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Transcript of Plate Tectonics
Faults and Folds
Sites of high tectonic activity
Ring of Fire
Major Task (see hand out for details)
Up to 1880, the earth's surface was considered to have been the same since it was created.
This was associated with the idea that the earth was flat and the sun and stars revolved around the earth.
By the 1900s, evidence was found that the continents were moving.
In 1912, Alfred Wegener proposed an explanation - the theory of continental drift
Wegener suggested that at one time, all the continents were joined together in a super continent called Pangaea.
Later it was understood that the earth was made up of distinct slabs of land called 'plates'.
It was discovered that these plates moved over molten crust - the Theory of Plate Tectonics was developed.
Fossils of the same organism found on different continents
Go here for an animated example: http://www.suu.edu/faculty/colberg/hazards/platetectonics/18_Pangaea.html
The Indo-Australian Plate
Sea floor spreading shows similarities either side of a mid -ocean ridge
650 million years in under 2 minutes
including 250 million years into the future!
Separation of Africa from Saudi Arabia is causing the formation of rift valleys (in red).
This is splitting the land open
Movement by convection current
Plate slip and slide (transform)
Simple summary of convection current
Nice summary of plate motion
The plates move on a bed of molten lava
The lava causes the mantle above it to expand and move to the surface.
It then cools and moves back towards the center of the earth creating a convection current.
A convection current with dye in water
Watch the lava move inside an active volcano
...which are thicker (up to 60km thick), lighter and found under...continents!
...which found under oceans, are thinner (up to 5km thick), denser and younger than...
This is what happens when they slide past each other
Continental plates consist of two types of crusts
Two tectonic plates may be separated by upwelling magma
This video is about the separation of the Juan de Fuco and Pacific plates.
This is how the mid-Atlantic ridge is formed
It is the point where the African and South American plates separate
Occurs when two tectonic plates collide into each other.
If one of the plates is an oceanic plate,
The oceanic plate sinks below the continental plate.
If both plates are continental plates (e.g. the Indian and Eurasian plates,
(e.g. the Himalayas) are formed.
The formation of the Himalayas
A satellite view of the Himalayas
Plates that slide past each other are a significant cause of earthquakes.
One of the best know examples of this is the San Andreas Fault in California.
Here it is from the air.
As the plates that make up the Earth’s crust slowly move, solid rock is pushed, pulled, bent and twisted.
The earth's layers are under tremendous pressure and often fold up or down as a result.
Five minute video giving good overview of plate tectonics and how they explain the San Andreas Fault.
Two minute video showing animations and examples of folds.
Sometimes rocks crack as a result of the huge forces acting on them. Once movement occurs along a crack, it is called a
The Gulf region of South Australia has been formed by a series of faults.
Gulf St Vincent
What a fault looks like:
If you have time go here: https://sarig.pir.sa.gov.au/Map for an interactive map showing South Australias fault lines.
(Go to Map Layers window, then Seismic lines)
Although Australia sits in the middle of the Indo-Australian plate, it does have many fault lines.
The Adelaide region is one of the most active in Australia.
Notice the link between tectonic boundaries and the presence of volcanoes (red)
Major earthquakes also occur at or near the plate boundaries.
of an earthquake is directly below the surface where the movement began
The whole Pacific ocean is surrounded by the edges of the North American, Nazca, Pacific, Indo-Australian and Eurasian plate (see
The region is called the Ring of Fire because of the significant number of volcanoes and earthquakes (locations marked in
An example of the destruction that occurs with in the Ring of Fire.
Recent seismic activity in the Australian region. Why not in Australia itself?
Volcanoes are formed when molten rock, or magma, from the Earth’s mantle bursts through a weakness in the Earth’s crust.
Note the difference between magma and lava.
Here is a list of the volcanoes in South Australia and when they last erupted.
The 10 most active volcanoes in the world
Active volcanoes also erupt under the sea. An active volcano below the sea is generally not visible. If layers of lava build up, however, they may eventually emerge from the sea as a volcanic island.
The formation of the Hawaiian Islands
Earthquakes result from movements in the Earth’s crust up to 700 kilometres below the surface.
These movements cause vibrations or tremors on the Earth’s surface.
Direction of movement of crust near California
When the tremors are sudden and strong, they are called earthquakes.
The destructive power of an earthquake in any location also depends on its distance from the epicentre.
