, you will look at different processes that occur in Earth’s spheres, thus, getting to know more about the water cycle, tectonic plates, the formation of mountains, volcanoes, earthquakes and erosion.

The Earth 150 and space

13846_ess_trad_ch5_148-197_ep3.indd 150 2016-11-23 11:50 AM

Earth’s internal structure and spheres

Earth’s internal structure is made up of three major parts: the core, the mantle and the crust.

The core is at the centre of Earth. It is the hottest part of the planet. It is made up of a solid portion (inner core) and a liquid portion (outer core). It is mainly made of iron and nickel.

Core

The mantle is sandwiched between the crust and the core. Near the crust, it is mostly solid rock. Underneath the crust, the rock is partially melted and has the consistency of a thick paste. Magma, which flows out of volcanoes as lava, comes from this section.

Mantle

The crust is the external part of Earth. It is made of solid rock. Continents (continental crust) and the bottom of the oceans (oceanic crust) are both part of it.

Crust

D E F I N I T I O N

Do you really know the planet you’re living on? What’s going on beneath its surface? Can we travel to Earth’s centre? Which areas of Earth are inhabitable?

What is the Earth’s internal structure? Earth’s interior is hot and uninhabitable. Just 10 km below the surface, the temperature is 300ºC; at the core, the temperature is several thousand degrees. As far as we know, very few organisms can survive temperatures hotter than 100ºC.

5.1

5.1.1

What would happen if you fell into a hole that went through Earth?

It is impossible to dig a hole through the entire planet. If the hole existed, someone who fell in would be stuck 6380 km deep, at the centre of the Earth. Gravity has no effect there. In addition, anyone who fell in would experience extreme heat (approximately 5000ºC) and enormous pressure (around 14.2 million times the pressure we feel on the crust).

Chapter 5 151 Earth: its characteristics and phenomena


The mantle is the largest part of Earth, making up 81% of its volume.

The crust accounts for less than 2% of Earth’s volume.The oceanic crust, which forms the bottom of the oceans, is thinner than the continental crust, which forms the continents.

At the centre of Earth is the core, which is made up of an inner and an outer core. This core is surrounded by the mantle and a thin, rocky crust. Earth’s temperature decreases as you travel from the core to the crust.

Magma from the mantle

Mantle (partially melted rocks; solid rock closer to the crust)

Inner core (solid)

Outer core (liquid)

Core (iron and nickel)

Crust (solid rock)

Oceanic crust (5 km to 15 km)

Continental crust (30 km to 65 km)

Part Percentage of Earth’s total volume

Core Approximately 17%

Mantle Approximately 81%

Crust Less than 2%

A look inside Earth Here’s what the inside of Earth looks like.

The inside of Earth has three distinct layers, all of which are composed of solid or liquid metal or rock.

3500 km

2800 km



The previous section on the living world looked at many elements of the biosphere. This chapter looks at the other three spheres.

What are Earth’s spheres? Living organisms inhabit the crust on Earth’s surface. They depend on the layer of air that surrounds the planet. The water that covers Earth is equally important. In other words, living organisms depend on all of “Earth’s spheres.” Living organisms themselves belong to a fourth sphere: the biosphere.

5.1.2

Earth’s spheres include the lithosphere (solid sphere), hydrosphere (water sphere), atmosphere (air sphere) and the biosphere (sphere that encompasses all living organisms).

D E F I N I T I O N

Earth’s four spheres The illustration below shows Earth’s four spheres.

The lithosphere is the layer of solid rock of Earth. It includes all of the elements of the relief: mountains plains, plateaus, volcanoes, etc.

The biosphere encompasses all life on Earth, in all its forms: plants, animals, bacteria, etc.

The hydrosphere is made up of all the water (oceans, lakes, rivers, etc.) that cover our planet. It covers the majority of Earth’s surface.

The atmosphere is the layer of gas that surrounds Earth. It contains the oxygen that we breathe and protects us from the Sun’s ultraviolet rays.

Earth’s four spheres interact with each other. For example, if heavy rains (from the atmosphere) cause rivers (from the hydrosphere) to overflow, this will cause flooding. These floods may end up destroying soil (from the lithosphere) and vegetation (from the biosphere).



A C T I V I T I E S 1. Indicate which part of Earth’s internal structure each statement is describing.

a) This layer is entirely solid. Crust.

b) Depending on the depth, this layer is made of solid or melted rocks. Mantle.

c) This section has the largest radius. Core.

d) The thickness of this layer changes from one area to the next. Crust.

e) This is the hottest layer. Core.

f) This layer is the largest. Mantle.

2. Complete this diagram of Earth’s internal structure.

Outer core.

Inner core.

Crust.

Mantle.

3. What is Earth’s core made of? Earth’s core is mainly made of iron and nickel.

4. What is magma? Answer the question by filling in the following text.

Magma is made of partially melted rocks .

It looks like a thick paste . It can be found in the

mantle . It comes out of volcanoes

as lava.



5. True or false? If a statement is false, correct it.

a) The mantle is made of magma and solid rock.True.

b) Earth’s core is completely solid.False. Earth’s inner core is made of solid matter, but the outer core is made

of liquid matter.

c) The solid inner core is colder than the liquid outer core. False. The temperature increases as you approach Earth’s centre. The solid

inner core is therefore hotter than the liquid outer core.

d) Lava and magma are both made of partially melted rock.True.

e) The continental crust is thinner than the oceanic crust.False. The oceanic crust is thinner than the continental crust.

6. Do you believe it would be possible to one day discover a lost civilization at Earth’s centre, like in Jules Verne’s or Roderick Gordon’s books? Explain your answer. No, it is too hot to allow life. In addition, living organisms need water and air

to survive and there isn’t enough of either that deep in Earth.

7. The Earth has four spheres.

a) Name each sphere, and describe it with one word.

b) Which sphere overlaps the three other spheres?The biosphere.

SPHERE WORD THAT DESCRIBES IT

Lithosphere. Rocks.

Atmosphere. Air.

Hydrosphere. Water.

Biosphere. Life.

Sample answer:



The crust is not the only part of the lithosphere. The upper part of Earth’s mantle is also included.

A diagram of the lithosphereThis image shows the first kilometres beneath Earth’s surface.

The lithosphere is Earth’s layer of solid rock. It is composed of Earth’s crust and the upper part of the mantle. It includes all of the elements of relief: mountains, plains, plateaus, volcanoes, etc.

D E F I N I T I O N

Lithosphere The word “lithosphere” comes from the Greek word lithos, which means “rock.” The lithosphere is a sphere of rock. This sphere is not the same everywhere. Volcanoes, earthquakes and other events shape it.

