Instructions

1) Before beginning the lab, ask students to think of their favorite beaches on Maui. What makes these beaches stand out from the others?

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2) Have each student identify a familiar beach and write a description of the sand at that beach. Challenge students to make that description as detailed as possible. (If students are keeping a journal, have them write these descriptions as entries.) If students are having difficulty, ask them questions such as:

• What does it feel like when you walk or sit on it? Is it smooth, sharp, gritty?
• What color or colors is it?
• Is the sand uniform size, or are there larger pieces of rock, coral, or shells mixed in with smaller sand grains?
• Does it stick to your body or is it easy to brush off?
• Are the grains coarse or fine? How do they compare with other beaches?

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3) Ask several students to share their descriptions until you have heard some clear contrasts. Then have the class draw comparisons among the sandy beaches described. Ask students to brainstorm about what might cause these kinds of differences in sands at different beaches. Write their ideas on the board or overhead.

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4) Have students brainstorm what sand is made of and record those ideas as well. (There are two basic components of sand: “Biogenic” components are the fragmented or whole remains of marine animals and plants that have hard skeletons of calcium carbonate. These organisms include corals, molluscs, sea urchins, single-celled animals called “foriminifera,” and algae. “Detrital” components are fragments of rock that have been worn down through weathering and erosion. They include eroded basalt, the most common material in lava flows; sharp fragments of lava called volcanic glass; and minerals such as garnet, olivine, and magnetite.)

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5) Have students brainstorm what could cause differences in grain size (how coarse or fine the sand is) at different beaches. (Particle size is influenced by the materials from which the sand is made and how easily they are broken and worn down. Another key factor in determining particle size is wave size and energy. Each crash of a wave on shore temporarily suspends some sediment—sand—in water. The amount of sediment is directly proportional to the size of the wave. The size of the sediment that can be transported by a wave is also proportional to its size and energy. A beach subject to large crashing waves will generally have coarser sand than one that is lapped by small calm swells because the larger waves can transport the finer sediments out to sea. This factor can account for seasonal differences in the sand size at beaches, as well.)

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6) Display the images of Oneuli and Oneloa beaches. Locate the beaches on the map of Maui (they are just north and south of Puʻu Ōlaʻi, near Mākena). Find out if any students have been to these beaches. They may know the beaches by other names. Oneuli is sometimes called “Black Sand Beach.” Oneloa is also known as “Big Beach.” Tell students they will be studying these two beaches more during this activity.

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7) Divide the class into lab groups of three to four students. Make sure they have all of the equipment they need and hand out the Student Pages “Sand Analysis Lab Procedures and Resources” and “Sand Analysis Lab Data Sheet.”

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8) Pass out labeled sand samples from Oneuli and Oneloa beaches. Ask students to look at the beach photos (leave the acetate images up) and the sand samples. Ask them to generate hypotheses about the composition and relative grain size of the sand at each beach, and record these hypotheses on their group’s lab sheet.

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9) Run the sand analysis lab, following the instructions on the Student Page “Sand Analysis Lab Procedures and Resources.”

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10) As homework, assign the Student Page “Questions Following the Sand Lab.”