Sedimentary Rocks Flashcards
What are sedimentary rocks?
- Sedimentary rocks are produced through the weathering and erosion of rocks.
- These sediments are then deposited and joined together through an increase in pressure, forming recognisable layers.
- They are able to contain the remain of life forms.
What is a soil?
A ‘bunch’ of particles which have no cohesion between them.
What are the different types of sedimentary rock?
Conglomerate:
- Made up of a range of particle sizes.
Sandstone:
- Made up of similarly sized particles which can be seen by the naked eye.
- You are able to see the sequence of deposition.
Shale:
- Made up of similarly sized particles which cannot be seen by the naked eye.
- You are able to see the sequence of deposition under a microscope.
What are the different sizes of sediment?
What are the different types of flow?
Laminar flow:
- Gravity acts on all particles causing them to sink to the bottom of the river bed.
Turbulent flow:
- Large amounts of mixing means particles do not settle.
- Instead, they jump downstream, disturbing even more particles.
- This can produce ‘pits’ in the river bed which collects more rocks, eroding larger and larger.
What are the features of a meander?
- Materials are deposited on the inside of a bend where water flow is slow.
- Materials are eroded in the outside of the bend where water flow is faster.
What are the different types of chemically formed sedimentary rocks?
Carbonates:
- Formed through the deposition of shelled organisms (made of calcium carbonate).
- e.g. carbonate sands, carbonate muds.
Marine Evaporites:
- Formed through the evaporation of sea water.
- e.g. gypsum, halite.
Siliceous:
- Formed through the deposition of shelled organisms (made of silica).
- e.g. silica. Continental
Evaporites:
- Formed through the evaporation of lake water.
- e.g. halite, nitrates.
Swamp:
- Formed through the compression of vegetation.
- e.g. peat.
What are the different types of sand dunes?
When wind blows, it transports sand up the slope before depositing it on the other side.
Symmetrical ripples:
- If the wind/water which transports the sand changes direction, a pattern of symmetrical ripples are produced in the sand.
Asymmetrical ripples:
- If the wind/water which transports the sand doesn’t change direction, a pattern of asymmetrical ripples are produced in the sand.
How can sediment be turned into a rock?
- Compaction
- Cementation
What is the rock cycle?
What are clastic sediments?
- Clastic sediments are accumulations of clastic particles derived from the weathering of pre-existing rocks.
- They are rounded by physical abrasion during transportation.
- They are dominated by quartz which is hard and does not weather.
What are the different structures of sedimentary rocks?
- Fossils
- Stratification (layers)
- Graded bedding (course rock is found at the base, reducing to fine rock at the top)
- Ripples
- Cross bedding
What are the different processes associated with sedimentation?
- Lithification: when sediment is turned into rock.
- Subsidence: when materials sink deeper and deeper.
- Compaction: when water is squeezed out of a material.
- Precipitation: when new materials are produced through cementation.
What are the features of limestone?
- Limestone is a sedimentary rock made up of organic materials (marine shell debris) or chemical carbonate.
- It is soluble in rainwater, producing open fissures, sinkholes and caves.
- e.g. oolite, chalk.
What are the features of sandstone?
- Sandstone is a medium grained, sedimentary clastic rock.
- Older sandstones are frequently better cemented and therefore stronger.
- It acts as a productive aquifer.
What are the features of clay?
- Clay is a very fine grained sedimentary rock.
- They are very weak, but their strength is related to water content.
- Clay acts as an aquiclude, as it has very fine particles with narrows channels between them meaning water cannot easily flow.
How does the velocity of water flow affect rocks?
Particle Size Distribution Chart
Red:
- Gap graded - contains some small particles and some large particles.
Blue:
- Well graded - contains a wide range of particle sizes.
Green:
- Single graded - contains only a small range of particle sizes.
