Unit E Lesson E5 The Earth's Crust: Slow and Steady Change
Completion requirements
Lesson E5: Earth's Crust: Slow and Steady Change
Video Lesson
Earth’s crust can change suddenly when an earthquake, volcano, or landslide occurs. Large sections of tectonic plates can shift, mountains can explode or collapse, and lava can spill over the landscape. The amount of change can be huge, and can occur
very quickly or very slowly.
Lesson E5: Earth's Crust: Slow and Steady Change
Slow and Steady Wins the Race
Some changes to Earth’s crust are slow, steady, and persistent. The time for these changes is measured in months, years, decades, and centuries. For example, particles of Earth's crust are broken bit by bit and are moved gradually to new locations.
This might be similar to you carrying dust into your house on your shoes – you will not live long enough to fill it with dirt!
Some changes to Earth’s crust are slow, steady, and persistent. The time for these changes is measured in months, years, decades, and centuries. For example, particles of Earth's crust are broken bit by bit and are moved gradually to new locations.
This might be similar to you carrying dust into your house on your shoes – you will not live long enough to fill it with dirt!
Reading and Materials for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 363–366
Materials:
aluminum baking pan or shallow plastic tray, gravel, sand, soil, ruler or stick, water source, drain bucket
Figure E.1.5.1 – Horsethief Canyon in the badlands west of Drumheller.
Figure E.1.5.2 – Some amazing features are left behind as the landscape changes.
Earth's Crust: Slow and Steady Change
Earthquakes, volcanoes, landslides, and other large, sudden changes to Earth’s crust receive much attention. People write newspaper stories, record film documentaries, produce photo books, develop websites, and document every moment before, during, and after the event.
But few people notice slow and steady crust change.. These processes break rocks gradually, slowly carry them away, and gently place them together in layers of tiny particles. Over long periods, these particles can become rocks again, only to have the whole process start again. In science terms, we say that the weathering of rocks leads to the erosion of tiny particles away from the rocks. Then, in the future, the particles are deposited in a new location.
Earthquakes, volcanoes, landslides, and other large, sudden changes to Earth’s crust receive much attention. People write newspaper stories, record film documentaries, produce photo books, develop websites, and document every moment before, during, and after the event.
But few people notice slow and steady crust change.. These processes break rocks gradually, slowly carry them away, and gently place them together in layers of tiny particles. Over long periods, these particles can become rocks again, only to have the whole process start again. In science terms, we say that the weathering of rocks leads to the erosion of tiny particles away from the rocks. Then, in the future, the particles are deposited in a new location.
Alberta is a good location to study these slow and steady changes. We may not have many sudden changes occurring here, but most of our province is shaped by gradual change. Keep these gradual changes in mind the next time you are walking somewhere, riding
your bike, or driving to the store. Try to identify some of the evidence of these slow and steady changes.
Figure E.1.5.3 – Moving water can result in mechanical weathering, and the growing roots of trees can produce biological weathering.
Figure E.1.5.4 – Limestone is a type of rock that weathers chemically through the acids in rainwater to form spectacular patterns in the landscape.
Weathering
Weathering is the gradual breaking of rocks into small particles. Weathering occurs in various ways. Rocks can be worn slowly by wind, moving water, or ice. Weathering can occur when certain materials react with chemicals in the rock to cause the rock to wear away slowly. It can occur when a plant or animal comes into contact with the rock and gradually breaks it into smaller pieces. No matter how it happens, weathering breaks larger rocks into smaller and smaller pieces.
Weathering is the gradual breaking of rocks into small particles. Weathering occurs in various ways. Rocks can be worn slowly by wind, moving water, or ice. Weathering can occur when certain materials react with chemicals in the rock to cause the rock to wear away slowly. It can occur when a plant or animal comes into contact with the rock and gradually breaks it into smaller pieces. No matter how it happens, weathering breaks larger rocks into smaller and smaller pieces.
- Mechanical weathering occurs when rocks are broken into smaller rocks. It is sometimes referred to as physical weathering.
- Chemical weathering occurs when a chemical reaction causes rocks and minerals to change into different rocks or minerals that might be weaker than the originals are.
- Biological weathering happens when living things cause rocks to break into a smaller pieces.
Figure E.1.5.5 – Usually, rocks at the bottom of a river are mechanically weathered smooth by running water and rock particles bashing into them.
