Home Geography for Primary Grades · Lesson XXI · Unit 5: Rivers
21. The work of flowing rivers
Goal: Your child shows with a jar of muddy water how rivers carry soil and drop it, explains how flood plains become fertile, and explains why river stones are smooth and round.
You'll need
- A clear jar with a lid
- A handful of mixed soil, sand and small pebbles (from the garden or a stream bank)
- A few rough stones and a few smooth river or beach stones
- Optional: a sloping patch of dirt and a watering can or hose
- A geography notebook (any notebook kept just for these lessons) and a pencil
What's in the book
The lesson asks the child to watch rain run off a slope and carry soil away, then fill a jar with water and mud, shake it and let it settle. Rivers drop their load where the water slows, building fertile meadows from loam washed down from the hills. Coarse material settles first. Rough stones are rolled and rubbed into pebbles, gravel and sand. Streams everywhere are carrying the mountains to the valleys.
The lesson, step by step
Watch the rain work
On a rainy day (or with a watering can on a slope of bare dirt), watch the little streams that form.
Ask: What do they carry away? Why is the water muddy?
The jar
Do the book's experiment.
Fill a jar with water. Put in a handful of mud from the nearest stream.
Screw the lid on tightly, shake it hard, and set it down. Watch for a few minutes, then leave it until tomorrow.
Safety: if the mud comes from a stream, wash hands well afterward.
What settled first?
Look at the jar with your child. The heavy pebbles and coarse sand are at the bottom, with fine mud on top, and the water slowly clears.
Ask the book's questions: Which settled first, the coarse material or the fine loam? So near the top of a river, where it runs fast, what will it drop? And near its mouth, where it is slow?
Rich meadows
Read about rivers overflowing.
SayWhen a river floods and goes down again, it leaves a layer of rich mud. That is why the flat land beside rivers is often good for farms and grassy meadows.
Smooth stones
Hand your child a rough, sharp stone and a smooth river or beach stone. Ask: Do you know what made this one round?
Read how stones are rubbed together in rushing water, worn into pebbles, then gravel, then sand.
Shake the stones
For a home model: put a few small, soft stones (chunks of chalk or sandstone work best) in a plastic jar with water and shake it hard for a few minutes. Pour off the water and look: corners worn off, and fine grit at the bottom.
Say it back
Read the last paragraph aloud.
This is what the streams are doing everywhere
Ask your child to tell in their own words what rivers are always doing to the land.
Afterwards
Leave the jar on a shelf and look at the layers each day this week.
Answers to the book's problems
Little streams formed by rain cut away loose soil and carry it off, which makes the water muddy. In the jar, the coarse material (pebbles, sand) settles first and the fine loam last. So a river drops coarse stones and gravel in its upper course, where it runs fast, and fine mud and sand toward its mouth, where it runs slowly. When a river overflows, it leaves a layer of rich mud that makes the meadows fertile. River stones are smooth and round because the rushing water rolls them along and they rub against each other, wearing off their sharp edges; at last they are ground into gravel and sand.
Worked out for this site from the scan. If a number in your copy differs, trust the book.