Browse the Natural Resources Conservation Service's Index to Maps, Facts, and Figures . Light in color. Crust The Earth's outer surface and layer of material. Gravel Soil made up of lots of little rocks and pebbles. Humus Soil material that comes from the decaying and decomposing of plants, animals, and insects.
Decayed materials provide minerals and other food for plants growing in humus.
Loam Soil that is a mix of sand and clay. Organic Material that is made up from the decaying and decomposing of dead plants, animals or insects. Humus soil is made up of organic material. Rock A bunch or hunk of soil, pebbles and stone material. Rock is made from soil, stones, and pebbles being heated up and pressed upon for a very long period of time.