Types of Rocks

Types of Rocks

1. Igneous

   • Formation
     • Formed by the cooling of molten magma caused by volcanic activity
       • Magma cools underground > Intrusive
       • Magma cools on ground surface > Extrusive
   • Characteristics
     • Crystalline
       • Made up of interlocking crystals
     • Tough, Hard, Resistant to Erosion
   • Examples
     • Granite
       • Widely used for construction and monuments
     • Basalt

2. Metamorphic

   • Formation
     • Formed within the Earth's crust
     • When another rock is changed by huge amounts of heat and pressure
   • Characteristics
     • Often exhibit layering called cleavage
     • Tough and resistant to erosion
   • Examples
     • Slate
       • SHALE (Sedimentary) > SLATE (Metamorphic)
       • Used for roofing
     • Marble
       • LIMESTONE (Sedimentary) > MARBLE (Metamorphic)
       • Used for buildings and ornate statues

3. Sedimentary

   • Formation
     • Sediment eroded from land by wind/rivers/ice is deposited in the sea
     • LITHIFACTION
       • Sediment is compacted on the sea bed until it forms layers of solid rocks
   • Characteristics
     • Usually found in layers called BEDS
     • Normally weaker than other rocks
       • Some i.e. Limestone are tough
     • Vertical Joints, Horizontal Bedding Planes
   • Examples
     • Limestone
       • Used in cement and glass
     • Chalk
       • Formed from COCCOLITHS
       • Used to make quicklime and mortar
     • Sandstone
       • Consists of Sand particles
       • Used in construction