The high tide on the side of the Earth facing the moon is called the high high tide. The high tide caused by the bulge on the opposite side of the Earth is called the low high tide. In the open ocean, the water bulges out toward the moon. Along the seashore, the water rises and spreads onto the land. Low Tides and Ebb Tides One high tide always faces the moon, while the other faces away from it.
Between these high tides are areas of lower water levels—low tides. The flow of water from high tide to low tide is called an ebb tide. Most tides are semidiurnal , which means they take place twice a day.
Now it is low tide in that area. As the Earth keeps rotating, another high tide occurs in the same area when it is on the side of the Earth opposite the moon low high tide.
The Earth continues spinning, the tide ebbs, another low tide occurs, and the cycle 24 hours long begins again. The vertical difference between high and low tide is called the tidal range. Although the sun is almost times farther away from the Earth than is the moon, its high mass still affects the tides. The shape of a seacoast and the shape of the ocean floor both make a difference in the range and frequency of the tides.
Along a smooth, wide beach, the water can spread over a large area. The tidal range may be a few centimeters. In a confined area, such as a narrow, rocky inlet or bay , the tidal range could be many meters. The lowest tides are found in enclosed sea s like the Mediterranean or the Baltic. They rise about 30 centimeters about a foot. The largest tidal range is found in the Bay of Fundy, Canada.
There, the tides rise and fall almost 17 meters 56 feet. Twice each month, the moon lines up with the Earth and sun. These are called the new moon and the full moon. This is the new moon. When the Earth is between the sun and moon, the moon reflects sunlight. This is the full moon. The combined pull can cause the highest and lowest tides, called spring tide s. Spring tides happen whenever there is a new moon or a full moon and have nothing to do with the season of spring.
When this happens, the pull of the sun and the moon are weak. This causes tides that are lower than usual. These tides are known as neap tide s. Tidal Features Tides produce some interesting features in the ocean. Tides are also associated with features that have nothing to do with them. A tidal bore occurs along a coast where a river empties into the ocean or sea. The tidal bore is a strong tide that pushes up the river, against the river's current. This is a true tidal wave.
The huge tidal bore of the Amazon River is called the pororoca. The pororoca is a wave up to 4 meters 13 feet tall, traveling at speeds of 15 kilometers 9 miles per hour. The pororoca travels 10 kilometers 6 miles up the Amazon. While a tidal bore is a tidal wave, a tsunami is not. Tsunamis are associated with tides because their reach surpass es the tidal range of an area.
A red tide is another term for an algal bloom. Algae are microscopic sea creatures. Finally, rip tide s are not a tidal feature. Rip tides are strong ocean current s running along the surface of the water.
A rip tide runs from the shore back to the open ocean. Rip tides can be helpful to surfers, who use them to avoid having to paddle out to sea. Rip tides can also be very dangerous to swimmers, who can be swept out to sea. Intertidal Life The land in the tidal range is called the intertidal zone. The intertidal zone is often marked by tide pool s. Tide pools are areas that are completely underwater at high tide but remain as pockets of seawater when the tide ebbs.
The intertidal zone can be hard-bottomed or soft-bottomed. A zone with a hard bottom is rocky. A zone with a soft bottom has silt or sand. Wetland s and marsh es are often soft-bottomed intertidal zones. Different creatures have adapt ed to different types of intertidal zones. Hard-bottom zones often have barnacles and seaweed s, while soft-bottom zones have more sea plants and slow-moving creatures like ray s. Intertidal zones are marked by vertical zonation. Different organisms live in different zones in the tidal range, depending on how much water reaches them.
This zonation can often be seen vertically, with dry plants near the top of the tidal zone and seaweeds near the bottom. The intertidal zone can be broken into four major mini-zones. The highest is called the splash zone 1. This area is splashed by water and mist during high tide, but is never fully underwater. Barnacles live on rocks in the splash zone. Many marine mammal s, such as seals and sea otters, can live in the splash zone.
The high-tide zone 2 is pounded by strong waves. Animals that live in the high-tide zone often have strong shell s and are able to cling tightly to rocks to avoid being swept out to sea. These animals include mussels and barnacles. Crabs, which have tough exoskeleton s and can hide under rocks, also live in the high-tide zone.
The mid-tide zone 3 is usually the busiest part of the intertidal zone. This is where tide pools usually form. It should be noted that it is the wave that moves , not the water itself for the most part. Additionally, the behavior of waves in water adheres to the same principles that govern the behavior of other waves such as sound waves in air.
Tidal waves are the largest oceanic waves on our planet. Tidal waves are formed by the gravitational forces of the earth, sun, and moon. The gravitational forces of the sun and to a greater extent the moon pull on the oceans causing the oceans to swell on either side of the earth the side closest to the moon and the side farthest from the moon. As the earth rotates, the tides go 'in' and 'out' the earth moves but the bulge of water remains in line with the moon, giving the appearance that the tides are moving when it is, in fact, the earth that is moving.
Tsunamis are large, powerful oceanic waves caused by geological disturbances earthquakes, landslides, volcanic eruptions and are normally very large waves. Now that we've defined some types of ocean waves, we'll look at how waves behave when they encounter other waves this gets tricky so you may want to refer to the sources listed at the end of this article for more information. When ocean waves or for that matter any waves such as sound waves meet one another the following principles apply:.
Superposition: When the waves traveling through the same medium at the same time pass through one another, they do not disturb each other. At any point in space or time, the net displacement that is observed in the medium in the case of ocean waves, the medium is seawater is the sum of the individual wave displacements.
Destructive Interference: Destructive interference occurs when two waves collide and the crest of one wave aligns with the trough of another wave. The result is that the waves cancel each other out. Constructive Interference: Constructive interference occurs when two waves collide and the crest of one wave aligns with the crest of another wave. The result is that the waves add together each other out.
Where Land Meets Sea: When waves meet the shore, they are reflected which means that wave is pushed back or resisted by the shore or any hard surface such that the wave motion is sent back in the other direction. Additionally, when waves meet ashore, it is refracted. As the wave approaches the shore it experiences friction as it moves over the seafloor. This frictional force bends or refracts the wave differently depending on the characteristics of the seafloor. Gilman S. Even the impressive surf of the Pacific got its start as wind blowing across the open water.
The height of such waves depends on how fast the wind is blowing, and how much open water the wind travels across. Tsunamis, however, have nothing to do with wind. They're caused by the sudden movement of the Earth's crust during an underwater earthquake or a volcanic eruption. Imagine a child's plastic wading pool filled with water in the back yard.
Ordinary waves are like the little surface ripples from the afternoon breeze. A tsunami is what you'd get if you kicked the side of the pool.
0コメント