Plate boundaries

Question 1

Divergent plate boundaries - what happened + eg

Answer 1

Occur when 2 plates separate due to convention currents rising upwards towards the lithosphere creating endogenic forces
Eg. North America + Eurasian

Question 2

Sea floor spreading

Answer 2

2 plates separate + gap develops between them. Magma rises up through the gap, spilling out as lava hardens+ forms a new ocean floor. As the plates keep moving, the ocean floor widens

Question 3

Mid Atlantic Ridge

Answer 3

Repeated eruptions => chain of underwater volcanoes. Formed between North American+Eurasian plates. 130 mill years old. => Formation of Atlantic. Layers of hardened lava build up+form volcanic mountains/islands

Question 4

Rift valleys

Answer 4

plate is pulled apart by convection currents process =drifting. Land is stretched by endogenic forces, land thins => valley. Crust tears creating a new divergent boundary. Eg. East African Rift valley

Question 5

Convergent plate boundaries - what happens + eg

Answer 5

2 plates collide also known as destructive boundaries as the crust is destroyed. Earthquakes are common
Eg. Indian + Eurasian

Question 6

Types of convergent plate boundaries

Answer 6

Ocean-Ocean
Ocean-Continental
Continental-Continental

Question 7

Ocean-Ocean collisions

Answer 7

The heavier subducts + melts @ 107km, deep ocean trench is formed at the boundary eg. Marianas Trench. As plate melts water vapour+CO2 are released => magma rises+erupts onto ocean floor. Repeated eruptions =>volcanic islands. Eg Phillipines

Question 8

Oceanic-Continental Collision

Answer 8

Oceanic subducts, forming a deep oceanic trench along the boundary. The magma is rich in silica=>thick+pasty =>gas builds up, cant escape + forces magma up through the continental crust before it melts through the surface => volcanic chain w strong eruptions. eg. Nazca+ South American plate + fold mountains

Question 9

Continental-Continental Convergent boundaries

Answer 9

The crust buckles => mountain ranges eg. Eurasian + Indo-Australian form Himalayas. Magma goes through gaps in the crust + cools over millions of years = new rock. Powerful earthquakes cause from the pressure releasing. eg 2015 Nepal 9,000 dead

Question 10

Passive plate boundary eg

Answer 10

San Andreas fault between the Pacific + North American. Both moving west at different speeds

Question 11

Passive plate movement

Answer 11

Jagged layers cause plates to lock together, pressure builds up from endogenic forces, increasing pressure on the rock. Eventually rock breaks causing the plates to jolt forward, triggering earthquakes

Question 12

Ireland’s tectonic journey: key points

Answer 12

Iapetus ocean subducts
Caledonian folding
Sandstone formation
Limestone formation
Armorican folding
Antrim Derry Plateau

Question 13

Iapetus Ocean subduction

Answer 13

Northwest + southeast begin moving together

Question 14

Caledonian folding

Answer 14

Both sections closed from subduction + welded together from pressure forming Caledonian mountain range. Magma rises between folded rocks => Leinster Batholith. Heat from magma + collision => metamorphic rock on peaks, eg. sugarloaf

Question 15

Sandstone formation

Answer 15

Ireland was dessert climate, new Caledonian mountains eroded, sediment washed to sea => sandstone

Question 16

Limestone formation

Answer 16

Sea levels rose, Ireland submerged under tropical sea, fish fossils => limestone

Question 17

Armorican folding

Answer 17

Eurasian + African collide, folded southwest of Ireland. Limestone + sandstone folded => Munster ridge valley

Question 18

Antrim-Derry plateau

Answer 18

North American + Eurasian begin splitting causing intense volcanic activity as lava poured out + contracted into hexagonal squares. eg Giant’s causeway