Transcript Rocks - Home

Rocks, Resources and Scenery
Types of rock
Rocks, Resources and Scenery
Geological Time
•
•
•
•
•
Geological time is on a different
scale from human time.
Chalk was formed during the
Cretaceous period
Clay was formed during the
Mesozoic - Jurassic, Cretaceous
and Tertiary periods
Granite was formed about 280
million years ago in the Permian
period of the Late Palaeozoic era.
Carboniferous Limestone was
formed 340 million years ago
during the Carboniferous period of
the Late Palaeozoic era
Simplified
diagram
Rocks, Resources and Scenery
Rock Classification and Cycle
Rocks belong to
one of three
groups.
Metamorphic
rocks are formed
by heat
underground.
They change from
one type of rock
into another.
Igneous
rocks e,g.
granite. An
intrusive
igneous rock
is formed by
the cooling of
magma deep
underground.
Sedimentary rocks e.g. limestone,
chalk and clay. Limestone (an
organic rock) is precipitated from
solutions and is
formed by the accumulation of
calcium carbonate in warm tropical
seas. Clay (an inorganic rock) is
formed by the compaction &
cementation of sediments under the
sea.
Limestone
in Yorkshire
Granite in
the
Southwest
Chalk
and
clay in
the
south
east
The rock cycle
shows that all
rocks are
weathered and
eroded and are
washed into the
sea where they
form new rocks
Rocks, Resources and Scenery
Weathering
Exfoliation – the
outer layers of the
rock break off
Rocks are susceptible to
weathering. The type of
weathering that is most
effective is determined
by the composition of the
rock and the climate.
Mechanical
weathering –
freeze thaw
weathering and
exfoliation.
Chemical weathering
– solution and
carbonation.
Biological
weathering.
Freeze-thaw
weathering
Carbonation: Rock is dissolved
Calcium carbonate (CaCo3) is dissolved
carbon dioxide in rainwater or moisture
in surrounding air forms carbonic acid
and reacts with the minerals in the rock.
The process weakens the rock thus
breaking it down in the process.
e.g.: Calcium Carbonate + Water +
Carbon Dioxide ---> Calcium Carbonate
(soluble)
Biological
weathering – the
roots from plants
and trees break up
the rock.
Rocks, Resources and Scenery
Different rocks create contrasting
landforms and landscapes - granite
Moorland is the landscape
formed on granite. It consists of
poorly drained land as the
granite is impermeable and so
bogs and marshes (mires) form.
There are few trees and peat
covers large areas. The land is
suitable for pastoral farming and
tourism.
Moorland
Tors
Tors are hilly
outcrops of
granite. They are
formed when the
overlying rocks
are eroded leaving
a mound of solid
granite which is
deeply jointed.
Dartmoor is
known for its tors
e.g. Yes Tor,
619 m and Haytor
457 m.
Rocks, Resources and Scenery
Different rocks create contrasting
landforms and landscapes – chalk
Escarpment/cuesta
Scarp
and clay
slope
Dry valley
Dip slope
Clay
vale
chalk
Dry valleys are
valleys without
water. They
were formed
during a wetter
periods.
Escarpment/cuesta – a range of
chalk hills with a steep scarp
slope one side and a gentle dip
slope the other side.
Spring line
Spring line
settlement
Clay vale – an
area of
lowland.
Spring lines are found where the chalk
changes to clay or where the water table
reached the surface. A series of springs are
found in a line along the base of the
escarpment.
Rocks, Resources and Scenery
Different rocks create contrasting landforms and
landscapes – limestone
Surface features:
Limestone pavements – areas of bare limestone which Limestone pavement –clints
has been weathered. The joints are called grykes and the (slabs) and grykes (joints)
slabs clints.
Swallow holes – deep holes in the limestone down which
rivers disappear.
Dry valleys – valleys where the river has disppeared.
Caverns – large underground caves formed by the
solution of the liemstone by the underground rivers.
Resurgences – springs where the underground river
reappears at the surface.
Swallow hole
Underground features:
Stalactite – a column which hangs down from the
ceiling.
Stalagmite – a column that grows up from the floor.
