what is the cause of under- water currents?

Answer 1

What sort of current, the little ones at the beach or the ones that wrap around the world???

Currents are controlled by the sun, the moon, and the pole regions. The large currents involve the shifting of cold and warm water, and relate to how cold water sinks, and warm water rushes in to replace it.

Answer 2

We'll assume you aren't talking about the basic water currents, as in the tides and the currents of a river, but rather the variations in currents that are found underwater, and which can be critically important to SCUBA divers and others who work in an underwater environment.
The underwater currents are affected by the same types of things as wind currents. Projecting masses of various sorts, deep chasms, that cause a sudden downturn in the normal flow of water, thermal differences, that can cause turbulence, and so on.
Hope this is helpful.

Answer 3

The tide is always moving but the sea bed is not flat so the sea will run faster in some places than others .
put some things in a bath full of water then pull the plug , a piece of paper floating on the surface will slowly move closer to the plug , but if you push the paper under water in different places it will move towards the plug at different speeds depending on what currents are caused by the objects

Answer 4

I think it's the same as winds in air - differences of pressure will cause the water to move from one place to another. The pressure may be because of depth, salty-ness of the water (therefore its density), air tempeartures (hours of sunlight), etc. These determine the more-or-less permanent currents (e.g., Gulfstream). Then there are the rip currents (as in the above answer). It all depends which currents you are curious about.

Answer 5

Rip current
From Wikipedia, the free encyclopedia
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Riptide redirects here. Riptide may also refer to an American TV series.
A rip current is a strong flow of water returning seaward from the shore. It is often mistakenly called a "rip tide" or "riptide", though the occurrence is not related to the tides. Colloquially a rip current is known simply as a rip. Although rip currents would exist even without the tides, tides can make an existing rip much more dangerous (especially low tide). Typical flow is at 0.5 metres per second (1-2 feet per second), and can be as fast as 2.5 metres per second (8 feet per second). Rip currents can move to different locations on a beach break, up to a few hundred feet a day. They can occur at any beach with breaking waves, including the world's oceans, seas, and large lakes such as the Great Lakes in the United States and Canada.

Contents [hide]
1 Recognizing a rip current
2 Uses
3 Dangers
4 Causes and occurrence
5 Surviving an encounter with a rip current
6 Safety tips
7 External links



[edit]
Recognizing a rip current

A sign warns hikers on the trail to Hanakapiai Beach.There are signs to look for in the water to see if a rip current is present. Rip currents can be recognized by unusually calm waters, caused by the channel of water flowing out. The color of the water may be different from the surrounding area. Also, the waterline is lower on the shore near a rip current. It is advisable to look for the existence of a rip current before heading into the water.

[edit]
Uses
Rip currents can also be extremely useful for surfers as they save the effort of having to paddle out to catch a set. They can also be used by lifeguards on paddleboards, who can use them to get out from the shore to perform a rescue much quicker than they could by paddling through the waves.

[edit]
Dangers
Such currents can all be extremely dangerous, dragging swimmers away from the beach and leading to death by drowning when they attempt to fight the current and become exhausted.

Although rare, rip currents can be deadly for non-swimmers as well: a person standing waist deep in water can be dragged out into deeper waters, where they can drown if they are unable to swim and are not wearing a flotation device. On April 14, 2004, Daniel Cho, an 18-year-old university student, was killed by a rip current simply by standing in the ocean water at La Jolla Shores, near San Diego, California, USA. This occurred at low tide after midnight (no lifeguards present), and unfortunately, he was a non-swimmer without a flotation device.

Rip currents cause approximately 100 deaths annually in the United States, more than all other natural hazards except heat. Over 80% of rescues by surf beach lifeguards are due to rip currents. A common misconception is that a rip occurring under the water, instead of on top — an undertow — is strong enough to drag people under the surface of the water; this is not true.


A rip current mechanism[edit]
Causes and occurrence
While the precise conditions leading to a rip current are not known, the general picture is as follows. When wind and waves push water towards the shore, the previous backwash is often pushed sideways by the oncoming waves. This water streams along the shoreline until it finds an exit back to the sea. The resulting rip current is usually narrow and located in a trench between sandbars, under piers or along jetties. The current is strongest at the surface, and can dampen incoming waves, leading to the illusion of a particularly calm area, luring some swimmers in.

Rip currents are stronger when the surf is rough (such as during high onshore winds, or when a strong hurricane is far offshore) or when the tide is low.

[edit]
Surviving an encounter with a rip current
When caught in a rip current, one should not fight it, but rather swim parallel to the shoreline in order to leave it. If you see a person caught in one, yell at them to do so. Floating until the current disperses into deeper waters is another method of surviving such a dangerous incident, but it may leave the swimmer farther out from shore.

[edit]
Safety tips
Posted warnings, where available, should always be heeded. It is advisable to stay at least 100 feet away from piers and jetties, which impede waves, encouraging rip currents to form. Also, check the local newspaper and internet for tide timetables. (Beware that tides can be substantially different at beaches relatively close to each other.) Never go into the water without lifeguard supervision from -2 to +4 hours of low tide -- especially at night.

Answer 6

Major studies reveal that most underwater currents are caused by farting whales.

Answer 7

The turning of the earth and the rising and falling tide.

Answer 8

Careless disposal of a rock cake?

Answer 9

moons pull

Answer 10

tsunami