Coasts (LJ) Flashcards

Question

How does tidal range have an important influence on coastal processes?

Answer 1

It controls the vertical range of erosion and deposition. Weathering and biological activity is affected by the time between tides. Velocity of tidal flow is influenced by tidal range and has an important scouring effect.

Answer 2

Rip currents are caused by tidal motion or by waves breaking along the shore. A cellular circulation is caused by differences in wave height parallel to the shore. Water from the higher sections of the breaker travels further up the shore and returns back through the points where lower sections have broken. Once rip currents are formed, they modify the beach by creating cusps. which perpetuate currents. Rip currents are important for transporting sediment.

Answer 3

Storm surges are changes in the sea level caused by intense low-pressure systems and high winds speeds. High air pressure depresses the ocean surface, lowering local sea level, low air pressure allows the ocean surface to dome upwards, raising the local sea level.

Answer 4

Storm surges can produce severe coast flooding on low lying. Forces of onshore current of storm surge water can cause rapid coastal erosion which is where the local sea level rise strong wave action and coastal flooding wear down or carry away rock, soils and sand along the costs.

Answer 5

sea water is raised by 10 centimetres.

Answer 6

Surges are common in the Bay of Bengal, on the south-east coast of the USA and Japan.

Answer 7

In areas where coastline if funnel shaped.

Answer 8

The Ganges delta experiences many storm surges. These may exceed 4m and the accompanying storm waves can add a further 4m to wave height. The funnel shape of the Bay of Bengal forces water to build up, thereby intensifying the rise in sea level.

Answer 9

As a wave crashes onto a rock or cliff face, air is forced into cracks, joints and faults within the rock. As the wave retreats, high pressure causes the cracks to widen as air expands. Over time this causes the rock to fracture. Bubbles found within the water may implode under high pressure creating tiny jets of water that over time erode the rock. This erosive process is called cavitation.

Answer 10

Sands and pebbles are picked up by the sea from an offshore sediment sink or temporal store are hurled against the cliffs at high tide, thereby wearing the cliff face. The shape, size, weight and quantity of sediment picked up, as well as the wave speed, affects the erosive power of this process. For example, it could be argued that heavier rock will have more erosive power the lighter rock. However, the lighter rock may have a more erosive power in coastal environments that have faster wave speed.

Answer 11

The process of water dissolving rocks and material into solutions. In areas of calcareous rock (lime-rich) rock, the mildly acidic seawater can cause alkaline rock such as limestone to be eroded. Eval: Igneous rocks, such as granite and basalt, are primarily composed of silicate minerals that are less soluble in water. Therefore, solution may not be significant erosive process in coastal environments composed of igneous rocks.

Answer 12

Wave action cause rocks and pebbles to hit against each other, wearing each other and so becoming round and eventually smaller. Eval: Although attrition is an erosive process within the coastal environment, it has little to no effect on erosion of the coastline itself.

Answer 13

The break down of rocks in situ. It differs from erosion in that no movement or transportation of the broken-down material takes place.

Answer 14

On cool temperature coastlines, freeze-thaw weathering can be very effective. Water seeps into cracks in the cliff face and freezes overnight. When liquid water freezes to form ice, it expands by 10%. This widens and weakens the cracks. Repeated freezing and thawing can make the rock crumble and split. This process takes place on the exposed cliff face.

Answer 15

Repeated heating and cooling of rocks can also cause rocks to be broken down and weathered away. Rocks can EXPAND RAPIDLY when hot and CONTRACT RAPIDLT when cold, causing the breaking apart of layers of rock. For example, on desert coastlines when days are extremely hot and nights are extremely cold (high diurnal range), the changes in temperature causes shear stress on the outer layers of the rock. This causes the outer layer of the rock to peel off in a process called exfoliation. The increased availability of water (which leads to chemical weathering) at the coastline (e.g. morning fog) can accelerate this process.

Answer 16

Occurs in areas with large diurnal differences eg deserts. Excessive heating and cooling results in exfoliation occurring.

