Waves...waves....waves....

Ocean Waves are periodic displacement of water which occurs on the surface of the oceans.

When the wind blows over the sea surface it generates waves with a wide variety of shapes, sizes, and speeds. It is difficult to relate the complicated surface of ocean waves to the much simpler wave forms studied by mathematicians, but the larger waves that dominate the pattern agree with the theory: the longer the time interval between successive wave crests (the period), the greater the interval distance between successive wave crests (the wavelength) and the greater the wave speed. The wave speed is proportional to the period; the wavelength to the square of the period.




:dia:  :dia:  :dia:   Please feel free to contribute to this topic.....

mbhcsf

let 's us talk about TSUNAMI..the concept is quite simple i think , don't you reckon? with the helpof a diagram..

Originally posted by mbhcsf at 19-6-2004 10:14 PM:
let 's us talk about TSUNAMI..the concept is quite simple i think , don't you reckon? with the helpof a diagram..

maybe you can help to explain or find a diagram to illustrate it....

Tsunami comes from the Japanese word meaning 揾arbour wave

Coastal Features are landforms created by the erosional and depositional action of marine forces on the coastlines of land masses. The relative importance of particular marine forces varies with the type of coastline. Coastlines which are exposed to the oceans and seas are susceptible to high levels of incident energy, particularly through the action of waves. They are affected to a lesser degree by tidal currents, the water movements associated with the rise and fall of the tides. Sheltered coastlines in bays and estuaries, by contrast, are often dominated by the action of tidal currents, with waves playing a minor role. The action of these coastal processes, combined with the availability of sediment, and the influence of local rock type and structure, leads to the formation of distinct suites of landforms. Each of these suites of landforms presents particular problems for coastal zone conservation and management.

Example of Coastal Feature

Cliffs of Normandy Composed of the same form of limestone as England抯 White Cliffs of Dover, the Cliffs of Normandy are a distinctive landmark on the French coastline. They are vertical, or nearly so, because the strata, or layers, of the limestone are bedded horizontally, as can be clearly seen in the photograph. This means that the limestone is harder for the sea to wear away梚t has to work 揳gainst the grain

mbhcsf

and iam too busy but the effect of tsunami is  my oh my so disasterous, but its concept is rather fairly easy to understand.
yes the quake cause the movement of the seabed and then this will cause the wave to raise about 10 m high..really..
how exactly ?? well a pic worths 1000 wrds..

nevberg

gambar pada tahun 1946...di Keaukaha, hawaii....





perasan tak ada light house kat situ....light house tu tingginya hampir 100 kaki dari paras laut. gambar ni diambil di Scotch Cap Light House, Uminak Island, Alaska pada April 1, 1946.


tengok big waves macam ni teringat lak kat movie the day after tomorrow.

[ Last edited by nevberg on 22-6-2004 at 09:44 AM ]

TIDAL CURRENTS AND WAVES

Accompanying the vertical rise and fall of water are various horizontal or lateral movements commonly known as tidal currents or tidal streams, which are very different from the common ocean currents. In confined areas, a tidal current flows for about 6 hr, 12 min in an upstream or shoreward direction, corresponding to high water; it then reverses and flows for approximately the same time in the opposite direction, corresponding to low water. During the period of reversal, the water is characterized by a state of rest, or calm, known as slack water. A current flowing towards the shore or upstream is called flood current; that flowing in a direction away from land or downstream is known as ebb current.

At various times on the open sea gigantic waves, called tsunamis or tidal waves, strike the surrounding shore with tremendous force and cause considerable damage to life and property. These waves are not caused by natural tidal phenomena, but by earthquakes, midocean volcanic eruptions, and serious atmospheric disturbances.

Another related phenomenon is the seiche, which usually occurs in landlocked seas or lakes, such as San Francisco Bay in California and Lake Geneva in Switzerland. The water surface is observed to oscillate between a few centimetres and several metres mainly because of local variations in atmospheric pressure aided by high winds, but sometimes as a result of a distant seismic shock. The movement of water occurs in long waves and may last from a few minutes to several hours.

