Teacher’s Corner: The Earth’s Surface – The Only Constant is Change
By Sandra Eldredge
The earth’s surface is constantly remodeled by various geological processes. The changes are one of the most exciting things about geology – not only are they continuous, but in many cases, observable.
Some geological processes, such as those that make mountains or wear them down, typically take place at imperceptible rates. Sudden events, however, can change the landscape in a minute (for example a single earthquake can create a 3-meter-high fault scarp, alter stream courses, and drop the valley floor 1 meter).
Earth’s changes are a topic covered in Utah’s Elementary Science Core Curriculum, in which specific standards and objectives are directed toward increasing knowledge of geological processes and resulting geological features (landforms).
Utah is the ideal place for students to observe geology in action. The state contains many types of landforms, such as mountains, plateaus, mesas, river-eroded canyons, glacier-eroded canyons, volcanos, and basins.
By observing landforms, students can learn where geological processes, including erosion, mountain building, crustal stretching, earthquakes, geothermal activity, landslides, and rock falls are currently active in Utah.
Rates of these geological processes vary. The image is a comparison of the rates at which some of the slower geological processes transpire.
Crustal plate movement, mountain building (except some volcanic mountain building), and erosion are part of the slow evolution of earth’s landscape. This evolution is sporadically interrupted by more sudden geological events, such as earthquakes (following the Borah Peak, Idaho earthquake in 1983, the mountain range rose 0.2 meters, and the adjacent valley dropped 1.2 meters), and volcanic activity (in Mexico in 1943, a volcano called Paricutin appeared in a farmer’s field and rose 160 meters within a week).
Erosion can also happen quite suddenly, and in some cases, may be greatly accelerated by human activities. Flash floods can erode more than 25 centimeters of soil in only a few hours.
Survey Notes, v. 27 no. 1, November 1994