Science Fenns K-5Grades K to 5
A creek bank in Texas showing a crumbling rock, sandy soil, dark soil with roots and a small green sprout.

Science / All lessons / Weather and a Changing Earth

Where Soil Comes From

Broken rock plus old plants and animals.

Lesson 28 of 41

Try this first

Before we start

Today’s story

Where Soil Comes From

Dig a hole by a creek in North Texas. You find sand, some clay and a few dark crumbs. Where did all of it come from?

Rock breaks down. Wind, rain, ice and roots slowly crack stone into tiny pieces. This is weathering. Sand and clay are weathered rock. Over years, leaves and animals die and rot into the soil. That dark crumbly part is called humus.

Together they make soil. Sand has big grains. Clay has tiny, sticky ones. Here are the steps.

See it

Five steps. Every time.

    Hands on

    Soil Jar Test

    30 minutes plus 1 day · Do this with a grown-up nearby

    You need

    • A clear jar with a lid
    • A cup of garden soil
    • Water
    • A spoon
    • A marker
    • A ruler

    Do this

    1. Fill the jar one third with soil.
    2. Add water until it is two thirds full.
    3. Put the lid on tight.
    4. Shake the jar for one minute.
    5. Set it down and wait one day.
    6. Look for layers and mark them.
    Write or draw: Draw the layers you see and label sand, clay and any floating bits.

    Watch for: Notice which layer sinks first. Notice anything that floats.

    Safety: Wash your hands after you touch soil.

    Same every time

    Three rules

    Rule 1Soil takes a long time.

    Many years make only a little.

    Rule 2Rock gives sand and clay.

    Sand is big. Clay is tiny.

    Rule 3Dead things feed the soil.

    Humus helps plants grow.

    Grandpa Fenn’s notebook

    Say it like a scientist

    weathering
    Wind, water and ice slowly break rock into smaller pieces.
    sand
    Gritty bits of rock bigger than clay.
    clay
    Tiny, sticky bits of weathered rock.
    humus
    Crumbly dark stuff made from rotted plants and animals.

    Poppy’s quiz

    Six questions

    Tap an answer. Green means right. You will see why.

    Talk about it

    Say it out loud

    • How do you know rock turns into soil? What evidence could you find?
    • What kind of soil is in your yard? Is it sandy, sticky or dark?
    Did you know

    It can take hundreds of years to make about one inch of soil.

    Someone who does this

    A soil scientist tests soil to help farmers choose crops.

    BeforeWeather ToolsNext lessonVolcanoes and Earthquakes