Have a good look at what’s under your feet at the beach. There is more to beach sand than many of us realise. Here are some suggestions to guide your observations and help you learn more about sand.
A first look at sand
Pick up a single handful of sand and just look at. What do you notice about? What colour is it? Are all the grains the same colour? Are they all the same shape? Are they actually all grains? Some sand contains more than just sediments from worn away rocks; some contain shells, coral pieces and even forams (the remains (tests) of single celled, ocean dwelling animals called foraminifera).
Use a child’s plastic spade or garden trowel, dig down into the sand. If you just use your hands watch out for broken glass or other sharp objects that can be buried in the sand. Stop every 5 cm and set a handful of sand aside for comparison. You can place it on a beach towel, a piece of cardboard, something solid like a clipboard or just place it in ordered piles on the sand. As you dig down deeper into the sand, do you notice any differences? Things to look out for are:
- Colour variations – depending on where the sand was formed and transported from layers of sand on the beach may differ in colour.
- Grain size – small fragments get sorted naturally be the size of the pieces, can you work out if the grain size gets bigger, smaller or stays the same as you do deeper?
- Sand density – you may need to bring along some kitchen equipment like digital scales and standard measures to do this. Take e.g. a level ¼ cup or tablespoon full of sand and place it on the scales. Record how much it weighs (actually its mass). Toss out all the sand and repeat with other samples. Is there any difference in the weight? If so this will be due to density (amount of weight per unit volume – the higher the weight for the same size sample, the higher the density). Some mineral sand types such as rutile are much denser than other sands.
- Repeat these observations at different parts of the beach: near or away from the water, at different points along the beach. Do you notice any differences? How can these be explained?
What else can you do?
Do some research into different types of sand. Here are two interesting websites to get you started. Rob Holman, a coastal oceanographer from Oregon State University, has collected more than 860 samples of sand, from all continents. This interactive website shows you where each sample was collected and has photos of each that you can compare.
This is an article from the New York Times that has a wonderful story about Rob’s work. There is also a fabulous Audio slide show about his research that includes findings from Palm Beach in NSW.