Earth Materials: From Boulders to Clay

0:00How are rocks, sand, clay and soil connected?

0:05Up close, most rocks are made of minerals.

0:08This granite is made mostly of quartz, feldspar and mica.

0:13Over a long time, rocks break into smaller pieces.

0:18Let's sort the pieces by size, from biggest to smallest.

0:22A boulder is a rock bigger than a basketball.

0:26A pebble is a small, rounded stone, small enough to pinch between two fingers.

0:32Sand is made of tiny grains that feel gritty.

0:36Silt is finer still, and feels smooth like flour.

0:41Clay is the finest of all, and it is sticky when wet.

0:46Soil is usually a mix of sand, silt and clay.

0:51Soil also has humus, made from rotted bits of plants and animals.

0:56Water and air fill the spaces between the bits.

1:00Which of these can you find near your school?

1:04Rocks break down from boulders to clay, and help make soil.