Volcanic eruptions, earthquakes and mountain
ranges are signs that the Earth beneath us is
moving. For example, the Atlantic ridge has
lava coming out all the time because the American
plates are moving away from the African and
European plates. If you look at a map, you will
see that Africa and South America look like they
fit together; this is because they were originally
next to each other and drifted apart.
Volcanic eruptions in mountain ranges (like the
Andes) occur because one tectonic plate is going
under another tectonic plate (subduction zone),
which pushes lava to the surface. The lava is
under a lot of pressure, which is why the
eruptions are so impressive. Oceanic plates
usually go under continental plates, because they
You will also find mountain ranges near
subduction zones (e.g. the Andes, the Rockies…)
because the oceanic plate under pushes the
continental plate upwards.
Earthquakes occur when two tectonic plates slide
against each other. The plates are usually
stationary, but when enough pressure builds up,
they slide violently at areas called fault lines,
causing earthquakes. Our major fault line in
California is the San Andreas fault line.
See this picture:
Click Here to return to the search form.