Download Transform Boundary

 We know the Earth is broken into 8 major lithospheric
plates ….
 We know these plates move ….
 We know there are boundaries between the plates ….
 Now, let’s look at the three types of boundaries in a
little more detail . . .
 Lithosphere: Earth’s hard outer shell; divided into plates.
 Diverging Plate Boundary: Plates are moving apart as new ocean
crust is formed ~ most divergent boundaries are found in the
ocean.
The African and Arabian plates continue to rift apart (diverge),
with the result that the Red Sea is ever widening.
 Convergent Plate Boundary: Plates moving
together/toward each other. Can be subduction or
collision; subduction results in the formation of
oceanic trenches.
 Andes Mountains: Mountain range on the west coast of
South America resulting from the collision of two
continental plates.
 Transform Boundary: Plates sliding past each other.
(San Andreas Fault)
 Subduction/Subduction Zone: Type of convergent
boundary; one plate slips under another plate.
 Plate boundaries can be found using page 5 of
your ESRT . . .
 [Seek and ye shall find!]
 The west coast of South America is a subduction
zone.
 The Nazca Plate (oceanic & more dense ~ 3.0g/cm3)
is sliding under the South American plate (less dense
~ 2.7g/cm3).
 Earthquakes occur at the boundary between the
plates – the earthquakes get deeper as the plate slips
farther under . . .
Cross Section of Subduction Boundary
( km below surface)
0
100
200
300 Oceanic Crust  
3
400 3.0 g/cm
(Nazca Plate)
500
 (South American Plate)
Continental Crust
2.7 g/cm3
Depth of
Earthquakes
A
*


B
* = Shallow
 = Intermediate
= Deep
As we move
along the line
from A (west) to
B (east), the
depth of the
earthquakes
increases. as
oceanic plate
subducts (goes
below) under
continental plate.
Cross Section of Subduction Boundary
( km below surface)
0
100
200
300 Oceanic Crust  
3
400 3.0 g/cm
(Nazca Plate)
500
 (South American Plate)
Continental Crust
2.7 g/cm3
Earthquake depth increases moving
east where the Nazca and South
American plates converge.
2. Earthquake depth increases because
the Nazca Plate is subducting under
the South American Plate.
3. The Andes Mountains have formed
on the west coast of South America
as a result of a convergent collision
boundary.
1.
4. Most divergent plate boundaries
5.
6.
7.
8.
are found in the oceans.
The San Andreas Fault is a
transform boundary.
A subduction zone is found at a
convergent boundary.
New oceanic crust is created at a
divergent boundary.
Oceanic trenches are associated
with convergent/subduction
boundaries.
 Divergent boundaries form when two plates are
moving away from each other and result in the
formation of ridges.
 Convergent boundaries occur when two plates are
moving toward each other; can be subduction
(forming a trench) or collision (forming mountain
ranges).
 Transform boundaries move horizontally past each
other.