While we don’t tend to notice Earth and atmospheric tides, they do affect both the land and the world’s largest freshwater resource located underneath our feet: groundwater. This occupies the pores that exist in geological materials such as sand or soil, much like water in a kitchen sponge.
You might be thinking “Do tides also affect land?”
– Yes, though land rises and falls by a much smaller amount than the oceans. Tides affect the entire Earth, but they are much more noticeable for the oceans because water flows so much more easily than land.
King tides bring unusually high water levels, and they can cause local tidal flooding. Over time, sea level rise is raising the height of tidal systems. Average daily water levels are rising along with the oceans. As a result, high tides are reaching higher and extending further inland than in the past.
What are land tides?
Land tides, also called Earth tides, are very small deformations or movements in the Earth’s lithosphere (surface) caused by the gravitational fields of the sun and moon as the Earth rotates within their fields.
– Yes, though land rises and falls by a much smaller amount than the oceans. Tides affect the entire Earth, but they are much more noticeable for the oceans because water flows so much more easily than land. Still, the land rises and falls measurably (by about 1 centimeter) with the tides.
They have found that although the forces causing land tides and the deformations in the Earth’s surface are very small they do have the power to trigger geologic events because they are causing changes in the Earth ‘s surface.
How does the sun affect land tides?
The sun does have an effect on land tides as well because of its very large size and strong gravitational field. As the Earth rotates around the sun and the moon each of their gravitational fields pull on the Earth. Because of this pull there are small deformations or bulges on the Earth’s surface or land tides.
Tides affect the entire Earth, but they are much more noticeable for the oceans because water flows so much more easily than land. Still, the land rises and falls measurably (by about 1 centimeter) with the tides.
Credit: Bazonka, CC BY-SA 3.0 Tides affect water levels and current speeds in rivers as they approach the ocean. These effects can reach much farther inland—sometimes hundreds of kilometers—than the brackish estuary, where salty seawater mixes with fresh river water.
What is the importance of tides in GIS?
Geographic imaging systems (GIS) rely on tidal calculations. GIS must account for tides when mapping, especially when mapping the ocean floor. Tides affect the report on an area’s depth. Predict ing tides is very important for shipping and travel across oceans.
Land tides are small though and the actual movement of the Earth’s surface is usually no greater than 12 inches (30 cm).
What causes tides to ebb and flood in opposite directions?
The vertical motion of the tides near the shore causes the water to move horizontally, creating currents. When a tidal current moves toward the land and away from the sea, it “floods.” When it moves toward the sea away from the land, it “ebbs.” These tidal currents that ebb and flood in opposite directions are called “rectilinear”.
This of course begs the question “Why do tides occur twice a day?”
Most tides are semidiurnal, which means they take place twice a day . For example, when an area covered by the ocean faces the moon, the moon’s gravitational force on the water causes a high high tide. As the Earth rotates, that area moves away from the moon’s influence and the tide ebbs.
What is the difference between tidal and flood current?
This is called the tidal current. The incoming tide along the coast and into the bays and estuaries is called a flood current; the outgoing tide is called an ebb current. The strongest flood and ebb currents usually occur before or near the time of the high and low tides.