Transcript Did you know?

Plate Tectonics and
Continental Drift
Tectonic plates
 large, solid pieces of the Earth’s lithosphere
that are continuously moving in different
directions atop the asthenosphere
Did you know?
 All of the
Earth’s crust –
even the bottom
of the oceans –
are sitting on
tectonic plates.
Did you know?
 There are about
seven major tectonic
plates, and several
minor plates.
 We are on the North
American plate.
Pangaea
 A large, ancient supercontinent, composed
of all continents joined together
Did you know?
 Pangaea broke up in
stages, first breaking
into smaller
supercontinents
including:
 Laurasia
 Gondwanaland
Convergent boundary
 boundary between two tectonic plates that
are moving toward each other
Did you know?
 Volcanoes are common
along convergent
boundaries.
 A circle of volcanic
zones called the Ring
of Fire surrounds the
Pacific Plate on
converging boundaries.
Did you know?
 Convergent
boundaries are
DESTRUCTIVE
because old crust at
plate edges is
destroyed and
recycled as they
come together.
Divergent boundary
 boundary between two tectonic plates that
are moving away from each other
Did you know?
 Divergent
boundaries are
CONSTRUCTIVE
because this is
where we find
Earth’s youngest
crust.
Did you know?
 There is a HUGE
divergent boundary
running down he
middle of the ocean
floor in the Atlantic
Ocean.
Transform boundary
 boundary where two tectonic plates slide
past each other horizontally
Did you know?
 Transform boundaries
are commonly active
earthquake zones.
 Southern California has
about 10,000
earthquakes each year
(most too small to feel).
Theory
 A possible explanation that is supported by
a large amount of evidence
Did you know?
 The Theory of
Continental Drift
proposed by Alfred
Wegner only dates
back to about 1912.
Did you know?
 Fossils of the
same species of
plants and
animals can be
found on different
continents.
Convection currents
 circular movement of
heating, rising, cooling,
and sinking molten
material in Earth's
mantle transfers heat
that results in the
movement of tectonic
plates
Did you know?
 You can also find
convection
currents in
The air
The oceans
Lava lamps
Subduction zone
 A convergent
boundary where one
tectonic plate slides
under another
tectonic plate
Did you know?
 Subduction zones
often produce
volcano chains
offshore or along
the coast of a
continent.
 Example: Ring of
Fire around the
Pacific Ocean including the west
coast of the US
Sea Floor Spreading
 Hess's theory that
new seafloor is
formed when
magma is forced
upward toward the
surface at a midocean ridge
Did you know?
 Sea floor
spreading
happens at ocean
floor divergent
boundaries.
Did you know?
 Sea floor spreading
happens at a rate of
about 5 cm each year.
Continental Drift
 Wegner's hypothesis
that all continents
were once
connected in a
large, single
landmass that broke
apart about 200
million years ago and
drifted slowly to their
current positions
Did you know?
 In the future,
another
supercontinent
may form as
continents run into
each other again.
(millions of years
from now)
Earth’s Future
Supercontinent???