What is the lithosphere? Let’s take a closer look at the lithosphere.

5.2

5.2.1

Earth’s internal structure and spheres, p. 151

The lithosphere is made up of Earth’s crust and the upper part of the mantle. Both of these parts of Earth are made of solid rock.

The lithosphere is where earthquakes happen and rocks, mountains and volcanoes are formed.

The continental crust is thicker than the oceanic crust. The lithosphere’s thickness changes from place to place; it can be anywhere from 70 km to 150 km thick.

Lithosphere

Crust

Mantle



Humans have many different relationships with the lithosphere because it provides us with many of the materials that we need.

The lithosphere and human activity Human beings have a constant relationship with the lithosphere. Here are some of the activities that link humans to this sphere.

Humans extract minerals, like copper, and materials, like sand, from the lithosphere. For example, here is an iron mine.

Humans are transforming the lithosphere: for example, by burying our waste in the ground.

Many living organisms, including plants, live in the lithosphere. Plants draw the water and nutrients they need from the soil. Humans grow and harvest plants to feed themselves and their animals, to make clothing, and more.

Humans live on the lithosphere. We build roads and houses there. To do so, we use materials that come from the ground like stone, sand and oil.

Principles of GeologyBetween 1830 and 1833, Charles Lyell published three volumes on geology (the study of Earth’s crust). The main theme of these works was the idea that “the present is the key to the past.” In other words, today’s geological events can be explained by tiny changes over very long periods of time. Lyell’s works influenced Charles Darwin, who used them as inspiration for his theory of evolution.

Charles Lyell (1797–1875)

1 8 3 0 – 1 8 3 3 B R I T A I N



The relief is the shape of the lithosphere’s surface (peaks, valleys, plains, etc.).

Plateaus are vast stretches of flat land that are located at a certain altitude (at least 300 m) above the surrounding areas.

Shields form a very ancient relief which have the appearance of slighlty rounded plateaus. The Canadian Shield is an example.

Plateaus and shields

Plains generally have a low, flat relief. They sometimes come from ancient riverbeds or seabeds, where sand, gravel and rocks once accumulated. The Saint Lawrence Plain, in Québec, is an example of this.

Hills are low bulges in the relief. They can be found on plains. Mont Saint-Hilaire is a hill.

Plains and hills

Mountains are a very high type of relief, characterized by steep slopes. They are formed when Earth’s crust folds and juts out after two tectonic plates collide. When many mountains are grouped together over a long distance and occupy a large area, they are called a “mountain range.”

Valleys are long, low stretches of land. They are generally situated between two mountains and etched out by a body of water. Valleys are caused by erosion from water running off the mountains.

Mountains and valleys

D E F I N I T I O N

What is relief? As you might be able to tell from the relief in your area, the surface of the lithosphere is not even. Do you live in the Appalachians, on the Canadian Shield, or on the Saint Lawrence Plain?

5.2.2

Where do all of Québec’s lakes come from?

More than 15 000 years ago, most of Canada was covered in a layer of ice several kilometres thick. When this layer of ice melted and receded, the massive holes caused by the weight of the glaciers filled with water. The extra water ran off towards the oceans. The water that remained in the holes formed most of the lakes that you see north of the Saint Lawrence River.

Orogenesis, p. 182

Erosion, p. 192



The Saint Lawrence Plain extends along both sides of the Saint Lawrence River, from the south-west of Montréal to the city of Québec.It comes from the drying of the Champlain Sea. The sea covered almost the entire plain, from the Canadian Shield to the foot of the Appalachians. The plain has a few hills (called the “Montérégiennes”) like Mont Saint-Hilaire, which is shown in the photo.

Québec’s relief Here are the main types of relief found in Québec.

As you can see, Québec has a diverse relief.

The Appalachians cover a large part of the east of North America. In Québec, these mountains cover the following regions: Estrie, Centre-du-Québec, Chaudière-Appalaches, Bas-Saint-Laurent and Gaspésie.The Appalachians are ancient. Therefore, they are lower and flatter than newer mountain ranges like the Rockies, in British Columbia.

Saint Lawrence Plain

Appalachians

The Canadian Shield is a massive region that occupies the north-east of Canada and covers 90% of Québec.It’s a very old mountain range that has been flattened by erosion. It’s between one and four billion years old.Because it is a plateau, the Canadian Shield is slightly elevated compared to the surrounding areas.

Canadian Shield



Relief and human activity Humans need to learn to live with the many different types of relief on Earth. Swift-moving rivers to cross, steep slopes to climb, and soil that is hard to dig are all examples of obstacles that humans might face.

These examples show that humans have managed to adapt their activities to the relief quite well.

People don’t only farm on plains. They have also managed to grow rice on terraces, like here, in Vietnam.

Originally, skiing was used as a means of transportation on snowy peaks in winter. Other sports started in much the same way. For instance, kayaking and canoeing were used to cross stretches of water.

Most human activity happens on plains. Some 60% of all humans live there. The flat land makes driving and transportation easier. The soil is generally richer and better for farming.

The Millau Viaduct is an example of human ingenuity. It spans the Tarn Valley, in France, measuring 2460 m long and up to 270 m high.



A C T I V I T I E S 1. True or false? If a statement is false, correct it.

a) The upper part of the mantle, which is made of solid rock, is part of the lithosphere.True.

b) Humans use the lithosphere only for oil and minerals.False. Humans also use the lithosphere for other things.

It’s where we bury our waste, harvest the soil and build houses.

c) Relief describes all the shapes you can see on the surface of a mountain.False. Relief describes all the shapes you can see on the surface of

the entire lithosphere.

2. For each photo below, describe a link between human activity and the lithosphere. Sample answer:

Humans cultivate the land to feed

themselves and their animals.

Humans build roads and houses.

Humans eat the plants that they grow

or that they harvest.

a)

b)

c)



a) What makes New Zealand’s mountains different from its hills? Where can you find this type of relief?Mountains have a very high relief. They are located on South Island. Hills

are lower and can be found on North Island.

b) Why is most of New Zealand’s agriculture in Canterbury? Because the relief is flat, which makes it easier to cultivate than

in mountainous or hilly regions.

c) In New Zealand, receding glaciers did not form lakes. What did they form instead? The receding glaciers carved enormous valleys that are now submerged.

3. Read the text with the photo below, then answer the questions using your knowledge of relief. (New Zealand is a country south-east of Australia.)

Northland’s relief is relatively low. It has hills and large bays.

The country has many volcanoes. The largest of these can be found in Tongariro and Taranaki.

Fiordland was formed by ancient glaciers that carved enormous valleys, which are now submerged.

South Island is crossed by the Southern Alps mountain range.

The Marlborough Sounds are inlets that go deep into the earth.

