physical systems - landscape systems - mr rawlings

Question 1

define coasts?

Answer 1

the coast is an area where sea, land and atmosphere meet

this unique combination is a dynamic environment
where change occurs frequently and at regular intervals

it produces some spectacular landscapes and
landforms, and offers a variety of opportunities for human activity

Question 2

the coast is an open system what does this mean?

Answer 2

means that energy and matter can cross the

boundary to/from the surrounding environment as an input or output e.g. sediment from the river system

Question 3

what is a sediment cell?

Answer 3

a sediment cell is regarded as a closed system, which suggests that no sediment is moved from one cell to another; only energy can transfer between cells

Question 4

draw a sediment cell?

Answer 4

the system is in equilibrium, however a change
in energy or sediment input can upset
equilibrium & cause feedback

Question 5

where does majority of the energy in coastal zones come from?

Answer 5

from moving water, as waves, tides and currents

Question 6

what do waves do?

Answer 6

carry’s out much work (geomorphic processes) on a

coastline – eroding, transporting and depositing materials

Question 7

how are waves generated?

Answer 7

waves are generated by the atmospheric process of wind

Question 8

waves are described by height, define height?

Answer 8

distance from trough to crest

Question 9

waves are described by length, define length?

Answer 9

distance from crest to crest

Question 10

waves are described by wave period, define wave period?

Answer 10

time taken between 2 crests

Question 11

how are waves generated?

Answer 11

waves are caused by the frictional drag between wind and water

wind in contact with surface slows down - friction

upper winds move faster because of friction and tumble over the lower wind, where is presses on the sea surface causing a trough and crest to form

gravity pulls the crest back down

the result is a circular movement of water

Question 12

how does the greatest wave generation occur?

Answer 12

the greatest energy transfer in to waves occurs when strong winds blow in the same direction over a long distance (fetch) and for a long period of time; this
produces the highest waves

Question 13

define fetch?

Answer 13

Fetch is the distance over which the wind blows

Question 14

what does energy help to move?

Answer 14

energy helps to move sediment into, through the system from store to store and out of the system

Question 15

what are tides?

Answer 15

tides are the daily rise and fall of Earth’s waters on its coastlines

as the tide comes in, the level of water on the beach rises, and as the tide goes out, the level of water on the beach goes down

Question 16

what causes tides?

Answer 16

tides are caused by the interaction of Earth, the Moon, and the Sun
gravity is the reason for tides

gravity is the force exerted by an object that pulls other objects toward it

Question 17

how does the moon’s gravity affect the tides?

Answer 17

the Moon pulls on the water on the side nearest to it more strongly than it pulls on the centre of the Earth.

this pull creates a bulge of water, called a tide bulge, on the side of Earth facing the the Moon

the Moon also pulls the earth towards itself

so water on the opposite side is “left behind” and forms a second bulge

Question 18

what occurs when there is a tidal bulge and between the bulges?

Answer 18

high tide is occurring along the coastline

between the bulges low tide is occurring

Question 19

how does the sun affect the tides?

Answer 19

at times, the Sun and Moon
pull together on Earth’s waters in the same direction

at other times they pull in
different directions

Question 20

what are the daily tide cycles like?

Answer 20

most seashores have four tides every day – two high tides and two low
tides

a change of from low to high tide or vice versa takes about 6 hours and 12
minutes

Question 21

how often do spring tides occur?

Answer 21

spring tides occur 2 times a month, during a full and new
moon when the Earth, Sun, and Moon are lined up

spring tides are higher and lower than normal tides i.e. “strong tides”

Question 22

how do neap tides occur?

Answer 22

neap tides occur in between
spring tides, at the first and third quarters of the Moon when the Sun and Moon pull at right angles to each other

neap tides are not as high or low as normal tides

these are “weak tides”

Question 23

define weathering?

Answer 23

the breakdown and decay of rocks in-situ related to elements of the weather (e.g. temperature, rainfall, frost etc.)

Question 24

define erosion?

Answer 24

involves the breakdown and removal of material

Question 25

three types of weathering?

Answer 25

physical
biological
mechanical

Question 26

what is freeze thaw weathering?

Answer 26

this is the breakdown of rocks due to the expansion of water during freezing, a process common in upland Britain where evening temperatures often fluctuate around 0 degrees

freeze thaw is most effective in jointed rock (e.g. granite). During freezing, water expands by 9% in volume

water freezing in cracks in rocks, exerts pressure

alternating freeze-thaw cycles gradually force the rock to split or cause rock fragments to break off

Question 27

how do thermal expansion work?

Answer 27

this process results from large diurnal temperature ranges which result in
heating and cooling of the rock

when heated, expansion of the rock occurs, whilst during cooling the rock
contracts. This expansion and contraction during cycles of temperature change results in stresses in the rock layers

outer layers of rock heat and cool quicker than inner layers and over time the upper layers flake / peel off (exfoliation)

Question 28

explain salt crystallisation?

