Under Your Feet

10

SOIL HORIZONSOur lifetimes are short compared to the thousands of years it can take for soil to form into layers, called horizons. Soil can stretch down for 50 m (164 ft).

SubsoilA lot of digging would reveal this pale layer. Amongst tree roots, there are minerals and materials carried down by rainwater from above.

Topsoil You might have seen the mid-brown topsoil layer if you’ve planted seeds near the surface of soil. This mixture of dead matter, minerals, and small rock fragments is where most soil animals live.

Humus

The top portion of soil is called

humus. This dark horizon is made of

dead things that have decayed

(broken down).

Millipedes

and other soil dwellers eat humus for its nutrients.

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