Sunday, March 14, 2010

Apakah di samping Allah ada tuhan(yang lain)?

Surah an-Naml,ayat 60,Firman Allah swt:

Bukankah Dia(Allah) yang menciptakan langit dan bumi dan yang menurunkan air dari langit untukmu,lalu Kami tumbuhkan dengan air itu kebun-kebun yang berpemandangan indah?Kamu tidak akan mampu menumbuhkan pohon-pohonnya.Apakah di samping Allah ada tuhan(yang lain)?Sebenarnya mereka adalah orang-orang yang menyimpang(dari kebenaran)

Surah an-Naml,ayat 61,Firman Allah swt:

Bukankah Dia(Allah) yang menjadikan bumi sebagai tempat berdiam,yang menjadikan sungai-sungai di celah-celahnya,yang menjadikan gunung-gunung untuk mengukuhkannya dan yang menjadi pemisah antara dua laut(muara,estuary).Apakah di samping Allah ada tuhan(yang lain?)Sebenarnya kebanyakan mereka tidak mengetahui.

Surah an-Naml,ayat 62,Firman Allah swt:

Bukankah Dia(Allah) yang memperkenankan doa orang yang berada dalam kesulitan apabila dia berdoa kepada-Nya,dan menghilangkan kesusahan dan menjadikan kamu(manusia) sebagai khalifah(pemimpin) di bumi?Apakah di samping Allah ada tuhan(yang lain)?Sedikit sekali(nikmat Allah) yang kamu ingat.

Surah an-Naml,ayat 63,Firman Allah swt:

Bukankah Dia(Allah) yang memberi petunjuk kepada kamu dalam kegelapan di daratan dan lautan dan yang mendatangkan angin sebagai khabar gembira sebelum(kedatangan)rahmat-Nya?Apakah di samping Allah ada tuhan(yang lain)?Mahatinggi Allah terhadap apa yang mereka persekutukan.

Surah an-Naml,ayat 64,Firman Allah swt:

Bukankah Dia(Allah) yang menciptakan (makhluk) dari permulaannya,kemudian mengulanginya(lagi) dan memberikan rezeki kepadamu dari langit dan bumi?Apakah di samping Allah ada tuhan(yang lain)?Katakanlah,'Kemukakanlah bukti kebenaranmu,jika kamu orang yang benar'.

Classification(estuary) based on Hydrography.

Salt wedge estuaries

In this type of estuary, river output greatly exceeds marine input and tidal effects have a minor importance. Fresh water floats on top of the seawater in a layer that gradually thins as it moves seaward. The denser seawater moves landward along the bottom of the estuary, forming a wedge-shaped layer that is thinner as it approaches land. As a velocity difference develops between the two layers, shear forces generate internal waves at the interface, mixing the seawater upward with the freshwater. An example of a salt wedge estuary is the Mississippi River.

Partially mixed estuaries

As tidal forcing increases, river output becomes less than the marine input. Here, current induced turbulence causes mixing of the whole water column such that salinity varies more longitudinally rather than vertically, leading to a moderately stratified condition. Examples include the Chesapeake Bay and Narragansett Bay.

Vertically homogenous estuaries

Tidal mixing forces exceed river output, resulting in a well mixed water column and the disappearance of the vertical salinity gradient. The freshwater-seawater boundary is eliminated due to the intense turbulent mixing and eddy effects. The lower reaches of the Delaware Bay and the Raritan River in New Jersey are examples of vertically homogenous estuaries.

Inverse estuary

Inverse estuaries occur in dry climates where evaporation greatly exceeds the inflow of fresh water. A salinity maximum zone is formed, and both riverine and oceanic water flow close to the surface towards this zone.This water is pushed downward and spreads along the bottom in both the seaward and landward direction.An example of an inverse estuary is Spencer Gulf, South Australia.

Intermittent estuaries

Estuary type varies dramatically depending on freshwater input, and is capable of changing from a wholly marine embayment to any of the other estuary types.

Tectonically produced estuary.

