Exercises: Ocean Tides: Daily, Spring and Neap Cycles

Ocean tides are the regular rise and fall of sea level. Name the main force, caused by the Moon and the Sun, that produces tides. Which of the two, the Moon or the Sun, has the stronger effect on Earth's tides?

At a beach in Galveston, Texas, Sofia sees the water at its highest level in the morning. About how many high tides and how many low tides do most coasts have in one day? Is the water level at that beach likely to stay the same all day?

Name the Moon phases at which spring tides and neap tides happen. Choose from: new moon, first quarter, full moon, third quarter. Say which kind of tide has the largest difference between high and low water, and which has the smallest.

Explain why the ocean has a bulge on the side of Earth facing the Moon. Use the idea that the Moon's gravity pulls more strongly on nearer water. Then explain how Earth's rotation causes a place on the coast to move through high tide and low tide during the day.

Aaliyah records the water level at a dock in Maine over one day.

1. a) Estimate when each of the first two high tides happened. b) What is the largest difference in water level in the data? c) Predict whether the next low tide happens before or after 9:00 p.m. and explain why.

During a full moon, the Sun, Earth and Moon are in a nearly straight line, with Earth in the middle. During a first quarter moon, the Moon, Earth and Sun form a right angle. Compare the gravitational effects of the Sun and Moon in each case. Explain which one makes a spring tide and which makes a neap tide.

Spring tides also occur at new moon. Draw or describe the positions of the Sun, Moon and Earth at new moon and at full moon. Explain why both phases produce spring tides even though the Moon is on opposite sides of Earth. Then explain why the moon phase cycle of about 29.5 days means that spring tides occur about twice each month, and say how many days apart they are, approximately.

A town on the Gulf Coast plans a beach cleanup. The organizers know a full moon will occur on Saturday. Marcus says, "We should hold it on Saturday because the low tide will be extra low, exposing more trash." Priya says, "Neap tides will make the beach larger." Evaluate both statements using spring and neap tide ideas. Say who is correct, justify your answer, and explain what you would check in a local tide table before choosing the time of day.