Most of North Island is covered in verdant hills.

The Canterbury Plains are the country’s main agricultural centre.

The large mountain lakes are famous for their deep blue waters.

Tasman Sea

PACIFIC OCEAN

Relief of New Zealand

South IslandSouth Island

North IslandNorth Island



4. Geologically speaking, New Zealand is relatively young. It is approximately 80 million years old. Name the type of relief shown in each of the pictures taken in the country.

5. Name the human activity and the type of relief shown in each picture.

a) Agriculture on a plain. b) Climbing the rocky side of a plateau or a mountain.

c) Snowboarding on the side of a mountain.

d) River rafting in a valley.

a) Hill. b) Plain. c) Valley.



Hydrosphere If you look closely at a globe, you will see that the oceans and seas cover more than half of Earth’s surface. Actually, they cover 70% of the planet. This water is extremely important. It allowed life to form and is essential for life to continue.

What is the hydrosphere?Some people call Earth the “blue planet” because it looks blue to astronauts observing it from space. This colour comes from the water that covers so much of its surface.

5.3

5.3.1

Earth’s waters What percentage does each form of water in the hydrosphere take up?

D E F I N I T I O NThe hydrosphere encompasses all of the waters on Earth, no matter what state they’re in (liquid, solid or gaseous): oceans, lakes, rivers, groundwater, glaciers, ice floes, icebergs and even the water vapour in the atmosphere.

As the above diagram shows, the hydrosphere is almost entirely composed of salt water or freshwater that is not easily accessible. This means that freshwater is a rare and precious resource.

Distribution of Earth’s waters

The water that we drink is freshwater. Freshwater available on the surface accounts for only 0.02% of all water on Earth. Québec has 3% of the planet’s freshwater resources (lakes, rivers and groundwater).

Almost all of the water on Earth is salt water.Salt water 97.2%

Oceans and seas

Freshwater 2.8%

Glaciers and ice floes 2.15%Groundwater 0.63%Surface water 0.02%Water vapour 0.001%



Interactions between the hydrosphere and the atmosphere The hydrosphere and the atmosphere are in direct contact, since part of the hydrosphere is actually water vapour in the atmosphere. This interaction has three main roles.

Some interactions between the hydrosphere and the atmosphere are partly responsible for the water cycle: evaporation, condensation and precipitation.

Phase changes in water, p. 9

Water cycle, p. 172

Energy from the Sun’s rays.

Evaporation: water transforms

into gas (water vapour).

Condensation: water vapour transforms into

droplets of liquid water, creating clouds.

Every day, the oceans store a large amount of energy from the Sun’s rays.

This leads to the evaporation of some water from the ocean’s surface. The total amount of water that evaporates is mind-boggling: around 16 billion litres per second.

Once the water is in the air, it condenses and releases the energy it has accumulated, which increases the air temperature.

Role 1. This cycle of evaporation and condensation causes almost all of the meteorological events on Earth. For example, hurricanes gain their power over oceans and lose that power as they travel over continents.

Role 2. This cycle causes heat transfers between the oceans, the atmosphere and the continents. The heated air is transported by atmospheric circulation (wind).

Role 3. The water in the atmosphere helps protect living organisms from the Sun’s ultraviolet rays.



A C T I V I T I E S 1. Complete the diagram below.

2. Circle the situations that show interactions between the hydrosphere and the atmosphere.

A. Hot air from the ocean rises and is replaced by cooler air coming from the continents. This pushes sailboats out to sea.

B. In the Alps, skiers sometimes have trouble breathing because the air is thinner high on the mountain.

C. On fall mornings, valleys are sometimes covered in fog (condensed water vapour).

D. Vancouver is located near the Pacific Ocean. As a result, its winters are warmer than cities that are farther away from the ocean.

3. Vancouver’s proximity to the Rockies and the Pacific Ocean means that it has a very mild climate. However, it rains very often. Why do you think that is?

The Sun heats the ocean water, which facilitates water

evaporation. The water vapour cools in the atmosphere

and condenses into clouds. The clouds are kept over the city

by the Rocky Mountains.

0 0.5 1 1.5 2 2.5

2.15

0.63

0.02

0.001

Type

s of

fre

shw

ater

Percentage of all water

Groundwater.

Surface water.

Water vapour.

Glaciers and ice floes.

Distribution of freshwater on Earth



Atmosphere

The atmosphere is the envelope of air that surrounds Earth. It is invisible because air, which is a mixture of gases, is transparent.

• The troposphere is the layer of the atmosphere that is closest to Earth.

• It is approximately 10 km thick.

• The air is thickest in this layer. It accounts for up to 75% of the atmosphere’s mass.

Troposphere

• The stratosphere is the layer of the atmosphere that sits directly on top of the troposphere. It starts approximately 10 km above sea level.

• The ozone layer is in the stratosphere.

Stratosphere

• The mesosphere is the layer of the atmosphere that starts approximately 50 km above sea level. It sits on top of the stratosphere.

Mesosphere

• The thermosphere is the layer of the atmosphere that is the farthest away from Earth.

• It starts approximately 80 km above sea level and extends right to the limit where outer space begins, some 500 km above the ground.

Thermosphere

D E F I N I T I O N

The atmosphere is invisible. You can’t see it, even though it stretches almost 500 km over our heads!

What is the atmosphere? Do you know what the atmosphere is made of? Here is a description of the atmosphere and its layers.

5.4

5.4.1

Why do airplanes leave white trails in the sky?

Jet planes are the only planes that leave white trails in the sky. As jet engines burn fuel, they produce water vapour. When this vapour comes into contact with the cold, dry air of the troposphere, it condenses into fine drops of water, exactly like clouds. That’s why these trails are called “contrails” (condensation trails).



The layers of the atmosphere Here are some characteristics of each layer of the atmosphere.

Each layer of the atmosphere has a different temperature and air composition. That’s why different phenomena happen in each one.

The air is thickest in the troposphere. This is where most of the water in the air is found. This also explains why most meteorological events such as rain, snow, clouds, storms and rainbows happen in this layer.As you go higher into the troposphere, the temperature decreases. The temperature drops by approximately 10ºC per kilometre. Planes often fly at the top of the troposphere. The air is less dense there, so planes encounter less air resistance. As a result, they burn less fuel.

Thermosphere

Altitude above

sea level

Troposphere

Stratosphere

Mesosphere

Polar aurora

Shooting star

130 km

120 km

110 km

100 km

90 km

80 km

70 km

60 km

50 km

40 km

30 km

20 km

10 km

Sea level

In the mesosphere, the temperature can drop to -80ºC. When objects coming from space (rocks, dust, etc.) penetrate this layer, they disintegrate, creating “shooting stars” or “meteors.”

