How tides work

How tides work


Imagine entering a bay on a yacht planning an anchorage. The depth is good. Almost no waves. A great place for “parking”. But the next morning you see less water and the boat falling on board. This means that you entered the bay at high flow. And in the morning the water left the banks.

The ebbs are dangerous not only for sailors, but also for surfers. At low tide reefs and stones are exposed.

Tides affect the water level not only on the coast, but also on the entire surface of the ocean. When the ocean level rises as much as possible — it is a high tide. At ebb-tide the water level drops to its lowest. During high tide the water flows to the coast, at ebb-tide — from the coast.

Why the water level can change?

Reason 1. The Sun and the Moon

The first reason is the gravity of Earth and that of the Moon. Because of this, a peculiar hump or wave forms on the water.

The tides also appear due to the Sun’s gravity. But the power of the Sun is much less than that of the Moon, because it is much farther.

Reason 2. Earth's rotation

Due to the rotation of the Earth, a wave formed due to the gravity pull of the Moon or the Sun changes its position relative to the globe. The wave follows the Moon, while the Earth continue to spin. This affects the constant movement of the water hump, which causes tides.

Plots of land (islands, continents) and the Coriolis effect interfere with the straight-line propagation of tidal waves. Therefore, there are many small waves that differ in the mass of water that is nailed to the shores at high tide.

Due to the fact that the planet rotates around its axis, the Coriolis force acts on all moving objects, including air masses.

It works like this: if a body moves along the surface of the earth, it is deflected to the right all the time in the Northern Hemisphere, and to the left — in the Southern Hemisphere.

Effect of the Moon on tides. Valerya Milovanova /



Cover photo: Bobby Stevenson / Unsplash

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