Geology: Rock Types and Formation Processes
Rock Cycle
Weathering: Process of breaking down rocks into sediments.
Sedimentary Rock Formation: Sediments compact and cement to form sedimentary rocks.
Metamorphic Rock Formation: Igneous and sedimentary rocks can become metamorphic due to heat and pressure.
Recycling: All rock types can melt back into magma, restarting the cycle.
Weathering: Process of breaking down rocks into sediments.
Sedimentary Rock Formation: Sediments compact and cement to form sedimentary rocks.
Metamorphic Rock Formation: Igneous and sedimentary rocks can become metamorphic due to heat and pressure.
Recycling: All rock types can melt back into magma, restarting the cycle.
Igneous Rocks
Types: Intrusive (formed within the earth) and Extrusive (formed at the surface).
Intrusive Rocks: Slow cooling, large crystals; e.g., Granite.
Formed from magma in the earth's crust.
Examples: Connemara, Donegal, Leinster Batholiths.
Extrusive Rocks: Quick cooling, small or glassy crystals; e.g., Basalt.
Formed from lava at the surface.
Example: Antrim-Derry plateau from volcanic activity 65 million years ago.
Sedimentary Rocks
Formation Areas: Formed on land, lakebeds, or beneath the sea.
Types: Inorganic, Organic, and Chemical sedimentary rocks.
Lithification Process: Transformation from loose particles to solid rock through compaction and cementation.
Example: Sandstone from sand grains.
Organic Sedimentary Rocks: Formed from remains of organisms; e.g., Limestone.
Chemical Sedimentary Rocks: Formed from evaporating water, leaving minerals; e.g., Gypsum and Rock salt.
Metamorphic Rocks
Definitions: Formed from igneous or sedimentary rocks changed by heat/pressure.
Types: Thermal (heat-induced) and Regional (heat and pressure over large areas).
Key Examples:
Marble: Formed from limestone by regional metamorphism.
Quartzite: Formed from sandstone via extreme heat/pressure.
Ireland's Context: Many metamorphic rocks formed during the Caledonian Folding 400 million years ago.