BREAKWATER

Breakwater or barrier, either natural or artificial, that extends into the open water of a sea or lake to break the force of the waves and provide calm water in a harbour. Natural breakwaters are offshore islands and promontories that shelter the shore from waves. Artificial breakwaters may be attached to the land or separated from it and have been constructed in various shapes and sizes. They can be built of stones and rubble, of masonry, or of a combination. Floating breakwaters, securely moored so that they do not ride too readily on the waves, are sometimes used. Breakwaters, first constructed by the ancient Greeks and Romans, are used throughout the world.

Beach
Beach is a gently sloping strip of land bordering an ocean or other body of water. Beaches form by the action of rivers, waves, currents, tides, and wind, and they are usually covered with sand or gravel. The material that forms beaches is composed of whatever type of sediment is brought to the shore. It may be sediment carried to the land by rivers, sediment eroded from coastal rocks, or offshore material brought by waves. Therefore, beaches may be made up of brown sand brought from distant mountains, black sand eroded from a volcano, or white sand from nearby coral reefs.

Beaches change shape from day to day and season to season. Waves, tides, currents, and the wind sometimes broaden a beach by depositing sand and sometimes narrow a beach by carrying sand away. Beaches along the ocean are divided into a foreshore and a backshore. The foreshore extends from the place the ocean reaches at low tide to the place it reaches at high tide. The backshore consists of the remaining portion of the beach that is only submerged during unusually high tides and storms. The steepest part of the foreshore is called the beach face. The backshore may contain one or more berms, ridges of sand and debris running parallel to the beach and deposited by a storm at its high-water mark. The backshore may also contain sand dunes, piles of sand built by wind blowing across a sandy beach.

Some beaches consist chiefly of materials derived from one kind of rock, which may give the beach a distinctive colour. Coral or limestone produces white sand, and quartz usually produces yellowish sand. Sands formed from volcanic rock are black. Wave action tends to carry away lighter minerals, leaving behind sand that is enriched in heavier minerals. These heavier minerals often contain valuable metals, such as titanium, zirconium, uranium, and gold, and many beaches are mined for them.

Some of the world抯 major recreational beaches are barrier beaches, which are formed when the action of waves and currents is not strong enough to wash sand fully to the shore. The sand is instead deposited in the water near the shore, forming a sandbar. The bar may grow outward until strong waves pile the sand high enough that it rises above water level, forming a barrier beach. Barrier beaches are generally elongated islands, but the beach may be joined to the mainland as sand and silt accumulates in the water between the two land areas. Well-known barrier beaches include those at Miami Beach, Florida, and Coney Island in New York. Loe Bar near Helston in south-western England is an example of a shingle barrier beach. In some cases a barrier beach may be the same as a spit.

Other famous recreational beaches are located at Acapulco on the western coast of Mexico, at Cannes on the Mediterranean coast of France, and at Rio de Janeiro in Brazil with Copacabana Beach. Attractive beach areas are often developed into resorts that support substantial tourist industries梂aikiki Beach on Honolulu, the Costa Brava in eastern Spain, and Gold Coast in eastern Australia are all examples of beach-oriented tourist resorts.






[ Last edited by PeNinGLaLaT on 1-7-2004 at 09:55 PM ]

SURFIN'

Surfing is a sport of riding waves with the aid of a board or other floating object, or sometimes with the body alone. The surfer usually stands on a tapered, hollow board and rides down the face of a breaking wave, steering the board by shifting the weight of the body. Although it is possible to surf on waves only 0.3 m (1 ft) high, steeper waves provide a faster, more exciting ride. Southern California, with more than 40 surfing beaches, has become a major United States centre for small-wave riding. The best surf is found in Hawaii, where waves may peak at 9 m (30 ft). Many Australian beaches, such as Bondi, also provide ideal conditions.

Surfing originated in Oceania and was highly developed in the Hawaiian Islands by the time the English explorer Captain James Cook reached them in 1778. The surfboards of that time were long hardwood slabs weighing 68 kg (150 lb) or more; so only the strongest athletes could handle them.