Figure E.1.5.6 – The Okotoks erratic, nicknamed “Big Rock”, is a huge boulder that is breaking apart slowly with the help of frost weathering.
Mechanical Weathering
Mechanical weathering occurs when air, water, or ice moves against rock. These are called physical forces because they physically hit the rock and break off tiny pieces.
Water and ice cause the most weathering. Water can flow quite quickly in rivers and streams, and it will mechanically weather softer rocks such as sandstones in relatively short time. Ice is very effective at mechanically weathering rocks, especially big rocks with tiny cracks. This breakage of rocks is sometimes referred to as frost weathering.
Water can get into a crack in a rock quite easily as rain, melting snow, or dew. When water freezes into ice, the ice takes up more space than the water did. This increase in volume causes the ice to push against the sides of the crack, forcing it wider until the rock breaks. A few freeze-thaw-freeze cycles can split a large rock in half! Did you know that many hoodoos are formed by frost weathering? Rocks that heat and cool in places such as deserts expand and contract when the temperature changes. This can break the rock into smaller pieces.
Figure E.1.5.7 – Wind weathering can produce some beautiful rock formations.
Ocean waves repeatedly bashing into exposed rock can physically weather that rock. Even the salt crystals that accumulate over time from ocean wave spray can force tiny cracks to open further. Falling rain causes very little mechanical weathering, but
it does cause chemical weathering. Moving air does not usually cause much physical weathering, but in places such as deserts, strong winds can carry small particles of sand or other materials. The weathered rock left behind usually looks very smooth
and polished as if it has been sandblasted.
Figure E.1.5.8 – Note the colours of the hoodoo match the colours of the canyon wall.
Figure E.1.5.9 – Hoodoos with large rock caps overhanging the narrow rock neck below.
Mechanical Weathering and Hoodoos
The hoodoos near Drumheller, Alberta are famous worldwide. These amazing natural structures seem to rise from the surrounding desert and plains, resembling peaceful figures gazing over the landscape. How do these interesting structures form?
If you asked ask a sculptor how to make a statue of a horse, and she might say, “Just chip away all the parts that don’t look like a horse!” Hoodoos form in a similar way. Hoodoos were once just a large area of rock, but mechanical weathering has removed the surrounding materials. Most of the rock formation has weathered away by natural processes over thousands of years. Harder parts of the rock formation remain and protect the layers beneath. All the parts that aren’t the hoodoo are gone!
What about the horizontal strips and layers that we see in most hoodoos? Those are various layers of rock. Each layer is made of particles of rock and other materials that slowly formed into solid rock in the ancient past. Rain soaks slowly into the types of rock that absorb water, softening these layers. Water soaks deep into any cracks that form in the rock. Wind-blown grit from the surrounding area can wear away slowly the softened areas, and this helps to smooth the outer surface of the hoodoo. Frost weathering involves water that finds its way into cracks and expands as it freezes, crumbling the rock surrounding it. These processes never stop, changing hoodoos slowly year by year.
The hoodoos near Drumheller, Alberta are famous worldwide. These amazing natural structures seem to rise from the surrounding desert and plains, resembling peaceful figures gazing over the landscape. How do these interesting structures form?
If you asked ask a sculptor how to make a statue of a horse, and she might say, “Just chip away all the parts that don’t look like a horse!” Hoodoos form in a similar way. Hoodoos were once just a large area of rock, but mechanical weathering has removed the surrounding materials. Most of the rock formation has weathered away by natural processes over thousands of years. Harder parts of the rock formation remain and protect the layers beneath. All the parts that aren’t the hoodoo are gone!
What about the horizontal strips and layers that we see in most hoodoos? Those are various layers of rock. Each layer is made of particles of rock and other materials that slowly formed into solid rock in the ancient past. Rain soaks slowly into the types of rock that absorb water, softening these layers. Water soaks deep into any cracks that form in the rock. Wind-blown grit from the surrounding area can wear away slowly the softened areas, and this helps to smooth the outer surface of the hoodoo. Frost weathering involves water that finds its way into cracks and expands as it freezes, crumbling the rock surrounding it. These processes never stop, changing hoodoos slowly year by year.
Figure E.1.5.10 – A striped hoodoo..
Figure E.1.5.11 – These rocks have turned red because of the chemical weathering effect oxygen has on the iron in them.
Figure E.1.5.12 – The exposed limestone shown on the right has been chemically weathered by acid rain. The freshly uncovered limestone on the left is not weathered.
