1. Rock Types & Formation 5 th year Geography

2. Learning Outcome Identify the three main rock groups. Locate examples of each rock type on a map of Ireland. Understand the formation & main characteristics of two types of rock from each group. Answer an essay style exam question, explaining in detail the formation of one rock type.

3. Rocks Rocks vary in their:  Origin  Formation  Characteristics

5. Rock Groups Three major rock groups exist:  Igneous  Sedimentary  Metamorphic

6. Igneous 1.Magma rises, cools and solidifies to form igneous rocks 2.Magma reaches the surface, it forms volcanic rock 3.Magma cools and hardens within the crust, it forms plutonic rock

7. 2 Types of Igneous Rock I.Plutonic or intrusive rocks  Formed when lava cooled and solidified on the Earth’s surface or close to the surface  e.g. basalt I.Volcanic and extrusive  Formed when magma cooled down and solidified inside the Earth’s crust  e.g. granite

8. Igneous rocks contain crystals  Size tells length of time it took rock to cool  Large crystals cooled slowly within the Earth’s crust  Small crystals, cooled quickly on the Earth’s surface

9. Granite

10.  Coarse-grained  Formed when magma cooled deep within the Earth’s crust  Contains minerals of feldspar, quartz and mica  Varies in colour – white, grey, pink or black  Crystals are large, the rock cooled slowly  e.g. Wicklow Mountains

12. Basalt

13.  Fine-to-medium- grained  Ranges in colour – black to dark grey  Formed when lava cooled quickly on the Earth’s surface  Small crystals  e.g. Antrim-Derry Plateau  Giant’s Causeway  Six-sided columns, hexagonal in shape

15. Giants Causeway

16. Sedimentary  Rock is destroyed where denudation occurs on the surface  Weathering  Erosion  Break down into sediments  Sediments are then deposited and compressed

17. Lithification A process where sediments compact under pressure and over time become solid rock. Eg; Loose particles of sand become sandstone.

19. Sedimentary rock  Formed over millions of years  Rock fragments and the remains of animals and plants compressed under pressure to form solid rock  e.g. limestone and sandstone

20. Two types of sedimentary rock I.Inorganic sedimentary rock  Inorganic sedimentary rock formed from the broken down remains of pre- existing rock I.Organic sedimentary rock  Organic sedimentary rock formed from the remains of animal and plant life

21. Limestone  Organic sedimentary rock  Most common type of rock in Ireland  Cemented and compressed remains of fish and other sea creatures  Over millions of years compressed and formed slowly into solid rock  Carboniferous period  Contains calcium carbonate  Varies in colour - greyish white, black, dark grey  e.g. the Burren in Co. Clare

22. Limestone

23. Sandstone  Inorganic sedimentary rock  Coarse  Usually brown or red  Formed approximately 400 million years ago  Sediments laid down in layers  Each successive layer compressed the next layer  Cemented to form sandstone  e.g. Comeragh Mountains, Co. Waterford

24. Sandstone

26. Metamorphic Modified due to either great heat or pressure or both

27. Metamorphic Rock  Sedimentary or igneous rocks changed by either great heat or pressure (or both)  Formation can depend on;  Magma  Folding  Appearance, texture and chemical composition change

28. Types of metamorphism i. Thermal  heat from magma  rocks change in composition ii. Regional  great heat and pressure over a large area  fold mountain  colliding plates  rising magma

29. Marble  Metamorphic rock  Limestone  Heat and pressure  Various colours  Connemara (green)  Kilkenny (black)  Cork (red)  Rathlin Island, Antrim and Carrara, Italy (white)

31. Quartzite  Metamorphic  Sandstone  Heat and pressure  Mountain building  Sandstone came into contact with magma  Light-coloured rock, e.g. Croagh Patrick, Co. Mayo

32. Croagh Patrick

33. Exam Question Name one type of igneous / sedimentary rock. Name one Irish location where this type of rock was formed and explain in detail how it was formed. (30m)