Geoscience Reference
In-Depth Information
O
UR SURVEY BY REGIONS AND AREAS
is now complete, so we can conclude
the journey by contemplating the broader patterns across Southern England as a whole,
and why it has its present form and location.
In Chapters 1 to 3 I developed the idea that all landscapes are the result of a variety
of processes, operating, sometimes spasmodically, over long periods of time. I also con-
cluded that two distinctive groups of processes can be involved:
1.
Surface modification,
largely caused by moving water (rivers, mudflows,
waves, tides and sometimes ice). All of these water-based processes are strongly
influenced by climatic variations in temperature, rainfall and storm intensity.
2.
2. Solid Earth movement,
resulting from processes originating and operating
within the Earth, rather than on its surface. Although most solid Earth move-
ment is difficult to detect, except where earthquakes or volcanoes are involved,
it is likely that such movement plays a key role in landscape development.
Without movement of this sort, surface modification would, over millions of
years, turn hilly landscapes into flat plains.
In this final chapter we shall examine a time-sequence of three major episodes that have
resulted in many of the distinctive landscape features of Southern England, both loc-
ally and regionally. We start with the Variscan mountain-building episode, an example
of solid Earth movement, and end with river erosion and the Flandrian rise of sea level,
a remarkable example of surface modification.
EPISODE 1: THE VARISCAN MOUNTAIN BUILDING
The Variscan mountain building occurred over many millions of years, but was partic-
ularly active between 400 and 300 million years ago. It was the result of Earth move-
ment between a tectonic plate that included the crust of northern Europe (from central
Wales northward) and a southern plate, or plates. The movement and detailed shape of
the plates is not clear, and there were probably a number of small plates involved in the
generally convergent boundary. However, the convergence must have had a major com-
