What Your Bottom Is Made Of
Clay, Silt, Sand and Dead Stuff
The sediment on the bottom of lakes, ponds and rivers is comprised of organic material (dead stuff or “humus”) and soil particles.
There are three particle sizes: clay, silt, and sand. If you have mostly sand, you’ll have a firm bottom. The more clay and silt you have, the softer the bottom will be.
Clay:
Clay particles are the smallest of the three, measuring less than 0.002 millimeters in diameter — they can’t be seen with the naked eye. Clay particles tend to stick together when wet and have the ability to retain water and nutrients.
Silt:
Silt particles are larger than clay particles, ranging from 0.002 to 0.05 millimeters in diameter. Silt particles larger than 0.04 mm can been seen with the naked eye.
Sand:
Sand particles are the largest of the three, measuring from 0.05 to 2 millimeters in diameter. Sand particles are coarse, they don’t retain water or nutrients. That’s why they say, “Grass doesn’t grow in a desert.”
Sand particles are 40 times larger than silt particles and 1,000 times larger than clay particles.
When soil particles, blow or wash into a water body, the much heavier sand particles sink first, nearest shore. The lighter silt and clay particles settle farther out. That’s why it’s muckier the deeper you go.
Humus:
This is NOT the dip you eat at parties with veggies and chips. That’s hummus. Don’t confuse the two. Humus is made up of dead stuff.
There’s dead stuff — and then there’s really dead stuff. Humus is mostly the really dead stuff. Great farmland is 10% humus. A peat bog can be 90% humus. Mucky bottoms can be anywhere in between, but are usually 20% to 35% humus, which is also called “fantastic fertilizer,” especially for lake weeds.
That’s all there is to it
This is the composition of every lakebed anywhere; some combination of clay, silt, sand and humus. Even rocky bottoms have soil particles and dead stuff washing and blowing in 24/7. The difference is: more sand means a firmer bottom with fewer weeds. That’s all there is to it.
And so ends Lake Soil Science 101 — Congratulations! Now, would someone please pass the hummus?
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