## Classroom activity: Exploring the Sands

#### Purpose:

Students will compare two samples collected from the same beach to explore the reasons for differences in grain size.

#### Materials:

 Two sand samples collected from a San Francisco Beach. One labeled "F" for fore beach and the other labeled "B" for back beach. Graduated cylinder Hand lens Sieve set. Two sieves should be used, each with a different mesh size, so that the sand can be separated by grain size into coarse, medium, and fine.

#### 1. Observations:

Using the hand lens, observe each sand sample and record observations for each sample on the back of this paper.

#### 2. Predict:

Predict what you expect to see when you compare the grain size of the sand collected from the back beach to that collected from the front beach.

#### 3. Measure, sieve and record:

1. Using the graduated cylinder, measure the total volume of sand for one sample. Record below.

2. Pour the sample into the sieve set and shake over a piece of paper to separate the sand by grain size: coarse, medium, and fine.

3. Pour the amount of fine sand that passes through the sieves and is collected in the paper into the graduated cylinder. Measure and record below.

4. Pour the coarse sand trapped in the first sieve onto the paper and pour into the graduated cylinder. Measure and record below.

5. Subtract from the total and determine the volume of medium-grained sand. Record.

6. Repeat with the second sand sample

 Total volume of Sample F:________ Total volume of Sample B: _______ Volume of fine-grains:___________ Volume of fine-grains: __________ Volume of medium-grains:________ Volume of medium-grains: _______ Volume of coarse-grains: _________ Volume of coarse-grains: ________

#### 4. Interpret:

Discuss the differences between the two samples. What do you think is responsible for these differences?

#### 5. Results from teacher teams:

Hypotheses were made, tested, and in some cases revised as shown below:

Results from sieving the beach sand: F = Forebeach B = Backbeach

 Amount of Fine Sand Amount of Medium Sand Amount of Coarse Sand Group #1 F B 5 ml 0.5 ml 5.5 ml 29 ml 1 ml 4.5 ml Group #2 F B 14 ml 4 ml 10 ml 8 ml 6 ml 20 ml Group #3 F B 2 ml 0.3 ml 29 ml 25 ml 2 ml 9 ml Group #4 F B >5% 30% 40% 50% 50% 20%

Discussion:

The slope of the back beach is less.
The sand's origin is terrestrial from cliff erosion. It is coarser near the source of origin.
Energy transfer - waves carry finer materials further. Heavier grains stay closer to source of origin.
Wave action removes finer materials.
There is an "energy of removal" and an "energy of accumulation".
Wind is another distributing factor of sand.