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.
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.
