Grades: 4 – 6

Focus Question: Why do some sand beaches have fine grains of sand and others have coarse grains of sand?

Lesson at a Glance: Students will be asked to collect a small amount of sand from their favorite beach, identify the sand based on provided criteria, and test a hypothesis regarding the type of beach it came from.

Key Concepts: Beaches are formed by the interaction between the forces of the ocean and the material available to create a beach. Beach material comes from either terrestrial or marine sources. The white sand beaches of Hawai‘i have a marine source (coral), and the size of their grains of sand differ based on whether the beach is flat like Kailua Beach or steep like Sunset Beach.

Time: 30 to 45 minutes

Materials: 
Collection - small zip lock bags, paper and pencil.
Identification- small glass jar filled with table salt, observation log.

Preparation and Procedure: Teachers may elect to collect sand from various beaches on their island or ask students to collect the sand as part of the lesson.

A small amount of dry sand should be collected at a point on the beach no more than one foot above the high watermark. Place the sand in a zip lock bag and record the name of the beach and whether it is flat (like Kailua Beach) or steep (like Sunset Beach).

Students should observe the samples of sand and complete the observation log. A determination of whether the sand is fine or coarse should be made based on a comparison with the grains of table salt in a glass jar. After completing the observation log, students should test the hypothesis that coarse sand is found on steep beaches and fine sand is found on flat beaches. Upon completion of the exercise, teachers are encouraged to return the sand to the beaches where it was collected.

Teacher Background: Beaches are made of either terrestrial or marine material. Examples of this in Hawai‘i are the white sand beaches made of pulverized coral (marine) and black or green sand beaches made of basalt or volcanic (terrestrial) material. White sand beaches are familiar to most people, but black sand beaches can be found at Kalapana on the island of Hawai‘i, and green sand can be found at places such as Hakioawa on Kaho‘olawe. Teachers should identify beaches on their own island (if any) where black or green sand might be found. Coarse sand can be found on beaches that are exposed to the forces of the ocean, such as most north facing beaches in Hawai‘i. On these beaches, the force of waves is great enough to carry coarse grains of sand to the shore creating steep beaches that drop off rapidly to the ocean. Fine sand can be found on beaches that are not exposed to large surf, or at beaches protected from the forces of the ocean by a land formation such as a bay.

Extension: Students can use the information they learn during this lesson and NWHI website to determine the type of sand (coarse or fine, terrestrial or marine) that the education team should find during the expedition. The team will collect sand at each atoll or island and record its findings on the website.

Click here for a Sand Identification and Classification Log to Download and use with the lesson above