With the development of a lighter surfboard, however, surfing became a popular sport. By the 1930s, solid planks had been replaced by plywood and balsa boards with fins for steering. A still lighter board was produced in the 1960s, using such new materials as Styrofoam and fibreglass. The modern surfboard measures 2.7 to 3.0 m (9 to 10 ft) in length, 56 to 58 cm (22 to 23 in) in width, and 7.6 to 10.2 cm (3 to 4 in) in thickness. Weighing less than 11.3 kg (25 lb), this board is particularly popular among teenagers.

As a recreation and a sport, surfing was developed in Australia and in the US States of California and Hawaii in the 20th century. The Outrigger Canoe Club, which popularized surfing, was founded in Waikiki, Hawaii in 1907. D. P. Kahanamoku of Hawaii was largely responsible for popularizing the sport. Surfing was particularly developed in the 1950s and 1960s in many parts of the world, and professional surfers began to emerge. The first World Amateur Championships were staged in 1964. World Professional Championships were first held in 1970. The grand prix circuit is held throughout the year.

Pun tak faham! Kenapa tak pos dalam bahasa melayu untuk orang bodoh seperti saya?

mok_nik

Bukan tak nak tulis dalam BM Gembala, kekadang bahan yang banyak adalah dalam BI...jadi terus ambil saja...nak translate tuh makan masa....senang cut and paste aje.

Seboleh mungkin kami kat sini cuba cari bahan BM..tapi maklumlah kekadang tak ada, itu sebab kena guna juga bahan BI...

Mok nik yakin, Gembala tidak bodoh untuk memahami BI  kan:bgrin: Mok nik pun bila pos sesuatu seberapa cuba cari bahan BM dahulu,sebab mok nik yakin tidak semua antara kita yang fasih, mahir dan faham BI..tetapi bila dah tak ada bahan BM, terpaksalah guna bahan BI.

matdue77

Setuju ngan moknik, hai moknik, lame dok cakap ngan moknik....

Vocabulary on Coastal Features and Processes

Arch
When caves, which have developed on either side of a headland, join together they form a natural arch.

Attrition
The process whereby rock particles wear down through collisions with other rock particles. This often occurs when pebbles are thrown against cliffs, boulders or other pebbles, causing them to shatter and break.

Backwash
Water moves up a beach as a wave breaks. This is called the swash. The return movement of the water, back down the beach, is called the backwash.

Bar
A bar is very similar to a spit. It is a ridge of sand or shingle which forms across the mouth of a river, the entrance to a bay or harbour. It is usually parallel to the coast.

Bay
A wide indentation into the land by the sea, protected on each side by a headland. The water in a bay is usually relatively shallow; the wave action less strong than at the headlands.

Bay-bar
A bar across the entrance of a bay.

Bay-head beach
Bay head beaches develop at the head, or inner most part, of a bay. In this area wave action is usually not very strong and deposition occurs. The beach will not extend to the headlands since erosion from waves increases strongly towards the headlands and deeper water.

Beach
A gently sloping deposit of sand, pebbles or mud, deposited along the coast.

Blow hole
A blow hole is formed when a joint between a sea cave and the land surface above the cave becomes enlarged and air can pass through it. As water flows into the cave, air is expelled through the pipe like joint, sometimes producing an impressive blast of air or spray which appears to emanate from the ground.

Cave
A weakness, such as a joint, is enlarged by wave action, finally creating a cylindrical tunnel which follows the line of weakness. Caves developing back to back may give rise to arches and stacks.

Cliff
A steep, and usually high, rock face found at the edge of the land where it meets the sea. Cliffs can be formed from most rocks, height generally increasing with hardness of rock.

Cliff Line
The margin of the land. The cliff line is identical to the coastline, but consists of cliffs rather than lower features such as dunes and beaches.

Coastline
The margin of the land. Where the margin consists of cliffs, it is known as the Cliff line

Constructive wave
When waves break at a rate of ten or less per minute each wave is able to run up the beach and drain back again before the next wave arrives. The swash is more powerful than the backwash so deposition can occur.

