2019-07-01_Discover

PACIFIC

INDIAN

AUSTRALIAN

EURASIAN

ANTARCTIC

AFRICAN

Somali

Arabian

Burma

Philippine

Caroline

Sandwich

Anatolia

Yangtze

Amurian

Okhotsk

Okinawa

Mariana

Sunda

Balmoral

Reef

South Bismarck

North Bismarck

Manus

Futuna

Niuafo'ou

New Hebrides

Conway Reef

Kermadec

Solomon Sea

To n ga

Timor Molucca Sea

Maoke

Woodlark

Banda Sea

JULY/AUGUST 2019. DISCOVER 41

TRANSFORM:

Where plates slide

past each other

horizontally; also

called fracture

zones because

the stress typically

causes splintering

into numerous

faults, or fractures.

Example: San

Andreas Fault.

DIVERGENT:

Where plates pull

apart, stretching

and often splitting

open the crust;

this allows magma

to seep up. The

magma cools,

creating new

crust. Examples:

Mid-Atlantic Ridge,

East African Rift.

MAJOR PLATE

Minor Plate

Microplate

Convergent

Subduction

Divergent

Transform

Select hotspots

(small and large)

Direction/speed of

movement

(longer arrows indicate

PLATE BOUNDARY faster moving plates)

ZONES: Where

multiple plates

meet in complex,

often poorly

understood areas

of activity that

don’t fall neatly

into one of the

other categories.

These zones

involve larger

plates and one or

more microplates

that may be

both squished

and stretched

between them.

Other Activity

HOTSPOTS: These areas of volcanic

activity often exist thousands of miles

from the nearest plate boundary. Below

the solid lithosphere, thermal plumes in

the semiliquid asthenosphere send out

heat energy so intense that it melts the

plate above it, allowing magma to seep up

through the crust and sometimes reach the

surface. For decades, geologists thought

the plumes’ positions were fixed, and that,

as the plates above them continue to move,

they create arcs of volcanoes. However,

newer research hints that the plumes

B themselves may also be able to move.
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MAP KEY