Think of Ireland and peat comes to mind. One-sixth of the country is covered with the stuff -- a creamy simmering heap of partly decayed plant matter, slathered onto the western hills and central lowlands like gobs of rancid brown butter. Not much useful will grow on it. You need a good pair of rubber boots to walk across it. But in a country with almost no coal and few trees, peat (or turf as the Irish call it) has one great advantage: Cut into chunks and properly dried it will burn, with a coolish but fragrant flame. The smell of a turf fire is as uniquely Irish as the taste of Guinness, and the memory of that sweet aroma is enough to make any Irish emigrant long for home.
In effect, a peat bog is a poorly functioning compost heap. The compost heap at the back of your garden turns recognizable plants into a uniform brown humus that is perfect for planting. To do its job properly, the heap must be neither to dry nor too wet. Unbalanced, the heap stagnates, plants do not fully decompose, and the whole thing becomes a sour smelly mess. As a compost heap, the Irish bog is too wet. The mass of decaying plant life is supersaturated with water. Microscopic organisms that are the agents of decomposition are aerobic; that is, they depend on oxygen. But oxygen is not very soluble in water, and in stagnant water, as in the bog, the supply of oxygen is soon depleted. Decomposition comes to a screeching halt.
Ireland's history is buried in the bog. Because of the non-decomposing conditions of the soil, whatever gets buried is beautifully preserved. Jeweled chalices, timber trackways, tubs of butter, clothed bodies. And now -- miracle of miracles -- a thousand year-old book of Psalms has been found intact in the black goo. We haven't heard yet which Psalms are recorded. Perhaps the 104th: "From your palace you water the uplands until the ground has had all that your heavens have to offer." (Jerusalem Bible)