28th November 2019

weather

15

How does rip current form?

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Rip currents form when waves break near the shoreline, piling up water between the breaking waves and the beach. One of the ways this water returns to sea is to form a rip current, a narrow stream of water moving swiftly away from shore, often perpendicular to the shoreline.

What is a rip current and what causes it?

Causes and occurrence. A rip current forms because wind and breaking waves push surface water towards the land, and this causes a slight rise in the water level along the shore. This excess water will tend to flow back to the open water via the route of least resistance.

What is an undercurrent in the ocean?

Undercurrents are currents of water that flow under the surface of a large water body; they are like a small stream or river within the larger water body itself. They are a natural part of the flow of lakes and oceans and are essential to maintaining a balance of heat and nutrients in the water.

1

Can a river have an undertow?

Caught in the Undertow. I grew up near two rivers: the Sacramento and American River. The other thing you learn about the river is that if you ever do get caught in the undertow, don't fight it. You have to go with it and the water will eventually spit you back out upon the surface, somewhere, at some point.

2

How do summer beaches differ from winter beaches discuss the reasons for these differences?

Summer - The lower waves of summer build sand onshore and widen the beach. Winter - Higher winter waves move sand offshore and narrow the beach. Seasonal differences - Beach just north of the Scripps pier, part of the UC Natural Reserve System. Cobbles are heavier and remain on the beach.

3

Why do deep currents form?

Currents may also be generated by density differences in water masses caused by temperature and salinity variations. These currents move water masses through the deep ocean—taking nutrients, oxygen, and heat with them.

4

What are upwellings and Downwellings?

Upwelling is a process in which deep, cold water rises toward the surface. Upwelling occurs in the open ocean and along coastlines. The reverse process, called “downwelling,” also occurs when wind causes surface water to build up along a coastline and the surface water eventually sinks toward the bottom.

5

What drives currents at ocean surface?

Winds drive currents near coastal areas on a localized scale, and in the open ocean on a global scale. A third factor that drives currents is thermohaline circulation - a process driven by density differences in water due to temperature (thermo) and salinity (haline) in different parts of the ocean.

6

What is an upwelling and what causes it?

Upwelling often happens where wind blows along a coastline. The wind causes the water at the ocean surface to move perpendicular to it, away from the coast, because of a process called Ekman transport. When surface water moves away from the coast, water from deeper in the ocean rises up and takes its place.

7

How longshore currents are formed?

Longshore currents are common at any beach that is exposed to breaking surf. A longshore current is an ocean current that moves parallel to shore. It is caused by large swells sweeping into the shoreline at an angle and pushing water down the length of the beach in one direction.

8

What is longshore drift caused by?

The transport of sand and pebbles along the coast is called longshore drift. The prevailing wind (the direction the wind ususally blows from) causes waves to approach the coast at an angle. The swash carries the sand and pebbles up the beach at the same angle (usually 45º).

9

How does a spit form?

A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end. Spits are formed where the prevailing wind blows at an angle to the coastline, resulting in longshore drift. An example of a spit is Spurn Head, found along the Holderness coast in Humberside.

10

Where does a spit occur?

A spit or sandspit is a deposition bar or beach landform off coasts or lake shores. It develops in places where re-entrance occurs, such as at a cove's headlands, by the process of longshore drift by longshore currents.

11

What is a baymouth?

A baymouth bar is a depositional feature as a result of longshore drift. It is a spit that completely closes access to a bay, thus sealing it off from the main body of water.

12

How is a barrier island formed?

Formation. There are three main theories that explain how barrier islands form. The offshore bar theory proposes that individual barrier islands formed when waves stirred up sediment from the sea floor. When the waves broke, their energy was used to deposit sand into a bar along the sea floor.

13

How is a Tombolo?

A tombolo is a spit connecting an island to the mainland. An example of a tombolo is Chesil Beach, which connects the Isle of Portland to the mainland of the Dorset coast.

14

Is Chesil Beach a Tombolo?

Chesil Beach is 18 miles (28 kilometres) long and, on average, 160 metres wide and rises to 12 metres in height. It is a pebble and shingle tombolo connecting Portland to Abbotsbury and then continuing north-westwards to West Bay near Bridport. It is the largest tombolo in the UK.

15

What is a bar on the coast?

Coastal bars (shallow banks formed by the movement of sand and sediments) build up at the seaward entrance coastal rivers and lakes. They cause waves to become steeper and, in some cases breaking as they approach the bar. There are many bars along the Australian coastline.

16

What is an undercurrent in the ocean?

Undercurrents are currents of water that flow under the surface of a large water body; they are like a small stream or river within the larger water body itself. They are a natural part of the flow of lakes and oceans and are essential to maintaining a balance of heat and nutrients in the water.

17

Do lakes have Undertows?

You may have heard about the rip tide or undertow before. These are terms that people commonly use to describe dangerous currents. However, since there are no tides in the Great Lakes (needed to form a rip tide) and currents don't pull a person down under the water (undertow), they are a bit inaccurate.

18

Do small lakes have currents?

Currents. The principal forces acting to initiate water movements in lakes are those due to hydraulic gradients, wind stress, and factors that cause horizontal or vertical density gradients. Lake water movement is usually classified as being turbulent.

19

Are there currents in quarries?

Ghostly Currents: Quarries do not have hidden currents beyond the flow from filler streams and springs, and there are no currents that will drag a swimmer under the water.

20

What is the current of a river?

A current, in a river or stream, is the flow of water influenced by gravity as the water moves downhill to reduce its potential energy. The current varies spatially as well as temporally within the stream, dependent upon the flow volume of water, stream gradient, and channel geometry.

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