metamorphic rock

metamorphic rocks

• rocks subjected to tremendous heat and or/ pressure - they change to another type of rock

• E.g marble - limestone and gneiss (originates from clay mineral-rich rocks)

formation of metamorphic rocks

occur at plate boundaries

• metamorphism occurs at destructive plate boundaries

factors that affect metamorphic rocks

1) temperature increases

2)pressure caused by increasing weight

3) pressure caused by folding

temperature increases

• oceanic plate goes below continental plate (subduction) - friction between plates increases temperature

• heat created will cause metamorphism to occur

• deeper the layer of rock descends the hotter the temperature and the more likely it is to be metamorphosed into another rock

thermal metamorphism

• deeper the layer of rock descends the hotter the temperature and the more likely it is to be metamorphosed into another rock

pressure increased by increasing weight

• subduction causes layers of rock to be buried deep under surface of the Earth, pressure will increase by growing weight of rocks abov

• increase in pressure will lead to the creation of metamorphic rocks

pressure caused by folding

• two continental plates collide and neither plates are forced under - they collide and form fold mountains

  • pressure created by folding is powerful enough to change nature and structure of rock layers - regional metamorphism

appearance of rocks

• striped or banded appearance

• foliated metamorphic rocks: occur when mineral grains are squeezed flat into layers by pressure

• non folaited rocks: nearby hot igneous changes mineral structure of rock without adding pressure

metamorphic rocks in ireland

• during Caledonian period, continents Laurentia and Avalonia collided - resulting in great heat and pressure → sandstone into quartzite

• e.g Sugarloaf Mountain, Co Wicklow

• Croagh Patrick, Co Mayo

• creation of Connemara Marble - Clifden Co. Galway