Unit E Lesson E13 The Rocky Mountains
Completion requirements
Lesson E13: The Majestic Rocky Mountains
Video Lesson
The Rocky Mountains are a very important part of Alberta’s landscape. They are beautiful reminders of nature, and they are home for various plants and animals not found anywhere else in the province. They provide popular tourist destinations for hiking
and camping in summer and skiing and snowmobiling in winter. They contain valuable natural resources such as trees, fossil fuels, and minerals, and they help produce climate and weather patterns that we experience throughout Alberta. But where did
they come from, and how did they get so tall?
Lesson E13: The Majestic Rocky Mountains
What are Mountains?
Earth’s crust might be a relatively thin shell that covers our planet, but it has incredibly deep and tall features. Did you know that the tallest mountain above sea level is Mt. Everest? This Tibetan mountain is almost 9 km tall. How deep do you think the deepest part of the ocean is? Parts of the Mariana Trench, off the coast of the Philippines, are more than 10 km below the surface of the Pacific Ocean. That changes in Earth’s crust can result in almost 20 km of difference between its lowest and highest points is amazing.
The Rocky Mountains are one of the most impressive ranges of mountains on Earth. All the types of mountains you will study in this lesson are located within the Rocky Mountain range.
Earth’s crust might be a relatively thin shell that covers our planet, but it has incredibly deep and tall features. Did you know that the tallest mountain above sea level is Mt. Everest? This Tibetan mountain is almost 9 km tall. How deep do you think the deepest part of the ocean is? Parts of the Mariana Trench, off the coast of the Philippines, are more than 10 km below the surface of the Pacific Ocean. That changes in Earth’s crust can result in almost 20 km of difference between its lowest and highest points is amazing.
The Rocky Mountains are one of the most impressive ranges of mountains on Earth. All the types of mountains you will study in this lesson are located within the Rocky Mountain range.
Reading and Materials for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 402-408
Materials:
waxed paper, graham wafers, plastic spoon and/or knife, a knife with a sharp point, frosting or whipping cream, glass of water
Figure E.3.13.1 – The summit of
Mount Everest, at 8848 m above sea level, is the highest point on Earth.
Figure E.3.13.2 –
Mount Logan is Canada's tallest peak. It is 5959 m tall, but is not part of the Rocky Mountains.
Figure E.3.13.3 –
Mount Robson is the tallest peak in the Canadian Rocky Mountains. It is 3954 m tall.
Mountain Building
A mountain is any part of the crust that rises steeply higher than its surroundings. Mountains are located everywhere on Earth’s crust, including the bottom of the ocean. Mountains such as volcanoes often are alone in their environments. Mountains such as the Rocky Mountains appear grouped in mountain chains (ranges). All tall mountains are built during long periods of time, and they always involve tectonic plates or hot spots.
Mountains are classified into three main types:
A mountain is any part of the crust that rises steeply higher than its surroundings. Mountains are located everywhere on Earth’s crust, including the bottom of the ocean. Mountains such as volcanoes often are alone in their environments. Mountains such as the Rocky Mountains appear grouped in mountain chains (ranges). All tall mountains are built during long periods of time, and they always involve tectonic plates or hot spots.
Mountains are classified into three main types:
-
Volcanoes
-
Fault-block mountains
- Fold-and-fault mountains
Figure E.3.13.4 – The tallest mountain in Alberta is
Mount Columbia. It is a Rocky Mountain that is 3747 m tall.
Volcanoes
Volcanoes are located where Earth’s crust is thin. This can be near the edges of tectonic plates or in special locations called hot spots in other parts of the tectonic plates. Hot spots are places where the crust is thin and magma can rise towards the surface. Volcanoes can build into wide, flat mountains called shield volcanoes or into tall, majestic peaks called composite volcanoes. Often, they are found alone, but they can also be part of a chain of volcanoes.
Earth's largest and tallest mountains, as measured from the crust upwards, are both volcanoes. The tallest mountain on Earth is Mauna Kea, the active volcano on the island of Hawaii. It is over 10 000 m tall. Tamu Massif is the largest mountain on Earth. It is an underwater volcano off the coast of Japan that is about the same size as the island of Newfoundland.
Volcanoes are located where Earth’s crust is thin. This can be near the edges of tectonic plates or in special locations called hot spots in other parts of the tectonic plates. Hot spots are places where the crust is thin and magma can rise towards the surface. Volcanoes can build into wide, flat mountains called shield volcanoes or into tall, majestic peaks called composite volcanoes. Often, they are found alone, but they can also be part of a chain of volcanoes.
Earth's largest and tallest mountains, as measured from the crust upwards, are both volcanoes. The tallest mountain on Earth is Mauna Kea, the active volcano on the island of Hawaii. It is over 10 000 m tall. Tamu Massif is the largest mountain on Earth. It is an underwater volcano off the coast of Japan that is about the same size as the island of Newfoundland.