As you go higher into the stratosphere, the temperature increases. The ozone layer is in the stratosphere. It absorbs 90% of the Sun’s UV rays, which are harmful to living organisms.

Polar auroras are produced in the thermosphere. Many satellites also orbit the thermosphere.

The thermosphere extends out to the limits of space, some 500 km above the Earth. At this altitude, air particles are very rare. The Sun’s rays make these particles extremely hot.



What is air made of? When we breathe in, we absorb oxygen. When we breathe out, we expel carbon dioxide. That tells us that these two gases are present in air. Are there other gases in the atmosphere?

Humans benefit from the atmosphere in many ways: we use it to breathe and perform many different tasks.

The air in the atmosphere contains many gases. It is thicker in the troposphere than it is in the other layers of the atmosphere.

The atmosphere and human activity Humans have a strong relationship with the atmosphere, mainly because it provides us with the oxygen we need to breathe. Here are some of the other activities that link humans to this sphere.

Air is mainly made up of two gases: nitrogen (78%) and oxygen (21%). Other gases (carbon dioxide, argon, water vapour, etc.) make up only 1% of the air.

Around 75% of the air’s mass is located within 10 km of the ground. As you rise through the atmosphere, the air becomes thinner and thinner.

78%

21%

0.03%

0.97%

Nitrogen

Oxygen

Other gases

Carbon dioxide

Composition of pure air

Humans use the atmosphere to travel quickly in planes or helicopters.

Humans can transform energy from the wind into electricity using wind turbines.

The air in the atmosphere is essential to life: living organisms use it to breathe and plants use it to produce food.

Many hobbies (like parachuting, hang-gliding, hot-air ballooning and even kite flying) take place in the atmosphere.



A C T I V I T I E S 1. Fill in the following table.

2. What am I?

a) I am the most common gas in the atmosphere. Nitrogen.

b) I am a gas that is essential for life. I make up 21% of the atmosphere. Oxygen.

c) I am a machine that produces electricity using atmospheric circulation (wind). A wind turbine.

3. While attempting to reach the top of Mount Everest (altitude: 8.8 km), many climbers wear an oxygen mask to help them breathe. Why do you think they need to do that?As you go higher in altitude through the atmosphere, the air becomes thinner.

That means there are fewer oxygen particles available to breathe. Oxygen

masks allow climbers to compensate for the lack of oxygen.

LAYER OF THE ATMOSPHERE ALTITUDE TEMPERATURE CHARACTERISTICS

Troposphere 0 km to 10 km.

Decreases with altitude.

• 75% of the air’s mass.

• Most meteorological events happen here.

Stratosphere 10 km to 50 km.

Increases with altitude. • Location of the ozone layer.

Mesosphere50 km to 80 km.

Decreases with altitude (down to -80°C).

• Objects from space disintegrate

here.

Thermosphere 80 km to 500 km.

The few existing

particles have a very

high temperature.

• Polar auroras happen here.

• Many satellites orbit here.



Breathing

Flying

Mining

Mountain climbing

Parachuting

Scuba diving

Skiing

Swimming

4. Underline the activities that take place in the atmosphere.


a) Planes fly in the mesosphere.False. Planes fly at the top of the troposphere.

b) Living organisms inhabit the troposphere.True.

c) Most clouds are found within 10 km of the atmosphere.True.

d) You could jump from the stratosphere in a parachute without needing an oxygen mask.False. There is not enough oxygen in the stratosphere to breathe normally.

That means you’d need an oxygen mask.

6. Name the layer of the atmosphere described in each statement.

a) This layer accounts for 75% of the atmosphere’s mass. Troposphere.

b) The ozone layer is here. Stratosphere.

c) Many satellites orbit in this layer. Thermosphere.

d) Most meteorological events happen in this layer. Troposphere.

e) Polar auroras happen in this layer. Thermosphere.

f) It’s the coldest layer of the atmosphere. Mesosphere.

g) You can see meteors in this layer. Mesosphere.

h) Planes often fly at the top of this layer to save fuel. Troposphere.

i) This is the hottest layer. Thermosphere.



The water cycle is the natural cycling of water through its different states (solid, liquid and gaseous). In this cycle, the water moves between the hydrosphere, the atmosphere, the lithosphere and the biosphere.

Seven phenomena occur to water during the water cycle:

• evaporation;

• condensation;

• precipitation;

• transpiration;

• runoff;

• infiltration;

• groundwater flow.

D E F I N I T I O N

Water cycle Water appeared on Earth several billion years ago. Since then, the amount of water on Earth has essentially stayed the same. The water that we swim in is the same water that the first fish swam in. We’re drinking the same water that dinosaurs drank! How does water move through the Earth’s spheres?

What is the water cycle? Here, you are going to learn what is in the water cycle. The illustration on the opposite page gives you a closer look.

5.5

5.5.1

The seven phenomena of the water cycle Evaporation, condensation and precipitation can occur repeatedly over the ocean. The water evaporates, condenses into clouds over the ocean then falls as rain into the ocean.

Phase changes in water, p. 9

Hydrosphere, p. 164

Evaporation. Evaporation happens when the water, which has received energy from the Sun, transforms into water vapour and rises into the atmosphere. Most water loss from evaporation happens in the oceans, but lakes and rivers lose water this way too.

Condensation. Condensation happens when the water vapour in the atmosphere cools and becomes liquid or solid and forms clouds. This doesn’t just happen in the atmosphere; it also happens above the ground, where it is called “mist” or “fog.”

Precipitation. Clouds are made up of tiny droplets of water. When these droplets become too heavy, they fall. This is called “precipitation.” Some precipitation is in a liquid state (rain, mist), while other precipitation is in a solid state (snow, hail).

What are Earth’s spheres?, p. 153



When the water returns to the ocean through streams, lakes and rivers, the cycle begins again.

Transpiration. Transpiration is a form of evaporation in living organisms. Humans and animals generally don’t produce much water vapour when they transpirate or exhale. However, plants emit a lot of water vapour when they transpirate (think of the damp air in a forest).

Runoff. Water from precipitation often follows the slope of the land. When it stays on the surface of the ground without soaking in, it’s called “runoff.” Water runs down mountains until it meets a body of water. Runoff water accumulates in streams, lakes and rivers. Sooner or later, most of this water will reach the ocean.

Infiltration. Infiltration is what happens when water from precipitation penetrates into the ground. When the ground is porous (has small holes), the water can infiltrate. Infiltration is the reason plants can draw water from the soil.

Groundwater flow. Groundwater flow is the movement of water through the ground. The water that soaks into the ground moves around, sometimes very slowly, before running into a body of water.

