Under The Atlantic Ocean
The longest mountain range in the world, the Mid-Atlantic Ridge, runs right down the middle of the Atlantic ocean.

It's the giant letter "C"
between South America
and Africa.

In fact, the Mid-Atlantic Ridge is only one part of a whole series of
connected ridges under the ocean that circle around the globe...

Under The Pacific Ocean
The tallest mountain on the planet is not Mt. Everest, which is only 29 028 ft/8848 m high!  The tallest mountain in the world is actually Mauna Kea, in Hawaii, which is closer to 31 000 ft/
9449 m high.

You just can't see the two-thirds of the mountain that is under water.

Way Under The Pacific Ocean
The deepest place on the surface
of the planet is the Mariana Trench,
to the east of Guam.  If Mt. Everest
were put into the deepest part of
the Mariana Trench, there would be
1m/1.6km of water on top of it.

As big as you might think all of these mountains and trenches are,
if the earth were shrunk down to the size of a billiard ball,
it would actually be smoother!

(And a billiard ball is pretty smooth,
in case you didn't know.)