Figure E.3.13.6 –
Mount Garibaldi is Canada's most famous volcano. It is 2678 m tall, and is located 80 km northeast of Vancouver.
Figure E.3.13.7 – Erupting volcanoes can continue to grow larger and taller, but massive eruptions can blow sections of the mountain apart.
Fault-block Mountains
Fault-block mountains form when huge slabs of Earth’s crust break apart. One part can move or tilt down, and another part can move or tilt up. These mountains are called fault-block mountains because the cracks that separate the pieces of crust are called faults, and the pieces that form the mountains are huge blocks of crust.
Fault-block mountains form when huge slabs of Earth’s crust break apart. One part can move or tilt down, and another part can move or tilt up. These mountains are called fault-block mountains because the cracks that separate the pieces of crust are called faults, and the pieces that form the mountains are huge blocks of crust.
Imagine a whale coming up to breathe to find a layer of ice covering the ocean. The ice might break into pieces, and the whale pushing from below would cause some pieces to be pushed upwards while other pieces would fall back into the water. Earth’s crust
can break in the same way when faults appear from the crust being pushed apart by the pressure from below.
Fault-block mountains can have very steep, sheer faces. This is because one end of the broken part of the crust can get pushed almost straight up. An example of fault-block mountains in the Rockies are the Teton mountains of the United States. The Tetons are especially interesting because they are very young and have not eroded significantly. Also, they rise dramatically from the valley without foothills such as we see in Alberta when we travel west towards the Rockies.
Fault-block mountains can have very steep, sheer faces. This is because one end of the broken part of the crust can get pushed almost straight up. An example of fault-block mountains in the Rockies are the Teton mountains of the United States. The Tetons are especially interesting because they are very young and have not eroded significantly. Also, they rise dramatically from the valley without foothills such as we see in Alberta when we travel west towards the Rockies.
Figure E.3.13.8 – Block mountains form when huge sections of crust break off and are pushed up.
Figure E.3.13.9 – An example of a block mountain is
El Capitan, a
famous spot for rock climbing in the Sierra Nevada mountains. El Capitan is located in
Yosemite National Park in California.
Figure E.3.13.10 –
The Tetons are amazing block mountains in the Rockies. Most of the Rocky Mountains are not block mountains, but the Tetons are.
Fold-and-fault Mountains
The Himalayas are only 50 million years old, and they are the youngest tall mountains on Earth. In fact, they are still becoming taller at a rate of 1 cm per year. Thus, Mount Everest is about 60 cm (2 feet) taller now than it was when Sir Edmund Hillary was the first to reach its top in 1953.
Fold-and-fault mountains are not the broken sections of crust being pushed upwards as with block mountains. Fold-and-fault mountains result from the slow bending of the rock up and down from huge forces and pressure compressing rocks. Often, this pressure occurs when two plates ram against each other.
Imagine pushing on a piece of clay from both ends. The clay will push slowly upwards, folding upward into a mountain and perhaps breaking along faults if it is bent too quickly. Another way to imagine how fold-and-fault mountains form is to imagine a rug on a hardwood floor. You and a friend are on opposite sides of the rug when you start to push towards the middle. Imagine how the rug will bend as it piles up in the middle.
The Himalayas are only 50 million years old, and they are the youngest tall mountains on Earth. In fact, they are still becoming taller at a rate of 1 cm per year. Thus, Mount Everest is about 60 cm (2 feet) taller now than it was when Sir Edmund Hillary was the first to reach its top in 1953.
Fold-and-fault mountains are not the broken sections of crust being pushed upwards as with block mountains. Fold-and-fault mountains result from the slow bending of the rock up and down from huge forces and pressure compressing rocks. Often, this pressure occurs when two plates ram against each other.
Imagine pushing on a piece of clay from both ends. The clay will push slowly upwards, folding upward into a mountain and perhaps breaking along faults if it is bent too quickly. Another way to imagine how fold-and-fault mountains form is to imagine a rug on a hardwood floor. You and a friend are on opposite sides of the rug when you start to push towards the middle. Imagine how the rug will bend as it piles up in the middle.
Figure E.3.13.11 –
Mount Everest is part of the mountain range named the Himalayas that formed when India crashed into Asia.
The Rocky Mountains are fold-and-fault mountains, but they are much older than the Himalayas are. The Himalayas began to form about 50 million years ago, but the Rocky Mountains formed almost 500 million years ago. Back then, , two huge tectonic plates, the Pacific Plate and the North American Plate, crashed into each other and forced the crust of the North American Plate to fold up to become the Rocky Mountains. Since they formed, the Rockies have been eroded by wind, water, and especially glaciers. They are still tall mountains, but they are being eroded slowly.
