Download Metamorphic rocks.

The rock cycle describes the perpetual recycling of minerals by
* weathering and erosion processes on the surface
* transport and deposition processes involving water, ice, waves or wind
* rock creation and transformation involving crustal and tectonic processes
* Landscape creation
Weathering and
erosion
Landscape creation
Transport and
deposition
Rock creation
Rock transformation
Weathering &
erosion
Transport &
deposition
Rock creation
Rock
transformation
Landscape
creation
Alistair McNaught; Peter Symonds College 2001
Erosion is distinguished
from weathering because
erosion involves removal
of material whereas
weathering involves only
rotting of material.
Erosion therefore implies
transport of weathered
material
Rocks
Chemical weathering:
Water penetrates rocks
The presence of water results in
Physical weathering:
• solution weathering (soluble minerals
dissolve)
•Water in rocks freeze expanding joints
• carbonation (CO2 enriched water
dissolves limestone)
•Extremes of heating cause
thermal weathering
• hydrolysis (feldspars degrade to clays)
•Release of pressure as
surface layers wear away
• hydration - salts swell on water uptake
Weathering &
erosion
Transport &
deposition
Rock creation
Rock
transformation
Landscape
creation
Alistair McNaught; Peter Symonds College 2001
Deposition of eroded
sediment sets the scene
for the creation of new
rocks (sedimentary rocks)
from the rotted,
weathered and eroded
remains of the old rocks.
Transport takes place by:
Deposition takes place in:
Ice - glaciers wear down
highland areas
•the ocean
Water - rivers and streams
move material to the oceans
from the land
•inland lakes
Wind - particularly in areas
of low rainfall
•inland basins (eg rift valleys)
Weathering &
erosion
Transport &
deposition
•river floodplains
Rock creation
Rock
transformation
Landscape
creation
Alistair McNaught; Peter Symonds College 2001
Ocean
The first stage of rock creation is burial - sediment
is buried by later layers of sediment being
deposited.
The pressure of overlying sediment squeezes the
water out of the sediment - this is dewatering and
compaction.
Finally, cementation takes place as minerals dissolved in the
in the sediments precipitate out and cement together
adjacent grains of sediment. At this stage the rock is forming
and lithification has taken place
Weathering &
erosion
Transport &
deposition
Rock creation
Rock
transformation
Landscape
creation
Alistair McNaught; Peter Symonds College 2001
Sedimentary rocks laid down in the ocean become increasingly buried by
younger sediments. As they gradually subside into the crust they experience
increasing heat and pressure. This changes the structure and composition of
their minerals to create Metamorphic rocks.
Metamorphic rocks can also be created dynamically by crustal plate movements.
Intense heating and pressure at plate collisions eventually melts the rock.
Molten rock (magma) rises through the crust. Some solidifies underground to
form intrusive igneous rocks. Others rise to the surface erupting as extrusive
igneous rocks - for example, lavas.
Extrusive igneous rocks
Sedimentary
rock
Intrusive igneous
rocks
Pressure
Metamorphic
rock
Heat
Weathering &
erosion
Transport &
deposition
Rock creation
Rock
transformation
Landscape
creation
Alistair McNaught; Peter Symonds College 2001
Extrusive igneous rocks create distinct
volcanic landscapes like those of central
America.
After many millions of years of erosion
the underlying intrusive igneous rocks
may be revealed, creating a distinctive
granite landscape like Dartmoor in
SW.England
The plate collisions - resulting in
large scale regional metamorphism
underground - are expressed on
the surface as large scale fold
mountain ranges such as the
Himalayas.
As soon as new rocks are exposed on the
surface by either uplift (fold mountains) or
eruption (volcanoes), weathering and erosion
start the whole cycle again.
The Rock Cycle is powered by two energy sources -
1) geothermal heat (to drive plate tectonics)
2) solar energy (to drive climate and therefore
weathering and erosion systems)
Weathering &
erosion
Transport &
deposition
Rock creation
Rock
transformation
Landscape
creation
Alistair McNaught; Peter Symonds College 2001
Weathering and
erosion
Landscape creation
Transport and
deposition
Rock creation
Rock transformation
Alistair McNaught; Peter Symonds College 2001