Unit E Lesson E2 Earthquakes and Landslides
Completion requirements
Lesson E2: Earthquakes and Landslides
Video Lesson
Earthquakes and landslides are two of nature’s most powerful events. They remind us that the planet is in constant motion and that the face of our world is always changing. Watch the following video and make notes about how, when, and where earthquakes
and landslides occur.
Lesson E2: Earthquakes and Landslides
When the Earth Moves Under Your Feet
Building solid structures can be very challenging in many parts of the world. Rigid materials like wood, iron, and concrete can be expensive, and little attention may be given to safety standards. Unfortunately, some of these locations are found in places where the ground is not stable.
Earth’s crust is not solid. It is made up of many different materials, and pieces of it are constantly in motion. Quick, destructive movements of the ground include earthquakes and landslides. Major damage can occur if a structure is unlucky enough to be near an earthquake or landslide.
Building solid structures can be very challenging in many parts of the world. Rigid materials like wood, iron, and concrete can be expensive, and little attention may be given to safety standards. Unfortunately, some of these locations are found in places where the ground is not stable.
Earth’s crust is not solid. It is made up of many different materials, and pieces of it are constantly in motion. Quick, destructive movements of the ground include earthquakes and landslides. Major damage can occur if a structure is unlucky enough to be near an earthquake or landslide.
Reading and Materials for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 357–359
Materials:
cardboard, scissors, white glue, masking tape, ruler, some hardcover books
Figure E.1.2.1 – Buildings destroyed by an earthquake in Sichuan, China.
Figure E.1.2.2 – Earthquakes and landslides can make travel difficult.
Haida Gwaii – Beautiful Scenery and Powerful Earthquakes
The Haida Gwaii archipelago is a beautiful series of islands along the British Columbia coast. Of the 4500 people living on these islands, about half are of the Haida First Nation. The islands are famous for their beautiful scenery, the amazing artistic talents of the people living there, and earthquakes. Three of the top five strongest earthquakes ever recorded in Canada have occurred in, on, and under these islands.
The Haida Gwaii archipelago is a beautiful series of islands along the British Columbia coast. Of the 4500 people living on these islands, about half are of the Haida First Nation. The islands are famous for their beautiful scenery, the amazing artistic talents of the people living there, and earthquakes. Three of the top five strongest earthquakes ever recorded in Canada have occurred in, on, and under these islands.
Figure E.1.2.4 – Aerial view of the Haida Gwaii (formerly called Queen Charlotte Islands).
Figure E.1.2.5 – "The Spirit of the Haida Gwaii," by Canadian artist Bill Reid.
The west coast of the Haida Gwaii islands are directly above where three large sections of Earth’s crust meet. These sections are referred to as tectonic plates, and they look like pieces of a gigantic puzzle when shown on a geologic map. The plates rest
on the fluid lower mantle far below and move about two to five centimetres per year. That means these plates move about as fast as your fingernails grow. However, because they are so massive, a small amount of movement carries a huge amount of force.
Where two (or more) of these plates bump into each other is called a fault. Thus, a fault is a place where two very large masses of rock are moving in different directions past each other. Many faults are only two plates moving past each other. Under the Haida Gwaii, at least three plates grind against each other, and they meet in several places. By examining the maps in Figures E.1.2.7 and E.1.2.8, you can see throughout the world most earthquakes occur where tectonic plates meet. You can visit the Seismic Monitor web page to see the most recent earthquakes recorded worldwide. As you can see, most of Canada’s earthquakes occur along the coast of British Columbia.
Where two (or more) of these plates bump into each other is called a fault. Thus, a fault is a place where two very large masses of rock are moving in different directions past each other. Many faults are only two plates moving past each other. Under the Haida Gwaii, at least three plates grind against each other, and they meet in several places. By examining the maps in Figures E.1.2.7 and E.1.2.8, you can see throughout the world most earthquakes occur where tectonic plates meet. You can visit the Seismic Monitor web page to see the most recent earthquakes recorded worldwide. As you can see, most of Canada’s earthquakes occur along the coast of British Columbia.
What Causes Earthquakes?
As the sections of Earth’s crust move past each other, they can move without any problem. However, rocks are rough, so pieces of the plates become snagged on each other. The remainder of the plate keeps trying to move, and pressure builds. The pressure can become so great that the rock around the plate bends or swells. Eventually, the snag lets go and the plates lurch suddenly and violently. This is an earthquake.
The place where the plates first let go and lurch forward is called the focus (also known as a hypocentre). Usually, the focus is far underground. (Remember that the plates usually are many kilometres thick). So much energy is stored in the snag that waves of energy spread out from the focus and travel through the surrounding Earth. These waves are called seismic waves. Directly above the focus, on Earth’s surface, is an imaginary point called the epicentre.
