Download Chapter 5: The Rock Cycle The rock cycle

Chapter 5: The Rock Cycle
Plutonic rocks
• Formed within the Earth
• Intrusive
• e.g. granite
Chapter 5: The Rock Cycle
Volcanic rocks
• Formed at the surface of the Earth
• Extrusive
• e.g. basalt
Chapter 5: The Rock Cycle
The rock cycle
• Rocks continually form, change, are destroyed and
reconstituted
• Endogenic forces – construct and modify
• Exogenic forces – destroy
• Deposition – reconstitute
Chapter 5: The Rock Cycle
Magma
• Rock layers subduct into the crust and mantle
• Rock layers melt and form molten rock
Chapter 5: The Rock Cycle
Rocks vary in their:
• Origin
• Formation
• Characteristics
Chapter 5: The Rock Cycle
Three major rock groups exist:
• Igneous
• Sedimentary
• Metamorphic
Chapter 5: The Rock Cycle
Rock Formation
1. Igneous
• Magma rises, cools and solidifies to form igneous rocks
• Magma reaches the surface, it forms volcanic rock
• Magma cools and hardens within the crust, it forms
plutonic rock
Chapter 5: The Rock Cycle
Rock Formation (continued)
2. Sedimentary
•
Destroyed where denudation occurs on the surface
•
Weathering
•
Erosion
•
Break down into sediments
•
Sediments are then deposited and compressed
Chapter 5: The Rock Cycle
Rock Formation (continued)
3. Metamorphic
•
Modified due to either great heat or pressure or both
Chapter 5: The Rock Cycle
Characteristics of the different types of rocks
1. Igneous rock
Two types:
I. Plutonic or intrusive rocks
•
Formed when magma cooled down and solidified inside
the Earth’s crust
•
e.g. granite
II. Volcanic and extrusive
•
Formed when lava cooled and solidified on the Earth’s
surface or close to the surface
•
e.g. basalt
Chapter 5: The Rock Cycle
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
Chapter 5: The Rock Cycle
Granite
•
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
Chapter 5: The Rock Cycle
Basalt
•
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
Chapter 5: The Rock Cycle
Characteristics of the different types of rocks
2. 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
Chapter 5: The Rock Cycle
Two types of sedimentary rock
i. Inorganic sedimentary rock
•
Inorganic sedimentary rock formed from the broken
down remains of pre-existing rock
ii. Organic sedimentary rock
•
Organic sedimentary rock formed from the remains of
animal and plant life
Chapter 5: The Rock Cycle
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
Chapter 5: The Rock Cycle
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
Chapter 5: The Rock Cycle
Characteristics of the different types of rocks
3. Metamorphic rock
Formation:
•
Sedimentary or igneous rocks changed by either great
heat or pressure (or both)
•
Magma
•
Folding
•
Appearance, texture and chemical composition change
Chapter 5: The Rock Cycle
Types of metamorphism
i. Thermal
•
heat alone
•
rocks change in composition
ii. Regional
•
great heat and pressure over a large area
•
fold mountain
•
colliding plates
•
rising magma
Chapter 5: The Rock Cycle
Examples of sedimentary rock changing into
metamorphic rock
•
Limestone changes to marble, e.g. Connemara in Co.
Galway
•
Sandstone changes to quartzite, e.g. Sugarloaf
Mountain, Co. Wicklow
Chapter 5: The Rock Cycle
Marble
•
Metamorphic rock
•
Limestone
•
Heat and pressure
•
Various colours
•
Connemara (green)
•
Kilkenny (black)
•
Cork (red)
•
Rathlin Island, Antrim and Carrara, Italy (white)
Chapter 5: The Rock Cycle
Quartzite
•
Metamorphic
•
Sandstone
•
Heat and pressure
•
Mountain building
•
Sandstone came into contact with magma
•
Light-coloured rock, e.g. Croagh Patrick, Co. Mayo
Chapter 5: The Rock Cycle
Active plate margins
•
Oceanic plate subducting under a continental plate
•
Faulting, mountain building, volcanoes and earthquake
activity
•
e.g. west coast of North America Pacific plate
subducting under North American plate
Chapter 5: The Rock Cycle
Trailing plate margin
•
Absence of earthquake, volcanic activity or folding
•
Sedimentary rocks form, e.g. sandstone and limestone
Chapter 5: The Rock Cycle
Quarrying case study
•
Important resource
•
Energy
•
Building materials
Chapter 5: The Rock Cycle
1. Methods of quarrying
I. Plug and feather
•
drilling holes
•
split the rock
•
extracting large pieces, e.g. floor covering
II. Explosive
•
extracting large and small pieces of rock
III. Channelling
•
machinery cuts large slices of rock
•
metamorphic rock such as marble
Chapter 5: The Rock Cycle
2. Positive impacts of quarrying
•
Direct employment
•
Construction
•
Indirect employment
Chapter 5: The Rock Cycle
3. Negative impacts of quarrying
•
Visual pollution
•
Noise pollution
•
Heavy machinery damage to infrastructure
•
Dust pollution
•
Water pollution
•
Disused quarries
Chapter 5: The Rock Cycle
4. Carrara marble
•
Tuscany, Italy
•
White or blue-grey marble
•
Used since the time of ancient Rome
•
Statue of David – Michelangelo
•
Exported all around the world
•
Construction of buildings
•
Warm countries
•
Reflect light
•
Create an air of coolness