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Transcript
Lab 06
ONLINE
LESSON
1
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3
Do take notes as we
peruse through this
lesson…
4
Plate Tectonics
5
Plate Tectonics is a
geologic idea that states
the surface of the planet is
covered by a series of
rigid plates that move…
6
These plates move
away each other
7
These plates move
toward each other
8
These plates move
past each other
9
Plate Tectonics is driven
by heat within the interior
of the planet…
10
A current theory suggests
that radioactive materials are
the source for the earth’s
internal heat…
11
This heat melts the
surrounding rock
12
Melted rock (magma)
rises to the surface and
pushes the plates…
13
There are three types
of plate boundaries
14
Divergent,
Convergent and
Transform
15
Divergent boundary: the
plates move away from
each other
16
Convergent boundary:
the plates move toward
each other
17
Transform boundary: the
plates move past each
other
18
A transform boundary:
cuts across a divergent
boundary…
19
A divergent boundary
is also referred to as
a spreading center,
such as the Mid
Atlantic Ridge…
20
A divergent boundary
is a part of the earth’s
surface where new
crust is formed…
21
A convergent
boundary is also
known as a
subduction zone…
22
Subduction is the
process of pushing
seafloor crust into the
interior of the
planet…
23
A convergent
boundary is where
crust is destroyed and
massive earthquakes
occur…
24
A transform boundary
is also known as a
fracture zone or
fault…
25
The San
Andreas Fault
is a well
known
transform fault
in this area…
26
27
Earthquakes occur at
all of these
boundaries because
solid rock is moving
against solid rock…
28
The bigger
earthquakes occur at
the convergent and
transform
boundaries…
29
But small and shallow
earthquakes can
occur at transform
and divergent
boundaries…
30
Shallow earthquakes
occur at divergent
boundaries because
the crust is thin…
5 -10 km thick…
31
The following is a
map of many
divergent, convergent
and transform
boundaries…
32
33
Plate Tectonics can
be thought of as a
grand unifying theory
in geology…
34
Meaning that many
geologic phenomena
are associated with
Plate Tectonics
35
And can be explained
by Plate Tectonics
36
At convergent
boundaries …volcanoes,
earthquakes and
mountains and deep sea
trenches can be
formed…
37
Right click to play
38
Also at convergent
boundaries …the deepest
earthquakes occur
39
Subducted seafloor is
pushed into the interior of the
planet….
40
As much as 650 kilometers
41
At divergent
boundaries …heat,
volcanoes,
earthquakes and new
seafloor can be
formed…
42
43
Since new seafloor is
formed at the divergent
boundaries…the notion of
seafloor spreading can
also be observed…
44
Seafloor crust is made
primarily of iron rich (MAFIC)
minerals
45
These MAFIC minerals are
subject to the earth’s
magnetic field…
46
Magma rises up from the
interior of the planet…
47
And punches through the
ocean crust to form new
crust…
48
The newly formed MAFIC
crust can record the
prevailing magnetic field
49
The earth’s magnetic field
has changed direction over
the course of the life of the
planet
50
North has become south and
the other way around…
51
These magnetic reversals
have been recorded in the
seafloor crust
52
These records can tell us
such things as the rate of
movement of the plates…
53
Each recorded event is a
time marker…
54
The newest crust is at the point
where magma rises from the
interior of our planet…
55
The older crust is further
away…
56
Oceanic crust as old as
200,000,000 years old can
be detected…
57
How can spreading rates be
determined from magnetic
reversals?
58
Here is a section of the
ocean floor’s magnetic
reversals…
59
Seafloor spreading begins
here…
60
And ends up here…
61
The distance of seafloor
movement is read here…in
this case…1425 kilometers…
62
The time is read here…in this
case…78,000,000 years…
63
Spreading rates are always
noted in
cm/year
64
1425 km = 142,500,000 cm
142,500,000 cm
78,000,000 years
65
So the spreading rate is
1.83 cm/year
66
Hot Spots are places
on the planet where
magma rises up to
produce pinpoint
volcanic eruptions…
67
There are about 40 hotspots
on the planet…
68
A hotspot can be described as a
plume of magma rising up and
punching through the crust…
69
The Hawaiian Islands are an
example of a hotspot…
70
The hotspot plume is currently
under the main island of
Hawaii…
71
The Pacific Plate is moving
northwest…
72
The plates move while the plume
is stationary…
73
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END
L06
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