Types of rocks

• Igneous

• Sedimentary

• Metamorphic

Igneous Rocks

Example: basalt and granite

Formed as a result of volcanic activity when molten magma escapes from the mantle and cools and hardens. If it reaches the surface as lava it cools and solidifies quickly whereas magma inside the crust cools slowly

Basalt

• Fine - medium grained

• Black - Dark grey

• Formed when lava cooled quickly on the Earth’s surface => small crystals

• Basalt is used for road chippings

• Example: Giant’s Causeway, Antrim-Derry plateau

Granite

• Coarse grained

• White, Grey, Pink or Black

  

• Formed when magma cools slowly deep inside the earth’s crust => Large crystals

• Contains minerals of feldspar, quarts and mica

• Granite is used for counter tops, monuments, headstones and fireplaces

  

• Example: Wicklow moutains and the Mourne moutains in County Down

  Sedimentary Rocks

Sedimentary Rocks

Example: Sandstone and limestone

Formed from particles of dead plants and animals. Sediments are deposited on the sea and lake beds and on land. Layers of this material builds up and is compressed and cemented together creating solid rock.

Limestone

• Grey

• Coarse grained

• Formed over millions of years

• Made from the particles of shells and the skeletons of small creatures. When sediments sink to the bottom of the seabed, layers are built over time. The weight of the upper layers compresses and cements the lower layers of sediments into strata (layers) to form solid rock

  

• Limestone is used for monuments and in construction of buildings

• Ground down => lime => spread on soil to increase fertility

Example: The Burren in County Clare

Sandstone

• Red/brown

• Coarse grained

• Formed from sand that has been worn away from the earth’s surface. This sand is carried away by wind and rivers and deported as sediment in seas, lakes and deserts. The layers that are built up over time are compressed and cemented together forming solid rock.

  

• Cork and Kerry

• Sandstone is used for patios and as building material

Metamorphic Rocks

Example: Quartzite and Marble

Formed from rocks that already exist such as igneous or sedimentary rocks. These rocks are changed into harder rocks due to great heat and/or pressure.

Marble

• LiMestone => Marble

• Hard and smooth

  

• White => Antrim

• Red => Cork

• Green => Conemara

  

• Black => Kilkenny

• Formed when limestone is put under great heat and pressure due to plate movement or when limestone comes in contact with molten magma

• Marble is used in sculptures, monuments, kitchen worktops, floortiles , fireplaces and headstones

Quartzite

• Sandstone => Quartzite

• Grey/white

• Formed when sandstone is put under great heat and pressure due to plate movement or when sandstone comes in contact with molten magma

  

• Extremely hard and grainy

• Found on mountain tops => not easily broken down

• Used in glass making and in road surfaces

• Example: Croagh Patrick in Mayo

  

  Uses of rock

  Natural resource: something in the natural world that people can use to their advantage

• Rocks are Natural resources

  • Sources of energy and building materials

  Energy

• Some rocks can be used to create energy => fossil fuels

  Coal

• If close to the surface => mined in open pits

• If underground => mined in a mine

• Extracting from within the earth’s core => shaft mining

  Oil and gas

• Extracted from rock by drilling and pumping

• Can be done offshore in a rig

  Building materials

  • Usually extracted by quarry

  • Limes stone, sandstone + marble

  Impacts of quarrying and mining

  Positive impacts

• Employment => supports local economy

• Supports other economic activities => provides material

• Provides raw materials to make:

  • Glass

  • Copper

  • Steel

  • Iron

  Negative impacts

• Pollution

• Eyesore

• Traffic congestion