As the sections of Earth’s crust move past each other, they can move without any problem. However, rocks are rough, so pieces of the plates become snagged on each other. The remainder of the plate keeps trying to move, and pressure builds. The pressure can become so great that the rock around the plate bends or swells. Eventually, the snag lets go and the plates lurch suddenly and violently. This is an earthquake.
The place where the plates first let go and lurch forward is called the focus (also known as a hypocentre). Usually, the focus is far underground. (Remember that the plates usually are many kilometres thick). So much energy is stored in the snag that waves of energy spread out from the focus and travel through the surrounding Earth. These waves are called seismic waves. Directly above the focus, on Earth’s surface, is an imaginary point called the epicentre.
Figure E.1.2.7 – The plates that make up Earth’s crust.
Figure E.1.2.8 – Every earthquake between 1963 and 1998.
About 90% of earthquakes occur near faults between tectonic plates. Where do the other 10% happen?
Earthquakes can occur in places such as Rocky Mountain House, Fox Creek, and southwestern Ontario for various reasons. Rocky Mountain House is near the Rocky Mountains, which means it is affected from some slight movements in the crust left from when the mountains formed originally. Fox Creek has many oil and gas wells that have been hydraulically fracked, which geologists suspect weakens the surrounding rocks in the crust. In southern Ontario, the weight of the glaciers during the last Ice Age compressed the crust so much that it is still rebounding into shape today - and you thought you lived on “solid Earth”!
The following animation clearly shows how movement of sections of the Earth's crust can result in earthquakes.
Watch the following video to learn how fracking can cause earthquakes.
Watch More
Powerful Haida Gwaii Earthquake
The 2012 Haida Gwaii earthquake’s epicentre was nearly 20 km below Earth’s surface. It measured 7.8 on the moment magnitude scale, which is the second most powerful earthquake ever measured in Canada. It was felt as far away as Kamloops. In the ten days following the earthquake, 94 aftershocks were recorded.
In these videos, hear some reactions from the locals on Haida Gwaii to the earthquake, including their concern about a delay in the tsunami warning from the B.C. government. The second video is probably something you have never heard – the sound of an earthquake underwater! This is an audio recording of the 2013 Haida Gwaii tremor made under the surface of the ocean, including some local humpback whales.
The 2012 Haida Gwaii earthquake’s epicentre was nearly 20 km below Earth’s surface. It measured 7.8 on the moment magnitude scale, which is the second most powerful earthquake ever measured in Canada. It was felt as far away as Kamloops. In the ten days following the earthquake, 94 aftershocks were recorded.
In these videos, hear some reactions from the locals on Haida Gwaii to the earthquake, including their concern about a delay in the tsunami warning from the B.C. government. The second video is probably something you have never heard – the sound of an earthquake underwater! This is an audio recording of the 2013 Haida Gwaii tremor made under the surface of the ocean, including some local humpback whales.
What are the effects of Earthquakes?
When an earthquake occurs, tremendous energy is released suddenly at the focus. This energy travels through the surrounding Earth similar to the ripples on a pond but in all directions. Several types of seismic waves are produced by this energy release. Geologists can measure these waves very accurately. This allows them to determine the location of the focus of the earthquake and to learn more about the structure of Earth.
When an earthquake occurs, tremendous energy is released suddenly at the focus. This energy travels through the surrounding Earth similar to the ripples on a pond but in all directions. Several types of seismic waves are produced by this energy release. Geologists can measure these waves very accurately. This allows them to determine the location of the focus of the earthquake and to learn more about the structure of Earth.
Try It!
Making Waves
Several types of waves? How is that possible? Many ways of modelling the types of earthquake waves are possible, but two of the best are with a slinky and with your body.
Materials:
Several types of waves? How is that possible? Many ways of modelling the types of earthquake waves are possible, but two of the best are with a slinky and with your body.
Materials:
-
Slinky or long rope
Instructions:
-
Watch the following video, then use a slinky or yourself to model each of the three types of earthquake waves.
Earthquake Waves
Two types of seismic waves (called body waves) do very little damage as they pass through the inside of Earth. The other two types of seismic waves (called surface waves) can do large amounts of damage to the area near the epicentre of the earthquake. These damaging surface waves move along the top of Earth’s crust similar to waves moving along the surface of a body of water. Ground materials do not ripple nicely the way water does. Rocks, trees, and the structures that we build are solid and rigid, and a wave carrying the energy from an earthquake causes them to sway, crack, or collapse. When designing structures to withstand earthquakes, engineers must consider all these seismic waves. Ironically, one of the best methods engineers have discovered to minimize damage is to allow structures to sway with the seismic waves. A structure that is designed to sway without breaking can withstand far more wave energy than a rigid, unmoving structure. Flexibility is better than rigidity!
