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Science
and
Tourism
Geology of
Settle-Carlisle
Railway
Introduction
The rocks that form the landscape of the Settle-Carlisle Railway
cover a vast period of geological time from about 488 million
years ago to the present day. They tell a story of the journey of
the region as it has drifted north from close to the South Pole to
its current position. This story includes the opening and closing
of oceans, the building and erosion of mountain ranges and the
formation and break-up of a vast super-continent. The rocks were
laid down in warm, shallow tropical seas, huge delta systems,
arid deserts and beneath thick ice sheets.
This leaflet details the main rock types and geological features
along the railway’s route and gives an insight into what it was
like when the rocks were deposited.
Geological Terms Explained
Plate Tectonics The generally accepted theory that the outer layer of
the Earth is divided into plates which move relative to each other.
The plates can move apart, creating new oceans and depressions in
the Earth’s surface known as sedimentary basins (see diagram
below); one plate can be pushed down (subducted) beneath another,
destroying oceans and creating mountain belts; or the plates can
grind past each other. The continents are part of the plates and so
move, join together and tear apart as the plates interact.
Sedimentary Rocks These form when older rocks are eroded and the
grains of sand, silt or mud are transported by wind and water before
being deposited again in layers. Limestones are formed in a similar
way when the remains of tiny sea creatures settle on the sea bed.
New layers of sediments bury and compress older layers squeezing
out the water and cementing them together into rocks.
Igneous Rocks These form when molten rock (magma) cools and
crystallizes. Magma may erupt at the surface from volcanoes or
remain underground forming structures such as dykes and sills.
Faults These are cracks in the Earth’s surface where the rock layers
on either side of the fault have moved relative to each other.
Formation of a
sedimentary basin
1 Earth’s surface is pulled apart due to movement of the plates
2 Faults form and a sedimentary basin is created 3
4 Sediments are washed from the surrounding high ground into
the basin where they are deposited in layers 5
6 Shallow sea invades the basin also depositing sediments
The Rocks
Ordovician & Silurian 488-416 million years
The oldest rocks found along the Settle-Carlisle Railway are
Ordovician and Silurian in age. They are found in Ribblesdale and
on either side of the Vale of Eden, most notably to the west where
they form the northern Lake District hills.
These rocks, known as the Ingleton and Skiddaw Groups, were laid
down on the edge of a thin continent made up of islands similar to
today’s Indonesia which lay near the South Pole. As this continent
drifted northwards, sand and silt were washed into the shallow
seas along its northern margin.
The Borrowdale Volcanic Group which forms the distinctive landscape
of the Southern Lakes is the remains of volcanoes associated with the
closure of the ocean that lay to the north of the continent.
Carboniferous 359-299 million years
Much of the most spectacular landscape along the route of the
railway is formed by Carboniferous rocks. These were deposited in a
series of basins with large faults at their edges which separated the
basins from higher ground (see diagram). The rocks are divided into:
Carboniferous Limestone Series is dominated by massive layers of
limestone (oldest)
Millstone Grit Series is a mixture of mudstones and sandstones
Coal Measures Series is a form of layers of coal, mudstones and a
few sandstones (youngest)
The Carboniferous Limestone was deposited in a series of tideless,
shallow sea basins which frequently dried up leaving behind layers
of salt and gypsum. On the edge of the higher ground reefs formed
(similar to the Bahamas today). As the basins were filled, a large
delta system developed. Rivers flowing from the Scottish Southern
Uplands in the north brought down sediments which were
deposited in the channels of the delta (similar to the Mississippi
delta). These sediments form the Millstone Grit Series. As the
closure of the ocean to the south progressed, the region was
uplifted and what had been delta became a vast area of swamps
and jungle, cut by rivers and frequently invaded by the sea (similar
to the Amazon basin). As the giant mosses, tree ferns and other
plants died, they were buried and compressed and became the
coal seams in the Coal Measures.
Permo-Triassic 299-201 million years
With the closing of the oceans to the west and south, the area
became landlocked and close to the centre of the Pangaea supercontinent. Desert conditions prevailed. Huge dune fields blown by
east to south-easterly winds and made up of sand eroded from the
Millstone Grit form the brick-red Penrith Sandstone. Near Penrith
reptile footprints are preserved in the sandstone.
During the Upper Permian, the region was a flat salt plain surrounded
by rocky desert. The Boreal ocean in the north flooded low lying areas
depositing the Eden Shales – cyclic layers of sediments with gypsum
and anhydrite (similar to the Persian Gulf today).