Mount Rundle is a very interesting example of a fold-and-fault mountain. Mount Rundle is a huge mountain 12 km wide. The ‘mountains’ you see on the south side of the Trans-Canada highway as you drive between Canmore and Banff are all Mount Rundle!
Originally, Mount Rundle was a massive sheet of crust in the North American Plate. When the Rocky Mountains were building, this chunk was pushed up and above the surrounding crust to form a wide, tall mountain. Where did all those peaks come from? Millions of years of erosion have left behind what looks like a mini-mountain range.
Figure E.3.13.11 – This animation shows how Mount Rundle was formed.
Figure E.3.13.12 – The mountains that surround
Moraine Lake, similar to the remainder of the Rocky Mountains, represent fold-and-fault mountain building.
Figure E.3.13.13 –
Mount Rundle formed as a fold-and-fault mountain, but instead of folding, a huge slab of crust was pushed up and over the other crust.
Try It!
Building Sweet Mountains
This experiment explores mountain building. You will use graham wafers and frosting as a model of Earth. Using this model, you will simulate mountain building, faults, and folds.
Materials:
This experiment explores mountain building. You will use graham wafers and frosting as a model of Earth. Using this model, you will simulate mountain building, faults, and folds.
Materials:
- waxed paper
- graham wafers
- plastic spoon and/or knife
- a knife with a sharp point
- frosting or whipping cream
-
water
Safety Warning
Take care with the sharp knife and scissors; don't cut yourself or anyone else!
Download:
DOWNLOAD this document. It provides a space for you to write answers to questions later in this activity.
DOWNLOAD this document. It provides a space for you to write answers to questions later in this activity.
Instructions:
Mountain Building: Volcano
1. Use a knife with a sharp point to drill a hole gently in the middle of a graham cracker.
2. Place two dollops of frosting on a piece of waxed paper. Spread it a bit to make a thick layer.
3. Place the graham wafer on the frosting layer so the hole of the wafer is over the frosting.
4. Press down gently on the wafer. Observe what happens.
Mountain Building: Fault-Block Mountains
5. Break a graham cracker into three equal pieces.
6. Place two dollops of frosting on a piece of waxed paper. Spread it a bit to make a thick layer a little larger than one full graham cracker.
7. Place the three wafer pieces side-by-side on the frosting layer so they look like one large piece.
8. Press down on the middle of the three wafer pieces. Observe what happens.
Mountain Building: Fold-and-fault mountains
9. Break a graham cracker into two equal pieces.
10. Place two dollops of frosting on a piece of waxed paper. Spread it a bit to make a thick layer a little larger than one full graham cracker.
11. Dip 1 cm of one end of each wafer into a glass of water for 2 seconds -- just a quick dip!
12. Place the two wafer pieces side-by-side on the frosting layer so they look like one large piece. Be sure the wet ends are closest together.
13. Push the wafers together gently so the wet ends meet. Continue pressing the wafers together gently. Observe what happens. (You might want to try various versions of this, changing the wetting time of the wafers to ensure various degrees of softness.)
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
The frosting is the lower mantle, and the wafer is the lithosphere or crust. These items works as simple models because the frosting is a fluid that allows the lithosphere to move on top of it, and the wafer is rigid. However, to be more accurate the
frosting should be hot with convection currents, and the wafer should be more complex than a single type of material to represent so much lithosphere.
Pressing down on the graham wafer represents a volcanic eruption. The model works because the fluid escapes through a break in the crust. However, in reality, the magma rises up because of pressure from below and not because of pressure from above as
this model uses. Volcanic eruptions vary, and this “magma” did not flow and spread as it would naturally.
Pressing down on the graham wafer represents the rise, fall, and tilt of the pieces of crust in fault-block mountains. As in the volcano example, in the real world the force does not push down. Instead, tectonic forces push from the sides, and the sections
of crust can move up, down, or tilt on the mantle below.
Rocks normally do not fold and bend. In our model, the wet wafers bend in a way similar to the rocks in fold-and-fault mountain building. Rocks that fold are under large amounts of pressure for long periods. Heat, water, and other factors can help make
the rock fold.
Many factors determine how, when, and why your wafers (and Earth’s crust) fold and when they fault. If you soaked your wafers well, you probably noticed that they folded much before they faulted. If your wafers were still quite dry, they faulted much
more quickly. Also, if large amounts of pressure are applied very quickly, the wafers (and crust) fault more quickly. The materials in the wafer (or crust) are also factors. For example, igneous rocks are harder than sedimentary rocks and,
therefore, igneous rocks fault more easily.
Figure E.3.13.14 – The Lewis Overthrust, in Waterton Lakes National Park in southern Alberta:
1 A block of Earth's crust in Glacier National Park 60 million years ago. The two layers represent many layers of sedimentary rocks.
