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Geographic Regions and Backyard Geology with the USGS Tapestry Map

Summary:
Students explore the USGS Tapestry of Time and Terrain map while answering questions about the topography and geology of their home, state, country and continent. Materials:

This lesson can be accomplished in either of two formats: one in which students use paper maps and the other in which they use a web site that contains the same map.

Using paper maps:

  • One North America Tapestry of Time and Terrain map for each group of four students (Print it yourself from the pdf file or purchase from the USGS for $12 each.)
  • One North America political map for each group of four students.
  • One Map Worksheet for each student
  • Rocks from the local area (Ask student to bring in rocks they have found.)
  • If possible, rocks from around the country or continent

Using the Tapestry web site:

  • One computer with web connection for each student or pair of students with browsers at the Tapestry of Time and Terrain web site
  • One Web Worksheet for each student
  • Rocks from the local area (Ask student to bring in rocks they have found.)
  • If possible, rocks from around the country or continent

Worksheets:

Purchase PDF/PPT versions

Source:
A Windows to the Universe original activity made possible by the USGS Tapestry project team.
Grade level:
7-12
Time:
10 minutes prep time and 30 minutes class time (much longer prep time if you collect the rocks yourself)
Student Learning Outcomes:
  • Students will interpret the map to find the answers to questions.
  • Students will understand the types of rocks found in their area.
  • Students will understand how the rocks in their area fit into the larger context of the country or continent.
Lesson format:
Hands-on activity with the Tapestry map or web-based activity with group discussion

National Standards Addressed:

National Science Standards:

National Geography Standards

DIRECTIONS:

Using paper maps:

  1. Have students bring in rocks that they have collected including those that they find near home and those that they found on vacations within North America. Describe the things that should not be brought in like concrete, driveway gravel, rocks purchased from a shop of unknown locality. For this activity it is important that we know approximately where each rock was found (at least the state or province where it was found).
  2. Have each student take out a rock they found in their local area or somewhere in the country. If rock identification was a part of earlier lessons, this is a good opportunity to reinforce the concept by having students identify their rock as at least sedimentary, igneous, or metamorphic. Ask students how old they would guess the rocks are. Can you tell by looking at them? Can you tell if some rocks are younger or older than others?
  3. Provide each group of four with a Tapestry map, a political map, and worksheets. Discuss what is described in each map.
  4. Orient students to the unfamiliar Tapestry map. It shows topography of the land surface with shaded relief. Rocks that are exposed at the surface are indicated with various colors depending on the age of the rock. If the surface is covered with forests, grass, or dirt, geologists figure out what type of rock is below and put that on the map.
  5. Direct students to, as they fill out their worksheet, use the political map to find locations and then use the Tapestry map to find the topography and age of rock at those locations, discovering how geology of their region compares to the geology of the country. (Help them out by including a star on the Tapestry map that indicates the location of their city or town.)
  6. Once worksheets are filled in and students feel reasonably comfortable with the Tapestry map, bring out all rocks. Ask students to use the maps to find those locations and determine the approximate age of the rock. Discuss with students that this process is approximate because small rocks can be transported by wind and water and thus, their rocks may have come from elsewhere and may not be from that time period. Discuss relative and absolute dating methods that allowed scientists to make a map like the Tapestry map.

Using the Tapestry web site:

  1. Have students bring in rocks that they have collected including those that they find near home and those that they found on vacations within the United States. Describe the things that should not be brought in like concrete, driveway gravel, rocks purchased from a shop of unknown locality. For this activity it is important that we know approximately where each rock was found (at least the state where it was found).
  2. Have each student take out a rock they found in their local area or somewhere in the country. If rock identification was a part of earlier lessons, this is a good opportunity to reinforce the concept by having students identify their rock as at least sedimentary, igneous, or metamorphic. Ask students how old they would guess the rocks are. Can you tell by looking at them? Can you tell if some rocks are younger or older than others?
  3. In a computer lab, have students work to fill in their worksheets by surfing the Tapestry web site.
  4. Once they have finished the worksheet and feel comfortable with the Tapestry map, ask students again approximately how old their rock is. Ask students to use the maps to find those locations and determine the approximate age of the rock.
  5. Discuss with students that this process is approximate because small rocks can be transported by wind and water and thus, their rocks may have come from elsewhere and may not be from that time period. Discuss relative and absolute dating methods that allowed scientists to make a map like the Tapestry map.

BACKGROUND INFORMATION:

Relative dating methods divide Earth history into different time periods such as Paleozoic, Mesozoic and Cenozoic or smaller divisions such as Cambrian, Ordovician and so on, without any reference to numbers. For a long time, before absolute dating methods were discovered, all people knew was that the rocks found lower in a stack of sedimentary layers were older than the ones found higher in the stack of sedimentary layers (a concept called superposition). By looking at the fossils in different layers, scientists were able to correlate a layer in one area with a layer in another area and proposed that they were, at least relatively, the same age.

Absolute dating methods measure time in some units such as thousands or millions of years. Today there are a variety of absolute dating methods many of which determine dates based on the natural radioactivity of certain elements found in rocks. Radioactive elements decay, turning from one form to another, over time at a constant rate. Usually "parent" atoms lose particles from their nucleus to become "daughter" atoms. Since the rate of change from parent to daughter is constant over time, one can figure out when the mineral was made by chemically measuring the ratio between the parent atoms and daughter atoms.

Geologic maps are used for many different purposes. People use geologic maps to find suitable building locations, find locations to drill water wells, identify areas more prone to erosion, search for potential fossil localities, or to identify sources of rock for building stone, sand and gravel. Other, more complex, geologic maps have the types of rock and depositional conditions listed in the key. The Tapestry map simplifies this a bit to concentrate just on rock age. The colors of rocks of different ages have little to nothing to do with the colors of the actual rocks!

Topography is the shape of the Earth's surface. On the Tapestry map is shown as shaded relief. Although the shading looks like it was originally a picture of North America from space, it is actually made digitally.

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