Evaporation

Condensation

Condensation

Runoff

Infiltration

Groundwater flow

Ocean water

Precipitation (rain)

Precipitation (rain)

Precipitation (snow)

Transpiration

Evaporation



A C T I V I T I E S 1. Name the stages of the water cycle best associated with each of the following states.

a) Gaseous state.Evaporation, transpiration.

b) Liquid state.Condensation, precipitation, infiltration, runoff, groundwater flow.

c) Solid state.Precipitation, condensation.

2. Link each event (on the left) to its stage of the water cycle (on the right).

• Transpiration

• Evaporation

• Condensation

• Precipitation

• Infiltration

• Runoff

• Groundwater flow

a) The water vapour in the atmosphere changes states, forming a cloud.

•

b) The water turns into a gas and rises into the atmosphere. •

c) The clouds, which are made of droplets of water and tiny ice crystals, become too heavy and release water in liquid (rain, mist) or solid (snow, hail) form.

•

d) Humans, animals and plants release water vapour.

•

e) Water penetrates into the ground. •

f) Water moves through the soil. •

g) Water moves on the surface, without soaking in. It follows the slope of the land.

•



3. Complete the diagram by naming the stage of the water cycle indicated by each box.

4. Which stage of the water cycle is each of these statements describing?

a) The Saint Lawrence River runs from the Great Lakes to the Atlantic Ocean. Runoff.

b) You can see the first snowflakes in October. Precipitation.

c) Living organisms release water to maintain their body temperature. Transpiration.

d) The low temperature at the top of the troposphere makes it easy for clouds to form. Condensation.

e) At the cottage, you need to dig a well to get drinking water. Groundwater flow.

f) At the end of the summer, there is less water in the river than there was in the spring. Evaporation.

g) When you water the garden, the water disappears into the soil. Infiltration.

Precipitation.

Infiltration.

Groundwater flow.Runoff.

Transpiration.

Evaporation.

Condensation.



A tectonic plate is one of the massive pieces of the lithosphere (solid rock) that floats on the partially melted rocks of the mantle. Tectonic plates form the continents and the bottom of the oceans.

A tectonic plate can be entirely oceanic, like the Pacific Plate. It can also be mixed (partly oceanic, partly continental), like the South American Plate.

D E F I N I T I O N

Tectonic plates “Tectonic plates?” At first glance, this expression is complicated, but it refers to a fascinating field of study! The movement of tectonic plates is linked to some very impressive phenomena, like volcanoes, earthquakes and even the formation of mountains.

What is a tectonic plate?Read the following definition, then look at the map to get a better idea of what tectonic plates are.

5.6

5.6.1

The main tectonic plates The map below shows the outlines of the Earth’s main tectonic plates.

Tectonic plates cover Earth’s entire surface. These massive pieces of the lithosphere float on the partially melted rocks of the mantle.

Lithosphere, p. 156

The plates fit together like puzzle pieces.

Oceanic plates are the plates that form the bottom of the oceans.

Most of the plates are mixed: they are partly continental and partly oceanic.

North American

Pacific

NazcaSouth

American

Antarctic

African

Eurasian

North American

Pacific

Indo-Australian



The movement of tectonic plates is caused by the intense heat of Earth’s interior. This heat creates movement in the partially melted rock of the mantle. In turn, this causes the tectonic plates to move very slowly (a few centimetres per year, at most) against each other.

As they move, the plates can:

• collide with each other;

• move apart from each other;

• rub against each other.

D E F I N I T I O N

How do the tectonic plates move? The immense pieces of lithosphere move against each other.

5.6.2

Collision of tectonic plates As the tectonic plates move in different directions, sometimes they get too close to each other and collide.

The collision between two tectonic plates can form mountains and volcanoes and can cause earthquakes.

Often, faults form and earthquakes happen along the edges of the tectonic plates (see section 5.9).

The oceanic crust is thinner and denser than the continental crust. When an oceanic plate collides with a continental plate, the oceanic plate dives in the mantle, where part of it melts. That process is called “subduction.” Subduction can also happen when two oceanic plates collide.

In a subduction zone, the rocks of the sinking plate melt and turn into magma. This magma can sometimes rise to the surface and form volcanoes (see section 5.8).

The collision between two tectonic plates may cause a mountain range to form (see section 5.7).

Rising magma

Subduction zone

Plate movementContinental crust

Oceanic crust

Lithosphere

VolcanoesPlate

movement



Separation of tectonic plates Since all of Earth’s tectonic plates fit together like a puzzle, it stands to reason that if two plates can collide, they can also move apart. Does that mean there are giant openings in Earth?

Earth’s oceanic crust is formed by the separation of tectonic plates. This separation sometimes causes underwater earthquakes.

Rubbing of tectonic platesYou know that tectonic plates can collide and move apart, but did you know that they can also rub against each other?

Tectonic plates mainly move apart at the bottom of the oceans. This movement often causes underwater earthquakes.

Where the two plates moved apart, magma rises slowly and solidifies. It creates long underwater mountain ranges, called “mid-oceanic ridges.”

New oceanic crust forms in the mid-oceanic ridges. As a result, the oceans are expanding little by little.

The enormous amount of energy released when tectonic plates slide past each other causes earthquakes (see section 5.9).

Mid-oceanic ridge

Lithosphere

Plate movement

Lithosphere

Plate movementRising magma

Plate movement

Oceanic crust

Oceanic crust



CONTINENTAL DRIFT

At the beginning of the 20th century, scientists made some rather intriguing observations. They noted that, on a map of the world, the coasts of South America and Africa seemed to fit together almost perfectly. These observations led a German scientist, Alfred Wegener, to develop a theory called “the origin of continents” around 1915. This theory, which has evolved over the years, best explains the shape of Earth’s relief. Alfred Wegener built the foundations of what we now call “plate tectonics.”

According to Wegener’s theory, some parts of the continents were joined a very long time ago. Millions of years ago, the continents formed one “supercontinent” called “Pangea” (see illustration A). This supercontinent separated into two continents called “Eurasia” and “Gondwana” (see illustration B). Later on, Eurasia and Gondwana each split apart (see illustration C) and moved to form the shapes we know today. The continents are still drifting by a few centimetres per year.

CURRENT MOVEMENT OF TECTONIC PLATESThe black arrows on the map below show the direction in which each of the tectonic plates is currently moving.

North American

Pacific

NazcaSouth

American

Antarctic

African

Eurasian

North American

Pacific

Indo-Australian

220 million years ago 180 million years ago 65 million years ago

A B C

PangeaGondwana

Eurasia North America

South America

Africa

Asia

India

Europe

Atlantic Ocean



A C T I V I T I E S 1. Which of these events is/are causing the movement of tectonic plates? Circle the right answer(s).

