Topic 1 - Tectonic Processes And Hazards Flashcards
How many tectonic plates are there in total?
52 (7 main major tectonic plates and 8 main minor tectonic plates)
Name the 7 major tectonic plates.
African plate Antarctic plate Eurasian plate Indo-Australian plate North American plate South American plate Pacific plate
Name the 8 main minor tectonic plates.
Nazca plate Philippine plate Caribbean plate Cocos plate Arabian plate Juan de fuca plate Scotia plate Indian plate
Name examples of micro plates.
Somalian in East African Rift Valley
Sundar in Indonesia
Iranian and Iberian in the Middle East
How was the earth formed and differentiated into layers?
- Dust condensed out of solar nebula (hydrogen and helium clouds) through accretion
- Dust particles started to assemble into larger particles through electrostatic attraction creating large enough object to have own gravity = primitive earth (homogenous mixture)
- As planetesimals (small pieces of matter) crashed into primitive earth, motion energy converted to heat and radioactive elements disintegrated spontaneously releasing energy which was absorbed by surrounding matter and converted to heat
- Melting of earth due to heat brought lighter (H and He) materials to outer layers of earth and brought interior heat to surface where it could radiate into space
- Earth started to cool and solidify (oldest rock first e.g. Granite)
- Melting initiated escape if lighter gases from interior leading to formation of atmosphere and oceans
- Interior of earth melted to ‘soft’ state in which components moved around with heavy material e.g. Iron sinking to centre and lighter material floating upward towards crust
- This is called differentiation
How do you layout an answer to a describe question?
Use PDA
P - pattern - state the pattern that you are asked to describe
D - detail - include examples and data from the source given
A - anomalies - state the anomalies that don’t fit the pattern you are asked to describe
Oceanic to Continental Convergence (Destructive plate boundary)
- Explain the tectonic activity.
- oceanic plate and continental plate converge (move towards each other)
- denser oceanic plate subduct beneath less dense continental plate where it partially melts and becomes molten in subduction zone
Oceanic to Continental Convergence (Destructive plate boundary)
- State the landforms and activity.
Landforms:
Fold mountains (sedimentary and metamorphic rock)
Ocean trench
Volcanic arcs
Composite volcanoes
Activity:
- Shallow, intermediate and deep focus earthquakes along wadati Benioff zone with 8-9 magnitude
- Composite volcanoes (700km from trench) with andesitic magma with explosive infrequent eruptions VEI scale of 5-6
Oceanic to Continental Convergence (destructive plate boundary)
- Name examples for this plate boundary.
- Andes (fold mountains)
- Peru-chile ocean trench (Nazca plate subducting under South American plate)
- Japan 2011 earthquake and tsunami (magnitude 9 with focus 24km deep)
Oceanic to oceanic Convergence (destructive plate margin)
- Explain the tectonic activity at this plate margin.
- Two oceanic plates converge (move towards each other)
- the older, cooler and denser plate is subducted beneath younger more buoyant plate
- older plate partially melts due to hydration melting
- subduction causes low density floor sediment to accumulate off surface of ocean floor and thrown into beach - obduction
Oceanic to oceanic Convergence (destructive plate margin)
- state the volcanic activity and landforms.
Landforms: Bathymetry - obduction Volcanic island arc Wedges (accretionary) Oceanic trench Back arc and fore arc zones Activity: - shallow to intermediate foci earthquakes with moderate to high magnitude of 7-9 - composite volcanoes due to hydration melting
Oceanic to oceanic Convergence (destructive plate boundary)
- state examples for this plate boundary.
- Montserrat 2010 and 1995 eruptions
- Caribbean Islands (island arc)
- Aleutian Islands (island arc)
Continental to Continental Convergence (collision plate boundary)
- Explain the tectonic activity.
- two Continental plates converge (move towards each other
- both have equal buoyancy so neither subduct
- pressure and force causes plate sediment to be forced upwards to buckle into anticlines and synclines
Continental to Continental Convergence (collision boundary)
- state the activity and landforms.
Landforms: Fold mountains Activity: - typically shallow focused earthquakes with moderate magnitude 6-8 - no volcanic activity as no subduction
Continental to Continental Convergence (collision boundary)
- state examples for this boundary.
Himalayas mountains (fold mounstains) Eurasian and indo- Australian plate margin
Gujarat, India earthquake 2001
Sichuan, China earthquake 2008
Divergent (constructive) plate boundary
- explain the tectonic activity.
- Two plates of the same type diverge (move apart) due to conversion currents and buoyancy force
- known as sea floor spreading
- symmetrical alignment
Divergent (constructive) plate boundary
- state the activity and landforms.
Landforms:
Ocean ridges with Rift Valley and faulting at right angles
Volcanic arc
Underwater mountains
Activity:
-shallow focus earthquakes with low magnitude of 5-6
- volcanoes due to decompression melting made from basaltic lava with low VEI of 1-3 (effusive)
