pulled higher in the areas of the two high tides, there is less water in between the two high
tides. These areas are thelow tides(Figure14.11).
Figure 14.11: High tide is created by the gravitational pull of the moon which pulls water
toward it. Water on the opposite side of the Earth is pulled least by the moon so the water
bulges away from the moon. High tide occurs where the water is bulging. Low tide occurs
where it is not. ( 35 )
Thetidal rangeis the difference between the ocean level at high tide and the ocean at low
tide (Figure14.12). Some places have a greater tidal range than others. High tides occur
about twice a day, about every 12 hours and 24 minutes.
Figure 14.12: The tidal range is the difference between the ocean level at high tide and low
tide. ( 26 )
The Moon’s gravity is mostly responsible for our tides, but the Sun also plays a role (Figure
14.13). The Sun is much larger than our Moon. It has a mass about 27,500,000 times greater
than the Moon. A very large object like the Sun would produce tremendous tides if it were
as near to Earth as the Moon. However it is so far from the Earth that its effect on the tides
is only about half as strong as the Moon’s. When both the Sun and Moon are aligned, the
effect of each is added together, producing higher than normal tides calledspring tides.