If you’ve ever spent time at a beach, you probably noticed that the waves reached different points on the beach at different times of the day. For example, you might have made a sand castle near the water’s edge in the afternoon.
By evening, the water crept up the beach, covering the castle. In the morning, the sand castle is gone, but the water has receded and you can see remnants of the castle. What’s going on here? Why does the water level go up? The answer: tides.
- The tides are caused by the gravitational pull of both the moon and the sun on the earth’s surface. Because the moon is closer to the earth, its pull is stronger than the sun’s, even though the sun is much larger.
- Think of the moon as a magnet and the oceans of the earth as iron filings. If you drag the magnet across a surface, such as a table, the iron fillings will follow it. The magnet literally pulls the iron fillings across the table. The moon works similarly on the waters of the earth. It acts as a magnet, pulling the water along behind it. When the water is pulled to its highest level on the coast, it is at high tide.
- Most locations of the earth experience two cycles of high and low tides every day. The tides are highest during a full or new moon.
- Even large lakes experience tides.
Questions and Answers
Question: Are the tides dangerous?
Answer: During high tide, the water level rises. This can be dangerous if you get trapped somewhere, say in a cave or inlet, with nowhere to go. During high tide, waves sometimes break directly onto the beach with great force. If you’re swimming in this, the force of the waves can hurt you. In general, though, high tide is a fun time to go fishing and boating. If you’re careful and know what to expect, high tide can be fun.
At low tide, the water level is lower. You can explore tide pools and you’re more likely to find shells and sea animals. The sand at low tide is nice and wet for building sand castles. Of course, those castles will be washed away once the tide comes in again.
Learn more about how tides work.