How Soil Is Made

Lab Brief #9

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

Today's mountain was yesterday's ocean floor.

What you'll learn

Soil begins as rock broken down by frost, water and roots, then mixes with the remains of dead plants and animals. It takes centuries to build a few centimetres, which is why soil lost to erosion is not quickly replaced.

Key words

humus
The dark material in soil formed from decayed plants and animals.
parent rock
The rock that weathers to form the mineral part of a soil.

Make a hypothesis first

Guess: where will the water go first?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

jar with lid
soil
water
ruler

⚠️ Safety first

Wash hands thoroughly after handling soil and keep it away from your face.

Step 1 of 4 · Read

Think about what you just learned: say what "humus" and "parent rock" mean in your own words before you start.

Step 2 of 4 · Do

Shake a jar of soil and water and leave it overnight. Measure the depth of each settled layer in the morning and work out the percentage of sand, silt, clay and floating organic matter.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 2

The dark decayed material in soil is called:

How sure are you?😐 maybe

Question 2 of 2

Soil forms slowly because rock must first be:

How sure are you?😐 maybe

Mind = blown

🌋 There are 1,500 active volcanoes on Earth right now.

Nice work!

You got 0 of 2 right.

Next: Rivers Carry More Than Water All lessons

🎯

Next Smart Experiment

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✨ More to explore

🌍 Where you see this in real life: This is shaping the ground you walk on, slowly, every single day.

🏆 Stretch challenge (try it this week): Find a rock outside and try to guess how old it is.

👨‍👩‍👧 For the dinner table: “What's the slowest change you can think of?”

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