Sedimentary rocks - 🪨
Formed on or near the earths surface, commonly on lake or sea beds. They develop in layers known as strata, this is because sediments are deposited over long periods at different rates. Each stratum are separated by a bedding plane, a viable horizontal break. Some have vertical breaks known as joints. Lithification is when sediments are compressed, compacted and cemented into sedimentary rock. Cementation occurs when individual particles combine with cementing agent eg, silica, calcium carbonate
Mechanically formed inorganics - these are formed from sediments of weathered or eroded rocks. If particles are rounded by fluvial activity, then the rock is called a conglomerate. If they are angular as a result of weathering they are called breccia. Sandstone is an example, consisting ing or grains of sand deposited on land or in water
Organically formed organics - formed from sediments, remains and fossils of once living organisms. Limestone is the most common rock type in Ireland. It is found in 31 of the 32 counties, with Wicklow being the exception. It’s made almost entirely of calcium carbonate. Pure limestone is white, however it may also be exposed to carbon, sand or clay, varying its colour from grey to black. The most common colour is grey. It is a highly stratified rock, formed on sea beds from skeletal remains including bones, teeth and shells of marine life accumulated over millions of years before being lithification under great pressure. Limestone is believed to have finished forming 350 million years ago, when Ireland was 30° south of the equator, having a hot desert climate. It is used for construction, ie headstones or monuments, construction and in the manufacturing of cement or fertilisers (lime neutralises the ph of a soil)
Carboniferous - the oldest type of rock known. It is hard, grey and 50% calcium carbonate. It is highly stratified allowing for the development of karst landscapes. It can be found in the Burren.
Dolomite - younger than Carboniferous. Contains traces of magnesium, varying from light grey to black. It can be found in Kilkenny
Chalk - the youngest type of rock, it is pure, soft and white rock, highly susceptible to denudation. Believed to have covered most of Ireland, has long since been weathered and eroded away.