Theme 1: Landscapes and Physical Processes Flashcards
Define a cross-profile.
A cross-profile is a cross-section of the valley and channel of a river.
Define erosion.
The wearing away of pieces of rock, soil or other solid materials.
Define the hydrological cycle.
The continual movement of water between the rivers, oceans, atmosphere and land.
Define lateral erosion.
The wearing away of the landscape when a river erodes sideways.
Define ‘load’.
The particles of rock carried by a river.
Define the mouth and the source!
m= the place where a river meets the sea. s= the place where a river starts in its upper course.
Define transportation!
To move objects or people from one place to another.
Define tributary.
A small river that joins the main river channel.
Define valley and because that’s fairly simple, also define vertical erosion :)
Valley= A low area of land between hills or mountains, typically with a river flowing through it
Vertical Erosion= When the land is eroded or worn away in a downwards direction, eg a river that is high up will erode vertically because gravity pulls the water downwards.
Define long profile.
A section of the course of a river drawn from source to mouth.
Define confluence and watershed
Confluence= the point where two rivers meet. Watershed= the area of high land forming the edge of a river basin.
What are some things you know about the upper course?
- has a large load
- start of the river
- often in upland areas
- often downhill, so there’s more vertical erosion
- channel is narrow and shallow
- not much water at this stage
What are some things you know about the middle course?
- some vertical erosion but more lateral erosion
- the channel is wider and deeper
- more water than the upper course
What are some things you know about the lower course?
- flatter land
- load is fine sediment
- little erosion, mostly lateral
- greater influence of deposition
- channel is at its widest and deepest
Types of River Erosion 1: Hydraulic Action
This is the sheer power of the water as it smashes against the river banks. Air becomes trapped in the cracks in the rock of the river bank and bed, and causes the rock to break apart.
Types of River Erosion 2: Abrasion
When pebbles are picked up by the flowing water and smash against the river bank and bed, wearing it away.
Types of River Erosion 3: Attrition
When rocks that the river is carrying knock against each other. They break apart to become smaller and more rounded.
Types of River Erosion 4: Solution
When the water dissolves certain types of rock, eg limestone.
Types of River Transportation 1: Traction
Large, heavy pebbles are rolled along the river bed. This is most common near the source of a river, as here the load is larger.
Types of River Transportation 2: Saltation
Pebbles are bounced along the river bed, most commonly near the source.
Types of River Transportation 3: Solution
The transport of dissolved chemicals. This varies along the river depending on the presence of soluble rocks.
Types of River Transportation 4: Suspension
Lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river.
Define deposition.
As the river loses energy, it ‘deposits’ the material it has been carrying.
When a wave transports sediment/ sand up the beach but has not got enough energy to bring it back, so leaves it there.
What are the factors that lead to deposition?
- shallow water
- at the end of the river’s journey, or at its mouth
- when the volume of water decreases
What is alluvium/silt?
The sediment deposited by rivers/ fertile sand-sized particles found in the lower course of a river.
Define floodplain
An area of low-lying land next to a river which is prone to flooding.
Define gorge.
A deep, narrow passage that usually has a river running through it.
Define levee.
Ridges or banks formed by deposits of alluvium left behind by the periodic flooding of rivers. Can also be artificially constructed banks or walls.
What is a meander?
~ a bend in a river ~
Define ‘plunge pool’.
The pool of water found at the bottom of a waterfall. It is an erosional feature which has been created by a combination of hydraulic action and the abrasion of the plunging water.
What is a slip-off slope?
Gently sloping bank found on the inside of a river bend because of slow-flowing water, depositing sediment.
Define river cliff.
Steep bank created on the outside of a river bend by the erosive effect of fast-flowing water undercutting the bank.
Suspension (not the transportation one, the other one) means…
A mixture of two substances, one of which is finely divided throughout the other.
Define discharge.
The volume of water in a river passing a point in a given time. Measured in cumecs (cubic metres per second).
The process of creating a waterfall and then a gorge is… pt 1
- The soft rock is eroded quicker than the hard rock and this creates a step.