Pillar – a column formed where a stalactite meets a
stalagmite.
Curtain – a very wide column of limestone.
Rocks, Resources and Scenery
Resources, land and scenery
Granite, chalk and
clay and
Carboniferous
limestone provide
resources to extract,
land to farm on and
unique scenery for
tourism.
Production of
cement: Limestone
and chalk are both
quarried to make
cement.
Building stone: Granite
can be used for kitchen
work surfaces, floor
tiles and grave stones.
Limestone can be used for
dry-stone walls, house
building and garden stone
for patios/rockeries.
Opportunities and limitations for
farming: In granite areas 90% of the
land is farmed. Open moorland is
used for pastoral farming
(sheep,cattle and ponies)
Arable farming on fringes (hay
and grass. Granite has
poor thin soils, poor drainage and
very heavy rainfall which make
farming difficult.
In limestone areas sheep farming is
found but the thin soils make arable
farming difficult.
Chalk is good for pastoral farming
and some arable as short sprungy
grass grows well.
Clay is good for arable farming as it
has deep fertile soils and also for
dairy farming as grass grows well.
Rocks, Resources and Scenery
Chalk Aquifers
Aquifers are stores of
underground water. An
aquifer is under the London
basin. Rain falls on the chalk
hills and percolates down
through the rocks. It is stored
in the chalk sandwiched
between the clay layers. To
reach the water, wells are
sunk. Water supply in London
depends on this
groundwater.
Rocks, Resources and Scenery
Opportunities for tourism and costs
and benefits of this
Limestone:
Yorkshire Dales National Park
•Spectacular landscape
•Steep valleys
•Cliffs
•Extensive grassy plateaux
Granite:
Dartmoor National Park
•Wild open moorland
•Abundant wildlife
•Area of outstanding beauty
•Many types of outdoor activity
•Accessibility (near to motorways
and urban areas)
•Literature (Charles Dickens, Arthur
Conan Doyle)
Costs (problems)
Benefits (good things)
•Traffic jams
•Litter
•Farm gates left open
•Animals worried by
dogs
•High shop prices
•High house prices
due to demand for
holiday homes
•Visitors spend money
in shops, cafes and
hotels
•Jobs for locals are
created in restaurants,
hotels
•Local craft shops and
farms gain extra
income
Rocks, Resources and Scenery
Quarrying
Demand for resources
has led to quarrying.
Case Study: Hope Quarry, Castleton, Yorkshire
This is an important
Dales. One of the largest quarries in the Peak
issue and has led to
District. It supplies 2 million tonnes a year to Hope
conflict and debate.
Cement works.
Quarrying is digging
Hope Cement works produces 1.3 million tonnes of
out of rocks and
cement every year.
minerals from the
Creates jobs - 182 local people employed and it
earth’s surface
increases the local economy.
Limestone and slate
Economic
Social
Environmental
are the rocks usually
quarried.
Brings jobs into rural
People have jobs and When quarry finishes,
Quarrying can include community
feel more prosperous. can build new
sand and gravel
Higher tax revenue
resource e.g.
used to build new
extraction and open
shopping centre or
schools and roads.
ecocentre.
cast mining.
Dust, Noise, Blot on
When quarry closes
people lose their jobs. landscape, Large big
Advantages
Disadvantages
hole left, Wildlife
habitats destroyed,
Ground water polluted
Rocks, Resources and Scenery
Impact of quarrying
Impact of quarrying
on the environment
can be reduced by
careful, sustainable
management.
There are ways of reducing
the impacts. At Hope
Quarry they plant trees and
use landscaping. They aim to
reduce dust by using trains
to take stone away rather
than lorries. They
reduce CO2 by planting more
trees.
After quarrying has finished:
There are strict environmental
controls and quarry owners are
now expected to restore
landscape to a better state than
before. They can replace topsoil
and use for farming. For
recreation: they can make tracks
for mountain biking & can use
waste tips for dry ski slopes. They
can create wildlife areas by
planting trees and scrubs and
creating ponds and set up wetland
nature reserve in old pits. They
can be used for
retailing e.g. Bluewater and
science e.g. Eden Project.