[♪ INTRO]
Squeaks, I think I hear something.
Oh! Hi there!
Squeaks and I were just sorting the seashells
that Squeaks found during his trip to the beach.
Where did they come from?
Great question Squeaks!
They were probably washed ashore by waves.
Yeah, waves!
Not only are those waves fun to play in,
they also bring all kinds of things from deeper in the ocean right up to the shore.
The up and down motion we see in the water is called a wave.
The top of the wave is called the crest, and the bottom is the trough.
And one neat thing about them is that the water itself
doesn’t move forward with the wave.
The water moves up and down as the wave travels through the water.
Think about when you floated in the water.
When the waves went past you,
you bobbed up and down instead of just moving all the way back to the shore.
Yeah Squeaks, that’s right!
We can see waves in lakes and ponds too, not just in the ocean.
Any time there is a body of water and wind, you can have waves.
Great question!
There are a few different reasons that waves can happen.
And one of them is around us any time we go outside: Wind!
As the wind passes over the water’s surface,
the wind tugs on the water, creating waves.
The size of the wave depends on the strength of the wind and how long it blows.
So lots of wind can make really big waves!
Most of the waves we see on the beach are caused by the wind.
But can you guess something else that can make waves?
I’ll give you a hint: It’s big and round, and we can see it at night time.
It's the Moon!
I’ll tell you how!
The Moon makes waves when its gravity pulls on Earth.
Gravity is the force that pulls things together.
It’s everywhere!
Here, let’s all stand up, and jump up as high as you can do safely!
When you jumped, you didn’t just float away.
You fell back down!
That happened because Earth’s gravity pulled you down.
Everything on Earth is held down by gravity, including the ocean.
The heavier something is, the more gravity it has, and planets are pretty heavy.
That means Earth’s gravity is tugging on the Moon.
But the Moon has gravity too, and the Moon’s gravity is tugging right back!
Our moon’s gravity pulls on Earth as it orbits around us.
It pulls on us, the land, the Fort, and even the ocean.
And even though it doesn’t pull hard enough to move us,
or the ground, the water it pulls on does move.
Which means that sometimes when you’re at the beach,
the moon is pulling the water closer to where you are on the shore,
which is called high tide.
You might notice that the beach isn’t as big as usual at high tide.
That’s because the ocean is covering more of the beach!
But if the moon is pulling the water at a different place on the planet,
the water will move away from where you are on the beach.
That’s called low tide, and low tide can mean that
all sorts of things that are usually underwater are visible.
Yeah, Squeaks, that’s why the tracks from your wheels from early in the day
got covered up by the water by the time you left.
The tide came in!
After high tide, or when big waves hit the shore, like after a big storm,
they can bring lots of cool objects to the surface with them!
Those can be great times to look for things washed up on the beach.
Like Squeaks did on his trip!
And sometimes, waves can get really big, too.
Let me tell you about tsunamis, the biggest kinds of waves that ever happen.
Tsunamis are really big waves caused by one-time events,
like an earthquake or underwater volcano erupting.
When the waves hit the shore, they can be 30 meters tall.
That’s as tall as two fire trucks stacked on their ends!
Good question!
Tsunamis don’t happen just anywhere.
Tsunamis are more common in some parts of the world than others,
like the Ring of Fire in the Pacific Ocean.
That’s because there are lots of underwater volcanoes there.
Tsunamis are very dangerous, just like other extreme weather like tornadoes
and hurricanes, and can cause whole towns to be evacuated.
You should never be on a beach when a tsunami is coming.
Oh yeah, Squeaks, waves are pretty amazing and powerful!
Maybe we can even learn to surf and ride waves next time we go!
How about you?
Have you ever found anything cool at the beach?
Or played in the waves?
Thanks for learning about waves with us, and
watching this episode of SciShow Kids.
You can ask a grown up to help send questions to us.
They can get started at patreon.com/scishowkids.
And thank you all for joining us here at the Fort!