Tectonic plates move slowly over time, interacting in four main ways: diverging, subducting, converging, and transforming past one another. These interactions cause earthquakes and shape geographic features at plate boundaries like mountain ranges and ocean trenches. Geologists study plate tectonics to understand how these forces continuously reshape the Earth's surface over millions of years through volcanism and seismic activity.

2.  Tectonic plates are massive, moving pieces
of Earth’s lithosphere
 Plates ride above circulating, heated rock
 Geographers study plate movements to
understand:
- how the earth is reshaped
 - how earthquakes and volcanoes are formed
 The largest plates are named after
continents: page 37

4.  Plates move in one of four ways: page 38-39
 Divergent- by spreading, or moving apart
 Subduction - diving under another plate
 Convergent- collision, or crashing together
 Transform- sliding past each other in a
shearing motion

5.  Movement of plates effects surface
of the earth
 Saudi Arabia–Egypt’s plates are
spreading apart, widening Red Sea
 India’s plate is crashing into Asian
continent, building up Himalayas

9.  Peru-Chile Trench

15.  Two plates meeting can cause folding,
cracking of rock
 -Platesmove very slowly
 - Causes rocks to become more flexible and fold
under pressure

17.  Faults occur when pressure causes rock to
fracture, or crack.
-Sometimes the rock is not flexible and will
crack due to plate movement
 The crack is called a fault
 Fault line is place where plates move past
each other

19.  As the plates move past each other at a
fault, the earth shakes or trembles
 This movement may become violent, called
an earthquake

20.  Seismograph
 -Special
device used to detect earthquakes
-Measures the size of the waves created by an
earthquake

21.  Earthquakes release energy in the form of
motion, causing:
- landslides
 - land displacement
 - fires (broken gas lines)
 - collapsed buildings
 Richter Scale — numeric scale showing relative
strength of earthquake
 -Uses info from seismographs to determine the strength of
an earthquake
 -Has no absolute upper limit
 -Major quake measures a 7 or more

23.  Location in the earth where an earthquake
begins is called the focus
 Epicenter — the point directly above focus
on the earth’s surface
- In most cases, the epicenter is the area that
receives the greatest damage
 Nearly 95% of earthquakes occur at tectonic
plate boundaries

25.  Tsunami, a giant ocean wave, begins at
epicenter of an earthquake:
- travels at up to 450 mph
 - waves of 50–100 ft. or higher
 May travel across wide stretches of the ocean
and do damage on distant shores

26.  On March 11, 2011 an 8.9
magnitude earthquake struck
Japan.
 The earthquake and
subsequent tsunami has
caused vast amounts of
damage and the death toll
continues to rise.
 Nearly 16,000 people died as
a result.

27.  On December 26th, 2004, an
earthquake caused by
subduction caused a series
of tsunamis along the
coasts of the Indian Ocean.
 Some waves were said to
be upwards of 98ft. high.
 Killing over 230,000
people, the 2004 tsunami
is the worst natural
disaster in history.

29.  Volcanoes occur
where there are
cracks in the
earth’s surface.
Material, such as
magma, pours out
of the vent.
 Most volcanoes
occur at tectonic
plate boundaries

30.  There are several
types of eruptions—
violent explosions
where lava, gases,
ash or dust are
expelled from the
vent in Earth’s crust
 Lava — magma that
has reached the
earth’s surface; may
create landform

33.  Ring of Fire —
zone around rim of
Pacific Ocean:
- meeting point of
eight tectonic
plates
 - vast majority of
the earth’s active
volcanoes located
here

34.  “Hot spots” are where
magma rises to surface
from mantle
 Hot springs, geysers
indicate high
temperatures in earth’s
crust
 Some volcanic action is
useful:
 - volcanic ash produces
fertile soil
- hot springs are tapped
for heat, energy