Page 5 - My FlipBook

Deep pressure 1 Make three equal 3 See how the water squirts out
sized holes in the
much farther from the bottom
As you go deeper into the carton, one at the top, hole because of the greater
ocean, the water squeezes one in the middle and pressure.
harder. Submarines can go one at the bottom.
Tape over the holes
down about 0.6 miles (1 km) with sticky tape.
before the pressure begins
to crush them. You can see 2 Place the carton
how pressure increases with in a basin. Fill it with
depth with a plastic bottle water, then pull the
or cardboard carton. sticky tape off quickly
to open the holes.

Tide up
Full moon New moon

Tides are the rise and fall of
the sea that happens twice
Tides are at their most extreme every day. They are caused by
First twice a month, during “spring tides,” the pull of gravity between
quarter when the moon is in line with the sun
moon and they pull together. Earth and the moon. This
stretches the ocean out in
line with the moon, so there
is one high tide on the side
of Earth nearest the moon
and another on the far side.
This tidal bulge moves around
Earth as it turns, bringing high
In between, there are more
Third moderate “neap tides,” when the tides twice daily.
quarter moon and sun pull at right angles.
moon

Why is the sea salty?

The sea is salty because rivers carry the salty parts of dissolved
rock into the sea. Over time, enough salt has washed into the sea
to cover the entire world in salt to a depth of 500 feet (150 m)!

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