Chemical Weathering
Chemical weathering occurs when chemical reactions cause rocks and minerals to change into other substances. This weakens the rock as the new substances are washed away and as small pieces fall away from the weakened rock.
Most chemical weathering is caused by water and oxygen. Water quite easily can become an acid, and acids react with rocks such as limestone to cause chemical weathering. Rain, which is normally slightly acidic, can become an even stronger acid when it is exposed to pollution and extra carbon dioxide. Oxygen reacts with many substances, including iron. Any rocks that have iron in them will rust when exposed to oxygen. Rust not only changes the iron into a different, reddish-brown colour, but it changes it into something weaker.
Chemical weathering occurs when chemical reactions cause rocks and minerals to change into other substances. This weakens the rock as the new substances are washed away and as small pieces fall away from the weakened rock.
Most chemical weathering is caused by water and oxygen. Water quite easily can become an acid, and acids react with rocks such as limestone to cause chemical weathering. Rain, which is normally slightly acidic, can become an even stronger acid when it is exposed to pollution and extra carbon dioxide. Oxygen reacts with many substances, including iron. Any rocks that have iron in them will rust when exposed to oxygen. Rust not only changes the iron into a different, reddish-brown colour, but it changes it into something weaker.
Figure E.1.5.13 – Roots growing into tight spaces cause biological weathering.
Figure E.1.5.14 – Lichen are similar to moss in that they biologically weather the rocks on which they live..
Biological Weathering
Biological weathering occurs any time a living thing is responsible for a rock breaking down into smaller pieces. This is usually due to a plant’s roots growing into narrow spaces. The roots can exert pressure that cause cracks to enlarge. Lichen looks like moss growing on a rock, but it is actually an algae and a fungus cooperating to help each other survive. The lichen produces conditions and wastes that help break down the rock they live on. Lichen are living things that cause biological weathering. Other biological weathering includes burrows, paths, and other rock disturbances made by animals and insects. In addition, many human activities break rock as well.
Biological weathering occurs any time a living thing is responsible for a rock breaking down into smaller pieces. This is usually due to a plant’s roots growing into narrow spaces. The roots can exert pressure that cause cracks to enlarge. Lichen looks like moss growing on a rock, but it is actually an algae and a fungus cooperating to help each other survive. The lichen produces conditions and wastes that help break down the rock they live on. Lichen are living things that cause biological weathering. Other biological weathering includes burrows, paths, and other rock disturbances made by animals and insects. In addition, many human activities break rock as well.
Try It!
It’s Your Turn to Weather the Dishes!
Weathering is any process that breaks down rock into smaller pieces. These processes are impossible to observe in nature because of the long amounts of time involved. However, we can model the processes to understand each kind better.
Materials:
Weathering is any process that breaks down rock into smaller pieces. These processes are impossible to observe in nature because of the long amounts of time involved. However, we can model the processes to understand each kind better.
Materials:
- dirty dishes
- various kitchen resources
-
you
Instructions:
Type or write your answers elsewhere. When you have completed all the questions, click on the “Suggested Answers” to check your work.
Type or write your answers elsewhere. When you have completed all the questions, click on the “Suggested Answers” to check your work.
Questions:
Mechanical weathering - Moving water:
Running water from the tap over the dirty dishes washes away the loose particles of food but not the baked-on or sticky parts.
Mechanical weathering - Ocean waves: What dish washing process matches this?
Mechanical weathering - Moving air: What dish washing process matches this?
Mechanical weathering - Frost: What dish washing process matches this?
Chemical weathering: What dish washing process matches this?
Biological weathering: What dish washing process matches this?
Mechanical weathering - Moving water:
Running water from the tap over the dirty dishes washes away the loose particles of food but not the baked-on or sticky parts.
Mechanical weathering - Ocean waves: What dish washing process matches this?
Mechanical weathering - Moving air: What dish washing process matches this?
Mechanical weathering - Frost: What dish washing process matches this?
Chemical weathering: What dish washing process matches this?
Biological weathering: What dish washing process matches this?
Suggested Answers:
Running water from the tap over the dirty dishes washes away the loose particles of food but not the baked-on or sticky parts.
Similar to waves crashing against hard surfaces, sloshing the plates back and forth in the water can remove some of the sticky stuff.
Wind by itself does very little weathering, but when weathered particles are blown against a hard surface, erosion can occur. Blowing on the dirty dishes might dislodge loose particles, but sand-blast those plates and you might remove even the pattern!
