Transcript 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 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 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 Located 70km off Belmullet County Mayo 3500 meters below seabed v kinsales 1000m Advanced sub-sea technology required to extract it 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 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 Construction Materials: Sand and Gravel Crushed Rocks Building stone i.e. Granite, limestone Gypsum (plasterboard) Metallic Resources: Iron Copper, lead Gold, Silver Energy Resources Fossil Fuels Nuclear Fuels ( Uranium) Geothermal Energy Examine with reference to an example you have studied, the formation of one rock type and how it produces a distintive landscape (2008 LC)