teacher’s notes
Earth’s crust: thinner
than you think
Learning objectives:
that the Earth's crust is a tiny fraction of the
Earth’s radius
Timing: 20 minutes (less if the extension
calculation activity is not done)
Use a postage stamp stuck on the surface of a
football (or similar size balloon) to demonstrate
how thin the Earth’s crust is
The average thickness of the crust is 35 km below
continents, 6 km below oceans (plus 5 km of sea
water). The maximum thickness of the crust is
about 90 km, below the Himalayas. The average
crustal thickness is around 15 km.
Extension activity
Learning objectives:
problem solving
numerical skills
the use of effective models to aid
understanding of an idea
Pupils use the fact that the radius of the Earth
averages about 6400 km and the crust 15 km to
work out the thickness of a postage stamp.
Alternatively, they may use a micrometer to
measure the thickness of the postage stamp and
devise a method for measuring the radius of a
football to check whether this analogy is valid.
Pupils could discuss the use of models such as
this in science education as an aid to learning and
understanding.