- As erosion continues, the hard rock is undercut forming an overhang.
- Abrasion and hydraulic action continue to erode the soft rock to create a plunge pool (small scale landform).
The process of creating a waterfall then a gorge is… pt 2
- Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
- This process continues and the waterfall retreats upstream.
- A steep-sided valley is left where the waterfall once was. This is called a gorge.
How do you create a v-shaped valley?
In the upper course, traction and saltation are most common, eroding vertically. This erosion, and the movement of weathered material from the banks, create a V-shaped valley. The river will bend around any hard rock.
~ How do you make a meander? ~
As the river goes around a bend, most water is pushed to the outside thus increased speed and consequent erosion resulting in a river cliff. On the inside, there’s less water + energy so the river deposits hence a gentle slope called a slip-off slope.
How do you make a floodplain?
Erosion creates a wide, flat area on either side of the river. During a flood, material being carried by the river is deposited, heightening the floodplain.
Floodplains are often used by which industry?
Agriculture! The land is very fertile because of alluvium/ silt.
How to make a levee? pt 1
In the lower course, there is an increased volume of water flowing downstream and flooding occurs. During floods, energy is lost and sediment spreads over the floodplain.
How to make a levee? pt 2
Larger material is deposited first on the river’s banks and smaller material further away. Over time, sediment builds up to increase the height of the river banks, heightening the channel, leading to a greater discharge and smaller chance of flooding in future.
What factors affect the rate of landform change?
Geology – e.g. hard and soft rocks in the formation of waterfalls.
Climate – seasonal (UK), affects the discharge of a river and the level of energy it has to erode/deposit.
Human activity – intended and unintended consequences, e.g. building a dam which traps sediment and controls the flow of a river.
What do you know about waves?
- erode the landscape
- shape coast
The size and energy of a wave depend on different factors, they are…
- the fetch (defined on another card)
- the strength of the wind
- how long the wind has been blowing for
What does fetch mean?
How far a wave has travelled!
What is swash?
Water flowing up a beach in the direction of the prevailing wind.
Define backwash.
The perpendicular movement of water down a beach due to gravity.
What are constructive waves?
Waves with a strong swash and weak backwash, which help to build up material on the beach.
What are destructive waves?
Waves with a weaker swash than backwash, which remove material from the beach.
What are the characteristics of a destructive wave?
- occur in stormy conditions, with strong winds
- tall, with short wavelength
- arrive quickly, at a high frequency
What are the characteristics of a constructive wave?
- occur in calm conditions, without much wind
- short with long wavelength
- low frequency
Define longshore drift.
The movement of material along a coastline due to the angled approach of waves.
Define prevailing wind.
The wind direction that occurs most often throughout the year, or occurs most often at this time of year, in a certain geographical region.
What is mass-movement?
A large-scale downward movement of rocks and material.
other contexts vary
What is freeze-thaw weathering? ❄
The water enters the gaps in porous (contain holes) or permeable (allow water to pass through) rocks, freezes and splits the rock.
A detailed description of the process of freeze-thaw weathering. ❄
- Water enters cracks in the rock.
- When temperatures drop, the water freezes and expands causing the crack to widen.
- The ice melts and water makes its way deeper into the cracks.
- The process repeats itself until the rock splits entirely.
What is biological weathering? 🌿
Plants and animals can have an effect on rocks e.g. roots burrow into the rock, weakening the structure of the rock until it breaks away.
A detailed process of biological weathering. 🌿
- Plant roots can get into small cracks in the rock.
- As the roots grow, the cracks become larger.
- This causes small pieces of rock to break away.
What is chemical weathering? 🧪
Rainwater and sea water can act as weak acids. If a coastline is made up of rocks such as limestone or chalk, over time they can become dissolved by the acid in the water.
What is a landslide?
Large blocks of rock become detached and slide downhill.
Types of Coastal Erosion 1: Abrasion
Bits of rock and sand in waves grind down cliff surfaces like sandpaper.
