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Weathering SE - Answers to gizmo
Environmental Science
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Student Exploration: Weathering
Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.
Vocabulary: abrasion, chemical weathering, clay formation, climate, dissolving, frost wedging, granite, limestone, mechanical weathering, rusting, sandstone, shale, weathering
Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Compare the two pictures at right. Both pictures show the same kind of rock, granite.
- Which rock do you think has been exposed on Earth’s surface longer?
B
- Why do you think so?
While A shows visibly that the rocks have aged from the rust, rust forms a bit quicker than a rocks breaking down and form into clay. B shows the rocks have gone through clay formation, which probably took decades to fully form.
Gizmo Warm-up When rocks are exposed on Earth’s surface, they are gradually broken down into soil by the actions of rain, ice, wind, and living organisms. This process is called weathering. In the Weathering Gizmo, you will explore how weathering takes place.
To begin, select the SIMULATION tab. Notice the selected Rock type is Granite, a hard, dense rock.
- Click Play ( ). Wait for about 5,000 simulated years, and click Pause ( ). What do you notice?
The rock got smaller
- Click Fastplay ( ). Wait for about 50,000 simulated years. What do you notice?
The rock got even smaller
- Based on your observations, is weathering a fast or slow process?
Slow process
Activity A:
Types of weathering
Get the Gizmo ready:
● Select the ANIMATION tab. Check that Frost wedging is selected.
Introduction: Mechanical weathering occurs when rocks are physically broken or worn down. Chemical weathering occurs when the minerals in the rock are changed by chemical reactions.
Question: What are the most common ways in which weathering occurs?
- Observe: Read the text about frost wedging, then click Play.
A. In the process of frost wedging, how does ice cause cracks in rocks to become larger?
It solidifies, and hardens, expanding the rock because of its force against the cracks.
B. Is frost wedging more important in a warm or a cold climate?
Cold climate
- Observe: Read about and look at the animations for the other major types of weathering: Abrasion, Pressure release, Dissolving, Clay formation, and Rusting.
A. What are three different ways that rocks can be worn down by abrasion?
Wind carrying sand wears away rocks, rivers carrying sediments, and ice moving over the surface of the mountain drags the rocks along the bottom which grinds down the rocks below.
B. How can a large block of granite form layers like an onion?
By sediment building on it over time.
C. What type of rock is affected by dissolving, and what features result?
Limestone, making limestone pavements, underground rivers, caves, sinkholes, and oddly-shaped mountains.
D. How does clay formation affect a rock?
It makes it more weak and prone to crumble.
E. Which part of a rock will undergo rusting?
Iron
- Fill in: Scientists use the terms “oxidation,” “carbonation,” “hydrolysis,” and “exfoliation” for different types of weathering. Fill in each blank with the appropriate term.
Pressure release: Exfoliation Dissolution Carbonation
- Observe: Select Other. Read the descriptions of each type of weathering, then match each to its description below:
B Salt weathering
A. Weathering from chemicals produced by colonies of algae and fungi.
D Heat expansion B. Weathering that occurs when crystals grow.
C Root weathering C. Weathering caused by the growth of trees.
A Lichen growth D. Weathering common in desert climates.
- Categorize: List all of the types of mechanical weathering you have learned about in the left column of the table, and all of the types of chemical weathering you have read about in the right column.
Mechanical weathering Chemical weathering Frost wedging Abrasion Pressure release Salt weathering Root Wedging
Dissolving Clay formation Rusting Lichen Growth Rust
- Interpret: Based on the descriptions and images, guess which type of weathering is shown by each of the images below. Explain each answer.
“Honeycomb” rocks in Spain Stalactites in South Dakota Split rock in Scotland
Salt Weathering because the rocks were probably penetrated by nearby water with dissolved salt. As the water evaporates, the salt crystals expand, making the rock break apart.
Dissolving because when the rainwater and carbon dioxide, it forms weak carbonic acid which dissolves calcium carbonate in limestone leading to caves like these.
Frost Wedging because water inside cracks in the cave freeze over time, solidify, and expand resulting in caves like these
Describe what you see:
Look at Weathered rock above the outcrop. How much rock was weathered?
The rock got smaller, and 3 trees grew on it. 3,510 m
åLIMESTONE
Describe what you see: Look at Weathered rock above the outcrop. How much rock was weathered?
The rock got smaller, it grew trees on it, it crumbled at the bottom and cracks have formed in it
5,735 m
åSHALE
Describe what you see: Look at Weathered rock above the outcrop. How much rock was weathered?
The rock has drastically gotten smaller, it grew trees on it, and it crumbled at the bottom.
9,839 m
- Compare: Compare the results of weathering of different landscapes:
A. Which rock types tend to weather into rounded shapes? Sandstone
B. Which rock weathers into caves and lumpy hills? Limestone
C. Which rock weathers most quickly? Shale
Most slowly? Granite
Observe: Click Reset. Select Granite and click Fastplay. Run the simulation until you can see large cracks forming in the rock. (This may take a while, be patient!) Take a snapshot of the resulting outcrop and add it to your document. Label this image “Granite cracks.”
Challenge: Based on the weathering patterns, guess the rock type shown in each photo.
Limestone Granite
Sandstone Shale
Activity C:
Weathering rates
Get the Gizmo ready:
● On the Simulation tab, select Sandstone. ● Check that Frost wedging, Clay formation, and Other are all selected.
Introduction: The most important things that determines how quickly a particular rock type weathers is the climate, or typical weather conditions. Rocks in cool and dry climates weather much differently than rocks in hot and rainy climates.
Question: How does the climate and rock type affect how quickly a rock weathers?
- Predict: In each “Climate type” box, Highlight the condition you think will lead to the fastest weathering for the given weathering type.
Weathering type Climate type Frost wedging Hot Cold Wet Dry Clay formation Hot Cold Wet Dry Dissolving Hot Cold Wet Dry
- Experiment: Click Return to original settings. Using the Gizmo, test the effect of precipitation on the rate of weathering by measuring the amount of weathered sandstone in 20,000 years with low and high precipitation. Be sure to keep all the other variables the same. Describe your results below.
Weathered rock (low precip.) 733 m3 Weathered rock (high precip.) 354 m
How does the amount of precipitation affect the amount of weathering?
More precipitation results in less weathered rock, and less precipitation results in more weathered rock.
- Experiment: Click Reset and Return to original settings. Now test the effect of temperature on weathering rates. Describe your results below.
Weathered rock (low temp.) 1324 m3 Weathered rock (high temp.) 1560 m
How does the temperature affect the amount of weathering?
It increases it slightly
- Explain: Why do you think the rate of weathering tends to increase at hotter temperatures and higher amounts of rainfall?
Hotter temperatures and water can cause rocks to weather much quicker.
Weathering SE - Answers to gizmo
Subject: Environmental Science
Standard
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