The levels of rainfall on Dartmoor are considerably higher than in the surrounding lowlands. With much of the national park covered in thick layers of peat, the rain is usually absorbed quickly and distributed slowly, so that the moor is rarely dry.
In areas where water accumulates, dangerous bogs or mires can result. Some of these, up to 12 feet (3.7 m) across and topped with bright green moss, are known to locals as "feather beds" or "quakers", because they shift (or 'quake') beneath your feet. This is the result of accumulations of sphagnum moss growing over a hollow in the granite filled with water.
Another consequence of the high rainfall is that there are numerous rivers and streams on Dartmoor. As well as shaping the landscape, these have traditionally provided a source of power for moor industries such as tin mining and quarrying.
The Moor takes its name from the River Dart, which starts as the East Dart and West Dart and then becomes a single river at Dartmeet.
Holiday cottages Dartmoor South Devon