| Site of Special Scientific Interest | |
 Headley Heath | |
| Area of Search | Surrey |
|---|---|
| Grid reference | TQ 194 526 [1] |
| Interest | Biological Geological |
| Area | 1,016.4 hectares (2,512 acres) [1] |
| Notification | 1986 [1] |
| Location map | Magic Map |
Mole Gap to Reigate Escarpment is a 1,016.4-hectare (2,512-acre) biological and geological Site of Special Scientific Interest west of Reigate in Surrey. [1] [2] It is a Geological Conservation Review site [3] and a Special Area of Conservation. [4] Part of it is a Nature Conservation Review site, Grade I. [5] Two small private nature reserves in the site are managed by the Surrey Wildlife Trust, Dawcombe [6] and Fraser Down. [7]
A Site of Special Scientific Interest (SSSI) in Great Britain or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland is a conservation designation denoting a protected area in the United Kingdom and Isle of Man. SSSI/ASSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in the United Kingdom are based upon them, including national nature reserves, Ramsar sites, Special Protection Areas, and Special Areas of Conservation. The acronym "SSSI" is often pronounced "triple-S I".
Reigate is a town of over 20,000 inhabitants in eastern Surrey, England. It is in the London commuter belt and one of three towns in the borough of Reigate and Banstead. It is sited at the foot of the North Downs and extends over part of the Greensand Ridge. Reigate has a medieval castle and has been a market town since the medieval period, when it also became a parliamentary borough.
Surrey is a subdivision of the English region of South East England in the United Kingdom. A historic and ceremonial county, Surrey is also one of the home counties. The county borders Kent to the east, East Sussex and West Sussex to the south, Hampshire to the west, Berkshire to the northwest, and Greater London to the northeast.
This eight mile long site on the North Downs contains an outstanding range of wildlife habitats, including large areas of woodland and chalk grassland. Mole Gap has a variety of Quaternary landforms and there are well developed river cliffs where alluvial fans have diverted the River Mole against the valley sides. [8]
The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. Westerham Heights, at the northern edge of the North Downs, near Bromley, South London, is the highest point in London at an elevation of 245 m (804 ft). The North Downs lie within two Areas of Outstanding Natural Beauty (AONBs), the Surrey Hills and the Kent Downs. The North Downs Way National Trail runs along the North Downs from Farnham to Dover.
Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene. The informal term "Late Quaternary" refers to the past 0.5–1.0 million years.
Alluvial fans are triangular-shaped deposits of water-transported material, often referred to as alluvium. They are an example of an unconsolidated sedimentary deposit and tend to be larger and more prominent in arid to semi-arid regions. These alluvial fans typically form in elevated or even mountainous regions where there is a rapid change in slope from a high to low gradient. The river or stream carrying the sediment flows at a relatively high velocity due to the high slope angle which is why coarse material is able to remain in the flow. When the slope decreases rapidly into a relatively plain or plateau, the stream loses the energy it needs to move its sediment. Deposition subsequently occurs and the sediment ultimately spreads out, creating an alluvial fan. Three primary zones occur within an alluvial fan which includes the proximal fan, medial fan, and the distal fan.