Answer 17

In the spray zone above high water, salt crystallisation will be an effective weathering process as salt water soaks into the pores of the rock. Salt weathering occurs due to SALT CRYSTAL GROWTH inside the cracks and pores in rocks. When SALINE solutions (i.e. salt water) gets into cracks and evaporates, it leaves behind salt crystals that were in solution. As these salt crystals accumulate over time, pressure builds up and expands the gaps in the rocks. Eventually this causes the rocks to DISINTEGRATE.

Answer 18

Cliffs often contain cracks and halophytic (salt-loving) plants can grow in these cracks. When vegetation grows, their roots also grow and thus need more space. The growing roots exert pressure onto the surrounding rock, eventually causing the rock to break apart.

Answer 19

Hydrolysis is a form of chemical weathering that involves the breaking down of rock when it reacts with water (hydro-). Rocks can break down when they are SOLUBLE in water, for example chalk can react and break down in water

Answer 20

It is a form of chemical weathering that occurs when water is absorbed into a substance, causing a new substance to form. For example, anhydrite (CaSO4) reacts with water to form gypsum (CaSO4 . 2H20). Hydration causes rocks to expand in SIZE and VOLUME, which can make them susceptible to other forms of weathering.

Answer 21

Carbonation is when carbon dioxide dissolved in water (known as carbonic acid) reacts with rocks and breaks them down. Carbonic acid reacts with many rocks. For example, when carbonic acid seeps into the cracks of limestone, the rock dissolves.

Answer 22

Rain water seeping from the land as throughflow and baseflow lubricates the cracks, weakening the internal cohesion of the rocks of the cliff face. This water also adds weight (and therefore shear stress) to the rocks. Lastly, weathering is the breakdown of rocks over time. Together, these processes lead to rock falls and rotational slumps. In cliffs made of hard rock, rock falls are the main form of mass movement, often occurring after heavy rain. In contrast, cliffs made of unconsolidated material, such as clay or glacial deposits, rotational slumping is the main form of mass movement. Cliff retreat is the result of all these processes.

Answer 23

Also, wave action is constantly at work between high water mar (HWM) and low water mark (LWM), marine processes such as hydraulic action and corrasion causes undercutting of the cliff face, thereby forming a notch and an overhang. As undercutting continues, the notch becomes deeper and the overhang becomes more pronounced. Ultimately, the overhang will collapse, causing the cliff line to retreat. The base of the cliff will be left behind as a broadening platform, often covered with deposited material, with the coarsest near the cliff base, gradually becoming smaller towards the open sea.

Answer 24

Some birds such as puffins dig burrows into cliffs weakening them and making erosion more likely. Similarly, many species of clams secrete chemicals that dissolve rocks and piddocks may burrow into the rocks face. Some seaweeds such as Kelp contain pockets of sulfuric acid. If the seaweed is hit against the cliff face the acid will dissolve some of rock's minerals. Also, water flowing over decaying vegetation and then over coastal areas will be acidic, thus causing chemical weathering.

Answer 25

The coastal cell system/littoral system, is a simplified model that examines coastal processes and patterns in a given area.

Answer 26

The concept of dynamic equilibrium is important littoral cells. The concept states that any system (or in this case, littoral cell) is the result of the inputs and processes that operate within it. Change to once of the inputs (for example an increase in sediment to the shoreline following cliff collapse) causes a knock-on effect on the processes (such as longshore drift, transport, or beach protection) and a resulting change in the land forms (such as the stabilisation of cliffs or downdrift beach enlargement). THe balance changes, hence dynamic equilibrium.

Answer 27

A backshore has a storm beach made from large pebbles (e.g. pebble ridge). The swash has a large enough energy to throw pebbles up beach but backwash is too weal to remove it. Berms are formed fortnightly by the spring tide. Storms and spring tides can move existing berms up the beach, meaning that a new berm can develop, which changes the beach profile.

Answer 28

The zone of the HWM and LWM. Size of the foreshore depends on the gradient of the beach and the tidal range. Ridges running parallel to the water line are called fulls, these are pushed by constructive waves during the tide heights. The troughs between the fulls are called swales.

