The Southwest Region - Southern England - page 70

FIG 68. Hay Tor, Dartmoor, looking southeast. (Copyright Dae Sasitorn & Adrian Warren/
www.lastrefuge.co.uk)
FIG 69. Hound Tor, Dartmoor. (Copyright Landform Slides - John L. Roberts)
The slopes round tors tend to be covered with loose granite blocks (often referred
to as clitter ), generally angular and obviously derived from the tors (Fig. 70). Finer-
grained, crystal-size gravel or sand of quartz and feldspar is another weathering
product and is locally called growan or sometimes head. It is clear that much of the
alteration of the granite that has resulted in the appearance of the tors must have been
strongly influenced by the climate, vegetation and soil-forming conditions existing at
different times and in different scenic settings. Much of this has been compared to the
weathering and down-slope movement that is seen in high-latitude cold climates today,
and so is explained as a result of the cold climate conditions experienced repeatedly
during the Ice Age. However, weathering of granites is much faster today in the warm,
tropical jungle areas of the world, compared to drier, cooler and less vegetated condi-
tions. Early episodes of weathering of the Southwest Region granites may have taken
place under the warm, tropical conditions that are indicated by early Tertiary fossil de-
posits elsewhere in England.