February 2020

LEARNING ACTIVITY:

Pumice Rocks Ahoy! Credit: deltalimatrieste/ Wikimedia

GRADE LEVEL: 2–5 umice, scoria, and obsidian are all igneous rocks. Igneous rocks are rocks MATERIALS that either cooled from hot, liquid Scoria material on flank of Teide on Tenerife, Canary P Islands, Spain • Samples of pumice, scoria, magma within the Earth or from volcanic Credit: Chmee2/Wikimedia CC BY-SA 3.0 and obsidian (Samples can ash or lava on the surface of the Earth. The be purchased online through many types of igneous rocks come from • Why do you think pumice is mined for use school specialty stores. different types of magma that contain in abrasives (for personal care, industrial “Pumice stone” can also be different materials and cool at different rates cleaners, rubber erasers, stonewash jeans, found at bath and body depending on how they are placed. Obsidian etc.) and in absorbents (potting soil, pet suppliers. Scoria, or “lava Credit: ©Dr. Richard Busch, from the ESW Image Bank litter, etc.)? rock,” can be purchased at Pumice forms from magma that contains a garden supply centers.) large amount of gas bubbles, and when it of space taken up by the sample (its • Why do you think scoria is used in • A large, transparent, plastic erupts to the Earth’s surface and cools and volume). A sample that feels heavier than landscaping instead of obsidian? tank or bucket half-full of hardens, these gas bubbles remain in the rock. another sample of about the same size water, with the amount of has more material within the sample, • Why has obsidian been used throughout water significantly more than Scoria is another volcanic rock with holes in which is to say the heavier sample is more history to make sharp tools for cutting? the size of the largest sample it, though the amount of volcanic material dense than the other. A sample that sinks (It is important to use plastic between the holes is usually thicker, or more is denser than water. • What other materials are mined due to to ensure it won’t break compacted, in scoria than in pumice. It is their useful characteristics? during the tests.) often dark red. 2 Now test each sample by placing it into • Towels for spills the tank to see what happens. Note: Some NGSS CONNECTIONS • Tongs Obsidian is a shiny, dark, dense volcanic glass. specimens may become water-logged if • Science and Engineering Practices — ​ It was formed from lava that cooled very they sit in the water too long, so try to test Analyzing and Interpreting Data quickly. It normally contains very few gas dry specimens. • Disciplinary Core Ideas — ​Earth and bubbles, if any. Human Activity 3 Discuss the results. How do you think • Crosscutting Concepts — ​Cause and Effect PROCEDURE commercial use of these items would 1 Compare the samples by simply holding vary based on the differences of (For more standards correlations go to www. them and seeing which you find heavier these samples? MineralsEducationCoalition.org/standards.) and which feels lighter. Do you think these samples are heavier or lighter than FURTHER DISCUSSION This activity is based on the “Sink & Float water? Density describes the relationship • Why would pumice be used to make Rocks” activity on the MEC website. Learn Source: Minerals Education between the amount of material (mass) lightweight construction materials such as more about rocks and the rock cycle Coalition. Adapted with permission. contained in the sample and the amount concrete block and concrete? at www.MineralsEducationCoalition.org.