Answer 29

Also called the breaker zone. This is an area between the normal LWM and the lowest spring tide. Longshore bars are formed here. They are ridges of sand that run parallel to the coastline but they are larger and more permanent. Often occur where the wave break.

Answer 30

This part is always under water. Longshore bars are formed in this zone by wave action. Longshore bars are formed by the circular movement of water in the waves touching the sea bed; the friction slows the waves and changes the motion of the water allowing sediment to be deposited here. These occur in gently-sloping because with a low tidal range. Overtime, they can from barrier beaches or barrier islands.

Answer 31

Spring tides shape the berms at the top of the beach. Beaches with high tidal ranges have the greatest impact on the coastal environment, reshaping the sediment and potentially forming dunes.

Answer 32

Storm beach is created by large waves during the high spring tide. Constructive waves move material up the beach building berms and increasing the gradient. Destructive waves moves material down the beach creating longshore bars and reducing the gradient. The fetch, geology and wave angle will affect the nature of the beach.

Answer 33

Larger particles = steeper beach. Shingle is more permeable than sand - backwash drains into the rock. Shingle often makes the upper part of the beach - constructive waves throw it up and and cannot bring it back down. Sand is less permeable so there is often more backwash. This pulls sediment down the beach producing ripples/fulls, runnels/swales and possibly a longshore bar. Sand causes less friction so the beach is flatter and wider. Wave energy is therefore dissipated over a wider area.

Answer 34

Beach cusps are semi-circular, scalloped depression in the lower edge of the storm beach. Their formation is disputed - but form where the waves approach head-on, so swash and backwash are the same direction. Once created they are self-sustaining due to shape forcing the swash into the cusp around the horns and the backwash running down the middle of the cusp, removing the sediment and deepening the cusp.

Answer 35

Swash-aligned coasts are parallel to the crests of the prevailing winds. Swash and backwash run straight up and down the beach No longshore drift. Beach cusps often form as cuspate tombolos if waves are refracted around an offshore island

Answer 36

Drift-aligned coasts are oriented obliquely to the crest of the prevailing waves. The shore of a drift-aligned cost is primarily controlled by longshore drift. Drift-aligned coasts are open systems in terms of longshore transport. Spits, bars, tombolos and cuspate forelands are all feature of drift-aligned coasts.

Answer 37

There is upper beach (backshore), the foreshore (periodically exposed by the tides) and the offshore area (covered by water).

Answer 38

Waves result from from friction between the wind and the sea surface.

Answer 39

Waves in the deep open sea are know as waves of oscillation. Although the surface wave shape appears to move, the water particles actually move in roughly circular orbit within the wave.

Answer 40

Wave orbit is the shape of the wave. It varies between circular and elliptical. The orbit diameter decreases with depth, to a depth roughly equal to the wavelength (the distance between the neighbouring crests or troughs), at which point there is no further movement related to wind energy - this is called the wave base.

Answer 41

Swell waves travel huge distances and are created by large storms in the middle of the oceans.

Answer 42

Cuspate forelands are single ridges deposited in a triangular shape. They are the result of two separate spits joining, or the combined effects of two distinct sets of regular storm waves.

Answer 43

Polyps. Thousands of polyps join together to form coral reefs.

Answer 44

Polyps are tiny, soft animals which attach themselves to hard surfaces in shallow seas. As they grow the exude calcium carbonate (limestone) which forms their skeleton. when millions of polyps live together in colonies they form coral reefs. As one generation dies the next one grows on top of it, so the reef grows upwards and outwards. Once established they can grow 60cm a year.

Answer 45

Once established they can grow 60cm a year. Polyps have small algae, zooxanthellea, growing inside them. There is a symbiotic relationship between the polyps and the algae; that is, both benefit from the relationship. The algae get shelter and food from the polyp, while the polyp gets some food via photosynthesis.

