Tides

The steady rise and fall of the ocean water levels is called the tide. Tides are caused by the pull of gravity between the Earth, Moon, and Sun.

The Moon’s gravitational pull is much stronger on Earth than the Sun’s because the Moon is so much closer to us.

Earth’s ocean tides are caused by the Moon’s gravitational pull on Earth. The Moon’s gravity causes high tides to occur on the parts of Earth that are directly facing the Moon, and facing away from the Moon.

Low tides occur in the areas that are neither facing nor facing away from the Moon. Most places have two high tides and two low tides each day, about twelve hours apart from one another.

On the side of Earth that’s facing the Moon, the pull of gravity causes oceans to bulge outward. On the other side of the Earth, that’s facing away from the Moon, the Moon’s pull on solid ground causes the oceans to bulge there too.

Because the Earth rotates on its axis, this bulge is constantly changing location. Where the bulge is bigger, it’s high tide. Where the water doesn’t bulge, it’s low tide. The Moon’s orbit around Earth also causes tidal changes. Most places get two high tides and two low tides each day. These tides are usually spaced about twelve hours apart.

Spring tides – which give us our highest high tides and lowest low tides – occur only during a new or full Moon.

A tidal range is the difference in size between a high tide and a low tide.

Spring tides have the largest daily tidal range, where there is the biggest difference in size between a low tide and a high tide. These occur twice a lunar cycle, at a new Moon and a full Moon. Spring tides – highest high tides and lowest low tides.

Neap tides – which give us our lowest high tides and our highest low tides – occur only during first and third quarter Moons.

Neap tides have the smallest daily tidal range, where there is the smallest difference in size between a low tide and a high tide. These also occur twice a lunar cycle, at a first quarter and third quarter Moon. Neap tides = lowest high tides and highest low tides.