THE ROCK CYCLE

-shows relationship between igneous, sedimentary and metamorphic rock. -rocks are continually formed, changed, destroyed and reconstituted during the rock cycle: Formed/modified by endogenic forces (internal) Destroyed by weather and climate (exogenic) Reconstituted by deposition of sediments

GEOTECTONIC – formation, arrangement, structure of the rocks in the crust. Rocks result from distortion of the crust due to endogenic forces.

PLUTONIC ROCKS -intrusive (granite) crystallized magma.

VOLCANIC ROCKS -extrusive (basalt) Solidified lava.

Rocks are formed when: Magma rises, cools, solidifies – forms igneous rock: - magma reaches surface – volcanic/extrusive eg. Basalt - magma cools within the crust – plutonic/intrusive eg. Granite

Rocks are modified due to: Great heat, pressure – metamorphic rock.

Rocks are destroyed when: Denudation occurs, weathering, erosion – smaller rock pieces = sediments - sediments transported and deposited by water, ice, air (agents of erosion)

Rocks are reconstituted when: compressed sediments – solid rock (sedimentary rock) - deposited in layers ( strata)

MAGMA forms by subducted rock layers melting into the mantle.

LITHIFICATION – sediments compact and turn into solid rock (sedimentary rock) eg. Loose sand – sandstone.

CHARACTERISTICS OF ROCKS

Igneous – formed when magma cooled and solidified Eg. Granite, basalt, pyroclasts and lava

Sedimentary – compressed remains/sediments of sea creatures/plants/animals/ fragments of rocks. Eg. Limestone, Sandstone, coal and shale

Metamorphic – changed sedimentary/igneous rocks due to great heat/pressure or both Eg. Marble, Quartzite, schist, slate

IGNEOUS ROCK-formed from solidified magma-plutonic/intrusive(granite) -volcanic/extrusive(basalt) -contains crystals - large crystals = slow cooldown - granite - small crystals = fast cooldown – basalt

GRANITE FORMATION-coarse grained igneous rock-magma cooled deep within the crust-contains: minerals of feldspar, quartz, mica. -color: white, grey, pink, black-large crystals-formed during Caledonian fold mountain building period. -400 mil. years ago. -used for: kitchen worktops, fireplaces; building material-found in: Wicklow Mountains, Mourne Mountains, Co. Down.

BASALT FORMATION: -fine/medium grained igneous rock-color: black/dark grey-most common extrusive rock in IR-quickly cooled lava-small crystals-found on the Antrim-Derry Plateau (Giant’s Causeway) –cooled, contracted lava formed hexagonal columns

SEDIMENTARY ROCK-formed over millions of years-composed of: remains of animals/plants compacted-sandstone and limestone-layers called strata separated by bedding planes-bedding planes –horizontal cracks-joints –vertical cracks-two types: organic/inorganic sedimentary rock.

ORGANIC SEDIMENTARY ROCK formed from the remains of animal and plant life.INORGANIC SEDIMENTARY ROCK formed from the broken down remains of pre-existing rock.PERMEABLE means that water can pass through.

LIMESTONE: organic sedimentary rock-most common type in IR-the Burren, Co.Clare -made up of: cemented compress remains of sea creatures-formed over millions of years-present day limestone formed over 300 mil. years ago -formed during carboniferous period-colors: grayish white/black/dark grey-easily permeable and weathered-fossils often found (temperature and pressure of formation does not destroy them)

SANDSTONE: inorganic sedimentary rock-coarse rock-color: brown/red-most common type found in IR: old red sandstone (iron oxide present)-formed approx. 400 mil. years ago (IR desert type climate) -Caledonian fold mountains weathered and eroded –sediments carried by rivers and deposited in shallow seas/lakes-also formed from deposits of sediments in river channels/deltas/floodplains eg. Comeragh Mountains, Co. Waterford, Macgillycuddy’s Reeks, Co. Kerry.