A. The intense heat inside the Earth.

B. The solidity of the upper mantle.

C. The movement of the melted rocks in the mantle.

D. Fractures in the lithosphere.

2. Link each country (on the left) to the tectonic plate on which it’s found (on the right).

a) Australia (Oceania) • • African Plate

b) United States (North America) • • Eurasian Plate

c) Madagascar (Africa) • • Pacific Plate

d) Chile (South America) • • Indo-Australian Plate

e) China (Asia) • • North American Plate

f) Hawaii (Oceania) • • South American Plate

3. What is a subduction zone?A subduction zone forms when two tectonic plates collide. Subduction happens

when one of the two plates dives underneath the other and submerges in the

mantle, where part of it melts.

4. Name the motion (collision, separation, rubbing) that causes the following phenomena.

a) Earthquakes. Collision, rubbing and separation.

b) Formation of a mid-oceanic ridge. Separation.

c) Formation of a mountain range. Collision.

d) Formation of volcanoes. Collision.



5. Complete the diagram by writing the letters in the correct boxes.


a) Collisions between two tectonic plates can form mountains and volcanoes and can cause earthquakes.True.

b) When two plates rub against each other, one of the crusts dives into the mantle, where it ends up melting.False. This happens with collision, not rubbing.

c) Mid-oceanic ridges are mountain ranges created by the collision between two oceanic plates.False. Mid-oceanic ridges come from the separation of two oceanic plates.

d) The separation of tectonic plates creates mid-oceanic ridges.True.

e) Earthquakes happen only along the edges of subduction zones.False. Earthquakes can also happen when tectonic plates separate or rub

together.

A. Collision

B. Continental crust

C. Oceanic crust

D. Mid-oceanic ridge

E. Separation

F. Formation of mountains

G. Magma

H. Volcano

I. Subduction zone

IGB

AF D E C H



Mountains can be formed from folds in Earth’s crust after two tectonic plates collide.

When tectonic plates collide, it can cause folds in Earth’s crust. These folds form mountain ranges, like the Rockies and the Himalayas. This process is very slow: it can take millions of years.

In this example, the air mattresses represent tectonic plates and the pool water represents Earth’s mantle. The motion of the water makes the mattresses move. If two mattresses collide, they can end up folding. Mountains are created in much the same way.

Orogenesis is a series of processes that lead to the formation of mountains. Generally, a mountain range comes from the collision of two tectonic plates.

D E F I N I T I O N

Orogenesis Why does the lithosphere’s thickness vary from place to place? How and why do mountains form in Earth’s crust?

What is orogenesis?The word “orogenesis” comes from two Greek words: oros, meaning “mountain” and genesis, meaning “formation.” Therefore, “orogenesis” means “the formation of a mountain.”

5.7

5.7.1

Folding The lithosphere’s tectonic plates are moving slowly. When two plates collide, they often form mountains. We’ll look at this phenomenon using air mattresses as an example.

What is relief?, p. 158

Tectonic plates, p. 176

Lithosphere

Formation of mountains

FoldsPlate movement



Like folding, these types of mountains are also formed because of the movement of tectonic plates.

Some mountains are the result of magma rising from the mantle and forming volcanoes. Once the magma hits the air, it cools and turns into rock. Over time, this cooled and hardened magma accumulates and forms a mountain.

Other mountains are formed when Earth’s crust fractures and part of it becomes raised. The fractures, which are caused by immense pressure from the movement of tectonic plates, are called “faults.”

Other ways mountains are formed While many mountain ranges are the result of tectonic plates colliding, there are other ways mountains can form over time.

What is the highest mountain in Québec?

Québec’s highest mountain is Mont D’Iberville. It is part of the Torngat Mountains, a range located on the border between Québec and Labrador. The mountain’s name comes from Pierre Le Moyne d’Iberville, a Canadian explorer who founded Louisiana. Mont D’Iberville is 1652 m high. In comparison, Mont Royal (which is actually a hill in Montréal) is only 234 m at its peak.



1. Explain orogenesis in your own words.Orogenesis is a series of processes that lead to the formation of mountains.

Generally, a mountain range comes from the collision of two tectonic plates.

2. Name three ways that mountains can be formed.

• Collision between two tectonic plates.

• Volcanic eruption.

• Raised rock caused by a fault.

3. Why do you think this rock has so many folds?

This rock is probably folded because of a collision

between tectonic plates.

4. Mountains look like they’re unchanging. However, we know that they took millions of years to form. Why is this process so slow?Mountains form because of the movement of tectonic plates. These plates

move very slowly, so mountains also form slowly.

5. Explain faults in your own words.A fault is a break in Earth’s crust that is caused by pressure from the

movement of tectonic plates.

A C T I V I T I E S



Volcanoes

A volcano is an opening in Earth’s crust, through which magma from the mantle rises to the surface. The accumulation of lava and ash expelled by the volcano often form a mountain, which can erupt again.

D E F I N I T I O N

A volcano rumbles, gas escapes and lava runs down its sides. This incredible show is caused by events inside Earth.

What is a volcano? To define a volcano, it is necessary to describe how it is formed. Do you think a volcano can form anywhere in the world?

5.8

5.8.1

Where can you find volcanoes? There are approximately 1500 active volcanoes on Earth’s surface, not counting those that are found underwater. The red dots on this map show where the world’s main volcanoes are.


Most volcanoes form in the Ring of Fire, where several subduction zones are located. Others form over hot spots.

Pacific OceanPhilippines

Ring of Fire

HawaiiJapan

New Zealand

Most volcanoes are on the edges of the Pacific Ocean, in an area called the “Ring of Fire.” The Ring of Fire is located along the edges of several tectonic plates, where many subduction zones exist.

Some volcanoes form in the middle of tectonic plates, over areas called “hot spots.” The Hawaiian Islands were formed this way. In hot spots, Earth’s crust is very thin. It is therefore easier for magma to rise to the surface and cause volcanoes to erupt.

Many of the volcanoes on land form in subduction zones (see page 177).

Volcanoes



Volcanic eruptions happen when magma rises to Earth’s surface. Lava, ash and gas are expelled through the volcano’s vents.

Volcanic eruptions Let’s take a look at the inside of a volcano and what happens during an eruption.

Magma chamber

Secondary vent

Lava exiting the crater

Cone

Main vent

Magma accumulates in a reservoir underneath the volcano, called the “magma chamber.” Inside the chamber, gases combine and create an explosive mixture. Gradually, pressure increases inside the magma chamber.

1

Most of the magma escapes through the main vent. However, some volcanoes also have secondary vents.