Scientists try to learn from every earthquake. For this reason, instruments record many measurements every time Earth trembles. The magnitude, or strength, of every earthquake is recorded along with the location of the focus and any other data that might help scientists to understand better when the next earthquake will occur or how they can prepare better for future earthquakes.
Earthquakes have other dangerous effects. If the earthquake fault is under the ocean and the earthquake causes the plates to move up or down, a tsunami can occur. Think about how you can make waves in a swimming pool just by moving your hands up and down under the water’s surface. When the bottom of the ocean drops or rises several metres suddenly, huge amounts of water get ‘sloshed around’ to form gigantic waves. When these waves reach land, they can have devastating effects.
The magnitude 7.8 Haida Gwaii earthquake of 2012 was a back-and-forth earthquake. The plates of crust slipped past each other sideways, not up-and-down. This means the waves were much smaller than they might have been. The 1964 Great Alaska Earthquake, magnitude 9.2, was an up-and-down megathust earthquake that obliterated Earth's surface and produced huge tsunamis.
Two types of seismic waves (called body waves) do very little damage as they pass through the inside of Earth. The other two types of seismic waves (called surface waves) can do large amounts of damage to the area near the epicentre of the earthquake. These damaging surface waves move along the top of Earth’s crust similar to waves moving along the surface of a body of water. Ground materials do not ripple nicely the way water does. Rocks, trees, and the structures that we build are solid and rigid, and a wave carrying the energy from an earthquake causes them to sway, crack, or collapse. When designing structures to withstand earthquakes, engineers must consider all these seismic waves. Ironically, one of the best methods engineers have discovered to minimize damage is to allow structures to sway with the seismic waves. A structure that is designed to sway without breaking can withstand far more wave energy than a rigid, unmoving structure. Flexibility is better than rigidity!
Scientists try to learn from every earthquake. For this reason, instruments record many measurements every time Earth trembles. The magnitude, or strength, of every earthquake is recorded along with the location of the focus and any other data that might help scientists to understand better when the next earthquake will occur or how they can prepare better for future earthquakes.
Earthquakes have other dangerous effects. If the earthquake fault is under the ocean and the earthquake causes the plates to move up or down, a tsunami can occur. Think about how you can make waves in a swimming pool just by moving your hands up and down under the water’s surface. When the bottom of the ocean drops or rises several metres suddenly, huge amounts of water get ‘sloshed around’ to form gigantic waves. When these waves reach land, they can have devastating effects.
The magnitude 7.8 Haida Gwaii earthquake of 2012 was a back-and-forth earthquake. The plates of crust slipped past each other sideways, not up-and-down. This means the waves were much smaller than they might have been. The 1964 Great Alaska Earthquake, magnitude 9.2, was an up-and-down megathust earthquake that obliterated Earth's surface and produced huge tsunamis.
Figure E.1.2.10 – Each type of earthquake wave moves through Earth differently.
Another effect of earthquakes are aftershocks. As you can imagine, after a huge plate of Earth’s crust has shifted suddenly, much of the surrounding plate might also shift as well. This shifting and settling is felt as aftershocks, or smaller earthquakes,
in the hours and days after the main earthquake.
Other effects of earthquakes are possible as well. Buildings can crack or fall. Highways and overpasses can collapse. Dams can fail and rivers can change course, flooding nearby land. Landslides and avalanches can occur.
Other effects of earthquakes are possible as well. Buildings can crack or fall. Highways and overpasses can collapse. Dams can fail and rivers can change course, flooding nearby land. Landslides and avalanches can occur.
Watch More
Powerful Waves
Tsunamis are a fearsome effect of earthquakes, volcanoes, and landslides. Watch these videos to learn how tsunamis form from underwater earthquakes. Then, watch the amazing surge of water from an actual tsunami that caused devastation in Japan.
Tsunamis are a fearsome effect of earthquakes, volcanoes, and landslides. Watch these videos to learn how tsunamis form from underwater earthquakes. Then, watch the amazing surge of water from an actual tsunami that caused devastation in Japan.
What are Landslides?
Landslides and avalanches are the movement of large amounts of solid material down hillsides or mountainsides. This can occur randomly, but some conditions make a slide more likely. Rain or melting provides water to allow solid materials to flow downhill easier. An earthquake or other type of shock provides the energy to start the movement – and gravity wins! Erosion or digging might weaken the surrounding support of the materials. Human activities such as logging and mining can promote landslides, too.
