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Flashcards in Natural Systems Deck (47):

System Boundary

The outer edge of a system: zone between one system and another system


Closed System

This is a system where transfers of energy can occur both into and beyond the system boundary however it does not transfer matter


Open System

Where matter and energy can be transferred from the system boundary into the surrounding environment



If one of the elements of a system changes, for example, one of the inputs increases without any corresponding change in the outputs, the store change and the equilibrium is upset


Negative Feedback

This is where the effects of an action are nullified by its subsequent knock on effects


The Lithosphere

-The solid outer part of the Earth, it includes the brittle upper portion of the mantle and the crust, the outermost layers of the Earth's structure, it it bounded by the atmosphere above and the asthenosphere (another party of the upper mantle)
- Two types of Lithosphere...
- oceanic and continental
- Continental lithosphere, associated with continental crust, can be much thicker than its oceanic cousin


15 Tectonic Plates

North American
South American
Juan de Fuca


The Pedosphere

This is part of the lithosphere that it made up of soil and dirt


The Hydrosphere

This is the total amount of water on the planet, it includes water this is on the surface of the planet, underground and in the air- a planets hydrosphere can be liquid, vapour or ice


The Cryosphere

These are the places on Earth that are so cold that water is frozen solid


Cascading System

This is a system that is made up of a chain of open systems where the output of one open system forms the input into another
inputs- processes- outputs



These are energy and material flows which feed into the coastal system and may drive the processes or provide the substances upon which the processes operate



These are the consequences of the processes operating on the inputs, they often take the form as features of erosion or deposition that in combination give a selection of coastlines there characteristic landscape


Flows and Transfers

These can be the changing distribution of energy and material within a system


Things that influence the energy of waves...

Strength of the wind- determined by the pressure gradient
Duration of the wind- the longer it blows the more powerful the waves will become
Fetch- the distance of open water over which the wind blows- the longer the fetch, the greater the energy the waves absorb


Waves don't travel much at all...

...instead they only thing they do is transmit energy across the sea


Surface waves

These are caused by the wind blowing along the air-water interface, creating a disturbance that steadily builds as wind continues to blow and the wave crest rises

They occur all over the globe and are waves you would see at the beach under normal climate conditions



This is the maximum length of open water over which the wind can blow ; the wind creates ripples on the surface of the sea and this process is called FRICTIONAL DRAG


Waves with the highest energy levels will...

...result from a combination of a long fetch and a consistent dominant wind blowing in the same direction


What are tides and what causes them?

The tides are periodic variation in sea level and they are caused by the gravitational pull of the moon on the water of our planet



This occurs when the Earth's surface is close to the moon and it pulls on the water and causes it to rise up



This occurs when the Earth's surface is further away and the impact of this gravitational pull is less


What is a tidal bore?

This is a large wave caused by the construction of the spring TIDE as it enters long, narrow, shallow inlet


How is a spring TIDE cause?

A spring tide is caused when the earth, moon and sun are aligned and when the gravitational pull is the greatest


When do low spring tides occur?

They occur just after a new moon


High spring tides occur when...

After a full moon- when he moon and sun are aligned


When do neap tides occur?

When the sun and moon are at a right angle to the earth


What are storm surges and what causes them?

Storm surges are changes in sea level which are caused by intense low pressure systems and high wind speeds


CASE STUDY: 1953 Storm Surge in the North Sea

Occurred on the night of Saturday 31st January 1953 and the morning of 1st February 1953, and it struck, Netherlands, Belgium, England and Scotland

It was caused by a combination of high spring tides and a severe European wind storm over the North Sea, a combination of wind, high tide and low pressure led to a water level of more than 5.6 metres above the average sea level in some places

In Netherlands the government decided to construct a flood defence system called the Delta Works which was an extensive system of dams and storm surge barriers. Meanwhile in the U.K., government coordinated immediate efforts to defend home and save lives- Thames Barrier programme was started to secure Central London against future storm surges

- lots of people died
- over 1,600km of coastline was damaged and sea walls were breached
- an estimate 30,000 animals drowned and sea water flood1,365km of land



- low waves with a long frequency
- break gently with a low frequency of around 6-8 waves a minutes
- they have a strong swash and a weak backwash- as a result material is moved up the beach
- they are long waves and they roll onto to the beach rather than crashing into it
- they create wide, gently sloping beaches
- allow material to be deposited along the coastline



- high in proportion to their length
- have a high frequency, 10-14 waves per minute
- they rapidly steepen when they break and they plunge down to the beach
- the backwash is much stronger than the swash, henceforth they create a steep, narrow beach
- they erode the coastline and are commonly associated with steeper beach profiles


Three causes of ocean currents

Wind, gravity and variation of water density


How many gyres spin in subtropical waters



How does the heating of the water in summer trigger surface currents?

The heat triggers the water to expand which causes the surface to rise by several cm's


Explain why ocean currents do not flow parallel to the wind or straight down the steepest surfaces

The equator moves faster than the poles which means the northern hemisphere is deflected to the right whilst the Southern Hemisphere is deflected to he left, furthermore this means they move at angles, it is also known as the Coriolis effect


What are longshore currents?

They add currents along the coastline where waves rolls into the short at an angle- they bulldoze sand along the shoreline


How are RIP currents formed and why are they dangerous?

Obstacles which are in the way of waves Chanel water away from the coastline- the water would drag you away from the coastline so the more you tried to swim the harder it would be


Surface winds may push water away from the shore, how does this lead to an upwelling current...

The wind pushes the surface water away from the shore deep cold water which rises to fill the gap


Why is the current sometimes called thermohaline circulation?

Because it depends on the temperature and solidity


Sediment budget

This is the net sum value between quantities of input and output of sediment in a system - excessive is a positive budget, deficit is a negative budget and no overall difference is a neutral budget


Sediment (littoral) cells

These tend to be hundreds of kilometres in length and they are bounded by major headlands at either end - represent sections of the coast in which sediment is largely recycled


Sediment Sink

When sediment is lost to the system by transfer to a location beyond further access HOWEVER - these are different to a 'sediment store' where additions and removal of sediment is possible


Wave Refraction

The changes in wave orientation and frequency as they encounter a non-uniform coastline ; waves may be refracted towards a feature (convergence) or away (divergence) as water depth


Tidal Range

The vertical difference in height of sea level between high and low tide


Key sources of physical material inputs

River discharge : sediment and fine material brought to an estuary and entering the sea

Ocean currents : these may transport material thousands of miles and upwelling currents may bring material to surface waters from significant depths

Seabed disturbance : severe storms can destabilise material on the sea floor and move it towards the coast

Cliff and shore disintegration : the transfer of material as cliffs erode and upper beach material is removed into the active zone of coasts provides an input of solid material that can be transported


Features of costal erosion

Headlands and Bays : right angled to the coast (discordant ) , parallel to the coast (concordant )

Wave cut platform : represents the base of the cliff that lies below the dominant intertidal zone erosion processes - as the cliff line retreats , the wave - cut platform becomes wider and has an increasing frictional effect on advancing waves

Caves , blow holes, arches , stacks and stumps


Features of coastal deposition


Spit : a long narrow beach of sand or shingle with one end attached to the shore and the other extending into the sea or estuary

Bar : this is where the spit extends across a bay and rejoins the coast on the opposite shore confining saltwater behind it in a lagoon

Tombolo : in some cases a spit can extend from a shore and reaches on offshore island, joining the previously isolated land to the main shore by means of a shingle / sand beach