The Geology of Devon and
The county of
Devon gave its name to the Devonian geologic time period.
Running throughout the north and south of Devon and continuing
into Cornwall, the massive limestone deposits were the first to
be extensively studied and recognized as dating to this specific
time period based on the fossils contained in the limestone.
This rock was deposited in warm seas with coral reefs and
abundant life. It is older than the rocks exposed along the
Jurassic Coast representing a time when most life was still in
the seas. Reaching back from 359 to 416 million years ago, the
fossils found here include trilobites, ammonites, corals and the
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These rocks are greatly disturbed in some of the interior areas
of Devon, faulted, folded, and cut through with beds of volcanic
ash and massive intrusions of granite. The most extensive
section of igneous rock in southwest England and the largest
deposit of granite in Britain is found in Dartmoor National Park
in central Devon. A vast area of granite was intruded into the
surrounding rocks during the Carboniferous period during a time
of geologic activity about 300 million years ago. Erosion has
now exposed the granite in much of the area. Tors, tall spires
of exposed granite, dot the moors while low areas are covered
with peat deposits used as fuel for centuries. The tors are a
highlight of the Dartmoor Park; large hills of durable granite
are topped with odd outcropping formations. The highest points
here are the tops of the tors, some in excess of 2,000 feet in
elevation. Abundant rain in the Dartmoor area has lead to the
development of vast peat deposits. Made from centuries of
sphagnum moss growth, the bogs and peat deposits cover much of
the granite in the low-lying areas.
Quarries, where many of the rocks in the area are mined, abound.
Granite, sandstone, metamorphic rocks, and limestone have been
used since prehistoric times for monuments, buildings, and
religious structures. Along with quarrying, the ancient
inhabitants of Britain mined tin and copper in Devon and
Cornwall as well. During the Bronze Age, copper and tin were of
high value for fashioning weapons, tools, and ornaments. With
the addition of a small amount of tin to the copper, a much more
durable alloy, bronze, could be produced. Along with these two
metals, silver, zinc, and arsenic were also mined in this
region. Although no mines are active today, this was an
important part of the history of the region. Cornwall was one of
the most valued sources of metals in Europe. Without the heated
intrusion of the granite into the area, there would have been no
During the Ice Ages of the Pleistocene era, the southwest of
Britain was one of the few areas to remain unglaciated. The
soils in this area are much older than in other parts of Britain
as they remained relatively undisturbed during this time by the
heavy sheets of ice expanding down from the north.
The geology of this area is responsible for its scenery, much of
its history, and has brought wealth to the area from historic
mines and modern tourism.