Freezing to clean dishes might be a rare event, but a plate soaked in water and then put in the freezer will be much easier to clean. The expanding freezing water would force most of the food particles from the hard surfaces of the dishes.
Cleaners such as soap help loosen food stuck to our dishes. Other chemicals such as vinegar and baking soda can be used effectively. CAUTION: Chemicals can react to produce dangerous products.
As soon as we use our muscles to scrub the dishes, we are using biological weathering -- often with the help of a scrub pad, which is mechanical weathering. We could allow a pet to lick the plate or we could leave it on the counter for a few days so that
mould and bacteria start to break down the food particles, but those are not sanitary ways to wash dishes!
Figure E.1.5.15 – Valley erosion caused by the Colorado River formed the Grand Canyon.
Figure E.1.5.16 – The Wave is a stunning natural formation formed by erosion in Arizona .
Erosion
Erosion occurs when the rock bits and minerals produced by weathering are moved from one place to another. Usually, erosion is produced by water or wind, and where it is cold enough, glaciers. Erosion occurs even if the rock bits and minerals move only a few millimetres. Those bits of rock and minerals may also move thousands of kilometres.
Mechanical weathering and erosion are easily confused. Remember that weathering is the breaking apart, or wearing down, of a rock. The pieces that are weathered stay in place. Erosion occurs when the broken pieces move somewhere else. This can be quite confusing in situations such as the formation of the hoodoos. On one hand, mechanical weathering is occurring as the frost weathers the rocks of the hoodoo formation. But there is also erosion occurring as the rock bits are washed or blown away.
Figure E.1.5.17 – Eroding soil is carried by winds far from the fields it comes from.
Human activity can greatly increase erosion. Removing trees for lumber and clearing land for farming or construction removes many of the root systems and large rocks that stabilize large amounts of loose soil. Plowing and tilling on farms is designed
to loosen the soil and allow air and water to flow through it, but this also promotes erosion. Loose soil can wash or blow easily. In Alberta, occasional huge dust storms indicate wind erosion, and channels cut into fields by flowing water indicate
water erosion.
Erosion by Moving Water
Flowing water is one of the most powerful forms of erosion. After all, it was the Colorado River and the streams that flow into it that formed the amazing Grand Canyon! Consider any valley near you in Alberta – likely the result of erosion of soil in the past. Have you ever watched the process of erosion as running water moves over loose dirt?
Erosion by Moving Water
Flowing water is one of the most powerful forms of erosion. After all, it was the Colorado River and the streams that flow into it that formed the amazing Grand Canyon! Consider any valley near you in Alberta – likely the result of erosion of soil in the past. Have you ever watched the process of erosion as running water moves over loose dirt?
Think • Interpret • Decide
Stream Table
A stream table is a simple model that allows you to watch how flowing water erodes the particles and soils that it flows through.
Materials:
A stream table is a simple model that allows you to watch how flowing water erodes the particles and soils that it flows through.
Materials:
- aluminum baking pan, or shallow plastic tray
- gravel
- sand
- soil
- ruler or stick for packing
- water source
- drain bucket
Instructions:
1. Prepare your stream table by adding rock, sand, and soil to your tray. Do not fill the tray, but leave space at the end of the tray so you can see what flows away. You may layer the materials or mix them. It is up to you. Pack the materials down tightly with the ruler.
2. When the table is filled with particles, tilt it so the water flows from one end to the other. The low end will need a drain, so be prepared to make a mess! You will be adding water at the high end, and the tray will get quite heavy as the water is added. Be sure the high end of the tray is supported well.
3. A slow trickle of water at the high end of the tray will give you slow results, but it will be easiest to see what is happening if you keep the flow of water slow. Be sure you let the water drain at the other end. Stop the flow of water after a few minutes, and examine the particles deposited at the drain end of the pan when you are done.
4. Try the experiment a few times to see if you get various results. Try various types of soil materials, various angles of slope, and various amounts of water.
5. Put away the materials and tools you used -- and clean up your mess!
Watch this video to see a more complex stream table that was set up in a science lab.
Your variations to the stream table activity will have been interesting. Join Lego Steve to tour one of the most impressive stream tables we have ever seen!
This experiment allows you to watch how water erodes relatively loose particles as it flows.
The water follows the path that it does because of the slope of the terrain over which it is flowing and the obstacles that it faces as it flows. Water always follows paths of least resistance. As it flows, it causes large particles to tumble with the
flow, and it will pick up smaller particles and carry them until the speed of the flow slows.
