Mapping Rocks and Soil
Print Mapping Rocks and Soil Reading Comprehension
||edHelper's suggested reading level:
||grades 9 to 10
||Flesch-Kincaid grade level:
||lowercase, topography, geologic, cartographers, geology, composition, catalogue, geologist, classify, text, indicate, incorporate, soils, addition, approximate, navigation
||National Resources Conservation Service, United States Department
Mapping Rocks and Soil
By Trista L. Pollard
1 If the Earth's surface changes, you can bet a cartographer will be there to map it. History tells us that maps are used mostly for navigation. However, scientists have found ways to incorporate maps into their studies about the Earth's rock formations and soil composition.
2 Geologic maps and soil maps are two types of maps used by scientists to study our planet's surface. Geologic maps show where different types of rocks or geologic units are located. Cartographers first design a base map of the area that is being studied. This map includes the topography or land features of the area so that it is easily identified. The base map is usually printed in light colors or gray lines. The actual geologic map is placed on top of the base map. Geologic units are classified according to age and type. Rocks of similar ages are labeled with shades of the same color group. There is also a code that helps scientists to recognize the age and type of geologic unit. The code usually begins with a capital letter with one or more lowercase letters that follow. The capital letter stands for the age of the rock in geologic periods, and the lowercase letters tell what type of rock is in that area.
3 In addition to rocks, geologic maps also show special land formations and symbols. Contact lines are drawn to show where two geologic units meet or contact. When scientists classify contacts, they are labeled as either depositional contacts or faults. Depositional contacts are rock layers that form on top of one another. You always hear about faults when scientists report about earthquakes. Rocks that move past each other are called faults. Geologic maps also include symbols for rock beds which indicate the direction and the angle of the bed. Strike symbols represent the direction of the rock bed. Dip symbols give the angle of tilt for the rock bed.
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