2 Pressure begins to force the rock layers to bend.
3 A large fold forms, forcing the rock layers to fold over on themselves. A break, or fault, is forming from the stress.
4 The break has been completed and the layers west of the fault have slid eastward, up and over the rocks east of the fault.
5 The Glacier National Park landscape today. Erosion has worn away some of the sedimentary layers over millions of years.
2 Pressure begins to force the rock layers to bend.
3 A large fold forms, forcing the rock layers to fold over on themselves. A break, or fault, is forming from the stress.
4 The break has been completed and the layers west of the fault have slid eastward, up and over the rocks east of the fault.
5 The Glacier National Park landscape today. Erosion has worn away some of the sedimentary layers over millions of years.
Fold and Fault Mountains
Layers of sedimentary rock can bend and break when they are pushed and compressed during mountain building. Places where rock bends are called folds. To think of rock bending might seem strange, but when massive forces are applied by tectonic plates for thousands of years, even solid rock changes shape. Most mountains in Alberta and British Columbia are fold-and-fault mountains made from sedimentary rocks. The Lewis Overthrust (Figure E.3.13.14) is an amazing example of folding and faulting that can be found in southern Alberta and the northern United States.
Remember how pushing a rug from opposite sides was compared to fold-and-fault mountain building? In rocks, those places that the rug bends as it is pushed together are called folds. These appear as waves in the rock, and sometimes they can be quite severe – or even upside down! When the pressure becomes too much for folding, the rocks can break. When a rock breaks and either side moves in a different direction, a fault is formed. In fold-and-fault mountains, faults appear as straight line breaks between the sedimentary layers that normally follow each other.
Figure E.3.13.15 – An anticline forms where rocks are folded upward.
Figure E.3.13.16 – A syncline forms where rocks are folded downward.
Folds in Mountains
Where rocks fold upward, an anticline forms. Anticlines look a bit like rounded capitals of the letter A. Where the rocks fold downward, a syncline forms. Seen from a distance, a series of anticlines and synclines can look similar to waves on a body of water.
How does something as solid as rock bend and fold like this? The gradual, slow but tremendous pressure from the colliding plates produces folding, of course, but not every rock will bend under this pressure. Heat from the mantle below allows the rocks to change in this way – but not so much heat that the sedimentary rocks become metamorphic rocks.
Faults in Mountains
Often, faults are spoken of when earthquakes are discussed. The San Andreas Fault is a famous example of two large sections of crust moving in different directions, frequently becoming caught on each other and releasing the pent up energy as earthquakes.
A fault is any crack in rock that allows portions of rock to move in different directions. Faults can appear in any rock that is under pressure and cannot bend or move. Faults may or may not be near the edge of a tectonic plate, but they will appear in places where the rock is thin or brittle enough to break. Faults can be many kilometres long or as short as a few millimetres. A piece of rock small enough for you to carry can have faults!
Often, faults are spoken of when earthquakes are discussed. The San Andreas Fault is a famous example of two large sections of crust moving in different directions, frequently becoming caught on each other and releasing the pent up energy as earthquakes.
A fault is any crack in rock that allows portions of rock to move in different directions. Faults can appear in any rock that is under pressure and cannot bend or move. Faults may or may not be near the edge of a tectonic plate, but they will appear in places where the rock is thin or brittle enough to break. Faults can be many kilometres long or as short as a few millimetres. A piece of rock small enough for you to carry can have faults!
Figure E.3.13.17 – A fault in the layers of rock sometimes is very obvious. Here, you can see where one portion of the rock moved away from the other along the fault.
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 13 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.
Most of Earth’s tallest mountains have formed because of the movement of tectonic plates. Tall mountains such as Mauna Kea have formed from the buildup of igneous rock that forms from magma that spills from Earth’s crust.
Both block mountains and fold-and-fault mountains form near the edges of tectonic plates. The plates either break and fault to form block mountains or crash together with other plates to form fold-and-fault mountains. This happens almost always
at the edges of tectonic plates having oceans and seas. These are locations where thick layers of sedimentary rock can accumulate for thousands of years before the mountains building begins.
The Rockies and the Himalayas would look similar at an age of 60 million years, but the Rockies have been eroded for 450 million years more than the Himalayas have. This means that the Rockies likely are less steep but perhaps not as tall, and
they have many features left by glaciers and water erosion such as U-shaped valleys.
Fold-and-fault mountains form where tectonic plates collide with each other. Because Earth has many tectonic plates and because they are always moving, many collisions occur over long periods.
Anticlines are upward folds in rock. In sedimentary rock that has shale, the shale forms upside-down bowls that collect fossil fuels such as oil and gas as they rise against any groundwater in the area. Therefore, anticlines form upside-down
reservoirs that can become filled with oil and gas.