- mud: soft, wet earth.
- clay: (particles of less than 0.002mm); stiff,
sticky earth that becomes hard when baked.
- silt: (particles of 0.002- 0.0625mm); when
dried on hand will rub off easily.
- sand: (particles of 0.0625- 2.0mm); tiny grains
of crushed or worn rock.
- stone: a general term for rock fragments
ranging in size from pebbles and gravel to boulders or a large rock mass. (IHO Dictionary,
S-32, 5th Edition, 5059)
- gravel: (particles of 2.0-4.0mm); small stones
with coarse sand.
- pebbles: (particles of 4.0- 64.0mm); small
stones made smooth and round by being rolled in water.
- cobbles: (particles of 64.0- 256.0mm); stones
worn round and smooth by water and used for paving.
- rock: any formation of natural origin that
constitutes an integral part of the lithosphere. The natural occurring material that forms
firm, hard, and solid masses. (adapted from IHO Dictionary, S-32, 5th Edition, 4415)
- lava: the fluid or semi-fluid matter flowing
from a volcano. The substance that results from the cooling of the molten rock. Part of
the ocean bed is composed of lava. (IHO Dictionary, S-32, 5th Edition, 2680)
- coral: hard calcareous skeletons of many
tribes of marine polyps. (IHO Dictionary, S-32, 5th Edition, 1061)
- shells: exoskeletons of various water dwelling
animals. (adapted from IHO Dictionary, S-32, 5th Edition, 4680)
- boulder: a rounded rock with diameter of 256
mm or larger. (adapted from IHO Dictionary, S-32, 5th Edition, 527)