The sediment you find at the shore can tell you a lot about the processes that happen there. In this lab we have (usually) processed small sediment samples by sorting them into different sizes.The sediment you find at the shore can tell you a lot about the processes that happen there. In this lab we have (usually) processed small sediment samples by sorting them into different sizes.
Below are five sieves with different mesh spacing. The sieves are arranged with each above the next finer mesh. Particles put in the top spill through all of the sieves in turn with each sieve retaining everything to large to pass through. The bottom container, the catcher, is there to catch whatever makes it through all of the sieves. At right is a photo showing the sieves arranged in stack with a hand for scale.
Here's what the screen looks like. This is the sieve that passes only particles smaller than 0.25 mm (across their smallest axis - a long skinny particle could go through if it were aligned just right).
Here's the basic setup. A microscope to take a look. A scale, the sieves, and the sediments.
Here are the two samples. These were collected at different places on the Fraser River delta. One of the exercises in this lab is to determine where on the delta they were found. The samples are visibly different. Which one appears to be more poorly sorted?
Next, you'll need to use the stack of sieves. Hold the stack upright with one hand on top and one on the bottom. Gently shake the stack from side-side. Don't tip it over. Keep one hand above and below at all times to prevent the stack from coming apart.
After you've agitated the sediments long enough (five minutes or so) you can carefully pour out the different size fractions. They are shown below all together and then separately so you can see what they look like. These are all the size fractions, using this set of sieves, that were contained in the Fraser River B sample shown above. We've sorted them by size ranges.
Below is the largest size range: > 4 mm.
These are sediments in the range 4 mm > particle diameter > 2 mm.
Next: sediments in the range 2 mm > particle diameter > 0.5 mm.
Next: sediments in the range 0.5 mm > particle diameter > 0.25 mm.
Next: sediments in the range 0.25 mm > particle diameter > 0.125 mm.
Finally: sediments less than 0.125 mm in diameter are caught in the catcher.
You'll weigh and record each fraction. The results for the two Fraser River Samples are given below.
The table below lists the measured sample and size fraction masses for three samples collected at the Fraser River Delta. Use these values to complete the exercise in the Beach Processes lab.
We've prepared an Excel spreadsheet for you to use if you wish Fraser River Sediments Excel Spreadsheet.xlsx.