Weathering, Erosion,
and Plate Tectonics
The creation of Earth’s Face
Questions
► What
forces and phenomena create the
different features of the earth?
► What are tectonic plates?
► What are the three major Types of Plate
Boundaries?
► What are the two external processes that
change the earth’s surface?
► What are the different types of Weathering
and Erosion?
Forces that change the Earth’s
Surface
► There
are two major geological processes
that create features on the earth:
 Faulting and Plate Tectonics
 Weathering and Erosion
► They
both take a long time to change the
earth.
► Remember, nothing drastic on earth
happens at human speeds.
Plate Tectonics
► Huge
volumes of heated and molten rock
moving around the earth’s interior form
massive solid plates that move extremely
slowly across the earth’s surface.
 Tectonic plates: huge rigid plates that are
moved with convection cells or currents by
floating on magma or molten rock.
The Earth’s Major Tectonic Plates
Figure 15-4
The Earth’s Major Tectonic Plates
► The
extremely slow movements of these
plates cause them to grind into one another
at convergent plate boundaries, move
apart at divergent plate boundaries and
slide past at transform plate boundaries.
Figure 15-4
Fig. 15-4, p. 338
JUAN DE
FUCA PLATE
EURASIAN PLATE
NORTH
AMERICAN
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
ARABIAN
AFRICAN PLATE
PLATE
PACIFIC
PLATE
SOUTH
AMERICAN
NAZCA PLATE
PLATE
SOMALIAN
SUBPLATE
CHINA
SUBPLATE
PHILIPPINE
PLATE
INDIAAUSTRALIAN
PLATE
ANTARCTIC PLATE
Divergent plate
boundaries
Convergent plate
boundaries
Transform
faults
Fig. 15-4a, p. 338
Trench
Volcanic island arc
Craton
Transform
fault
Lithosphere
Asthenosphere
Divergent plate boundaries
Lithosphere
Rising
magma
Asthenosphere
Convergent plate boundaries
Lithosphere
Asthenosphere
Transform faults
Fig. 15-4b, p. 338
GEOLOGIC PROCESSES
► The
San
Andreas Fault is
an example of
a transform
fault.
Figure 15-5
Wearing Down and Building Up
the Earth’s Surface
► Weathering
is an external
process that
wears the
earth’s
surface
down.
Figure 15-6
Weathering
► Three
types of weathering:
 Physical
► Big
Rock becomes Small Rock due to wind, rain, and frost
wedging.
► Frost
wedging occurs when water freezes in between the pores
of large sedimentary rocks.
 Chemical
► When
a chemical reaction degrades or decompose rock.
► More common with rocks containing carbon and oxygen, like
limestone.
 Biological
► Conversion
of Rock and Minerals into smaller particles due to
living thing.
► Lichens, Tree Roots, Earthworms.
Parent material
(rock)
Biological
weathering
(tree roots and
lichens)
Chemical
weathering
(water, acids,
and gases)
Particles of parent material
Physical weathering
(wind, rain, thermal
expansion and
contraction, water
freezing)
Fig. 15-6, p. 340
Erosion
► Erosion
is another major external factor that
changes the surface of the earth.
► Erosion is different from weathering
because erosion deposits materials from one
place to another.
► Two major examples of erosion:
 Glacial Movement and Melt
 Mass Wasting
Glacial Movement and Mass Wasting
► Glacial
Movement
 The Movement of Glaciers grind away mountainsides
and form basins to capture melted ice water
 The Great Lakes were formed using this method.
► Mass
Wasting
 When Rock and soil masses become detached from
underlying material and move downhill under the
influence of gravity.
► Rockslides,
Mudslides, and Landslides
 Clearing of Trees and other vegetation increase Mass
Wasting Occurrences.