Less erosion occurs if the volume of water decreases, if the speed of the flow decreases, and if the materials the water flows through are bigger, heavier, or more tightly packed. The rate of erosion increases if any of these variables is changed.
Figure E.1.5.18 – As muddy river water flows into the Gulf of Mexico, sediment is deposited in the ocean water.
Figure E.1.5.19 – An easy way to identify if a river has sediments is to consider how muddy or cloudy it is.
Sedimentation (also called Deposition)
Erosion picks up and moves any particles that become caught in the moving air or water. In a river, these particles are called sediments. Sediments make the water appear muddy or cloudy. The sediments continue to move in the water as long as the current is strong enough to keep the particles suspended.
However, when the flow slows, the sediments begin to ‘fall’ in the water, with the heaviest particles falling first. This is the end of the process of erosion. The process of sediments falling to the bottom is called deposition or sedimentation. Usually, this occurs at the bottom of oceans, lakes, or slow moving parts of rivers.
Remember those stripes in the hoodoos? Those are very old layers of sediment that were eroded particles deposited in a lake or ocean millions of years ago. Those sediments accumulated over many years, deposited as a layers, sometimes with particles of a different colours. Those sediment layers dried and hardened to become rocks called sedimentary rocks.
Erosion picks up and moves any particles that become caught in the moving air or water. In a river, these particles are called sediments. Sediments make the water appear muddy or cloudy. The sediments continue to move in the water as long as the current is strong enough to keep the particles suspended.
However, when the flow slows, the sediments begin to ‘fall’ in the water, with the heaviest particles falling first. This is the end of the process of erosion. The process of sediments falling to the bottom is called deposition or sedimentation. Usually, this occurs at the bottom of oceans, lakes, or slow moving parts of rivers.
Remember those stripes in the hoodoos? Those are very old layers of sediment that were eroded particles deposited in a lake or ocean millions of years ago. Those sediments accumulated over many years, deposited as a layers, sometimes with particles of a different colours. Those sediment layers dried and hardened to become rocks called sedimentary rocks.
Figure E.1.5.20 – When the tide rolls out, the mud flats left behind reveal layers new sediment.
Moving water can produce many shapes and forms as it weathers rock, erodes particles, and deposits them. These shapes and forms are called fluvial landforms, which include waterfalls, islands in the middle of rivers, sandbars along the banks of rivers,
the bends of the river as it carves back and forth through the landscape, and deltas that form where deposition occurs when rivers empty into lakes and oceans.
Alberta has many lakes and rivers, and most of our rocks can be weathered and their particles eroded to new places. The next time you pass a river, stop for a few moments to identify some of the effects of water erosion.
Alberta has many lakes and rivers, and most of our rocks can be weathered and their particles eroded to new places. The next time you pass a river, stop for a few moments to identify some of the effects of water erosion.
Figure E.1.5.21 – Athabasca glacier, along the Banff-Jasper highway, is a valley glacier visible today.
Figure E.1.5.22 – Saskatchewan glacier is another modern-day valley glacier.
Glaciers
Alberta has evidence of glacial landforms everywhere. Glacial landforms are the shapes and patterns caused by glaciers. Most of Alberta has not had glaciers for 9000 years, but most of the province was covered in sheets of ice for 10 000 years before that!
Glaciers back then moved the same way that glaciers move now – very slowly. Glaciers are thick sheets of ice that form when temperatures remain cold and snow levels build higher and higher. Eventually, the snow packs so tightly that it becomes ice and begins cycles of melting and freezing. This causes the glacier to ‘move’. If it is cold enough to get larger, the glacier advances forward. If it is too warm and the glacier slowly melts away, it is said to be retreating. Whether it advances or retreats, the glacier can cause extreme changes to the landscape over which it moves.
Glaciers are sometimes called “rivers of ice” because they flow slowly across the landscape. Because of all that ice, they have different effects on the landscape than rivers have. The ice of the advancing glacier is so heavy that it grinds and scrapes all the way down through the dirt and soil to the solid bedrock of the crust.
