Folded Mountains

Materials / Preparation

• Each group of students will need:
  • Folded Rocks Photos. These can be accessed online on the Mountain Building Student Web Page, projected in the classroom, or you can make copies of the pictures for each group. Use the pdf version to print for the classroom.
  • 2 oz. each of four different colors of play dough
  • One butter knife
• Students will use pages 7 and 8 of their Mountain Building Journals.

Grouping

Groups of two to four

Teacher tips

Background information: Folded mountains are formed as the result of compression or squeezing of the Earth’s surface. These forces cause the rocks to bend (fold) and break (faulting). If the compression exceeds the rock’s strength and it can no longer withstand the strain, it will break. This can cause large blocks of the Earth’s crust to ride up and over the top of adjacent blocks in a process called thrust faulting.

Students should understand that while this activity only models folding; however, in actual folded mountains both folding and faulting occur.

If you would like to make your own Play Dough, you can get directions from the resource: Folds and Faults.

Procedures

1. Tell students that they will be building some mountains made up of sedimentary layers.
   a. Have students roll each color of play dough, forming a flattened pancake about 15 cm. (or 6 inches) in diameter and 1 cm (or 1/3 inch) thick. The greater the diameter and the thinner the layers, the more easily the model can be folded.
   b. Have the students stack the layers on top of each other. It doesn't matter in which order the colors are stacked.
   c. Ask students to observe the layers from the side; the layers should look flat.
   d. Have students draw a side view of this model of unfolded layers in their Mountain Building Journal on page 7.
2. Now, we will simulate compression: Have the students place their hands, one on either end of the play dough layers so that they can squeeze it along its longer axis. Tell them to gently push their hands together causing the play dough layers to fold and buckle. Try to make at least one upward fold (anticline) and one downward fold (syncline).
   a. Ask students what might cause similar compression to occur to the earth's crust? (Answer: plates moving toward one another)
   b. You might also want to ask students where that might occur: (Answer: at convergent plate boundaries)
   c. Ask students to draw the folded model on page 7 of their journals.
3. Have students cut the top off of their folded mountains to model surface erosion, discuss what they observe, and draw and label what they see on page 7 in their journals.
   Note: Repeating bands of sedimentary layers, such as in this model, when found at the surface of the earth tell a geologist that they have found an eroded fold.
4. Have the students try cutting their mountain any way they choose (as long as it is different than the views they already have). They should draw and label what they see on page 8 in their journal. Remind students that folding, faulting, and erosion can produce unpredictable results. A geologist uses the structures they see to interpret the history of the rocks.
5. Have students look at the images of the Folded Rocks Photos . These can be accessed directly from the Mountain Building Student Web page, or you can project the images for the class. Ask students how these images compare to their models.

6. Have students complete the Review and Reflection questions on page 8 in their journals.

   Optional questions for class discussion:
   Ask students what they think would happen if they had rocks that were less squishy and more brittle than play dough? When the rocks got squeezed, they might actually break instead of just bend. Tell them that natural mountains do both. Sometimes they bend and sometimes they break. The breaks are called faults, and faults that move because of compression are called "thrust faults." We therefore call this type of mountains "fold-thrust mountains" – the mountains both fold and have breaks called thrust faults.

Resources used

Folds and Faults
http://www.teachingboxes.org/catalog.jsp?id=DLESE-000-000-009-639

Folded Rocks Photos
http://www.teachingboxes.org/mountainBuilding/lessons/foldImages/index.html

pdf version of Folded Rocks Photos
http://www.teachingboxes.org/mountainBuilding/lessons/foldImages/FoldedRocksPhotos.pdf

Mountain Building Journal
http://www.teachingboxes.org/mountainBuilding/journal/MBJournal.pdf

Mountain Building Journal: Teacher's Guide
http://www.teachingboxes.org/mountainBuilding/lessons/journal/MBJournal_teacherGuide.pdf