So it’s nearing the end of September which should mean the temperatures are cooling off…except that they aren’t. Not really anyway. Yesterday the airport recorded a temperature of 91 degrees {Fahrenheit} and the forecast for today and the following week is in the upper 80’s and possibly hitting 90 degrees again! And to top it all off, tomorrow is the first day of fall! ::sighs:: Every summer I contemplate moving just a smidge farther north so that when it’s fall, it actually feels like fall. But, here we are and here we stay. And it’ll cool off….sometime. 😉 Anyway, let’s focus on something else for a bit, shall we?
This week I’ve shared our Rocks & Minerals Unit Study and have started diving deeper into some of the activities. Today I’ve got another one for you.
I started out our unit delving into the layers of the Earth. I followed this explanation with a soil 
exploration activity. We actually did this activity 3 times, each time following a different set of directions. Today I’m going to give you the one that worked best. We used soil from our own yard twice and soil from Gramma’s yard (who lives about 20 minutes away). We wanted soil from different locations to see how the compositions would vary.
Our objective here is to observe, examine, and identify the separation of the mineral components of soil by particle size in a sample of soil.
Materials needed: a jar with a lid, freezer ziplock bag, soil sample, dish detergent solution [see below]
Dish detergent solution: This solution provides good particle separation to make it easier to see the layers once everything has settled. You’ll need an empty 1 gallon jug, 1/4 teaspoon powdered dishwasher detergent, 1/4 cup baking soda, and water. In the jug, add the powdered dish detergent and baking soda. Fill the jug up with water. Shake it just a bit to make sure everything has mixed together.
Procedure:
- Take your soil sample(s).
- Place your soil into the freezer ziplock bag and crush any chunks. *I recommend the freezer variation of the baggies because they tend to be a little sturdier.* You could also spread the soil out on a paper plate and use the back of a spoon.
- Pour your soil into your jar. Fill your jar about halfway to two-thirds full- once the air is gone from the soil it will condense down. (First picture below.)
- Fill your jar the rest of the way with your dish detergent solution. (Second picture below.)
- Shake your jar for about a minute. (Third picture below.)
- Now set your jar down and don’t touch it for awhile. You’ll start to see some of the particles settle after a couple of hours. Check back on your jar after 24 hours to see all of the particles settled.
- Observe the layers. Write down your findings on your observation sheet. (I’ve provided one below!)
Explanation:
The basic mineral components are sand, silt, and clay particles and they account for 40-80% of soil. In different proportions, these components give soils different characteristics and textures. [ex: A soil that contains mostly sand with be gritty; a soil that contains mostly silt will be velvety smooth; and a soil that contains mostly clay will be sticky.
Sand is most commonly composed of quartz, though it may also include gypsum, chert, magnetite, chlorite, and glauconite depending on where you are. For instance, sand in coastal areas can also contain small fragments of shells. The particle size of sand has a range of .0625mm-2mm making it the largest particle. Since it is the biggest and thus the heaviest, this is why it is the bottom-most layer. Sand helps increase permeability of the soil but it does not maintain nutrients or water very well. While it isn’t ideal for growing in, sand does help move water down to the water table.
Silt is created when quartz and feldspar are weathered to a particle size between .0039mm and .0625mm, making it a “medium size”. Silt is easily carried in water and you will find deposits of silt on the shores of rivers that regularly over-flow, such as the Mississippi River and the Nile River. This is your middle layer in your jar. Silt actually pulls water up from the water table, making it accessible to the roots of plants.
Clay particles are the smallest at less than .002mm in size; this is the top layer in the jar. Clay absorbs water and can trap water particles so that they cannot be accessed by plant roots making it hard to grown much of anything in soil that is mostly clay.
Organic material will be settled on top of your soil layers or will be floating at the top of your jar. This comes from living things such as plants and animals. Organic material puts nutrients that plants need into the soil when it rots or decays. Organic matter that can be added to the soil, by farmers or gardeners, in the form of compost, manure, leaves, and mulch.
Instead of writing all of that down, print it out instead! Click on the picture to access the pdf file.
If that didn’t work, try this: Soil Exploration Activity (printable)
Here is the activity observation worksheet I promised. This isn’t just useful for this activity, but for any science activity or experiment where you’d like to take your activity a step further and have your child(-ren) to put words to what they are doing. Click either of the two pictures for the pdf file.
If that didn’t work, try this: Science Write-up
Want to check out more? Head over to the USGS site to take this activity even further with your older kids. Have them calculate the percentages of what’s in the soil! USGS What’s In My Soil?
Get the complete bundle of worksheets for this activity at my Etsy store! It’s complete with Soil Observation pages, as well as the Layers of Soil worksheets!
Have you done something similar? Share your results! Let’s compare soil compilations from around the country! Or even around the globe! I look forward to hearing from you!
Have a great day guys! And stay cool! 😉
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Growing Roots & Building Wings 