Answer 28

water passing through cracks and joints in rocks, may be saline (carrying salts in solution)

as the water evaporates, the dissolved salts precipitate and crystallise forming salt crystals

Question 29

explain pressure release?

Answer 29

this occurs when overlying rocks are removed by weathering and erosion, the underlying rock expands and fractures parallel to the surface

this is significant in the exposure of sub-surface rocks such as granite

Question 30

explain the five types of chemical weathering?

Answer 30

oxidation

some minerals in rocks react with oxygen in air or water. Iron is especially susceptible. It becomes
soluble under extremely acidic conditions. It often attacks the iron-rich cements that bind sand
grains together in sandstone.

carbonation

rainwater contains dissolved CO2 which forms a weak carbonic acid (H20 + C02 = H2C03)

solution

some salts are soluble in water. Water can act as a solvent by breaking down chemical bonds in
minerals causing them to dissolve in a process known as solution - carbonation is therefore a form
of solution although it is mineral specific in relation to calcium carbonate

hydrolysis

this is a chemical reaction between rock minerals and water. Silicates combine with water,
producing secondary minerals such as clays. This is a common process in the weathering of
granite

hydration

water molecules added to rock minerals created new minerals of a larger volume. This
causes minerals in rock to swell (by about 0.5%) as the mineral absorbs water (‘hydrates’)

Question 31

what are two ways biological weathering can affect rock?

Answer 31

usually consists of a combination of physical
(growth of roots into joints in rocks) and chemical
(e.g. impact of organic acids) processes

Question 32

what’s a concordant coastline?

Answer 32

at locations where the main rock types is parallel to the coastline

Question 33

define a cove?

Answer 33

an oval-shaped bay with a

narrow opening to the sea formed where there is a weak point in the geology or a river entering the sea

Question 34

formation of lulworth cove?

Answer 34

formation began after the last ice age, when a river of
meltwater flowed towards the sea, the river eroded a valley which removed the Portland limestone

as sea level rose after the ice age, waves started to erode the Purbeck limestone and clay, and a cove began to form
Lulworth Cove formation

Once the waves were able to breach the Portland limestone rock, the waves are refracted

the erosion in the cove becomes lateral, as the orthogonals

Question 35

role of a wave processes in transport and deposition?

Answer 35

when waves move in to shallower water the
movement changes from the circular motion seen
in deeper water

at this depth, friction with the sea bed changes
the speed, direction and shape of the waves

the movement becomes more elliptical as the
bottom of the waves drags across the sea floor,
and the bottom of the wave slows down

the wave increases in height as water is pushed
up and the wave breaks when it becomes too high

Question 36

what happens as a wave breaks?

Answer 36

as a wave breaks, water moves up the beach as swash due the kinetic
energy from the wind that created the waves

as it travels up the beach the waves gradually slows down, due to friction

when it can travel no further, it travels back down the beach as backwash,
this is due to the gravity of the sloping beach

Question 37

what is a spilling wave?

Answer 37

gentle waves; found where
there is a gently sloping sea bed; break at some distance from the shore; foam
forms at wave crest and becomes a line of surf as wave approaches the
shore

Question 38

what is a surging wave?

Answer 38

may not break at all; steep angled shore gradient; top of wave breaks close to shore; water slides up
and down the shore

Question 39

what is a plunging wave?

Answer 39

moderately or suddenly
changing sea bed shape; steep fronted; tend to curl over forming a tube of air and plunge down on to the
shore, producing lots of foam

Question 40

spilling waves characteristics?

Answer 40

responsible for a net movement of sediment
onshore

swash is greater than backwash

this is due to the low wave height and lower energy

they are found on gentle beaches & the swash will travel a long way forward

low frequency of 6-8 per minute

backwash returns to the sea before the next wave breaks so the swash is uninterrupted

constructive waves bring sediment from offshore locations adding sediment to the sediment budget of a coastal cell

this will lead to a beach that increases in angle over time

Question 41

plunging waves characteristics?

Answer 41

responsible for a net movement of
sediment from a beach

backwash is greater than swash

water plunges vertically downwards, and so there is little forward movement of
water

found on steep beaches, so the swash is slowed down

short wavelength so the next swash is also often slowed by the returning backwash

destructive waves take sediment offshore removing sediment from the sediment cell
budget

this will lead to a beach that decreases in angle over time

Question 42

define berms?

Answer 42

small ridges that develop at the postioln of the mean high tide mark

Question 43

define cusps?

Answer 43

small semi-circular depressions, they arr temporary features formed by a collection of waves reaching the same point when the swash and backwash have similar strengths

Question 44

high energy destructive waves?

Answer 44

remove sediment offshore and create flatter beach profile

Question 45

low energy constructive waves?

Answer 45

transfer sediment in the opposite direction to form steeper profiles

Question 46

how are ripples found?

Answer 46

found close to the shorelines these are small wavy ridges of sand