|Students learn the components of a bedrock geology map by mapping the surface of a cookie.||Materials:
|A Windows to the Universe activity inspired by an example in Structural Geology of Rocks and Regions, by G.H. Davis|
|7 - 12|
|5 min prep time and 25 min class time|
Student Learning Outcomes:
- Show students an example of a bedrock geology map. If possible, use a map that is from your region. Discuss how the map describes the type of rocks found near the surface of the Earth. (You may find the background information section towards the end of this activity helpful!) Point out important features of the map such as (a) title, (b) scale, (c) key to rock types and their ages, (d) key to symbols, (e) topographic contours, (f) orientation with North at the top (typically).
- Pass two pieces of paper, a transparency grid, and pencil to each student. Have them mark the plain paper with a North arrow pointing towards the top of the paper.
- Pass a cookie to each student. Tell them not to eat or break their cookie until finished with the activity!
- Have students place the cookie on the piece of paper that has the North arrow. The cookie is a place on the Earth's surface that they will map. It is very important that students not move the cookie until the activity is over because this will change where North is located. Have students mark the graph paper with a North arrow (in a direction that is parallel to one of the sets of lines).
- Have students place the transparent grid on top of the cookie with one direction of lines oriented parallel to North. Tell students that the scale for this activity, will be one square on the transparency grid equal to one square on the graph paper.
- Ask students how wide their cookie is in the East-West direction. How many squares of the grid does it cover at its widest point? Ask students to mark out that number of squares on their graph paper.
- Ask students how wide their cookie is in the North-South direction. How many squares of the grid does it cover at its widest point? Ask students to mark out that number of squares on their graph paper. Draw in the general shape of the cookie based on these measurements.
- Now ask students to identify the places on the cookie where the surface material is different. To do this accurately, use the squares of the grid to help you place objects into your map (if they are in a square within the grid they will be in the corresponding square on the graph paper map.
- Once all objects are placed in the map, color them according to their material. For instance, color a raisin differently than a chocolate chip, but color all chocolate chips the same color. Record what each color corresponds to in a key. The colors do not need to be the same as the colors of the cookie. In fact, in a bedrock geology map the colors are usually nothing like the color of the actual rock!
- Mark the scale on the map. The transparency grid has cells that are 5 mm long. Tell students to mark a scale that indicates that one box on the graph paper is equal to 5 mm on the real cookie.
- Next title your map with something that indicates the location and the type of features that the map shows. (For instance, "bedrock geology of an oatmeal raisin cookie"). Then label with name and class period.
1. Before consuming cookies, number each sheet of paper that contains a cookie.
2. Record the numbered cookie each student had on a separate piece of paper.
3. Have students line up the cookies in order of number and trade maps with another person in the class.
4. Can students identify which map describes each cookie?
As an extension, have students create a cross section through their cookie by breaking it in half and drawing what it looks like on the inside. Remember to emphasize the importance of both horizontal and vertical scales. Have students mark a line on their cookie map to indicate the location of the cross section.
For a more advanced version of this activity, have students make a map of a pizza. A pizza has a more complex surface with varied components such as cheese, sauce, crust and toppings. A pizza also allows students to make a cross section that resembles the layering of sedimentary rocks (layers of cheese, sauce, crust).
This example may seem simplistic, however, a non-geological example such as mapping a cookie can help students become familiar with bedrock geology maps and the information that they provide about a place on the Earth.
Importance of Bedrock Geology Maps:
Bedrock geology maps are important tools for land planners and government officials. For instance, Bob Shinn of New Jersey's Department of Environmental Protection was very enthusiastic when the new version of his state's bedrock geologic map was finished. About the new map he said, "it is invaluable for all ground-water contamination and water supply projects, and for protecting aquifer recharge areas and assisting land use planning and watershed initiatives. The geology of the state is crucial because it serves as the basis for other environmental maps, including characterization of watersheds, ground water recharge, aquifers, radon and sink hole potential as well as ecological habitat. The maps are also essential for the evaluation of water supplies and the clean up of contaminated ground water."
Bedrock Geology Map Symbols:
General Political Information: Usually listed in a gray color are roads, towns, buildings and borders.
Topography: Contour lines that connect areas of equal elevation are often on a bedrock geology map.
Water: Lakes, rivers, and oceans are shown in blue.
Rock Formations: Each rock formation has a different color and letter symbol. The first letter in the symbol refers to the geologic age and the following letters are for the formation name or rock type. Contacts between different types of rocks are shown as thin black lines, except when rock formations are separated by a fault, which is shown as a thick black line.
Strike and Dip Symbols: tell what happens to rock layers underground. Sedimentary rocks are formed as horizontal layers, but over millions of years they can become tilted or folded. Strike indicates the direction that a layer is tilted (if you were standing on top of the rock layer you could walk this direction without going uphill or downhill). Dip is measured in degrees and indicates how much it is tilted.
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