Global tectonics - Earth's interior, earthquakes and global geomorphology

?
  • Created by: sikemi__
  • Created on: 13-05-21 15:36
What are the differences between continental and oceanic crust?
- Continental is thicker (approx 35km) vs Oceanic (7km)
- Continental is older (approx 2 billion years) vs Oceanic (60 million)
- Continental is less dense than oceanic
1 of 21
Name 5 landforms formed by tectonic processes
- Fold mountains
- Ocean trenches
- Rift valleys
- Ocean ridges
- Island arcs
2 of 21
What are the main types of plate boundaries?
- Divergent
- Convergent
- Transform
3 of 21
How do volcanoes form?
- When one plate moves under another (usually oceanic under continental), creating a subduction zone, high pressure squeezes water out of the rock, lowering the melting temperature of the rock
- Melted rock (magma) rises up as it is less dense than surrou
4 of 21
How do fold mountains form?
- Convergent plate boundary
- Layers of accumulated rock crumple and fold
- Himalayas = newer fold mountains (50 million years ago). These tend to be higher.
- Appalachians = older fold mountains (480 million years). These tend to be smaller as they have
5 of 21
How do ocean trenches form?
- Convergent boundary (oceanic-oceanic or oceanic-continental)
- More dense plate subducts, forming an undersea trench
- Deepest is Marianas Trench (36,000ft below sea level)
6 of 21
How do rift valleys form?
- Called ocean ridges in the ocean
- Continental rift valleys e.g. East African Rift
- Further deepened by erosion
- When the tensional forces are strong enough to cause the plate to split apart, a center block drops between the two blocks at its flanks,
7 of 21
How do ocean ridges form?
- Divergent boundary
- Plates move away from each other due to mantle convection and slab pull, creating new crust as magma rises when the mantle upwells
- When eruptions happen along the boundary, lava builds up to create ridges
- As the plates move, new
8 of 21
How do island/volcanic arcs form?
- Created along a subduction zone, paralleling the trench
- Subducting plate expels water, lowering the melting point and creating magma which collects in chamber
- Eventually the magma ascends, forming a chain of volcanoes
- With island arcs, the lava bu
9 of 21
Name landforms formed at convergent boundaries
- Fold mountains
- Island/volcanic arcs
- Ocean trenches
10 of 21
Name landforms formed at divergent boundaries
- Ocean ridges
- Rift valleys
11 of 21
Name landforms formed at transform boundaries
- Fault lines (build up pressure due to friction creating an earthquake) e.g. San Andreas Fault
- Oceanic fracture zones (form large valleys, or trenches) e.g. Molokai fracture zone
- The Dead Sea Rift represents the combination of a rift (East African) w
12 of 21
What are the 5 types of volcanoes?
- Shield
- Composite cone
- Lava dome
- Cinder and Scoria Cones
- Other (Rhyolitic caldera complexes and mid-ocean ridge)
13 of 21
What are the characteristics of shield volcanoes? Give an example.
- Broad, gently sloping flanks
- Dome shape
- Built almost entirely of layers of solidified basaltic lava flows
- Most feature a central summit vent, and often flank vents, that eject low-viscosity basaltic lava that flows long distances in all directions
14 of 21
What are the characteristics of lava dome volcanoes? Give an example.
- Often form in the craters or on the flanks of composite volcanoes but they can form independently
- When high-viscosity rhyolitic magma flows from composite volcanoes, it solidifies quickly around a vent
- Pressure from magma within the volcano expands
15 of 21
What are the characteristics of composite cone volcanoes? Give an example.
- Steep upper flanks and a symmetrical appearance
- Alternating layers of material such as ash and cinders, blocks and lava deposited by past eruptions
- Also called stratovolcanoes
- Higher risk (explosive)
- Flying rocks and lava bombs, mudslides and su
16 of 21
What are the characteristics of cinder and scoria cone volcanoes? Give an example.
- Simplest and smallest volcano type (usually less than 1000ft)
- Circular cone of hardened lava, ash and tephra around a single vent
- Formed when volcanic material fragments and falls to the ground after being ejected into the air from the vent building
17 of 21
What are the characteristics of rhyolitic caldera complexes and mid-ocean ridge volcanoes? Give examples.
- Ancient volcanoes that erupted so explosively they collapsed into the magma chamber beneath them, forming a giant crater, or caldera (e.g. Yellowstone)
- Mid-ocean ridges are undersea areas along tectonic plate boundaries where the plates are diverging.
18 of 21
What are the different volcano eruption types?
- Explosive (gas-driven explosions that propels magma and tephra)
- Effusive (outpouring of lava without significant explosive eruption)
- Phreatic (heat from magma interacting with water)
- Strombolian and Hawaiian eruptions. (least violent)
- Subplinian
19 of 21
What comes out of volcanoes?
- Magma/lava
- Gas (water vapour, CO2, SO2, hydrogen sulphide). Released through eruptions and fumaroles
- Pyroclastic material (tephra)
- Ash (small grain/glass)
- Bombs
- Lahars
20 of 21
How do hotspots form?
- Hotspot - an area in the mantle from which heat rises as a thermal plume from deep in the Earth
- Magma is formed by melting rock (due to pressure and temperature) and magma rises and erupts to form volcanoes
- As the plate moves over the hotspot, the v
21 of 21

Other cards in this set

Card 2

Front

Name 5 landforms formed by tectonic processes

Back

- Fold mountains
- Ocean trenches
- Rift valleys
- Ocean ridges
- Island arcs

Card 3

Front

What are the main types of plate boundaries?

Back

Preview of the front of card 3

Card 4

Front

How do volcanoes form?

Back

Preview of the front of card 4

Card 5

Front

How do fold mountains form?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all NA resources »