Plate margins

Question 1

Seismicity

Answer 1

the frequency, intensity, and distribution of earthquakes in a given area

Question 2

volcanicity

Answer 2

the process through which gasses and molton rock are either extruded on the earth’s surface or intruded into the earths crust

Question 3

Constructive plate boundary

Answer 3

• Plates moving apart

- eg Mid-Atlantic ridge

Question 4

Mid-Atlantic ridge

Answer 4

• 7000km long

- Iceland lies on it, observe volcanoes and high temperature waters

Question 5

Features found at a constructive plate boundary

Answer 5

• MOR
• Rift valley e.g African Rift valley
• Oceans form in them eg Red Sea
• Continental crust, thinned by erosion, cools contracts and sinks beneath the sea eg Atlantic ocean

Question 6

Destructive plate boundary

Answer 6

Two plates colliding

Question 7

Oceanic- oceanic convergence example

Answer 7

Japan, Mt. Fuji

• slower plate carried downwards
• basaltic oceanic plat melts
• Melted minerals separate and rise
• magma erupts at the surface
• Volcanic islands created
• Metamorphasised rocks create island

Question 8

Oceanic- continental convergence example

Answer 8

The Andes, Nazca sub ducts under S. American

• same process
• more explosive volcanoes as silicic magma creates rhyolitic volcanoes
• large batholiths also form due to melted continental crust
• Fold mountains form due to compression of continental crust
• High mountains with deep roots created

Question 9

Continental-continental convergence example

Answer 9

Himalayas, India sub ducts under Asian
-shallow and intermediate earthquakes created
-subduction stopped due to no difference in density, plates crumpled together
-Fold mountains created instead
Subduction zone sank beneath collision zone without first feeding volcano
-Granite batholiths created as base of continental crust melted due to its thickness

Question 10

Conservatize plate boundary

Answer 10

Two plates slide laterally past each other
eg San Andreas Fault
-No subduction
-Shallow focus earthquakes
-Creeping movement of plates
-1906 last big earthquake (8.6 on richter scale) (700 killed)

Question 11

San Andreas Fault

Answer 11

• 1300km long
• 5cm movement annually
• East pacific plate moves North West
• North American plate moves West North West

Question 12

Fissures

Answer 12

lines of weakness in plates which allow magma to rise

Question 13

Where do the most explosive volcanoes occur

Answer 13

Convergent boundaries due to the greatest pressure

Question 14

Types of Lava

Answer 14

Basalt, Andesite, Dacite, Rhyolite

• Decreasing mobility
• Increasing viscosity
• Increasing silica content
• Decreasing eruption temperature

Question 15

Volcano classification

Answer 15

• Fissure
• Shield
• Composite
• Acid or Dome
• Caldera

Question 16

Minor landforms

Answer 16

• Geysers
• Hot springs
• Boiling mud pools
• Fumaroles

Question 17

intrusive landforms

Answer 17

• Plutons (sills and laccoliths)
• Dikes
• Batholiths