METAMORPHIC ROCK -formed by changing the appearance/texture/chemical composition of sedimentary/igneous rock due to great heat(magma) or pressure(folding)-two types: 1. Thermal metamorphism (heat alone) 2. Regional metamorphism (great heat and pressure over a large area) Eg. Limestone turning to marble-Caledonian fold mountain building period – colliding plates of Eurasia and America.

EXAMPLES- Limestone to Marble – Connemara, Co. Galway- Sandstone to Quatzit – Great Sugarloaf Mountain, Co. Wicklow

Croagh Patrick, Co. Mayo

MARBLE-hard crystalline rock-colour: green(Connemara), red(Cork), pure white marble(Rathlin Island, Antrim, Carrara –Iraly) -formed by heat and pressure on limestone-impure marble is not pure white eg. Iron oxides, silt, sand, clay.-can be cut, polished and used for: kitchen worktops, fireplaces, ornaments, gravestones

QUARTZITE-sandstone changed due to great heat and pressure-spaces in composition were filled with silica and then compressed-light colored rock-often white in color-found on peaks of mountains: Croagh Patrick, Co. Mayo ; Sugar Loaf Mountain, Co. Wicklow

THE NORTH AMERICAN CONTINENT : active and trailing plate margins

ACTIVE PLATE MARGIN-occurs where oceanic plate subducts under continental plateEg. West coast of North America – Pacific Plate subducts under the North American Plate-faulting, mountain building, volcanoes and earthquake activity occur.-america’s newest igneous and metamorphic rock forms this way

TRAILING PLATE MARGINS-occurs in the absence of earthquake or volcanic activity or fold mountain formation-sedimentary rocks such as limestone and sandstone form here-sediments eroded from mountains transported by rivers deposited into seas (limestone/sandstone)

HUMAN INTERACTION WITH THE ROCK CYCLE

QUARRYING-important resources: energy and building materials-rock based building materials: stone, gravel and sand Eg. Granite (igneous rock) Limestone (Sedimentary rock) Marble (Metamorphic rock)

WHAT IS QUARRYING? -the removal of rock from large pits on the Earth’s surface-over 400 active pits and quarries in IR –solid rock extracted-raw materials for houses, roads, paving and floors-100 mill. Tons per annum up to 2010

METHODS OF QUARRYING1. Plug and feather

-holes drilled into the rock -steel wedges/rods inserted in rock to split it-extracting large pieces used for floor covering

2. Explosive-used to extract large and smaller pieces of rock -for chipping for roads/fertilizing land

3. Channeling-machinery is used to cut large slices of rock-quarrying marble

Eg. 10,000 years ago (last ice age IR) , melting of glaciers – rich deposits of rock midland IRSand/ Gravels – esker ridges.Eiscir Riada- Dublin- Galway (Dublin, Meath, Kildare, Westmeath, Offaly, Roscommon, Galway)

PIT –loose sand/gravel dug directly out of groundQUARRY- bedrock blasted then processedESKERS – long ridges of stratified sand/gravel (Eiscir Riada)

POSITIVE IMPACTS OF QUARRYING

1. Direct employment-quarry workers

2. Construction-aggregates in construction

3. Indirect employment-construction employees-in decline (2007yr-250.000ppl, 2009yr-126.500ppl)

NEGATIVE IMPACTS OF QUARRYING

1. Visual pollution -quarries and pits scar the landscape

2. Noise pollution-heavy machinery -blasting -vibrations

3. Heavy machinery-damage roads

4. Dust-polluted air

5. Water pollution-waste/dust in rivers

6. Abandoned quarries-unauthorized rubbish tips

CARRARA MARBLE-found in Tuscany, Italy. -color: white or blue grey-exported worldwide-was used for: the Pantheon in Rome-Michelangelo’s David. -Taj Mahal, India.- is used in warm countries keeps cool air in-also used for: countertops, flooring, fireplaces and bathrooms