Lesson Plan

Sand Density

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Grade Level:
Third Grade-Fifth Grade
Subject:
Earth Science, Geology, Hydrology, Physical Science
Duration:
30 minutes
Group Size:
Up to 24 (4-8 breakout groups)
Setting:
in the park
National/State Standards:
Colorado Science: 3rd grade 3.1; 5th grade 1.1
Keywords:
magnetite, material density

Overview

Students will understand material density as it relates to water and sedimentary rocks.

Objective(s)

Students will understand material density as it relates to water and sedimentary rocks.

Background

Sedimentary rocks are formed from the accumulation of layers of sand, silt, clay, or the hard-shelled bodies of water-dwelling organisms. Geologists are able to closely inspect sedimentary rocks to explain what type of environment produced them.

While many sedimentary deposits are formed by water, others are deposited by wind-especially sand dunes. If a layer of rock is entirely composed of sand with cross-bedding features, geologists can safely assume that the rock was initially deposited by wind. Many thousands of years from now, sandstone may exist where the Great Sand Dunes stand today.

Understanding how water sorts materials of different density is also important to geologists who study sedimentary rocks. Many sedimentary materials are deposited in rivers, lakes, or oceans. Since materials of lighter density can be suspended in slow-moving water longer than denser sediments, lighter materials can travel farther in flowing water than materials of greater density. Gold miners know this well. When panning for gold, miners know that gold-with its high density-will tend to stay at the bottom of their pans, while the less-dense materials can be sloshed off the top.

At Great Sand Dunes, the process in which Medano Creek sorts materials of different density can be seen by following the creekbed upstream, whether or not the stream is in high flow. Larger and larger rocks can be found, the farther one travels upstream. If one was to travel downstream to the area where the terminus of the creek is during peak flow years, very fine sediments and silts may be found laying atop earth, some of which is blown back toward the dunes.

Explore Great Sand Dunes' web page on hydrology to learn more about the unique natural hydrological system of the dunes. 

Materials

clear quart jars, test tubes, pencil and paper, hand lenses, hand shovel or scoop, stirrers (spoons), water

Procedure

Assessment

Generally, smaller particles are found at the top after the sand settles. While magnetite is one of the smaller particles found in sand samples from Great Sand Dunes, it also settles quickly to the bottom of the tube. Why does magnetite settle to the bottom quickly? Is there a difference in the color of materials from top to bottom? How does this activity compare with All Sand Grains, Great and Small? What is the difference between density and size?

Extensions

Have your students compare sedimentary materials in Medano Creek at the Picnic Area with a location further upstream. Hike upstream to look for differences in creekbed materials. 

Use the Magnetic Sand activity as a follow-up to explore the unique properties of magnetite.

Vocabulary

density, sedimentary rock