When the glacier retreats (melts), it drops all the material it has picked up. This includes dirt, rocks, and even boulders. Remember the Okotoks erratic, nicknamed “Big Rock” discussed earlier because of the frost weathering that is slowly causing it to crack apart? Big Rock is one of those boulders moved by a glacier. Big Rock is located just south of Calgary, and it weighs about 16 500 tonnes. Do you know where the erratic Big Rock came from? A rockslide near Jasper, Alberta, a four-hour drive west of Edmonton! That is why large rocks such as Big Rock are called erratics; erratic means “strange or unpredictable”. Erratics show the power of glaciers.
Alberta has evidence of glacial landforms everywhere. Glacial landforms are the shapes and patterns caused by glaciers. Most of Alberta has not had glaciers for 9000 years, but most of the province was covered in sheets of ice for 10 000 years before that!
Glaciers back then moved the same way that glaciers move now – very slowly. Glaciers are thick sheets of ice that form when temperatures remain cold and snow levels build higher and higher. Eventually, the snow packs so tightly that it becomes ice and begins cycles of melting and freezing. This causes the glacier to ‘move’. If it is cold enough to get larger, the glacier advances forward. If it is too warm and the glacier slowly melts away, it is said to be retreating. Whether it advances or retreats, the glacier can cause extreme changes to the landscape over which it moves.
Glaciers are sometimes called “rivers of ice” because they flow slowly across the landscape. Because of all that ice, they have different effects on the landscape than rivers have. The ice of the advancing glacier is so heavy that it grinds and scrapes all the way down through the dirt and soil to the solid bedrock of the crust.
When the glacier retreats (melts), it drops all the material it has picked up. This includes dirt, rocks, and even boulders. Remember the Okotoks erratic, nicknamed “Big Rock” discussed earlier because of the frost weathering that is slowly causing it to crack apart? Big Rock is one of those boulders moved by a glacier. Big Rock is located just south of Calgary, and it weighs about 16 500 tonnes. Do you know where the erratic Big Rock came from? A rockslide near Jasper, Alberta, a four-hour drive west of Edmonton! That is why large rocks such as Big Rock are called erratics; erratic means “strange or unpredictable”. Erratics show the power of glaciers.
Figure E.1.5.23 – The last period of continental glaciation covered most of Canada under thick sheets of ice.
Figure E.1.5.24 – Moraine Lake is at the base of the Valley of the Ten Peaks. This U-shaped valley is one of the the ancestral homes of the Nakoda First Nations.
Figure E.1.5.25 – Erratics are random, large boulders that were picked up and then left behind by glaciers.
Figure E.1.5.26 – Drumlins are long hills with a distinct shape.
Figure E.1.5.27 – Moraines are piles of soil and rock were left behind by retreating glaciers above Lake Louise.
Glaciers leave other clues that they have been active. Deep piles of gravel are evidence of glaciers. Glaciers form U-shaped valleys through hills and mountains rather than V-shaped valleys that rivers erode away slowly.
Also, glaciers form drumlins, moraines, and eskers. Drumlins are low hills that have been eroded into a unique shape by the glacier scraping over the top. Moraines are piles of various rocks and soils left behind when a glacier retreats. Eskers are strange, snake-like ridges of sediments deposited in the rivers that flow under and through the glacier when it is at its largest.
Also, glaciers form drumlins, moraines, and eskers. Drumlins are low hills that have been eroded into a unique shape by the glacier scraping over the top. Moraines are piles of various rocks and soils left behind when a glacier retreats. Eskers are strange, snake-like ridges of sediments deposited in the rivers that flow under and through the glacier when it is at its largest.
Figure E.1.5.28 – Eskers are long, winding hills formed from rivers running under and through glaciers.
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 5 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!
|
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.
Mechanical weathering occurs when rocks break down into smaller particles. A flowing river has much more power than falling rain has, so it will weather the rocks much more quickly than the rain does.
The cap on a hoodoo is a harder layer of stone than the layers below it. The softer layers are being weathered and eroded more quickly than the harder cap is.
Weathering is any process that causes a rock to break down into smaller pieces or minerals. The smaller pieces do not move away; they stay where they fall. Erosion occurs when particles of rock are moved away, usually by wind or water.
The Wave was roughly formed long ago when great floods carved a deep channel in the sandstone. Then, thousands of years of blowing sand smoothed and polished the sandstone sides of the old river channel. The Wave was first constructed by water
eroding the sandstone, and then it was polished by wind eroding the surface until it became smooth.
As glaciers recede, they melt. This produces large amounts of water that run down the U-shaped valley left behind by the glacier. Because there are many loose sediments dropped by the receding (melting) glacier, many fluvial landforms occur
within the glacial landforms.