3

When magma reaches open air, it flows from the crater as lava.4

Some volcanic eruptions can be very violent. They shoot hundreds of tons of lava, ash and gas high into the air.Other eruptions are less violent: lava simply flows slowly down the sides of the volcano.

5 A volcano’s cone comes from cooled lava and hardened ash accumulating over the years.

7 Once the lava (molten rock) hits the air, it cools slowly and turns into solid rock.

6

When the pressure becomes too great, the top of the vent explodes. We call that “eruption.” Gas and magma are forced to the surface.

2



THE STRENGTH OF VOLCANIC ERUPTIONSAn eruption’s strength depends on the type of volcano and thickness of the lava. Sometimes, lava cools and hardens while in the air. It turns into rocks that can be thrown hundreds of kilometres by the explosion. Other times, the volcano has so much lava that it runs down the sides, triggering mudslides as it goes. The lava can cool on the way down or run over significant distances. If that happens, it can destroy everything in its path, cutting roads in half and swallowing houses whole.

TYPES OF VOLCANOESThere are many different types of volcanoes. The two main types are shield volcanoes and stratovolcanoes. The thickness of the lava after eruption is one of the factors that determine the type of volcano.

• Shield volcanoes, as their name suggests, look like shields. The lava from these volcanoes is relatively thin, so it flows easily. Shield volcanoes are large and have gentle slopes. Their peaks are often very wide. Eruptions from shield volcanoes are generally less violent and explosive than those from stratovolcanoes.

• Stratovolcanoes are the type of volcanoes that we usually imagine: high mountains with steep slopes and sharp peaks. The magma from these volcanoes is much thicker than magma from shield volcanoes. It therefore flows more slowly. Because the magma is so thick, stratovolcano eruptions are often more violent.

ACTIVE OR EXTINCT?Some volcanoes are considered active which means they can still erupt at almost any time. Other volcanoes are considered extinct. They haven’t erupted or shown any sign of activity for a very long time.

East Maui Volcano, Hawaii

Arenal Volcano, Costa Rica



1. a) Where are most of the world’s volcanoes found? Answer the question by filling in the following text.

Most of the world’s volcanoes are found on the edges of the

Pacific Ocean. This area is called the Ring of Fire .

Most volcanoes form when two tectonic

plates collide and form a subduction zone.

One of the two plates dives under the other. The

magma rises through the crust and

reaches the surface.

b) Name four countries where most of the world’s volcanoes are found.Sample answers: Japan, United States, the Philippines, New Zealand, Chile,

Canada, Russia, Indonesia, Mexico, etc.


a) Most of the world’s volcanoes are in Africa.False. Most of the world’s volcanoes are located around the edges of the

Pacific Ocean.

b) A volcano’s cone comes from cooled lava and hardened ash accumulating over the years.True.

c) Volcanoes are only created in subduction zones.False. Volcanoes can also be created in hot spots.

d) Some volcanoes form in the middle of tectonic plates.True.

3. The photo on the left is of Sakurajima, a volcano in Japan. Kagoshima, a nearby village, has a population of 700 000. Sakurajima is considered to be one of the most dangerous volcanoes in the world. Why do you think that is?

The volcano is located in an area where lots of people live.

A C T I V I T I E S



4. Complete the diagram by writing the letters in the correct boxes.

5. Some volcanic eruptions are very violent. Others are less so. Which volcanoes do you think have more violent eruptions: those that erupt often or those that erupt rarely? Explain your answer.Volcanoes that erupt rarely are more likely to have violent explosions. In these

volcanoes, pressure can build in the magma chamber over several years.

That means that the volcano has a lot of pressure stored when it erupts.

6. What is the difference between lava and magma?Magma is partially melted rock that is found in the mantle and in the magma

chamber of volcanoes. Lava is magma that has risen to the surface and

reached open air.

7. Which factor causes volcanoes to erupt? Circle the right answer.

A. Magma accumulates in the magma chamber.

B. A spark in the magma chamber makes the gases explode.

C. Pressure from gases in the magma chamber builds until the top of the vent blows off.

D. The heat of the magma melts the top of the vent.

A. Magma chamber

B. Main vent

C. Secondary vent

D. Lava

E. Cone

F. Cloud of ash and gas

A

C

D

F

E

B



An earthquake, or seism, is a shaking movement of the ground caused by a volcanic eruption, by the sudden movement of rocks along a fault or by other similar events.

D E F I N I T I O N

“Fault,” “focus” and “epicentre” are the key words to remember when you’re describing an earthquake.

Earthquakes Have you ever experienced an earthquake? They sometimes happen in Québec. It feels like the world is shaking, sort of like a big truck is passing by. These earthquakes are generally brief and don’t cause much damage. However, that’s not always the case elsewhere in the world.

What is an earthquake?Why does the ground tremble sometimes? What happens in Earth’s depths to cause that kind of shaking?

5.9

5.9.1


The birth of an earthquake The following photo and illustration show how the movement of rocks along a fault can cause an earthquake.

Most of the time, an earthquake comes from movement inside Earth. The starting point of the earthquake is called the “focus.” The area on the surface directly above the focus is called the “epicentre.”

4

The movement of the rocks releases energy, which causes vibrations. These vibrations spread in all directions, up to Earth’s surface. These “quakes” can last anywhere from a few seconds to a few minutes.

3

When masses of rock slide down a crack, the crack grows wider and becomes a “fault.” Rocks can move anywhere from a few centimetres to a few metres at a time. When they slide past each other, they can get stuck or change shape. This causes a massive shock that releases a huge amount of energy.

2

Earth’s crust can crack along the edge of two tectonic plates, or even in the middle of a plate. These cracks can be several kilometres deep.

1

Fault

Epicentre

Focus (origin of the earthquake)San Andreas Fault, in California



1. a) Which movement of tectonic plates is most likely to cause earthquakes?The rubbing of rocks along a fault; for example, along the edges of two

tectonic plates.

b) What is the link between this motion and an earthquake? When the plates rub against each other, the rocks collide, releasing energy

in the form of vibrations.

2. Underline the event that is not associated with earthquakes.


a) Earthquakes always happen on the edges of tectonic plates.False. They can also happen along faults in the middle of a plate.

b) Earthquakes are only felt near the epicentre.False. Earthquakes are often felt hundreds of kilometres away from the

epicentre.

c) Earthquakes are caused by the sudden movement of tectonic plates.True.

d) An earthquake can last for several hours.False. Earthquakes last several seconds or a few minutes.

A C T I V I T I E S

Energy

Epicentre

Fault

Fissure

Hydrosphere

Lithosphere

Quake

Rubbing

Sliding

Volcano



The Laurentides are very ancient, very eroded mountains. Today, they are part of the Canadian Shield.

