Picture this: A crab scuttles into a damp rock crevice.
Snails chug along rock faces, secretings mucus along the way.
Barnacles, glued in place, retreat into their protective shells.
An aggregation of anemone’s grab little pebbles with their tentacles. Hugging them close. All in an attempt to retain moisture and avoid desiccation — these critters all call the intertidal zone their home.
In other words, they are all reliant on the ocean’s tides: the daily rise and fall of the sea’s surface.
These organisms have all developed unique adaptations to help them deal with air exposure for several hours in a given day. Lucky for them, tides are predictable. In simple terms, tides are predicted by our understanding of the lunar cycle. The gravitational pull between the sun and the moon, and consequently its affect on the ocean, is dependent on positioning. When the moon is full, the orientation of the sun, the earth, and the moon look like this:
They are aligned with one another. This is when gravitational pull is at its strongest and causes the oceans to bulge. Right after a full moon the difference in height between a consecutive high and low tide, called a tidal range, is at its greatest. Another phrase for this effect is called a spring tide.
Even though the sun is about 27 million times larger than the moon, at the end of the day the moon will always have a greater impact on our tides than the sun. So why is this the case? The sun may be significantly larger however it’s a lot farther away from Earth (about 390 times farther) than the moon is from Earth. Essentially this means that the sun’s impact on tides is about half that of the moon!
As the moon and the suns gravitational pull comes into play tidal bulges begin to form on opposite sides of the Earth due to gravity and inertia. Both a lunar and a solar tidal bulge will form. As the moon rotates around Earth and Earth rotates around the sun the angles of these tidal bulges change. These change in tidal bulge angles directly affect our tides.
The most extreme tides occur when the moon, Earth, and the sun are aligned with one another. These extreme tides are referred to as Spring Tides – this is when we will have very high high tides and very low low tides. More moderate tides occur when the moon, Earth, and sun are aligned in a 90 degree angle. These moderate tides are referred to as Neap Tides.
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