plate boundaries

Question 1

divergent plate boundary

Answer 1

volcanoes are present here
lithospheres fractures and magma forcing through asthenosphere to surface via convection currents at mid-ocean ridges
EX - North Atlantic extrusion on magma = largest volcanic island - Iceland

Question 2

rift zones

Answer 2

• volcanic feature
• a set of linear rifts that develop in a volcanic formation
• forming into two or three well-defined regions along the flanks of the vent caused by internal and gravitational stresses generated by magma
• rift zones allow the intrusion of magmatic dykes into the slopes of the volcano itself
• EX - Red Sea, Dead Sea

Question 3

rift valley

Answer 3

• lowland region that forms at divergent plate boundary
• located on land and bottom of ocean via sea floor spreading
• plate being stretched causing cracks in surface and fissure eruption = plateau lava

Question 4

triple junction

Answer 4

• region where boundaries of three tectonic plates meet and interact at 120 degrees
• Rift Valley can be formed here

Question 5

Aulacogen

Answer 5

• failed rift within triple junction
• 2 arms can split causing an entire ocean
  EX Atlantic Ocean = starting point of Gulf of Guinea

Question 6

transform faults

Answer 6

• plates grinding past each other

EX the Salton Trough stretches California = San Andreas Fault

Question 7

landscape formed at a Rift Valley

Answer 7

Horst and Graten

Question 8

sides of Graben

Answer 8

fault scarp

Question 9

African Rift Valley - formation

Answer 9

• divergent plate margin = magma rising and heating crust
• faults and fissures appear allowing gas to escape
• plates move further apart = Rift Valley
• western rift valley -> graben with Tanganyika lake
• central plateau sinks -> Horst with lake Victoria
• eastern Rift Valley -> Kenyan rift (graben)

Question 10

normal faults

Answer 10

• planar / gently curved fracture in the rocks of Earth’s crust
• compressional or tensional forces cause relative displacement of the rocks on the opposite sides of the fracture

Question 11

reverse faults

Answer 11

• same process as normal faults just opposite direction of compression
• Reverse faults occur where two blocks of rock are forced together by compression

Question 12

East African Rift Valley - Afar triple junction in the Afar depression

Answer 12

• Somali, Arabian and Nubian sub plates meet
• elevated heat flows from the mantle = bulges in central Kenya and Afar Region causing fissures / faults = volcanic activity

Question 13

east pacific ridge

Answer 13

Pacific and Nazca plate
flat spreading
16.5cm per year
forms mountain chains, no rift valleys

Question 14

Galapagos Ridge

Answer 14

Nazca and Cocos plate boundary
medium spreading
5-10cm per yr
forms rift valleys and mountain chains

Question 15

Mid-Atlantic ridge

Answer 15

slow spreading
2-3cm per yr
forms: mountain chains and rift valleys

Question 16

convergent boundaries - oceanic - continental margins

Answer 16

• O subduct under asthenosphere = C buckle causing ocean trench - mountains
• O depends between 30-70degrees = increase pressure and friction and release of energy = earthquake
• O during subduction melts due to magma, intrusion of magma = uplift of fold mountains. magma reaches surface = volcano

Question 17

convergent boundaries - O & O

Answer 17

• denser one subduct = ocean trench

- descending plate melts, magma rises = volcanic islands

Question 18

convergent boundaries - C & C

Answer 18

little if any subduction causing mountains eventually

ex - Alps