Corrasive action
This is a form of wave erosion. Pebbles, boulders and rocks are thrown against the cliff face by breaking waves. This causes undercutting of the cliff and leads to the breakup of both the cliff and the objects being thrown against it.

Destructive wave
When waves break at a rate of more than ten per minute each wave is able to run up the beach but unable to drain back again before the next wave arrives. Thus the backwash of the previous wave interferes with the swash, reducing it's efficiency. Such waves remove material from a beach and are destructive.

Emerged coast
Coastal areas which have become raised above current sea level. The cause is believed to be isostatic adjustment.

Estuary
The mouth of a river where fresh water and sea water mix, and tides have an effect. Estuaries are often to be found on submerged coastlines, where a river valley has been flooded by the sea. See ria.

Fetch
This distance of open water over which the wind can blow and form waves.

Fiord Coast
When a glaciated coast, with deep valleys, becomes flooded by the sea, the valleys are known as fiords. These inlets are typically steep sided and deep.

Headland
Areas of harder rocks tend to resist the erosive powers of the sea. The resulting area of land, jutting out into the sea, is a headland. Bays are to be found between headlands.

Hydraulic action
When a wave breaks against a cliff it causes air ,trapped within cracks, to suddenly become compressed. As the water retreats the air is allowed to expand, often explosively. Repeated expansion and contraction of the cracks leads to the break up of the surrounding rock.

Lagoon
When a spit extends across the mouth of a river, to the extent that it causes the river to become diverted along the coast, an area of water is created separated from the sea by a narrow strip of land. This is a lagoon.

Load
Solid matter carried by water, including material in solution, material suspended in the water, and larger material moved along the water / ground interface.

Longitudinal Coast
These occur when valleys parallel to the coast become flooded by the sea. As the land becomes submerged, the ridges of land between the valleys become chains of islands parallel to the new coast. The area of water between the island chains are sometimes referred to as sounds.

Longshore Drift
When waves break on to a beach at an angle, material is pushed up the beach at an angle by the swash, but pulled back down the beach by the backwash at ninety degrees to the coast. In consequence, material is slowly moved along the coast, in the direction of the waves.

Mud Flats
Gently sloping coasts where fine sediments can settle, perhaps together with river sediments, can allow the build up of mud as a sheet known as a mudflat. Plants able to withstand salt water will often colonise the area. In tropical areas this may lead to the formation of mangrove swamps.

Ria
When a non-glaciated highland coast becomes submerged, the valleys fill with sea water. As the area becomes flooded the coast becomes indented and higher parts of the surrounding land may become islands. Plymouth Sound and Southampton Water are examples of rias in the United Kingdom.

Sound
Valleys flooded due to submergence under the sea along a longitudinal coast are sometimes called Sounds.

Spit
Longshore Drift transports material along the coast. When the mouth of a river, or an indented area, is encountered material starts to be deposited. The deposition begins where the coast changes direction and extends down coast in the direction of longshore drift. The result is a narrow ridge of material ( sand or pebbles ) attached to the mainland at one end and terminating in the sea. The spit may extend sufficiently to form a lagoon.

Stack
When a natural arch collapses, the remaining upright sections form stacks, isolated rocks sticking up out of the sea.

Storm beach
A ridge of material to the landward side of the normal beach. During storm conditions the waves may have sufficient power to throw material beyond the usual range ( between high and low water marks ). Such material will remain in place for a considerable time, being added to by subsequent violent storms.

Submerged coast
Coastal areas which have become lowered below current sea level. The cause is almost always a rise in sea level in consequence of ice melting since the last ice age.

Swash
The movement of water in a breaking wave as it moves up the beach.

Tides
The daily movements of the sea as it covers and exposes the area between the high tide and low tide marks. Tides are the result of lunar activity, and to a much lesser degree, winds and atmospheric pressure.

Tombolo
A bar linking an island to the mainland.

Undertow
A current taking water away from the beach and out into deeper water. The undertow prevents the build up of water from breaking waves along the coast.

Wave-cut Platform
As cliffs become eroded down to beach level they appear to migrate inland. The remains of the former cliffs form a flat rock platform. This is known as a wave cut platform.