These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faulting, volcanoes, and landslides. Inundation from eustatic sea level rise during the Holocene Epoch has also contributed to the formation of these estuaries. There are only a small number of tectonically produced estuaries; one example is the San Francisco Bay, which was formed by the crustal movements of the San Andreas fault system causing the inundation of the lower reaches of the Sacramento and San Joaquin rivers.[5]

Fjord type estuary.

Fjord type estuaries are formed in deeply eroded valleys formed by glaciers. These U-shaped estuaries typically have steep sides, rock bottoms, and underwater sills contoured by glacial movement. The shallowest area of the estuary occurs at the mouth, where terminal glacial deposits or rock bars form sills that restrict water flow. In the upper reaches of the estuary, the depth can exceed 300 meters. The width-to-depth ratio is generally small. When estuaries contain very shallow sills, tidal oscillations only affect near surface waters to sill depth, and waters below sill depth may remain stagnant for very long periods of time, resulting in only an occasional exchange of the deep water of the estuary with the ocean. If the sill depth is deep, water circulation is less restricted and a slow, but steady exchange of water from the estuary and the ocean occur. Fjord-type estuaries can be found along the coasts of Alaska, eastern Canada, Greenland, Iceland, New Zealand, and Norway.

Lagoon-Type Or Bar-Built Estuary.

These estuaries are semi-isolated from ocean waters by barrier beaches (barrier islands and barrier spits). Formation of barrier beaches partially encloses the estuary with only narrow inlets allowing contact with the ocean waters. Bar-built estuaries typically develop on gently sloping plains located along tectonically stable edges of continents and marginal sea coasts. They are extensive along the Atlantic and Gulf coasts of the U.S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 meters. The barrier beaches that enclose bar-built estuaries have been developed in several ways: 1) upbuilding of offshore bars from wave action, in which sand from the seafloor is deposited in elongate bars parallel to the shoreline, 2) reworking of sediment discharge from rivers by wave, current, and wind action into beaches, overwash flats, and dunes, 3) engulfment of mainland beach ridges (ridges developed from the erosion of coastal plain sediments approximately 5,000 years ago) due to sea level rise and resulting in the breaching of the ridges and flooding of the coastal lowlands, forming shallow lagoons, 4) elongation of barrier spits from the erosion of headlands, with the spit growth occurring in the direction of the littoral drift due to the action of longshore currents. Barrier beaches form in shallow water and are generally parallel to the shoreline, resulting in long, narrow estuaries. The average water depth is usually less than 5 m, and rarely exceed 10 m. Examples of bar-built estuaries include Barnegat Bay, New Jersey, Laguna Madre, Texas, and Pamlico Sound, North Carolina.

Drowned River Valley Estuary.

Many drowned river valley estuaries were formed between about 15,000 and 6000 years ago following the end of the Wisconsin (or 'Devensian') glaciation when a eustatic rise in sea level of 100 m to 130 m, flooded river valleys that were cut into the landscape when sea level was lower, creating the estuarine systems. Additionally, the general subsidence of coastal regions contributed to the development of drowned river valleys. Well developed drowned river valleys are generally found on coastlines with low, wide coastal plains. Their width-to-depth ratio is typically large, appearing wedge-shaped in the inner part and broadening and deepening seaward. Water depths rarely exceed 30 meters. Examples of this type of estuary include the Chesapeake Bay and Delaware Bay, along the U.S. mid-Atlantic coast, and along the U.S. Gulf coast, Galveston Bay and Tampa Bay[4].

WhaT Is Estuaries??

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Estuaries form a transition zone between river environments and ocean environments and are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries among the most productive natural habitats in the world.

A more thorough definition of an estuary would be “a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff; however the freshwater inflow may not be perennial, the connection to the sea may be closed for part of the year and tidal influence may be negligible.”

This definition includes classical estuaries as well as fjords, lagoons, river mouths, and tidal creeks. Estuaries are a dynamic ecosystem with a connection with the open sea through which the seawater enters accordingly to the rhythm of the tides. The seawater entering the estuary is diluted by the freshwater flowing from rivers and streams. The pattern of dilution varies in different estuaries and is dependent on the volume of freshwater, tidal amplitude range, and the extent of evaporation from the water within the estuary. [2]