Tides
The ocean is always moving. Waves are created by soft breezes and by huge storms. The sun and moon pull on the ocean, making the water level rise and fall. Ocean tides usually rise and fall twice a day.
When the water level rises, we say the tide is coming in. With each wave, water flows farther up onto the beach. Soon, the water covers the intertidal zone(潮汐带). Intertidal means "between the tides".
As the tide comes in, sand and seaweed wash onto the shore. No one can stop the tide, or even slow it down. The tide is too powerful. After the tide rises for about six hours, it begins to fall. Water flows away from the beach. The intertidal zone is uncovered. Sand and seaweed float out to sea.
It forms pools between rocks on shore. Many plants and animals live in these tide pools. Seaweeds, starfish, crabs and snails live there.
You might find a tide pool when you visit an ocean beach. Stay still and watch closely. You might see sea animals. You might see birds hunting in the pools. You might also see animals eating the seaweed and the algae, which is a kind of small plant that grows on rocks. But do be careful.
The ocean tides have been rising and falling for billions of years. All day and all night, the tide keeps coming in, then going out, covering and uncovering the beach.
A. So do shells and pieces of wood.
B. Then we say that the tide is going out.
C. Algae and seaweed make rocks slippery.
D. Some water stays behind when the tide goes out, though.
E. The water's rising and falling is called the ocean's tide.
F. Sometimes small fish get trapped there as the tide goes out.
G. The intertidal zone is the area that lies between high tide and low tide.
