- Describe the geologic forces that help create mountain ranges.
- Distinguish constructive from destructive geologic forces in landscape development.
Engage: Does North or South America have the most prominent mountain range?
Step 1: Go to the ArcGIS Online map, Mountain Building, and explore the map.
Step 2: With the Details button underlined, click the button, Show Contents of Map (Content).
Step 3: Click the button, Bookmarks and select Rocky Mountains. Explore the region of the map.
Step 4: Select the bookmark, Andes Mountains and explore the map again.
Step 5: Compare and contrast the Andes and Rocky Mountains. Analyze were the mountains are on each continent, how wide or long each mountain range is, and where the nearest tectonic plates are located.
Explore: Where do mountains form?
Step 6: Check the box to the left of the layer name, Tectonic Boundaries.
Step 7: Select the bookmark, All Mountains. Mountains are “built up” through pressures on the earth’s crust when tectonic plates collide.
- Q: Where do mountain ranges occur in relation to tectonic plates?
Explain: Do some tectonic plate boundaries produce mountains better?
Step 8: Count the number of mountains that occur near each type of tectonic plate boundary (convergent, divergent, and transform).
- Q: Which type of boundary (i.e., convergence, divergence, transform) has the most mountain ranges nearby?
The reason why this tectonic plate boundary type produces the most mountain ranges is because the greater relative velocity of converging tectonic plates colliding provides more energy for “piling up” mountains.
Elaborate: Are there exceptions to this rule?
Step 9: Turn off the layer, World Mountain Ranges, and turn on the Ranges Away from Boundaries layer.
Step 10: Explore the mountain ranges that do not appear to be located near tectonic plate boundaries.
- Q: From what you are learning about how mountains form, which tectonic plate would North America have likely collided with to form these mountains? Hint: look at the orientation of the Appalachian Mountains and the orientation of the plate boundaries.
The reason why some mountain ranges appear not to be located near tectonic plate boundaries is that many of them formed from older tectonic plate boundaries that are no longer active.
Evaluate: What influences the height of the mountains?
Step 11: Turn on the PlateMotions (mm/year) layer and World Mountain Ranges.
Step 12: Consider how mountain heights might compare to the speeds of the colliding tectonic plates.
- Q: Which of the following has the highest peak? The Himalayas, Andes, or Rocky Mountains.
- Q: What is the relationship between the speed of the tectonic plates and the height of the mountain ranges?