Teach About the Tides
At different times of the day, there is a noticeable difference in how far the water comes up on the beach. These are called tides. Tides are caused by the gravitational pull that the moon and sun have on the earth. The sun does not have as strong of a pull on the oceans as the moon does because it is so far from Earth. Tides are also affected be the rotation of the earth. When the ocean's waves reach high onto the shore and cover most of the beach, it is high tide. When the ocean's waves are very low and most of the beach is left uncovered, it is low tide. The high and low tides create a space on the shore called the intertidal zone. At high tide, the area is covered in water. At low tide, the area is an exposed rocky or sandy beach.
Look for Life on the Beach
Two great places to look for plants and animals on the seashore are the strandline and tide pools. The strandline is the farthest place the water reaches on the beach at high tide. Plants, animals, and other items in the ocean often get stranded there because the water is not strong enough to pull them back out to sea. Tide pools form when the high tide comes in and the holes in the rock are filled with salty ocean water. Tide pools provide sheltered places for many sea creatures that were washed in with the tide. Both of these places are best to observe during low tide. And since the ocean brings in new items and washes old items back into the sea, what you can find in the strandline and tide pools changes with each tide! The next section describes the four tidal zones and what kind of life to look for in each zone.
To help your child observe the seashore, use this coloring page as a scavenger hunt.
For more about tide pools and the animals that live in them, visit our Tide Pools Teaching Tip.
The Zones Where Land and Water Meet
- The Spray Zone. This area is usually dry and only gets sprayed by the ocean's waves at high tide. Barnacles and whelks often live in the spray zone. Barnacles are small marine animals with very hard shells. They cling to driftwood, rocks, piers, ships, and even whales! Whelks are large marine snails with spiral shells that look like conches. You may find a string of whelk egg capsules while walking along the beach. Explain that the female whelk lays an egg case at the bottom of the ocean, burying one end so that the case does not get carried to the shore and dry out until the eggs have hatched.
- The High Tide Zone. This area is wet during high tide, but only the tide pools in this zone stay wet all of the time. Along with barnacles and whelks, the high tide zone may have crabs, mussels, sea anemone, starfish, and snails. Underwater ocean plants, like seaweed and green algae, often grow in and near tide pools. Items also get tangled up in seaweed, so you may want to use a stick to help you uncover what may be hidden underneath. A very colorful and interesting creature you might find in a tide pool is a sea anemone. Its many tentacles stretching out from its round body make it look like a plant, but it is actually an animal that clings to rocks.
- The Middle Tide Zone. This area is wet and dry, making it a tough place for most animals to live. It is covered and uncovered twice a day with salty water from the tides. But there are plants and animals that can stand the change in wet and dry conditions and they call this area their home. Animals and plants that can live in the high tide zone can also live here, along with more unique ocean animals like sponges. Sponges are not able to move around on their own, so they attach themselves to stationary objects like rocks or sunken ships. You may find shells and clams in this zone. Due to the fact that it's a rough journey onto land, most of the shells will probably be broken. Pick up a shell fragment and see if your children can guess what kind of animal it belonged to or what the shell's original shape was. You may also want to collect shells and group them by the kind of animal they belonged to. This is always a good opportunity to talk about classification of animals.
- The Low Tide Zone. This is almost always wet unless the tide is extremely low. The creatures that live here are used to the environment of ocean water and cannot be exposed to extreme dryness. Mussels, sea cucumber, sea lettuce, sea palms, sea stars, sea urchins, shrimp, surf grass, and tube worms all live in this area. Sea cucumbers get their name because they look like cucumbers grown in a garden. They eat plankton found near the sea floor and have spiny tentacles on their body to help them catch food.
This visual guide is helpful for explaining the zones to children.
Click here for seashore science projects.