Rocks and the Rock Cycle Flashcards
Draw diagram of plutonic and volcanic igneous rock formations
See notes
What kind of texture does basalt have?
- Smooth, fine grained
- No visible crystals (microscopic) due to rapid cooling no time to form
Which type of metamorphism requires extreme compressional forces?
Regional metamorphism
Do sedimentary rocks erode easily?
Yes
How was the Antrim-Derry Plateaux formed?
- 65m years ago low viscosity lava poured out from North American - Eurasian divergent plate boundary
- Lava flowed into nearby river valley, cooled and built up to form flat-topped basalt plateaux
- As basalt cooled and contracted, it split apart into hexagonal columns -> Giant’s Causeway, Co. Antrim
How are sedimentary rocks formed?
Due to compaction and cementation (=lithification) of sediments in a lake/river/sea
Draw a diagram labelling where each form of metamorphism takes place
N/A
What are the three different types of sedimentary rock?
Mechanical, Organic and chemical
Which type of metamorphism invloves interaction with a high temperature fluid?
Hydrothermal metamorphism
What kind of crystals does granite have?
Large crystals due to slow cooling
Give an example of places where each type of igneous rock can be found
Instrusive: Granite in Wicklow Mountains
Extrusive: Basalt - Giant’s Causeway
Draw diagram showing rock cycle
See notes
When was limestone formed
350 million years ago
How was limestone formed?
It is created from compacted shells and skeletons of marine organisms in warm, shallow seas
What colour is basalt?
Black/dark green - varies due to lava properties
What texture does granite have?
Coarse (due to crystals)
Give an example of each of the three different types of sedimentary rock and where they can be found
Mechanical:
* Sandstone - Comeragh Mts, Munster
* Shale - Cliffs of Moher
Organic:
* Limestone:
-Carboniferous - Burren, Co Clare
- Dolomite - Johnstown, Co Kilkenny
- Chalk - Cliffs at Portrush, Co Antrim
Chemical:
* Gypsum - Kingscourt, Co Cavan
* Rock Salt - Carrickfergus, Co Antrim
What is the difference between the two different types of igneous rocks?
Intrusive: Made from cooled magma
Extrusive: Made from cooled lava
Give an example of where in the world basalt can be found
Mid Atlantic Ridge
How is granite formed?
- At convergent boundaries
- Magma forces it’s way between rocks at plate boundaries
- Slow cooling of molten magma deep within earth’s crust at a depth 5-30km -> plutonic rock
Give a global example of where rock salt can be found
Salar de Uyuni, Bolivia
Which type of metamorphism happens around intrusive igneous rocks?
Contact metamorphism
What is sedimentary rock made from?
Other rocks and sediments of plants and animals
What are the characteristics of regional metamorphism?
- Affects extensive regions
- Produces foliated rocks like slate, schist and gneiss due to directed pressure
- Common in zones of collision where plates converge
How is sandstone formed?
Sand-sized particles of feldspar and quartz are compacted in rivers, deserts or beaches
What type of rock makes up 90% of ocean floors?
Basalt
When was sandstone formed?
400 million years ago
What are the three different classifications of sedimentary rocks and how do they differ from each other?
Mechanical (clastic): Other rock particles
Organic: Once living things
Chemical: Due to environment eg. desert climate - evaporation
Give a global example of where limestone can be found
White Cliffs of Dover, England
How is basalt rock formed?
- At constructive boundaries magma forces through fissures (openings in earth’s crust) reaching surface as lava
- When it meets air/water it cools rapidly
Define metamorphism
The process by which rocks are transformed due to changes in temperature, pressure and/or chemical conditions without the rock melting
What is lithification?
The process of compaction and cementation where layers of sediment compact over time, and silica cements particles together to form solid sedimentary rock
How was rock salt formed?
Formed by evaporation of saline water in arid environments like salt lakes or lagoons
What causes regional metamorphism?
Occurs over large areas due to intense pressure and high temperatures, typically associated with mountain-building processes at convergent plate boundaries
What are the properties of basalt?
Mafic rock - Has magnesium and iron
Give examples of each different type of metamorphic rock foundation and where they can be found
Thermal:
* Quartzite (formerly sandstone) - Mt Errigal, Donegal
Regional:
* Marble (formerly limestone) - Connemara, Co Galway
* Gneiss (formerly granite) - Annagh Head, Co Mayo
Dynamic:
* Mylonite (formerly granite) - Roundstone, Co Galway
* Slate (formerly shale) - Valencia Island, Co Kerry
Give an example of where in Ireland basalt can be found
Derry-Antrim Plateaux - Giant’s Causeway
Examine with reference to Ireland the formation of igneous rocks (30m)
See notes
When was rock salt formed?
200 million years ago
What kind of mineral content does granite have?
- Due to high silica content (70%) -> acidic rock
- Key mineral components: quartz (colourless), feldspar (reflective, flat mineral) and mica (black/white crystals)
- High feldspar + High silica mineral content = felsic rock
Examine with reference to Ireland, the formation of sedimentary rocks (30m)
See notes
What are some economic uses of basalt and examples of these?
- Broken down basalt makes very fertile soil eg. In Brazil, coffee plantations grown in basalt areas
- Used in construction industry eg. Road chippings/tarmacadam
- Basalt plateauxs bring in tourism eg. Giant’s Causeway created from basalt eruptions
Give an example of regional metamorphism
- Shale transforms into slate or schist
Limestone transforms into marble
What type of climate are chemical sedimentary rocks found in?
Desert climate
Explain changes that can occur to rocks due to metamorphism
Recrystallization
* Existing minerals grow larger or form new minerals without melting
* Results in denser and more interlocking mineral grains, such as the transformation of limestone into marble
Texture changes
* Development of foliation: Minerals align in planes or layers due to directed pressure, as seen in slate or schist
* Development of non-foliated texture: In rocks without platy minerals (eg. quartzite and marble), as granular texture develops
Mineral changes
* New minerals form that are stable under the new temperature and pressure conditions such as garnet, staurolite or sillimanite
* Original minerals may break down or recombine, like the transformation of clay minerals into mica
Chemical changes (metasomatism)
* Interaction with chemically active fluids can add or remove elements, altering the rock’s composition
Banding
* Under high-grade metamorphism, minerals segregate into light and dark bands, as seen in gneiss
Hardness increase
* Rocks typically become harder and more resistant to weathering due to recrystallization and compaction
What are the layers sedimentary rock is made up of known as?
Strata/stratal layers
Draw a diagram showing the formation of sedimentary rocks
See notes
What are the three main rock types?
Igneous, Sedimentary and Metamorphic
Give a global example of where sandstone can be found
Grand Canyon, USA
How are intrusive/plutonic igneous rocks formed?
- When molten magma cools and solidifies deep within the crust of the earth
- Eventually come to the surface as a result of uplift and removal of overlying rocks
Which type of metamorphism requires the crushing and grinding of rocks?
Dynamic metamorphism
What are some uses of granite and why is it used in this way?
- Ornamental: Used in counter tops, table tops and headstones
- When broken down by weathering and erosion used to make kaolin/china clay used by porcelain industry
-> Hard, heavy rock resistant to weathering + erosion
What are the different ways metamorphic rocks can form?
- Thermal - Heat only
- Regional - Heat and pressure
- Dynamic - Pressure only
How are extrusive/volcanic igneous rocks formed?
Formed when magma cools and solidifies on or near earth’s surface
Point out rock types on map of Ireland
See notes
What colour is granite?
Black/grey - Red/pink
Varies depending on proportions of different minerals in rock
