The Relationships Between Plate Boundaries and Tectonic Landforms

1
The Relationships Between Plate Boundaries
and Tectonic Landforms
2
The earths surface is covered with a variety of
wonderful and interesting landforms
Island arcs
Volcanoes
Mountains
3
And valleys bordered by steep cliffs,
Just to name a few!
4
How did these landforms originate?
How does it relate to our dynamic, changing earth?
These are questions that curious and analytical
scientific minds have only really been able to
answer in the last 40-50 years!
5
Courtesy of pictures from NASAs website
Earth from Space http//earth.jsc.n
asa.gov/land.html
We are going to take a Virtual Tour of the
Earth to explore these Tectonic Landscapes and
put into real-world context what we have
learned in class.
6
But first a review An important modern theory
about the forces that drive plate tectonics is
that the plastic, partially melted asthenosphere
is undergoing convection. This movement of
materials below the earths lithosphere is
thought to be causing the plates of the earths
lithosphere to move too!
7
As you have learned, where there is upwelling of
the asthenosphere, the crust above spreads apart,
and new material from below bulges up into
ridges. Where there is subsidence of the
asthenosphere, the crust is being pulled down
along with it to form depressions, or trenches.
This can be visualized superbly in this diagram.
8
This movement of the astheno-sphere causes the
lithosphere plates to be pulled apart or pushed
together! This creates the different plate
boundaries, which in turn creates the landscapes
we see on earth today!
9
Lets review the 3 types of plate boundaries we
have discussed so we can better understand the
pictures we are about to see.
10
Plate Boundaries
1. Divergent Where tension forces are pulling
the earths plates
apart. (where plates move
away from each other)

• Convergent Where compression forces push
  the earths plates together
• (where plates crash into
  each other)

• Transform Where shearing forces cause the
  earths plates to slide
  past each other.
• (where plates rub against each other in opposite
  directions)

11
How do scientists know where plate boundaries
are, and of what type?
By studying where the earth is under stress.
How do scientists know where the earth is under
stress?
By identifying where earthquakes are and how deep
they are!
12
Shallow earthquakes are found along divergent,
transform, and rift boundaries, and where
continental crust is colliding.
Deep earthquakes are found along what kind of
zones?!



13
O.K.! Enough Review! Lets take off and look at
some real-life landforms!
Our first stops will take us to CONVERGENT
boundaries.
Stop 1 Oceanic crust colliding into oceanic
crust
14
COUNTDOWN.
5
4
3
2
1
15
LIFTOFF!!!!
16
We are going to fly over Alaska and the Aleutian
Islands
What features should we be looking for?
Aleutian Islands
17
Unimak Island
18
Unimak Island
19
Turn to page 5 in your Earth Science Reference
Tables
What tectonic feature do you see associated with
the Aleutian Islands?
20
(No Transcript)
21
Volcanic Island Arcs are associated with
trenches!
Why is this so?!
22
Stops 23 Oceanic crust colliding with
continental crust
23
We will be visiting the state of Washington in
order to view plate tectonic features that
resulted when the Juan de Fuca Plate (oceanic
crust) collided with the North American Plate
(continental crust.) Based on the map to the
right, and in the next slide, what features
should we be looking for?
24
(No Transcript)
25
Cascade Range, Washington
26
Mount Rainier
27
Mount Saint Helens
28
A similar situation exists in western South
America, but the plates involved are different.
What plates are involved in this collision
between oceanic and continental crust?
29
Now were off to Chile and Peru to check out the
landforms there!
Stop 3 South America
30
Chile
31
(No Transcript)
32
(No Transcript)
33
Look at your reference table again. What feature
do you see on the west side of South America that
is associated with convergent boundaries and the
subduction that results?
What is probably happening to the asthenosphere
here?
34
Stop 4 Continental crust colliding with
continental crust
What features do we expect to find here?
35
Were off to Southeastern Asia, one of the best
places to observe this type of plate boundary!
China
India
Nepal
36
Himalayas
India
China
37
(No Transcript)
38
Mount Everest 29,035 feet tall!
(8850 meters)
39
Use your reference table to determine what plates
are colliding to form the Himalayas.
40
Now we have reached the second part of our
journey
Stops 56
Exploring DIVERGENT boundaries
41
A flight over part of Africas Rift Valley will
demonstrate this.
42
First, find the East African Rift on your
reference table and determine what plate the rift
is found on.
43
Here are some volcanoes from the Rift
Valley. Knowing this is a divergent zone, what
type of lava will extrude from them?
Steep cliff of rift valley
Lengai Volcano
44
(No Transcript)
45
And here are some dramatic pictures of the lava
from these volcanoes!
46
(No Transcript)
47
And now to explain how rifting can form
volcanoes AND large lakes
48
The uprising asthenosphere here has caused
tension forces which have pulled apart the
continental crust.
..and magma coming from the spreading center can
form volcanoes!
The brittle crust has fractured and a section in
the middle has downfaulted into the developing
gap (rift.)
Water filled into the gap, creating a freshwater
lake.
There are two stunning examples of this in
Africa!
49
Stop 5 Malawi, Africa
50
Lake Malawi
51
And next to Tanzania
52
Lake Tanganyika
53
And the last part of our journey Stop 7 A
TRANSFORM BOUNDARY
Were still in AfricaZimbabwe this time!
54
Movement that occurs along a transform boundary
Transform
55
Where is the evidence for a transform fault in
this area of Zimbabwe?
56
(No Transcript)
57
And our final stop
A PASSIVE CONTINETNAL
MARGIN
58
(No Transcript)
59
Greenlawn
60
In Summary
Wait a secondIm tired from all this running
around and being a tour guideyou do it!!!
1. What are the three main plate boundaries?
Describe the movement at each.
2. How does each plate boundary affect what type
of landscape results? Give specific examples for
each one!
3. Explain how the asthenosphere drives plate
tectonics.