Travel Reference
In-Depth Information
The physical character of the Island is partly defined by its geology, which is an incredibly
complex subject. There are a number of sources of information available for those people
who are interested in this fascinating subject, including the excellent
Jersey Geology Trail
website.
At a simple level the cliffs of the south west and north west consist of the beautiful Jersey
granite, red in colour it looks particularly stunning in the early evening sunshine. It is the
granite, which erodes into the spectacular features, which will appeal to visitors who are
interested in activities such as climbing, coasteering or photography, to name a few.
The Jersey Shale formation forms a wide swath through the centre of the Island; the large
bays of St Aubins and St Ouen are formed on this rock. A further major rock type is the
Rozel Conglomerate, found in the north east of the Island, which looks like pebbles cemen-
ted together. This rock can be easily seen in the area around St Catherines.
Around the Island there are a large number of dykes, they seem to be particularly dense
around the southwest. The rock is dolerite, which was intruded into the granite and today
they appear as bands of darker rock. Frequently, they have been eroded by the sea to form
gullies, which fill with seawater as the tide rises.
Formed much more recently than any of the major rock types is the surface geology and
there are two distinctive deposits. At the rear of many of the bays and in the larger gullies
there are large deposits of largely unconsolidated material. This is known as “head”, and is
material, which was deposited when the Island had a much colder climate than the present
day. Normally yellowish in colour with jagged rocks surrounded by much finer particles
it is not the most stable of material resulting in landslips most winters, so exercise some
caution when walking close to cliffs.
The other material is loess, a fine wind blown material, which arrived on the island during
the last glaciation of northwest Europe. It is probably most easily seen on Green Island, al-
though the deposits are rapidly decreasing in size due to erosion. It has provided the basis
for the fertile soils of the island, which have supported the agriculture of the last few hun-
dred years.
The highest point of the Island is Les Platons, at a height of 136 metres above sea level; the
lowest area is in the southeast, in St Clement. At one time some areas were below sea level
but this is no longer the case. There are a number of small river valleys, mainly running
from north to south, which, dissect the land as it slopes from the higher north to the lower
southern coast. Many of the roads leading to the northern parishes follow the line of these
small valleys.
These valleys have been used by man, for a number of different reasons, over the last few
hundred years, for example Waterworks Valley, used to have a number of watermills, hence
the name Millbrook, where the stream from the valley enters the sea. The use of the valley
