Download plate tectonic theory p.point

PLATE TECTONIC THEORY
BBC - Learning Zone Class
Clips - New Zealand - plate
tectonics theory - Geography
Key concepts:
1. Continental drift
2. Paleomagnetism.
CONTINENTAL DRIFT
• BBC - Learning Zone Class Clips Investigating the Great Glen Fault –
Geography
CONTINENTAL DRIFT
http://www.wwnorton.com/colleg
e/geo/egeo/flash/2_1.swf
• Plate tectonics animation
• http://videos.howstuffworks.com/search.ph
p?media=video&terms=continental+drift
More detailed info on
continental drift and
paleomagnetism
• The above concepts led to the theory of SEA
FLOOR SPREADING. This then led to the
development of SUBDUCTION! All of these
need CONVECTION CURRENTS generated in
the Earths mantle to work!
• HowStuffWorks Videos "100 Greatest
Discoveries: Sea Floor Spreading"
PLATE MOVEMENT
• There are 7 major plates and many more minor
plates. As a result of convection currents they
move towards, away from or sideways along
adjacent plates. It is at these plate boundaries
that most of the worlds major landforms occur
and where earthquake, volcanoes and mountain
building take place.
• http://www.as.uky.edu/academics/departments_
programs/EarthEnvironmentalSciences/EarthEn
vironmentalSciences/Pages/default.aspx
RULES OF PLATE
TECTONICS
• 1. Continental crust does not sink because of its relatively low
density and so it is permanent. Whereas oceanic crust does sink
and is continually being formed and destroyed.
• 2. Continental plates, such as the Eurasian Plate, may consist of
both continental and oceanic crust.
• 3. Continental crust may extend far beyond the margins of the
landmass.
• 4. Plates can not overlap.Either they are pushed upwards to form
mountains or downwards into the mantle and destroyed.
• 5. No gaps may occur so if plates are moving apart new oceanic
crust must be formed.
• 6. If new oceanic crust is being formed, elsewhere it must be
destroyed.
• 7. Plate movement is slow, but usually continuous.
• 8. Most significant landforms are at boundaries.
Major landforms at plate boundaries.
TYPE OF PLATE BOUNDARY
CHANGES OCCURING
EXAMPLES
CONSTRUCTIVE(spreading or
divergent)
Plates move apart new oceanic
crust appears forming midocean ridges with volcanoes.
Mid-Atlantic ridge and East
Pacific Rise.
DESTRUCTIVE (subduction
zones, convergent)
Oceanic crust moves towards
continental crust and being
heavier sinks and is destroyed
forming deep sea trenches and
island arcs with volcanoes.
Nazca sinks under South
American Plate (Andes)
Juan de Fuca sinks under North
American Plate (Rockies)
Island arcs of the West Indies
and Aleutians
Indian collided with Eurasian
forming Himalayas.
African collided with Eurasian
forming Alps.
COLLISION ZONES
2 continental crusts collide and
are forced up into fold
mountains.
CONSERVATIVE
2 plates move sideways
San Andreas fault in
past each other. Land is
California
neither formed or destroyed.
Note: centres of plates are
a..Shield lands,
b. Depressions on edges of
the shield.
rigid (exception of a rift
Canadian shield
Amazon.
CONSTRUCTIVE MARGINS
• 1. OCEANIC PLATES = Mid-Oceanic
Ridges. Plates pull apart and new oceanic
crust appears. Such as the Mid-Atlantic
Ridge and the East Pacific Rise.
• 2. CONTINENTAL PLATES = Rift Valleys.
Plates pull apart in continental areas, such
as East Africa. The Red Sea was formed
as a result of this movement.
CONSTRUCTIVE PLATE
MARGINS
• ICELAND
Tectonic landforms on Iceland
•
VOLCANOES: Kerio( see photo), Hekla(signs that eruption is iminent, eruptions
every 4-5years). Katla and Eyjafjallajokull(2010 ash eruption, little lava). 36 volcanic
systems, fissures up to 500m long, extrude lava.
•
EARTHQUAKES: 2008 epicentre near Selfoss, 6.6 on R.scale. 40 houses in Selfoss
condemned, no fatalities. Fault line unzipping west from Hekla. Several earthquakes
occur every day on Iceland.
•
HOT SPRINGS, MUD POOLS AND GEYSERS:Strokkur geyser(photo), spouts every
4-5 minutes.Blue Lagoon is a geothermal lagoon in the middle of a lava field.
•
RIFT VALLEY:Thingvellir.(photo)Plates diverging leaving fissures and lava flows.
Subsidence of the grabon has created the largest natural lake in
Iceland(thingvallavatn).
•
•
BASALT CLIFFS: Vik.
Black, basalt beaches.South of Mt. Reynisfjall
East African Rift Valley
Iceland,s seismic setting.
• 2010 eruptions of Eyjafjallajökull Wikipedia, the free encyclopedia
• See p.point of Icelandic volcano.
• WHY DID THIS HAPPEN?
• BBC News - Could another Icelandic
volcano erupt soon?
DESTRUCTIVE PLATE MARGINS
•
•
•
•
•
•
Where 2 plates converge or collide.
Oceanic crust can not override continental crust and is forced to dip downwards at an
angle to form a subduction zone and its associated deep sea trench.
Earthquakes are triggered and heat generated by friction converts the crust back into
magma. This is less dense than the mantle and so rises to the earths surface. If it
reaches the surface produces volcanoes. Fold mountains are formed or, if offshore
Japan or the West Indies, as an island arc.
Destructive margin:
http://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es
0902page01.cfm?chapter_no=visualization
Fold mountain building:
• http://www.classzone.com/books/earth_science/terc/content/visualiz
ations/es1105/es1105page01.cfm?chapter_no=visualization
•
http://videos.howstuffworks.com/science/convergent-plate-boundaries-videosplaylist.htm#video-5933
CONSERVATIVE PLATE
BOUNDARY
SUMMARY OF PLATE MARGINS.
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es0804/es
0804page01.cfm?chapter_no=visualizatio
n
Types of volcanic material
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es0905/es
0905page01.cfm?chapter_no=visualizatio
n
• Use sheets to discuss the different types
of volcanic lava. They have implications
for the types of volcanoes produced.
HOT SPOTS!
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es0904/es
0904page01.cfm?chapter_no=visualizatio
n
• Video of how they happen!
• http://videos.howstuffworks.com/science/h
ot-spots-videos-playlist.htm#video-29183