: 6.7 on the Richter Scale
Place: Tennant Creek, Northern Territory Population: 3,000
Damage: two buildings and a pipeline
Distance from epicentre: 40 kilometres
: 5.6 on the Richter Scale
Place: Newcastle, New South Wales
Population: 250,000 +
Damage: 13 people killed, 160 injured, damage to 300 buildings
Distance from epicentre: 5 kilometres
"I was on the counter at the time. The first one came along and felt like a vibrating road roller coming down the road.
"It just got worse and worse and a couple of ceiling tiles fell down and one of the women screamed and I can appreciate what panic is all about because all the people just bolted the front doors.
"We didn't really realise what was happening until after it was over. The first one lasted for a good minute, it seemed like a year.
Workers repair the gas pipeline
Although there is not much in the way of seismic activity in Australia, the tectonic plate that we are on is moving by 7cm per year in the direction shown in the arrows.
Volcano, Mount Unzen, Japan, 1991.
Earthquake, Mexico, 1985
Earthquake and Tsunami, Japan, 2011
S-E Asian Earthquake and Tsunami, 2004
Earthquake, New Zealand, 2011
Volcano, Mt Tungurahua, Ecuador, South America, 2008.
Age of the earth's crust -
red is young
blue is old
Go here: (http://www.ga.gov.au/earthquakes/ ) to see a list of the most recent earthquakes in Australia.
Alternatively, go here (http://www.pir.sa.gov.au/minerals/earthquakes/recent_earthquakes_in_sa )to see a list of the most recent tremors in South Australia.
Movements are recorded onto a
Here is a
ment on the Earth's surface.
This is a seismograph for a recent 3.2 Earthquake in the Adelaide Hills (28 September 2012)
Earthquake strength is measured on the Richter Scale.
Nice interactive showing how different levels on the Richter Scale result in different amounts of damage.
Go here: http://www.iknowthat.com/mhscience/Earthquakes/earthquake_movie.html
Earthquakes in SA from 1885 to 1984
Size of blue dot indicates magnitude
This simulation shows the formation of tsunami waves and their characteristics as they approach land.
Footage of the 2011 Japanese Tsunami
A map of the Pacific 'ring of fire'
Earthquakes occurring under the water or near the coast can cause giant waves called
piers, columns or posts
Single diagonal bracing
Inverted "V" bracing
Focus on framework
spaghetti - cheap, easy to use
plastic straws - more expensive, stronger
skewers - strongest, most expensive
Tester / Builder
Your responsibility is to ensure that members of the group are taking part and fulfilling their role. You are responsible for identifying any issues to the project manager (your teacher) and overseeing all decisions made by the group.
You are responsible for your group’s account and purchasing of building materials. You must ensure that your budget will fund your design, and your money is spent appropriately on materials actually required.
You are responsible for testing your group’s different designs and assisting in determining what materials to use. You are also responsible for putting your group’s final design into action!
You will be assessed on:
your ability to identify and solve problems
the process you use to make decisions
your ability to involve each team member in the design/testing/evaluation processes.
Identify the problem
Choose designs which might solve the problem
Decide on potential solution
Decide what building materials to use
Build and test your design - modify it if necessary.
Present it to the rest of the class
Evaluate the results
It’s time to put your hard hat and steel caps on!
You have been hired to begin reconstruction of a location that has recently been devastated by an earthquake of magnitude 6.7.
Luckily there were no fatalities or serious injuries; however there was extensive structural damage to buildings.
You have been hired to design and construct a multi-story building that is earthquake proof, which would increase the chances of survival of the building and the occupants.
You are required to work with a team of people to create this Earthquake resistant multi story building. This building must meet the needs of the people living in the geological hotspot (of your choosing).
You have been given an allocated budget of $300,000 for this building project. You are also restricted to the size that your building can be.
The maximum dimensions are listed below:
Base can be no bigger than 20cm by 20cm
Height must be no less than 100 cm tall and of at least four stories high.
Excellent video showing the largest shake table in the world.
More detailed story here: https://www.windows2universe.org/earth/geology/movies/earthquake_testing_nsf.html
This includes the building methods they used.
Nice simulation of plate movement
What about other solutions:
Simulation of mountain formation using sand.
Go here to move the plates: http://www.geo.cornell.edu/hawaii/220/PRI/PRI_PT_contdrift.html#
The link below is a Google Maps view of 1300 volcanoes around the world. They have been active in the last 10,000 years.
NOAA video on all Earthquakes around the world from 2000-2015. Note big earthquakes in South-East Asia in late 2004 and near Japan in 2011.