The outer face of the wall originally consisted of hammer-dressed flint and stone, but now only the core with its lime mortar is visible. At its base the wall was about 3 metres wide.
The Wall is three metres thick at the base, it is built of flint quarried from the chalk and brought a distance of at least 6½ miles (10km). Every four to five courses of flint there is a bonding course of generally flattish slabs of stone. These consist of a variety of materials including limestone brought from as far afield as the Bath region about 50 miles (70-80 km). It has been estimated that at least 105,000 wagon loads of flint and 45,000 loads of bonding stones were required.
Although the wall has lost almost all traces of its outer surface, it remains an impressive monument. The southern section, with the south gate, particularly deserves a visit. The wall was originally fronted by a broad ditch about 14m wide of which a particularly good section is preserved in the copse around the south-western part of the wall.
In most areas across the region there is a direct link between the building materials used and the local, underlying geology. There is a wide variety of building stones available including chalk, flint, sarsen and clay for brick and tile making.
Types of Rock
IGNEOUS ROCK- granite is an example. Hard and non-porous rock formed from the slow or quick cooling of molten magma. It has at least 20% quartz per volume. It is popular as a building material. It can be used rough cut or finished on one or more sides. Granite can be white, pink or grey depending on its mineral content . Granite was often used as the corner stones in pavements due to its hardness .
METAMORPHIC ROCK.- Slate is a good example it is very fine grained. It can be cut into smooth flat sheets which are often used as roofing tiles. As slate can be engraved it makes a good material for plaques. It varies in colour from light grey to dark grey but can also be purple, green or blue.
SEDIMENTARY ROCK A river transports pieces of broken rock as it flows along. When the river reaches a lake or the sea, its load of transported rocks settles to the bottom. In a wind-blown desert, the dust and sand grains can fall out of the wind and be deposited. These sediments then build up in layers, like a "birthday cake" .
The weight of the sediments on top of those below squashes the lower sediments . Groundwater moving within these sediments often carries dissolved salts, which then glue the sediments together. This eventually makes a type of rock called "sedimentary rock". It may take millions of years for sedimentary rocks to form.
The oldest layers are generally at the bottom of the layers of strata that form and the youngest layers are at the top when formed. Sedimentary rocks may contain fossils of animals and/or plants that were trapped within the sediments as the rock was formed.
Flint is a hard sedimentary rock of mineral quartz, and is normally in nodule form and can be found in sedimentary rocks such as chalk and limestone. Inside the nodule Flint can be dark grey, black, green, white or brown, and has a waxy appearance, trace element contamination adds the colour to flint. The outside thin layer is normally white and rough in texture.
The exact mode of formation of flint is not yet clear but it is thought that it occurs as a result of chemical changes in compressed sedimentary rock formations during a process of diagenesis. .
To log this cache you need to send the answers to the following questions to me through the message center or email
- What size and shape are the flint nodules? Is the size and shape regular? Why do you think this has happened
- What is the colour of the inside and outside of the flints? Why do you think the colours have formed.
- At the given coordinates what do you think the stone slabs for the coursing are made of
- At the waypoint notice board how many gates were there in total and how many are left .
- Optional post a photo of yourself, your GPS or preferably your Dog if you have one, at the wall