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Chalk Geology

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Box Hill was not always known as such The geographer William Camden referred to it in 1586 as 'White Hill' and it is easy to see why. The whole of south-east England was once covered by a huge dome of chalk which, over the last two million years, has been eroded to form two ridges: the North and South Downs.

At Box Hill the true chalk soils can be found on the escarpment and the sides of the valleys where characteristic downland plants flourish On the top of the hill is an 'icing' ofclay- with-flints, which supports a mixed woodland - predominantly oak and beech - and different plant communities.

The 120-metre-high (394 feet) sheer chalk escarpment has been cut away by the River Mole as it flows unceasingly at the base of Box Hill. Still known as 'The Whites',it is the finest natural river cliff in the county, if not in southern Britain. And on it grows truly ancient box woodland that has certainly survived since the end of the last ice age and may well have existed before then.

The Whites is a sanctuary for these native box trees, offering them hot. dry growing conditions which few other British trees would tolerate. It has 40 per cent of all the naturally occurring box woods in the UK.

Chalk has certain characteristics which ; add to the peculiar charm of Box Hill, to the north of the scarp, the hill is deeply trenched with a series of dry valleys or combes running down to the Headley Little Switzerland Valley, part of an old tributary system of the River Mole Over time the river's natural drainage has subsided to lower levels underground in the porous chalk, leaving no surface streams in the original narrow, steep-sided drainage valleys.
Largely due to the nature of the rock, which is easily eroded, this is a land-scape of soft and smooth curves, of dazzling whiteness, on almost every slope there are patches of bare chalk not covered by vegetation and exposed to the weathering action of rain and frost and of lush greenness.

Chalk rarely dries out, which is why the downland vegetation remains fresh and green when plants on other types of soil are parched with drought. It has even been suggested that there is some quality in chalk which lends a vividness of colour not seen in the flowers of other rocks, this being particularly noticeable in hawk weed rock rose, bird's-foot trefoil, milkwort, squmancywort and dwarf thistle.

Near Box Hill the chalk can be observed at close quarters in a number of quarries, not least Surrey County Council's Brockham limeworks. Here, in the main heavy industry of the North Downs, chalk was quarried and burnt in kilns to produce lime and cement. The quarry, which can be seen from the Long Walk, is no longer used for lime extraction and is now a Site of Special Scientific Interest, but the scars that are left show the structure of the rock in dramatic fashion: as well as being minutely porous, it is cracked and separated all over into layers. It is this network of cracks and fissures which gives the chalk its great capacity for underground water storage.


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