Sea Level Lesson for Kids: Definition & Facts

Instructor: Kristen McNeely

Kristen has taught elementary students for five years and has a master's degree in teaching.

In this lesson, you will learn about sea level and how it is measured by scientists. We will also explore rising sea levels and what long-term effects global warming has on them.

Sea Level

Have you ever had the chance to visit a beach? Maybe you sat on the sand and looked out at the water, looking far beyond the shoreline. The water all seems to be flat, doesn't it? Sort of like it's the same level for as far as you can see.

Sea level is a term used to describe what the height of the ocean usually is. When the tide comes in and goes out each day, this changes the sea level, so there isn't ever a permanent height for the sea.

We also use the term 'sea level' to help describe land forms that are above the water, like mountains. We may say something like, 'Mount Everest is 29,029 feet above sea level' to describe the height of the mountain above the ocean's surface.

The Sea
The Sea

Noticeable Changes in Sea Levels

Determining the true height of the ocean is very difficult. So many factors affect sea level, and the ocean is always changing.

Scientists have studied sea levels throughout history and have been able to figure out how much they are rising over time. The height of the sea is rising approximately 3.2 millimeters each year. This may seem like a very small number, but one reason scientists are concerned is because this number has risen over the last century and at a faster rate than in previous years.

Global Warming

Sea levels are always changing for a variety of reasons. Global warming describes how the planet's overall temperature is becoming warmer as time passes. Global warming affects sea level for a couple of different reasons.

Think about large masses of ice that are in the water, like icebergs. As the planet becomes warmer, the ice melts, turning into liquid, which adds to the volume of water in the oceans. This is one cause of rising sea levels.


Another reason behind the levels rising is basic science. Did you know that as water particles heat up, they become larger? The heated water takes up more room, causing the height of the sea to increase.

Humans and Global Warming

Unfortunately, scientists believe that humans are part of the cause of global warming, which in turn affects sea levels. Some of the things humans do put gases into the air that affect our environment and increases temperatures of the air.

For example, when our cars burn gasoline or factories burn coal, the waste from these processes go directly into our atmosphere, which over time increases the temperature of our planet.

Factory Gases
Factory Gases

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