Between the Permian and Triassic periods was the largest mass
extinction in the history of the Earth, 80% of life died out.
The Triassic saw the first stages of the opening of the Atlantic and
with it the break up of Pangaea. The brick-red to yellow St Bees
Sandstone was deposited from a river flowing NNW through a region
of low lying desert plains. In the Late Triassic, the sea repeatedly
invaded the region and laying down the Mercia Mudstones. As the sea
dried out gypsum, anhydrite and salt were deposited.
Quaternary 1.8 million years to present
Today’s landscape has been strongly influenced by the last ice age.
The last glaciers to cover the region were during the late Devensian
ice age (26,000-13,500 years ago). These deposited boulder clay (a
mix of boulders, rock fragments and gravel held together by sandy
clay) which includes rocks carried great distances by the ice, such as
fragments of Scottish granites. Movement of ice over the boulder clay
moulded it into drumlins – mounds that taper in the direction of
movement. There are a large number of these drumlins across the
Vale of Eden and in Ribblesdale. Advancing and retreating glaciers
scoured the landscape creating open U-shaped valleys and limestone
pavements. The River Eden was blocked by boulder clay near Appleby
and as the ice melted it formed a lake. When the waters finally broke
through this natural dam the lake drained eroding the gorge between
Great Ormside and Appleby.
Since the ice age, groundwater has dissolved cave systems and
passages in the limestone; in cool periods, hill peat has been laid
down, up to 5m thick in places; and in the last 10,000 years rivers
and streams have created flood plains from the sediments they carry.
Time Line
The timeline shows key events in the geological history of
the landscape along the Settle-Carlisle Railway. The figures
on the left give the time of these events as if the age of life
on Earth were compressed into a year.
2 SECS AGO
4 MINS
8 HOURS
20 HOURS
12 DAYS
SETTLE-CARLISLE RAILWAY OPENS
1876
LAKE ORMSIDE
~13,000 years
DEVENSIAN ICE AGE
26,500 years
OLDEST HUMANOIDS – AUSTROPITHICUS
4 million years
ARMATHWAITE DYKE & OPENING
OF N. ATLANTIC
57 million years
13 DAYS
PALAEOCENE – REGION ~40˚ NORTH
14 DAYS
METEORITE HIT & DINOSAURS EXTINCTION
60 million years
65 million years
1.1 MONTHS
FIRST BIRD – ARCHEOPTERYX
1.6 MONTHS
FIRST DINOSAUR – EORAPTOR
1.7 MONTHS
ST BEES FORMATION & REGION ~16˚ NORTH
2.1 MONTHS
PENRITH FORMATION
2.2 MONTHS
COAL MEASURES & REGION ON EQUATOR
2.3 MONTHS
MILLSTONE GRIT
2.5 MONTHS
CARBONIFEROUS LIMESTONE & REGION
SOUTH OF EQUATOR
155 million years
228 million years
250 million years
299 million years
313 million years
326 million years
359 million years
2.9 MONTHS
FIRST LAND ANIMALS
3.2 MONTHS
BORROWDALE VOLCANICS
3.4 MONTHS
ORDOVICIAN – REGION NEAR SOUTH POLE
1 YEAR
420 million years
457 million years
488 million years
OLDEST SINGLE CELL LIFE
1750 million years
Fast Facts
• The rocks along the Settle-Carlisle Railway range in age
from 488 million years old to the present day.
• The oldest rocks were deposited when the region lay close
to the South Pole.
• The region was once part of the same continent as North
America.
• The red sandstones in the Vale of Eden were formed in a
desert the size of the Sahara and the limestones of the
Dales in warm, tropical seas.
• The rocks of the Lake District are the remains of ancient
volcanoes.
• The railway crosses over 50 faults, a few of which are still
active and produce (very small) earthquakes.
Information
www.settle-carlisle.co.uk/
www.see.leeds.ac.uk/scienceandtourism
References:
The Geology of England and Wales, 2006. Brenchley, P.J. and
Rawson, P.F. (eds) The Geological Society, London.
Earth: Portrait of a Planet, 2005. Marshak, S. W.W.Norton & Co.
Geology from rail journeys: the Settle-Carlisle Railway, Taylor, G.
Blackwell Publishing Ltd, Geology Today, Vol. 19, No. 4, July/
August 2003
Alternative
formats are
available from
0113 343 3929
The Science and Tourism Project
University of Leeds
Leeds LS2 9JT
e [email protected]
w www.see.leeds.ac.uk/scienceandtourism