HAZARDS 3 - Plate Margins and Magma Plumes

Question 1

What are constructive plate margins? (divergent)

Answer 1

Where two plates move away from one another e.g. North American and Eurasian plate e.g. Iceland

Question 2

What are destructive plate margins? (Convergent)

Answer 2

Where two plates move towards each other e.g. West Coast of SA

Question 3

What is a conservative plate margin? (Transform)

Answer 3

Slide past each other e.g. Pacific plate + NA plate

Question 4

What is a magma plume?

Answer 4

localised thermal currents in the mantle that rise vertically > hot spots

Question 5

What is seismicity?

Answer 5

Earthquakes

Question 6

What is vulcanicity?

Answer 6

Volcanic activity

Question 7

What are the two features of constructive plate margin features and what do they entail?

Answer 7

1. Mid-ocean ridges > pushed up magma
2. Rift valleys
   - continental divergence, formed when the lithosphere stretches (fracture into sets of parallel faults)
   - land between collapses into deep wide valleys

Question 8

Types of destructive plate boundaries and their features?

Answer 8

1. OCEANIC + CONTINENTAL
   - deep ocean trenches + subduction zone + benioff zone
2. OCEANIC + OCEANIC
   - denser or faster plate subducts
   - Benioff zone creates sub-marine volcanoes along the plate boundary
3. CONTINENTAL + CONTINENTAL (collision)
   - sediment uplifted to form fold mountains
   - friction > ‘sticking’ > shallow focus

Question 9

What are the exceptions to the rules of volcanic activity?

Answer 9

Hot spots + magma plumes where the crust is thin (localised)