Tides
Tides are the rising and falling of ocean waters. The main causes of tides are the gravitational pulls of the moon and sun and the Earth's rotation. Since the moon is much closer to Earth than the sun, the moon's gravitational pull has more effect than the sun's. When the ocean is pulled by the gravity of the moon, it bulges towards the moon. It bulges on the opposite side of the Earth, too, because the Earth itself is also pulled towards the moon and away from the ocean. At low tide, much of the shoreline is exposed, revealing more of the beach and stranding clumps of seaweed, large, smooth rocks, and small shells. At high tide, the water washes up higher than it usually does on the shore, covering large expanses of sand. In some places, large rocks are visible at low tide, but at high tide they are swallowed up by the ocean.
currents
A current is the steady, predictable movement of a fluid in a certain direction. There are many different types of currents, including air currents, electricity currents, and water currents. The ocean's currents flow around the world.
There are two different types of ocean currents: deep sea currents and surface currents. Surface currents are usually caused by wind and tides. Tides create currents near the shore and in bays and estuaries along the coast. These currents are called tidal currents. Wind creates currents that are at the ocean's surface. Winds drive currents near global areas on a certain localized scale and mid-ocean currents on a global scale.
Deep sea currents are caused by differences in water temperature, salinity, and thermohaline circulation, which is a process made by density differences in the ocean due to temperature and salinity in different parts of the ocean. Thermohaline circulation currents occur at both deep and shallow ocean levels. These currents move a lot slower than surface or tidal currents.
One of the most known ocean currents is the Gulf Stream, a current that flows from the Gulf of Mexico into the southern Arctic Ocean off the northern coast of Scandinavia. The temperature of the ocean currents helps to determine the specific climate in different regions of the world. For example, the Gulf Stream carries warm, tropical water up from the Gulf of Mexico to Europe. Without the Gulf Stream, Europe would be much colder than it is today.
There are two different types of ocean currents: deep sea currents and surface currents. Surface currents are usually caused by wind and tides. Tides create currents near the shore and in bays and estuaries along the coast. These currents are called tidal currents. Wind creates currents that are at the ocean's surface. Winds drive currents near global areas on a certain localized scale and mid-ocean currents on a global scale.
Deep sea currents are caused by differences in water temperature, salinity, and thermohaline circulation, which is a process made by density differences in the ocean due to temperature and salinity in different parts of the ocean. Thermohaline circulation currents occur at both deep and shallow ocean levels. These currents move a lot slower than surface or tidal currents.
One of the most known ocean currents is the Gulf Stream, a current that flows from the Gulf of Mexico into the southern Arctic Ocean off the northern coast of Scandinavia. The temperature of the ocean currents helps to determine the specific climate in different regions of the world. For example, the Gulf Stream carries warm, tropical water up from the Gulf of Mexico to Europe. Without the Gulf Stream, Europe would be much colder than it is today.
waves
Waves are vertical movements in the water caused by wind blowing across the surface. The top of the wave is called the crest, while the bottom of the wave is called the trough. The distance between a crest and a crest or a trough and a trough is commonly known as the wavelength. If the wind is strong enough, hurricane-sized winds can form, sometimes swamping beaches and flooding low land. Tsunamis (see the Weather and Climate tab) are huge waves caused by an underwater earthquake or volcanic eruption. Tsunamis are mistakenly called tidal waves, even though they have nothing to do with tides.