Page 231 - Fundamentals of Geomorphology

214 PROCESS AND FORM

Plate 8.17 Straw stalactites, Ogof Capel, Clydach, South Wales.
(Photograph by Clive Westlake)

but was unaffected by the drip rate (Genty et al. 2001). grapes. They are a variety of coralloid forms, which are
One site in the Grotte de Clamouse, which has little soil nodular and globular and look like coral. Anthodites
cover, failed to display a correlation between stalagmite are gypsum clusters that radiate from a central point.
growth rate and temperature, either because little carbon Moonmilk or rockmilk is a soft, white, plastic, moist
dioxide was produced in the thin soil or because calcite form of calcite, and often shaped like a cauliflower.
was precipitated before entering the system.
Water trickling down sloping walls or under a taper- Sub-aqueous forms
ing stalactite produces draperies (curtains and shawls),
which may be a single crystal thick (Colour Plate 7, Sub-aqueous forms are rimstone pools, concretions, pool
inserted between pages 208 and 209). Varieties with deposits, and crystal linings. Rimstone pools form
coloured bands are called ‘bacon’. Flowstone sheets are behind rimstone dams, sometimes called gours, which
general sheets of flowstone laid down over walls and build up in channels or on flowstones (Colour Plate 8,
ceilings. inserted between pages 208 and 209). In rimstone pools,
a suite of deposits precipitates from supersaturated mete-
Eccentric forms oric water flowing over the outflow rim and builds a
rimstone dam. Pool deposits are any sediment or crys-
Eccentric or erratic forms, which are speleothems of talline deposits in a cave pool. Crystal linings are made
abnormal shape or attitude, include shields, helictites, of well-formed crystals and are found in cave pools with
botryoidal forms, anthodites, and moonmilk. Shields or little or no overflow.
palettes are made of two parallel plates with a small cavity Pisoliths or cave pearls are small balls, ranging from
between them through which water seeps. They grow up about 0.2 mm to 15 mm in diameter, formed by regular
to5min diameter and 4–10 cm thick. Helictites change accretions of calcite about a nucleus such as a sand grain
their axis from the vertical during their growth, appearing (Colour Plate 9, inserted between pages 208 and 209).
to disobey gravity, to give a curving or angular, twig-like A few to thousands may grow in shallow pools that are
form(Plate8.18).Botryoidal formsresemblebunchesof agitated by drops of feedwater.