If you’ve been thinking that beach profiles look just a bit too complicated or “I’m not standing on a beach with a garden cane looking like a complete idiot” then here’s a measurement that you can do easily and unobtrusively!
All you need is a ruler and pen and paper to record your results.
Head to a pebbly beach. You can investigate to see whether the size of the pebbles varies at different places on the beach.
- Are the pebbles bigger nearer to the sea or nearer the cliffs / dunes / promenade?
- Are the pebbles bigger at the north / east end of the beach or at the south / west end?
But how do you measure a pebble?
You need to always take the longest measurement. It is called the long axis. If your pebble is oval shaped, it is easy to know where to measure, but if the shape is more irregular then you may need to test out a few different directions to find the longest one.
So that’s it? No, not quite.
You can’t just choose 1 pebble. That’s not going to prove that the pebbles are bigger at a certain place because you may have picked up the one huge one when all the rest are pretty small.
At each location on the beach you need to take a sample of at least 10 pebbles. You need to pick them up randomly. Close your eyes and take the first one that you touch.
Note the long axis measurement for all 10 pebbles. You can then add the numbers together and divide by 10 to find the average pebble size at each location on the beach.
And if you are measuring the beach profile, you can investigate whether the bigger pebbles form the steeper or gentler parts of the slope.