Landslides and avalanches are easier to predict than earthquakes are, and they can be controlled to some extent. Methods such as relieving the pressure by allowing smaller slides, draining excess water in the area, bracing materials with added structural support, or evacuating vulnerable populations can help. The best safety measure is to prevent the danger from occurring in the first place. Building regulations and cautious development of hillsides can save lives and reduce or prevent costly damage.
Landslides and avalanches are the movement of large amounts of solid material down hillsides or mountainsides. This can occur randomly, but some conditions make a slide more likely. Rain or melting provides water to allow solid materials to flow downhill easier. An earthquake or other type of shock provides the energy to start the movement – and gravity wins! Erosion or digging might weaken the surrounding support of the materials. Human activities such as logging and mining can promote landslides, too.
Landslides and avalanches are easier to predict than earthquakes are, and they can be controlled to some extent. Methods such as relieving the pressure by allowing smaller slides, draining excess water in the area, bracing materials with added structural support, or evacuating vulnerable populations can help. The best safety measure is to prevent the danger from occurring in the first place. Building regulations and cautious development of hillsides can save lives and reduce or prevent costly damage.
Figure E.1.2.11 – A large portion of Turtle Mountain broke loose in 1903.
Figure E.1.2.12 – Canada’s largest landslide occurred in Hope, B.C., in 1965.
Watch More
Landslides can be as simple as rocks rolling down a hillside. Most landslides, however, consist of wet, muddy materials flowing downwards.
Can an Earthquake or Landslide occur near me?
The coast of British Columbia has many earthquakes. Because of the many mountains in B.C., landslides will occur. In fact, the largest landslide in Canadian history occurred in Hope, B.C., in 1965.
Alberta and Saskatchewan have very few earthquakes, but landslides can occur anywhere unstable materials are on a hill or mountain. The deadliest landslide in Canadian history occurred on Turtle Mountain above the town of Frank, Alberta. On April 29, 1903, at 4:10 AM, a huge portion of the mountain slid through the town, killing approximately 80 people. From beginning to end, the landslide occurred in just 100 seconds -- about a minute and a half. The amount of debris was so huge that most bodies were never recovered and remain buried in the rocks at the bottom of the mountain.
Likely, Frank Slide was caused by a combination of factors. For many years among the local First Nations, Turtle Mountain had a reputation for being unstable. Settlers had been mining coal from the mountain, and the spring of 1903 was wet in Frank. Such conditions allowed a huge portion of the mountain to slide into the plains below.
The coast of British Columbia has many earthquakes. Because of the many mountains in B.C., landslides will occur. In fact, the largest landslide in Canadian history occurred in Hope, B.C., in 1965.
Alberta and Saskatchewan have very few earthquakes, but landslides can occur anywhere unstable materials are on a hill or mountain. The deadliest landslide in Canadian history occurred on Turtle Mountain above the town of Frank, Alberta. On April 29, 1903, at 4:10 AM, a huge portion of the mountain slid through the town, killing approximately 80 people. From beginning to end, the landslide occurred in just 100 seconds -- about a minute and a half. The amount of debris was so huge that most bodies were never recovered and remain buried in the rocks at the bottom of the mountain.
Likely, Frank Slide was caused by a combination of factors. For many years among the local First Nations, Turtle Mountain had a reputation for being unstable. Settlers had been mining coal from the mountain, and the spring of 1903 was wet in Frank. Such conditions allowed a huge portion of the mountain to slide into the plains below.
Figure E.1.2.13 – Landslide in El Salvador
Watch More
Turtle Mountain is only a kilometre from Highway 3, which runs through southern Alberta and into the Crowsnest Pass. The highway was built over the landslide debris that buried the town of Frank in 1903.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to
guide your learning.
Unit E Lesson 2 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Self-Check Time!
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Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
Canada’s west coast has several pieces of Earth’s crust, called tectonic plates, moving in various directions. If they catch on each other, pressure builds. When the pressure releases, an earthquake occurs.
Earthquakes happen much more frequently at the edges of tectonic plates. The middle of the plates are thick and stable, but the edges can become caught on other plates as they move slowly past each other.
The focus of an earthquake is where the pressure that has built in the crust is released. This is usually far underground. The epicentre is the location on the surface directly above the focus.
Violent shaking on the crust occurs when seismic waves called surface waves pass along Earth’s surface. These waves are similar to waves on the surface of water. They move the ground up and down violently. The other earthquake waves pass through
the inside of Earth, causing less motion and damage.
Landslides occur on slopes and hillsides where
- the earth is unstable
- earthquakes or explosions have occurred
- excess water has accumulated
- erosion has occurred
- digging, logging, or mining has been done