Plate Tectonics Flashcards
What are the 2 major types of tectonic plates?
- Oceanic plates
- Continental plates
What 3 landforms are created at constructive boundaries?
- Mid-ocean ridges (e.g., Mid-Atlantic Ridge).
- Rift valleys (e.g., East African Rift).
- Volcanoes due to rising magma.
What is the Pacific Ring of Fire? (Mention 2 things)
- A tectonically active zone around the Pacific Ocean.
- Contains 75% of the world’s volcanoes and 90% of earthquakes.
Explain what happens in the destructive plate margin in 5 steps?
- Destructive margins happen when the oceanic plate slides beneath the continental plate.
- Crust is destroyed as one plate dives under another at the subduction zone.
- The rocks catch against each other as the plates are not smooth.
- The pressure between plates builds until the plates can’t take the stress.
- The plates slip past each other, which can cause both plates to move resulting in the ground shaking.
Explain what happens in the constructive plate margin in 5 steps?
- At constructive plate margins, the plates move apart (diverge).
- The convection currents diverge (push apart) and cause a gap between the plates.
- Magma rises up to fill the gap that is created.
- New crust is generated as the plates pull away from each other.
- Rift valleys are created when the crust pulls apart, and land drops to create a valley.
Explain what happens in the conservative plate margin in 5 steps?
- At conservative plate margins, plates are sliding past each other horizontally.
- Crust is neither produced nor destroyed.
- The plates are made of rock that has jagged edges so they catch and snag against one another.
- Friction and pressure between the plates builds until the plates can’t take the stress.
- The plates slip past each other, which can cause both plates to move resulting in the ground shaking.
What are the 4 features of oceanic plates?
- High-density materials.
- Made of basaltic rock.
- Only 7-10 km thick.
- Oceanic plates can sink (subduct) under other plates.
What are the 4 features of continental plates?
- Thicker (25-75 km) than oceanic plates.
- Less dense than oceanic plates.
- Made of granitic rock.
- Continental plates do NOT sink (subduct).
What 4 landforms are created at destructive boundaries?
- young fold mountains (e.g. Himalayas)
- deep sea trenches
- island arcs
- volcanoes
What is a tectonic hazard?
A hazard is a natural/geophysical event that has the potential to threaten both life and property.
What is a hotspot?
An area where a hot plume of magma rises from deep in the mantle.
How do hotspots form volcanic islands in 3 steps?
- It pushes through a weakness in a tectonic plate, forming volcanoes.
- As the plate moves over the hotspot, new volcanoes form, creating a chain of volcanic islands.
- The Hawaiian Islands were all formed by a mid-Pacific hotspot.
How do intra-plate volcanoes form in 3 steps?
- Isolated plumes of convecting heat (mantle plumes) rise towards the surface generating basaltic volcanoes.
- The plume remains stationary, although the tectonic plate above moves slowly over it.
- Continuing plate movement over time produces a chain of volcanic islands, with extinct ones furthest from the plume location.
Give an example of intra-plate volcanoes?
Hawaii
How are intra-plate earthquakes form?
Zones of weaknesses are created as plates move and stresses increase
What are the 4 segments of the earth’s internal structure (in ascending order)?
1) The core
2) The mantle
3) The asthenosphere
4) The lithosphere
What is the core?
The core is the central part of the Earth. It is solid at the centre and more liquid further away. It’s a source of radioactive heat.
What is the mantle?
The mantle is a semi-molten body of rock between the Earth’s crust and its core
What is the asthenosphere?
The asthenosphere is the upper part of the mantle.
What is the lithosphere?
The lithosphere is the crust and upper mantle (80-90 km thick) which form the tectonic plates.
What are the 5 theories of plate tectonics?
1) Wegener’s Continental Drift
2) Holmes’ Hypothesis
3) Sea floor spreading
4) Gravitational Sliding
5) Slab pull
What does Wegener’s continental drift talk about?
In 1912, he said that our now separate continents had once been joined together as a supercontinent (Pangea)
What does Holmes’ Hypothesis talk about?
He said that the Earth’s internal radioactive heat was the driving force of convection currents in the mantle that could move tectonic plates.
What does Sea Floor Spreading talk about (2 facts)?
- In the 1960s, there was a discovery of magnetic stripes in the oceanic crust of the seabed.
- Palaeomagnetic signals from past reversals of the Earth’s magnetic field prove that new crust is created by the process of seafloor spreading at mid-ocean ridges.
