Geoscience Reference
In-Depth Information
Why is Southern England where it is?
Southern England has been reduced in size and changed in local detail by surface modi-
fication. But its location depends on the solid Earth movements that have influenced
this area of the Earth's lithosphere. The lithosphere plate movements that were respons-
ible for the growth of a convergent boundary through this area in Variscan times pro-
duced the land of Southern England, attaching it also to crustal material further north
with a very different history. Later movements, initiated in New Red Sandstone times,
started to form other elements that are recognisable in the western and eastern margins
of Southern England.
As we saw in Chapter 3, the Earth's surface is made up of lithosphere plates that
have been continuously moving and changing their configuration for 2-4 billion years.
By focusing on Southern England we have examined in detail the surface history of
one small area of the Earth's crust. Although small relative to most plates, it has non-
etheless seen an episode (1) of plate margin activity, followed by an episode (2) of
basin movement unrelated to a plate margin, and then finally an episode (3) of surface
modification, strongly influenced by climate change. During these episodes, Southern
England moved from equatorial latitudes to its present northern position, as shown by
measurements of rock magnetism.
Research on deep crustal and mantle structure is developing all the time, and is
now starting to detect the presence of rock volumes possessing distinctive physical
properties at these considerable depths. So the onion-skin model (as shown in Fig. 30)
is likely to be a gross oversimplification. Some of the distinctive deep rock volumes
appear to have a similar lateral extent to Southern England or the British Isles, and it
is likely to be at these great depths within the Earth that the reason for the existence of
such features of the Earth's natural landscape must be sought.
