Download Rocks

Rocks
Igneous: oldest; formed by magma cooling
Intrusive .. Cooled slowly within eg. Granite- mica, feldspar & quartz.
Dark grey, crystals, coarse & resistant. Found Wicklow mts.
Uses: Buildings & bridges. Weathered into kaolin (china clay).. Porcelain.
Extrusive… lava cooled rapidly on surface eg. Basalt- black, crystals,
Uses: road surface… weathered into fertile soil.
Sedimentary: Formed on surface on land or sea.
Mechanically…. Weathered & eroded rocks… laid down in layers called
strata. Pressure compacts (water & air squeezed out) & cements (particles
bonded tog.) the rocks-- lithification. E.g. Sandstone & shale.
Particle size distinguishes rock type.
Sandstone: Cemented grains of sand. Old red sandstone… red due to iron
oxide. Eg.Comeragh mts.
Limestone Calcium carbonate; white; stratified; formed under the ocean  skeletal remains of sea creatures- compacted & cemented. Eg
Burren.
Uses: Building, headstones, cement.
Metamorphic : Once Igneous or Sed Changed due to heat & pressure.
Heat from volcanic intrusion.
Limestone -- Marble
Pressure from folding
Sandstone - Quartzite
Marble: coarse, crystallised, white. Pure marble was once pure calcite.
Impurities colour marble such as carbon  grey.
Uses: headstones, sculptures, fireplaces. Eg. Kilkenny marble (black)
Connemara marble (green)
Rock dating relative dating- layers; oldest on bottom
absolute dating- fixed rate of decay. Eg uranium 235…
half life of 700m yrs. Carbon 14 half life 70,000yrs.
Rocks used in
1.construction,2. metallics (iron lead & gold) 3. non-metallics (diamond &
opal), 4. energy (coal & gas)
Plate margins in Nth America
Active margins: Leading edge of continent at plate margin. Eg.Western
margin of Nth Am. Where Am. & Pacific plate collide. Its active tectonically
with volcs., earthquakes & faulting.
Trailing margin: Edge of continent within a plate, so not active. EG.
Eastern margin of Nth. Am.
Natural Gas
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Also known as methane
Provides 25% of Irelands energy demands
Formation:
Decomposed animals and plants
Buried beneath layers of mud and sand
Heat and pressure prdouce chemical change that creates droplets of gas
Hydrocarbons held in pores between grains of sedimentary rock
Sedimentary rocks compressed gas squeezed out and moves upwards until
it meets layer of impermeable rock – anticline
Gas exploration
Geologists know where to look
Small explosions send seismic waves through the ground and a 3d maps
can be created
If gas is present a small exploratory well is drilled
Natural Gas in Ireland
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Kinsale: 1971
Gas pumped ashore to cork harbour
Almost exhausted
More found at seven heads in 2003
Corrib gas field off Mayo coast, worth one point seven billion euro & will last
up to 18yrs and provide 60% of needs
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Located 70km off Belmullet County Mayo
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3500 meters below seabed v kinsales 1000m
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Advanced sub-sea technology required to extract it
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Extraction hoped to commence in 2006 but delayed due to planning
difficulties
Controversy over bringing it ashore & its effects on environment & local communities.
Terrain makes escape impossible for residents in case of a pipe rupture
Toxic discharge is to be dumped in Broadhaven bay which is very sheltered and
might not wash away this waste out to sea
Violation of planning laws
Benefits:
Will be worth 1.7 billion to Ireland over its lifetime
Will create 800 temporary and 55 permanent jobs and will generate 181 million
for local economy
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Irish government has no involvement in searching for gas
Private companies i.e. Marathon run Kinsale while shell run corrib
To encourage exploartion companies apy 25% tax but no royalties
Due to increase in demand, ireland is now linked by two gas pipelines to
scotland
90% of gas being imported
Economic Value of Rocks
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Construction Materials:
 Sand and Gravel
 Crushed Rocks
 Building stone i.e. Granite, limestone
 Gypsum (plasterboard)
Metallic Resources:
 Iron
 Copper, lead
 Gold, Silver
Energy Resources
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Fossil Fuels
Nuclear Fuels ( Uranium)
Geothermal Energy
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Examine with reference to an example you
have studied, the formation of one rock
type and how it produces a distintive
landscape (2008 LC)