Rocks Flashcards
(31 cards)
What are Rocks?
Solid materials occuring in the earth’s crust, composed of one or more minerals.
(Set 1) Differences in rocks
- Mineral Content
- Hardness
- Origin
- Rocks are composed of one or more minerals, natural substances like quartz, calcite etc.
- Resistance to weathering + erosion
- Where and how they were created
(Set 2) Differences in rocks
- Texture
- Density
- Shape
- How It feels to touch.
- Amount of rock compared to space it takes up.
- How they were laid down (strata or shapes)
Rock cycle
- Magma cools to rock
- Magma melts rock during subduction
- Rock breaks down into sediments by the elements of weathering + erosion
- Reformation of rock through lithification.
- Changing of rocks structure by heat + erosion
Igneous Rocks
Formed when magma rises from mantle and cools either intrusively or extrusively
Basalt
Example, Characteristics, economic value
E.g Giant’s Causeway
Typically black to dark grey in colour, smooth hard rock
E. Value - Floor tiles, building veneer, road chippings etc.
Basalt formation
Volcanic + extrusive rock,
DIVERGENT boundaries, approx 65m yrs ago, lava flowed through fissures, low silica content, Basic igneous rock
Granite
Example, Characteristics, Economic Value
E.g Wicklow Mountains
Typically grey, has variations depending on proportions of various minerals like potassium and quartz. Course grained texture, hard + durable
E. Value - Construction of buildings, bridges, countertops, floor tiles etc.
Granite formation
Plutonic rock, CONVERGENT boundaries approx 400m yrs ago, collision forming fold mountains, molten magma intruded with high silica content, cooled slowly, contains feldspar and quartz
Deposition
Particles deposited as loosely packed sediments
Cementation
Over time, natural minerals glue the particles together
Compaction
The weight of water and overlying layers squeeze the sediments together.
Sedimentary rocks
Formed from particles of animals, sea creatures, plant life and broken down rocks.
Sediments are laid down in layers or STRATA and separated by horizontal gaps in rock called bedding planes
Organic sedimentary rocks
Formed from once living things or decayed vegetation
Inorganic Sedimentary rocks
Formed from broken down sediments of other rocks.
Limestone
Example,
Characteristics, economic value
E.g The Burren
Chalk like - pure limestone, white and easily eroded, - carboniferous limestone, over 50% calcium carbonate, grey in colour, more resistant
E. Value - Used in making of cement, glass and soil conditioner
Limestone formation
Organic, 300m yrs ago, near equator, living things built up on sea floor, deposited sand mixed, calcium carbonate in living things, rock forms
Sandstone example, Characteristics, economic value
E.g Caha mountains
Old red sandstone has colour due to presence of iron oxide, can be soft or hard depending on formation
E. Value: Sandstone is used as a decorative store in sculptures, headstones and pavment
Sandstone formation
Inorganic, 380 million yrs ago, South of equator desert climate, weathering and erosion, transported by flash floods, sediments of fine sand deposited, compressed by weight Of seawater, calcium carbonate, iron and silica cemented rock
Other sedimentary rocks
Coal - organic, Arigna, dead vegetation
Shale - inorganic, Slieve Elva - Burren, mud and clay. Quartz and calcite
Metamorphic Rocks
Igneous or sedimentary rocks are subjected to great heat or pressure
Metamorphic features
Smaller volume and minerals are transformed to high temperature minerals. Denser and more resistant to weathering or erosion.
Regional metamorphism
(Dynamic) Friction at convergent boundaries creates heat and pressure, composition changes. E.g zone of subduction
Contact Metamorphism
(Thermal): Rising molten magma changes composition of rocks in small area. E.g volcanic intrusion
