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| Llyn Idwal is a relatively shallow lake, on average, about 10 feet deep, and only 36 feet deep at its maximum.
In some parts the bottom is composed of mud and peat ( up to 14 feet thick). The lake contains trout and minnows.
Some of the pebbles here on this shingle beach contain fossils. They are usually trilobites or bivalve brachiopods
(eg. orthis). They are from the sedimentary marine deposits and volcanic ash of Ordovician age. These were originally
laid down beneath the sea about 450 million years ago, subsequently raised by earth movements. The soil profile, where the Afon Clyd flows out of its high hanging valley, has a layer of peat about 2-3 feet below the earth's surface. This was probably due to downwash of loose morainic material from the higher slopes, may be due to a change in stream course or particularly heavy rainfall. |
