M
AP
A Lot on Our Plates
MAP KEY
Borders of Tectonic Plates
Pacific Ring of Fire
Other Volcanic Activity
Volcanoes occur. But why?
e live on a crust of rock that floats like a raft on the sea of fluid magma.
Make that, floats like rafts, plural. The earth’s crust isn’t one piece. It’s
cracked into a dozen or more pieces called tectonic plates, which are
outlined on the map. Some plates contain both continent and ocean.
Because the fluid mantle underneath is moving, so are the plates. And
when they move, they either bump into each other, pull away from each other,
or scrape past each other. Volcanoes usually occur at the places where two
plates meet and magma under pressure can be squeezed to the surface.
W
DISCOVERY EDUCATION SCIENCE CONNECTION
H OT S POTS
W
N
E
Most volcanoes occur at
the edges of plates, but
some occur in the middle.
Why? The crust is thinner
at certain places, and the
hot magma melts through
like cheese bubbling up
through a crispy crust in a
macaroni casserole. These
places are called hot
spots. Chains of islands
like Hawaii are formed this
way, as the plate keeps
moving over the same
pocket of magma.
S
Hawaiian Islands
R ING
OF
F IRE
The Ring of Fire is a name for the
edges of the Pacific Plate. Along
these edges, plates grind past
each other. When this happens,
one plate dives below the other, a
process called subduction. When
one plate subducts the other,
magma is forced up—and it’s
explosive. There are more
volcanoes in the Ring of Fire than
anywhere else on Earth.
VOLCANO HUNT
Try to locate the famous volcanoes
mentioned on the Almanac pages (16–17) on this map. How
many of them occur at the edges of tectonic plates? Which
ones may be hot spots? Find the countries or regions with
the most volcanoes. Are they at the edges of plates?
DISCOVERY EDUCATION SCIENCE CONNECTION