Geologic maps can tell you a lot about the rocks beneath your feet. You can use the legend with the map to figure out what rock types are in various geographic areas. The legend can also tell you in what geologic period those rocks formed. Geologists use such maps to help identify where natural resources are and where natural hazards are likely to occur. They are also critically useful in other ways, such as in making wise land use decisions.
While you may be familiar with paper geologic maps, you may not have worked with interactive online geologic maps. For this investigation, you can start with exploring the U.S. Geological Survey’s (USGS) online version of the geologic map of Texas. The geologic time scale shown here will help you to figure out how old the rocks are in various parts of Texas. As you get familiar with how to use the USGS interactive maps, you can widen your exploration to your own geographic area.
- Computer with Internet access
- Color copier (optional)
- Go online to http://mrdata.usgs.gov/sgmc/tx.html. What you’ll see is an interactive geologic map of Texas.
- Click on any part of the map. A new window will open on your computer screen that will show this information:
- Name of the rock unit
- Age of the rock unit (geologic period)
- Primary rock type (such as limestone)
- Secondary rock type (such as dolostone)
Click here to download this activity: Texas Rocks! Activity