Answer 46

Saltmarshes are home to many species and various ecosystems, improving biodiversity in coastal regions. Store carbon at a rate of 10x greater than tropical forests, helping to mitigate climate change. They act as natural defenses against coastal erosion and in extreme weather events (such as flooding)

Answer 47

As tidal currents are slowed, they begin to deposit fine-grained material. Eel grass helps to slow the current further, and gradually uneven mud flats develop that are exposed at low tide. These mud flats become colonised by pioneer plant species which are tolerant of salt. Close vegetation develops over the mud.

Answer 48

An area where freshwater river or lake meet the ocean.

Answer 49

The way a tide dominated estuary is created is due to the rising tide inwards in the flood channel, while the falling ebb tides uses ebb channels. Where the tidal range is low, the effect of moving water is less important and wave action tends to block off the estuary from the sea.

Answer 50

When the flow of water from the river meets with the incoming tides and waves from the sea, the water flow virtually ceases so the water can no longer carry its sediment in suspension. As most of the sediment is small and fine it leads to the build up of mud which, over time, builds up until it is above water level. Deposition also occurs also occurs as a result of flocculation (clay particles clump together through electrical or chemical attraction, and become large enough to sink). Pioneer plants colonise this area, leading to more sediment becoming trapped. This colonises the transition zone between high tide and low tide.

Answer 51

East Africa, India, South East Asia, and Oceania, South America and the Caribbean.

Answer 52

-Mangrove swamps are limited to where the temperature is greater than 24oC in the warmest month and where rainfall exceeds 1250mm. -Most mangrove swamps do not tolerate high-energy localities due to the inability of seedling to become established in such environments.

Answer 53

When there is an increase or decrease in total water volume.

Answer 54

Changes in the height of the land relative to the sea

Answer 55

During the last ice age, land in Northern Europe and North America was covered by ice. The weight of the ice slowly compresses the land and pushed it down into the mantle isostatically. Bearing mind the the ice age was a colder period, sea level fell also eustatically because if thermal contraction and some water stored on the land as ice. As warmer period occurred, the melted ice and warmer temperatures swell the volume of sea water and cause it to expand thermally, causing sea level rise eustatically. Also, the land slowly rebounds up as the weight of the ice is removed, over thousands of years this causes local sea levels to rise isostatically.

Answer 56

Underlying tectonic force, including uplift through folding and faulting, can result in isostatic drops in sea level on regional scale. In the Huon peninsula of Papua New Guinea tectonic uplift resulted in a stairway of successively formed coral terraces representing previous sea levels.

Answer 57

As temperatures rise due to increasing greenhouse emissions, glaciers melt faster than they accumulate new snow. As these ice sheets and glaciers melt, the water eventually runs into the ocean, causing sea level to rise. Heavy sediment loading in deltas can cause compaction and subsidence, which lowers the land surface. This effectively causes an increase in sea level and such effects can be seen in many parts of major deltas including the Mississippi delta.

Answer 58

A ria is a drowned river valley formed when rising sea levels flood narrow winding inlets and river valleys. -In the cross section, rias are V-shaped and they have a smooth concave long section, reflecting the fact they are drowned river valleys. Examples: Kingsbury Estuary on the south Devon coast is a 6m long ria.

Answer 59

During low sea levels, Fjords form in valleys that were carved by glaciers during periods when sea levels were lower (such as during the last glacial maximum). Large glaciers move slowly down pre-existing river valleys toward the coast, eroding and deepening the valleys into U-shaped troughs with steep walls and flat floors. The immense pressure and erosive force of the glaciers carve these valleys much deeper than typical river valley In post-glacial periods, ice sheets melt leading to a rise in sea levels, inundating the valleys with seawater and transforming them into fjords. Rising seas flood the U-shaped glacial troughs, creating the distinctive appearance of fjords with deep, elongated inlets. Fjords are found mainly in Norway, Chile, New Zealand, Canada, Greenland, and the U.S. state of Alaska.

Answer 60

In Croatia during the last glacial period the rivers flowed parallel to the cost, producing a series of rivers and valleys. When sea level rose at the end of the last glacial period, the valleys were flooded and the ridges became long, narrow islands. These are known as Dalmatian coasts.

