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🌊 Tides, Waves, and Currents

Why does the sea rise and fall, where do waves come from, and how does water travel across whole oceans? Meet the three great motions of the sea.

lessons

~15 min

to learn

🔬 Science

subject

Ages 6–12

level

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What you’ll learn

WavesUnderstand that a wave carries energy through water, that wind makes waves, and name a wave's crest and trough.A wave is a moving ripple of energy that travels across the water while the water itself mostly bobs up and down in place. Nearly all ocean waves are made by the wind, and stronger, longer winds make bigger waves. Every wave has a high point called the crest and a low dip called the trough.
TidesLearn that tides are the daily rise and fall of the sea, caused mainly by the Moon's gravity.The tide is the steady daily rise and fall of the sea, caused mostly by the Moon's gravity pulling the ocean into a bulge. As the Earth spins, that bulge moves around, giving most coasts two high tides and two low tides roughly every day. The water creeps in to a high tide and slides back out to a low tide over and over.
CurrentsUnderstand that currents are steady streams of water, driven by wind and temperature, and compare them with waves and tides.Ocean currents are steady streams of water flowing in one direction, like rivers in the sea. Surface currents are pushed by the wind, while deep currents flow because cold, salty water sinks and warm water rises. Currents like the warm Gulf Stream carry heat around the world, helping to keep some coasts milder.

Questions this course answers

What makes most ocean waves?

Nearly all ocean waves are made by the wind pushing across the surface of the water into ripples that grow into waves.

What is the top of a wave called?

The crest is the highest point at the top of a wave, while the dip between waves is called the trough.

What mainly causes the ocean's tides?

Tides are caused mostly by the Moon's gravity, which pulls the ocean into a bulge and makes the sea rise and fall.

How many high tides do most coasts have each day?

Because of the way the Moon pulls the ocean, most coasts have two high tides and two low tides roughly every day.

What is an ocean current?

A current is a steady stream of water moving in one direction across the ocean, like a river flowing through the sea.

What does the warm Gulf Stream current do?

The Gulf Stream carries warm water from near the equator toward Europe, helping keep those coasts milder and sharing the Sun's heat.

Grounded in trusted sources

NOAA
National Geographic Kids
Smithsonian Ocean
Britannica Kids

Every Wunder lesson is built from real, reputable sources — never invented.

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