By Liz Snyder
Background:
All rocks on earth are a part of a large process called the rock cycle. In this cycle, rocks are created and changed by different processes. Let's look at one possible scenario in the life of minerals that make up rocks. Molten lava seeps into surrounding crust. The lava hardens underground and is composed of light colored minerals. The igneous rock that is formed is granite. As the years pass, water and wind erode the crust layers covering the granite in one area. Eventually, the granite is exposed to the surface. As wind and water continue to weather the rock, small bits are carried away and deposited somewhere else. These rock bits (sediments) gather and are pressed together. Now they have formed a sedimentary rock called sandstone. This sandstone is covered up by more sediments and pushed down farther into the earth's crust. The heat and pressure recrystallize the minerals in the sandstone. This rock is now the metamorphic rock called quartzite. This is just one possible sequence of events in the complex processes of the rock cycle. Below is a generalized chart that shows the relationship of rock classifications in the rock cycle.
Objectives: To relate the rock cycle to rocks found in Nebraska.
Materials: Nebraska Rocks from CSD, rocks collected by students, charts of igneous, sedimentary and metamorphic rock.
Procedure:
- Compare the rocks you have collected to those in the labeled rock collection. Name as many of your rocks based on this comparison. Record the name of rock and a brief description (color, crystal or particle size, etc.) In the data table.
- Using the rock charts, determine the classification of your rocks as igneous, sedimentary or metamorphic. Record each rock's classification.
Observations:
Rock Name Description Classification _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________
Conclusions:
- Draw a diagram of the rock cycle including the rocks in your collection.
- What rock classification has the most examples from your collection?
- What does this suggest about processes that are occurring in Nebraska? In other words, what is happening to make this type of rock?