Answer 61

As warmer period occurs (after a glacial period), the melted ice and warmer temperatures swell the volume of sea water and cause it to expand thermally, causing sea level rise eustatically. Also, the land slowly rebounds up as the weight of the ice is removed, over thousands of years this causes local sea levels to rise isostatically. This in turn creates elevate landforms, including beaches that were once at sea level but are now uplifted due to crustal rebound, hence the name raised beaches. The Isle of Arran has a raised beach 5 m above current sea level north of Drumadoon, Scotland.

Answer 62

In a glacial period, the weight of the ice slowly compresses the land and pushed it down into the mantle isostatically. Bearing mind the the ice age was a colder period, sea level fell also eustatically because if thermal contraction and some water stored on the land as ice. Due to a decrease in sea levels, coastal areas that were once underwater become exposed. This leaves behind flat, low-lying coastal plains that were once part of the seabed. An example of this includes the continental shelf that was exposed 18,000 years ago due to a fall in sea levels.

Answer 63

Winds move across the surface of the water, causing frictional drag (resistance to the wind by the water) which creates small ripples and waves. This leads to a circular orbital motion of water particles in the ocean. As the seabed become shallower towards the coastlines, the orbit of the water particles becomes more elliptical, leading to more horizontal movement of the the waves. Wave height increases, but the wavelength (distance between to waves) and wave velocity both decrease. This causes to back up from behind the wave until the wave collapses and surges of the beach.

Answer 64

12-15m long, formed in open sea, lower height, long wavelength, low frequency.

Answer 65

Short wave length, greater height, high frequency.

Answer 66

the greater the wave energy.

Answer 67

Waves of translation are waves that reach the shore. The base of the wave has contact with the seabed causing friction, slowing down the waves. This causes them to bunch up, reducing the wave length but increasing the wave height. This is called wave shoaling, which in turn creates three types of breaker waves.

Answer 68

Spilling breakers occur on a gentle breach gradient. The waves are steep (relative to wave length; gradual peaking of wave until crest becomes unstable and gently spills forward from the crest. These waves occur in Skern Lodge.

Answer 69

Plunging breakers occurs on steeper beaches; intermediate steepness waves; shore-wards face of the wave becomes vertical, curls and plunges forward as an intact mass of water.

Answer 70

Steep beaches with lows steepness waves: the front face and crest of the wave remain relatively smooth and the wave slides directly up the beach without breaking; a large proportion of the wave energy is reflected at the beach

Answer 71

Tides regular movements in the seas surface caused by the gravitational pull of the moon and the sun of the oceans. The moon accounts for the majority of the gravitational pull.

Answer 72

Tides are influenced by the size and shape of ocean basins, the characteristic of the shoreline, the Coriolis force and meteorological conditions

Answer 73

just after a new moon. Spring tides have a greater tidal range than neap tides.

Answer 74

after a full moon.

Answer 75

when the sun and moon are at right angles to the earth.

Answer 76

High tides occur 12 hours and 25 minutes apart. It take 6 hours and 12.5 minutes for the water at the shore to go from high to low or from low to high. A lunar day last 24 hours and 50 minutes.

Answer 77

Tidal range is the difference between high and low tide. The times and lengths of these varies between locations. There is almost no tide for example in the Mediterranean as it is enclosed. Tidal range varies with distance from the amphidromic point, the shape of the coast and the strength of the tidal currents. Tides range is the greatest in bays and along funnel-shaped coastlines.

Answer 78

If the tide is forced into a narrow space and as it advances it is concentrated then it is known as a tidal bore.

Answer 79

Storm surges are changes in the sea level caused by intense low-pressure systems and high winds speeds. High air pressure depresses the ocean surface, lowering local sea level, low air pressure allows the ocean surface to dome upwards, raising the local sea level.

Answer 80

Storm surges can produce severe coast flooding on low lying. Forces of onshore current of storm surge water can cause rapid coastal erosion which is where the local sea level rise strong wave action and coastal flooding wear down or carry away rock, soils and sand along the costs.