Erosion is the wearing away and transformation of soil and rock by glaciers, running water and weather (rain, wind, freezing and thawing).

D E F I N I T I O N

ErosionA sandcastle on a beach can easily be destroyed by the rising tide. The ebb and flow of the waves pulls at the grains of sand in the castle, until the whole structure disappears. It’s a perfect example of erosion.

What is erosion?Earth’s crust is constantly being shaped by different forces that cause erosion.

5.10

5.10.1

What is relief?, p. 158

Part of the Canadian Shield is actually what remains of a huge mountain range called the “Laurentides.” One billion years ago, the Laurentides were almost as tall as the Himalayas.

Over time, rain, running water and wind have crumbled rock and significantly eroded the Laurentides. A major ice age also contributed to the erosion; the slow movement of several kilometre-thick glaciers did much to wear away the rock.

Erosion of the LaurentidesHere is an example of erosion that has shaped much of Québec’s landscape.

Currently, the Himalayas’ highest peak (Everest) is 8848 m high, while the Laurentides’ highest peak (Mont Raoul-Blanchard) is 1181 m high.

Laurentides Himalayas



Water and freezing and thawing continue to shape the rocks. These agents of erosion shape relief and landscapes.

Other examples of erosion Here are three other examples that illustrate erosion.

How are caves formed?

On the coasts, waves crumble rocks by repeatedly smashing against them. Farther inland, running water is a more common erosive force. It gradually dissolves and carries away the minerals in rock, sometimes bringing these into an underground river. Either way, water is responsible for carving out the formations and hollow spaces inside caves.

Niagara Falls, which sits across the United States-Canada border and extends into Ontario, is receding by approximately 30 cm per year. This occurs because the fast moving water is eroding the rocks below.

The Mingan Archipelago, in Québec’s Côte-Nord, is made of ancient rocks. They were sculpted by the sea’s waves, which eroded softer rock and left harder rock behind. Other eroding forces, like wind and freezing and thawing, continue to wear away at the rocks.

The Vermillion Cliffs, in Arizona, in the United States, were sculpted by wind and water.



A C T I V I T I E S 1. The four main erosive forces are wind, water, movement of glaciers and freezing and thawing. Indicate the main erosive force for each of the following descriptions.

a) In Gaspé, Percé Rock, in the Gulf of Saint Lawrence, has a large hole in the middle. Water.

b) In the spring, the sidewalk often has cracks in it. Freezing and thawing.

c) The Colorado River runs along the bottom of the Grand Canyon. Water.

d) The Rhône Valley, in France, appeared after an ice age. Movement of glaciers.

e) The Sphinx, in Egypt, is showing signs of erosion. Wind.

2. The soil on Mars shows traces of erosion. Name two factors that might explain this erosion.

Sample answer: There may have been water on Mars.

Winds may have eroded the planet’s surface. Glaciers

may have shaped Mars’ relief. Freezing and thawing

may have eroded the rock.

3. The mountain on the left is older than the mountain on the right. How can you tell?

The mountain on the left has been very worn by wind

and water: its peak is low and rounded. The peak on

the right is very pointed. The wind has not had as

much time to damage it. Furthermore, it has very little

vegetation and is covered in snow. That means it’s

probably very high.



Chapter 5 Review1. The lithosphere, atmosphere and

hydrosphere are strongly linked. Name three phenomena examined in this chapter that affect at least two of these spheres.

• Erosion.

• The water cycle.

• Volcanoes.

2. Name, in order, the seven layers of Earth that you would find if you tried to dig a hole from Québec to Australia.

Crust, mantle, outer core, inner core, outer core, mantle, crust.

3. Name the type of relief described in each of these locations.

a) Chungara Lake, in Bolivia, is located on a flat stretch of land at an altitude of 4517 m. A plateau.

b) New Zealand’s coast is shaped by folds in Earth’s crust. Mountains.

c) Seville, in Spain, is in the middle of a large, flat stretch of land on either side of the Guadalquivir River. A plain.

d) The Amazon rainforest grows on an ancient, slightly elevated rocky formation. A shield.

4. Put the stages of a volcanic eruption in order.

A. Magma rises.

B. Magma turns into lava.

C. Magma accumulates.

D. Lava solidifies.

E. Ash, gas, rocks and lava are thrown into the air.

F. The volcano’s cone forms through the accumulation of layers of lava.

C, A, B, E, D, F.



5. The following table compares two mountain ranges.

Which event can happen in the Rockies, but not in the Pyrenees? Explain your answer. A volcanic eruption. The Rockies are located in a subduction zone. The oceanic

plate can slide under the continental plate and melt, producing magma. The

magma can then rise to the surface and cause a volcanic eruption.

6. What is a mid-oceanic ridge?A mid-oceanic ridge is a long underwater mountain range that forms when two

oceanic plates separate from each other.

7. Ocean water is salty, even though most of the water that feeds into it is fresh. Fill in the text using the words in the list to explain why.

During runoff and infiltration , the water

erodes the rocks in the lithosphere , changing

the relief . The water dissolves

the minerals in the rocks and becomes saltier. During

evaporation , only the water vapour leaves the

ocean, while the salt stays in the sea.

CHARACTERISTIC ROCKIES PYRENEES

Location Western North America Southeastern Europe

Plates causing the formation• North American Plate (continental)

• Pacific Plate (oceanic)

• Eurasian Plate (continental)

• African Plate (continental)

Plate movement Collision with subduction zone Collision without subduction zone

Dissolves

Erodes

Evaporation

Infiltration

Lithosphere

Relief

Rocks

Runoff

Water vapour



8. Name the main agent of erosion that shaped each of these landscapes.

9. In some mines, miners need to cause explosions before they can explore and collect the minerals in the lithosphere. Not too long ago, one of these explosions in a city in Québec released a large amount of nitrogen dioxide, a toxic gas. This gas reacted with water to form nitric acid. The city’s inhabitants were worried about the repercussions of the explosion.

a) What effect do you think this explosion could have on the environment?The toxic gas could build up in the atmosphere and change the air’s

composition.

b) The lowest layer of the atmosphere might be affected. What is this layer called?The troposphere.

c) Which stage of the water cycle could the nitrogen dioxide affect?Condensation.

d) Define “lithosphere,” naming the parts of the Earth that it is made up of. The lithosphere is the solid rock layer of Earth. It is composed of Earth’s

crust and the upper part of the mantle.

e) The type of explosion described in the text can lead to a man-made type of natural disaster. Which one?Earthquakes.

a) Water. b) Water. c) Glaciers.



chapter earth: its characteristics and phenomena · let’s take a closer look at the lithosphere....

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