Esri. Adapted with permission.
- Computer with internet access
1. Start the map at http://www.arcgis.com/home/webmap/viewer.html?useExisting=1.
2. Explore: Does North or South America have the biggest mountain range?
- Click Modify Map, and then click the Contents button.
- Click the Rocky Mountains bookmark, then click the Andes Mountains bookmark for closer examination.
- Compare and contrast the Andes and Rockies.
- Measure the Rocky Mountains and the Andes Mountains.
- Which mountain range is longer: the Rockies or the Andes? The Andes is longer.
- What factors help make the Andes the longest continental mountain range? The long edge of the continent happens to move perpendicular to its long axis, creating a range along its entire length.
3. Explore: Where do mountains form?
- In the Contents pane, turn on Tectonic Boundaries.
- Click the All Mountains bookmark. Mountains are “built up” through pressures on the Earth’s crust when plates collide.
- Where do mountain ranges occur in relationship to tectonic plates? Most form at the plate boundary edges because of collisions.
4. Explain: Do some plate boundaries produce mountains better?
- Count the number of mountains that occur near each boundary type.
- Based on this information, from which type of boundary are mountains more likely to occur? Convergent produces about 25, divergent produces about six, and transform produces about eight.
- Why would this plate boundary type be better at creating mountains? The greater relative velocity of converging plate crashes provides more energy for piling up mountains.
5. Elaborate: Are there exceptions to this rule?
- Turn on the Ranges Away From Boundaries layer.
- Find mountain chains that do not appear to be located near plate boundaries.
- Look at the Appalachian Mountains in the eastern United States.
- From what you are learning about how mountains form, which plate would North America have had to collide with to form these mountains? Europe — even the shape of how the continents appear to fit together hints at it.
- Is there evidence in Europe of this collision? Which range is it? The Scandinavian range was formed at the same time as the Appalachians. South America (Brazilian Highlands) also has a matching mountain range in Africa (Bie Plateau).
- Summarize why some mountain ranges are not located near plate boundaries. Many of these ranges formed from old plate boundaries that are no longer active.
6. Evaluate: What influences the height of the mountains?
- Turn on the Plate Motions (mm/year) layer.
- Think about how mountain heights might compare to the speeds of the colliding plates.
- With this in mind, rank which mountains you think are higher: Himalayas, Ural Mountains, and Rocky Mountains. Himalayas = 29,000 ft., Rocky Mountains = 14,400 ft., Ural Mountains = 6,200 ft.
- What is the relationship between the speed of plates and height of mountain ranges? The faster the plates are moving, the higher the mountain ranges.
- At the top of the map, click the Measure button.
- Hover and click the Distance button.
- Click continuously along what you want to measure.
- Double-click to finish.
- At the top of the map, click the Bookmarks button.
- Choose your bookmark; the map will take you there.
For more activities, visit http://www.esri.com/geoinquiries.