Small particles settle on the bottom of a sea, pond or stream and over many thousands of years may form thick layers called sediments. If most of the particles are very small (less than 0.06 of a millimetre) then the sediment is called silt. Clay has even smaller particles! Sand is made up of bits of rock that are between 0.06mm and 2.0mm. If the particles are bigger than 2 millimetres then the sediment is called gravel. As well as particles of rock, there are bits of plants and animals in the sediment such as pollen grains, dead leaves or snail shells and these can suggest what was growing in the area when the sediment was deposited.

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0 - 0.8m   Grey silty fine sand and gravel.   0.8m to 1.5m   Light greenish grey soft clayey silt.   1.5m to 2.5m   Soft grey silt and fine sand. Sometimes bedded/laminated.   2.5m to 3.5m   Very soft light grey clayey silt. Frequent fine rooting and areas of frequent bivalves.   3.5m to 5.5m   Soft grey silt-clay. Frequent organic fragments.   5.5m   Brownish grey soft humic silt. Occasional organic inclusions. Sharp (?erosional) interface   5.6m   Firm dark brown fibrous peat. Spongey. Frequent reed-like inclusions.   5.8m   Fining up sequence from gravel and sand to fine sand and silt.   5.8m to 7m   Flint gravel in silty fine sand matrix over poorly sorted chalk and flint gravel and then weathered bedrock.