Lecture 6 - Flow Of The Continents Flashcards
Harold William Welllan (1909-1999) as a young geologist what did he search New Zealand for?
Natural resources like Muscovite Mica
Also found in paints, plastics, electronics and cosmetics
When will the next Pangea occur?
+250Ma
What did Wellman do when he travelled NZ?
Mapped major geological structures
Wellman produced a detailed map showing what?
The relationships between faults and earthquakes in the region of New Zealand
What did Wellman think of the topography of Milford Sound, in fiord land of the South Island?
It was the result if major uplift linked to tectonic activity
The marine terraces on the Wairarapa coast, North Island, New Zealand, show what?
The uplift that takes place in response to multiple earthquake cycles
Each raised platform records a large earthquake
Why is there so much seismic activity and uplift across a 250km wide zone in NZ?
NZ lies on the boundary of two tectonic plates, the Australian and Pacific
The USA built listening stations to do what?
Detect nuclear explosions
What is the Comprehensive Nuclear Test Ban Treaty Organisation?
Shows location of nuclear explosions over a timeline
The WSSN (Worldwide Standardised Seismic Network) was able to detect what?
Earthquakes associated with fault movements
Narrow linear fault zones suggest what?
Spreading ridges
Where do more profuse earthquake zones occur?
Around mountain areas
What did Dan Mckenzie and Phillip England ask?
How do continents behave when they collide? And do mountains like the Himalayas behave like fluids or rigid plates?
As you travel north what happens to the topography and geology?
It changes
What is the Tibetan Plateau?
A flat area nearly 2000km wide, average elevation 5km
How did Phillip England attempt to model the Tibetan Plateau?
Using Newtons laws of motion, concepts of fluid behaviour and plate tectonic theory
What had a 6000km journey before it collided with Asia 40-20million years ago?
The India continent
What is the sacred amount Kaliash, 6638m high built from?
Ancient marine sediments once deposited at the bottom of Tethys Ocean which separated India and Asia
What resources can be found where India and Asia collided?
Petroleum
Mineral and metal
Subduction of Tethys ocean allowed what?
The Indian continent to move northwards at 5cm yr and push into Eurasia
How thick was the lithosphere and Indian plate, also continental crust?
100km
How thick was the Eurasain plate?
35km
When mountains flow up what type of root is formed?
And iceberg like roof
Explain 2 things which causes the Tibetan Plateau?
- Material flows upwards then reaches a max height
2. Rather than going higher, Himalayas becomes wider, forming Tibetan Plateau
Fluid mechanics explain a lot about Tibet, but what does it not explain?
Why it is so high
When continents collide and one ate is pushed below, what happens to this plate over time?
More of the lower plate is pushed into the mantle. It is cold and dense. The asthenosphere is hot, less dense and rises so the plate detaches the cold lithosphere.
Detachment of the lithosphere can cause volcanic activity why?
A great weight is lost, so it causes a sudden uplift and fracturing of Tibet, allowing magma to rise and escape.
But as it’s raised to high without support, the mountains collapse and flow away
What happened on October 8 2005?
7.6M Kashmir Earthquake
How many were killed, injured and homeless from the October 8 Kashmir Earthquake?
- 86k dead
- 69k injured
- 4milli homeless
Conclusion: when continents collide they do not subduct but…?
Push to form oreogenic belts or mountains
Conclusion: collision of continents thickens the continental crust, how?
It pushes up as well as down into the athenosphere
Conclusion: as rock is squeezed it will undergo solid state flow, what can this cause?
Part of the lithosphere to detach
Conclusion: what is the result from continents colliding in the Himalayas?
Rapid uplift and formation of the Tibetan Plateau
