Sedimentary rocks

• Sedimentary rocks are formed from the compressed remains(sediments) of animals plants or other rocks.
• • Sedimentary rocks develop in layers
• • They form when material is compressed over millions of years to form solid rock.
• • The process whereby sediments are compressed to form solid rock is known as Lithification.
• They can be classified according to how they are formed:

  • Organically formed Sedimentary rocks are composed of dead organisms (fish, shells, vegetation)
  • Inorganically formed Sedimentary rocks are composed of rock fragments.
• Limestone is an Organically formed Sedimentary Rock.
• Limestone is formed from the compressed and cemented remains of fish and other sea creatures.
• The remains of these creatures in limestone build up on top of each other.
• Over millions of years the remains were compressed by each of the overlying layers and formed slowly into solid limestone rock
• The deposits of the remains are cemented by calcium carbonate ( limestone )
• The limestone in Ireland was formed during the Carboniferous Period about 300 million years ago.
• At the time of the Carboniferous Period, Ireland was covered by a warm tropical ocean and was located close to the equator.
• Limestone is laid down in horizontal layers called strata.
• Bedding planes are the divisions between these layers in limestone
• Vertical cracks known as joints can occur in limestone.
• Limestone is permeable (allows water to pass through it)
• Fossils can be found in Limestone.
• Limestone is used for a variety of purposes including as a building material, for road chippings, as a soil fertiliser.
• Limestone is the most common rock in Ireland and can be found in The Burren Co. Clare.
• Sandstone is an inorganic Sedimentary Rock.
• Sandstone is formed when particles of eroded Igneous, Sedimentary and Metamporphic Rocks are carried by rivers and accumulate on the beds of lakes and seas.
• Most of Ireland's sandstone was formed 400 million years ago.
• Debris from Ireland's Caledonian fold mountains was compressed and compacted.
• Iron particles in the debris rusted giving the sandstone a reddish colour.
• Old Red Sandstone is the most common type of Sandstone in Ireland.
• Much of this sandstone was later covered by layers of Limestone however a lot of it has been exposed now due to weathering and erosion.
• Sandstone can be found in the Macgillycuddy Reeks.
• Sandstone is widely used as a building material due to its decorative appearance.