Types of plate boundaries Flashcards
What happens at a DIVERGENT plate boundary?
Two plates are moving away from each other.
What landforms are present at an oceanic vs oceanic divergent plate boundary?
- Mid Ocean Ridge
- Island/volcanic arcs
What hazards occur at an oceanic vs oceanic divergent plate boundary?
- Effusive volcanoes
- Shallow, low magnitude earthquake occur frequently
What landforms are present at a continental vs continental divergent plate boundary?
-Rift Valley
How are rift valleys formed?
- Crust stretches and breaks into two sets of parallel faults
- Land between faults collapse and form the valley.
What hazards are present at a continental vs continental divergent plate boundary?
Shallow, low magnitude earthquakes.
What happens at an oceanic vs continental CONVERGENT plate boundary?
- Two plates move towards each other
- Thinner, denser oceanic plate is subducted beneath continental plate
- Plates get put into a locked fault.
What landforms are present at an oceanic vs continental convergent plate boundary?
- Deep ocean trench
- Fold mountains
- Volcanoes
What hazards are present at an oceanic vs continental convergent plate boundary?
- Explosive volcanic eruptions
- High magnitude earthquakes occur a long Benioff Zone
Why do volcanoes form at an oceanic vs continental convergent plate boundary?
Magma created from melting oceanic plate pushed up through faults in continental crust to reach surface.
What happens at an oceanic vs oceanic CONVERGENT plate boundary?
The denser or faster oceanic plates subducts below the other.
What landforms are present at an oceanic vs oceanic convergent plate boundary?
- Deep ocean trench
- Underwater volcano
What hazards are present at an oceanic vs oceanic convergent plate boundary?
- Effusive volcanic eruptions
- Low or high magnitude earthquakes occur a long the Benioff zone.
What happens at a continental vs continental CONVERGENT plate boundary?
Plates collide and sediments between them are crumpled and forced up.
Why doesn’t one plate subduct at a continental vs continental convergent plate boundary?
Both plates are the same density and are less dense than the asthenosphere.
What landforms are present at a continental vs continental convergent plate boundary?
- High plateau (high, flat land)
- Fold mountain range
What hazards are present at a continental vs continental convergent plate boundary?
Shallow, high magnitude earthquakes.
What happens at a CONSERVATIVE plate boundary?
Two plates are sliding past each other, parallel to one another.
What hazards are present at a conservative plate boundary?
High magnitude, shallow earthquakes.
What is the global distribution of earthquakes?
- Oceanic fracture zones
- Continental fracture zones
- In continental interiors, a long old fault lines
What is the global distribution of volcanoes?
- Majority occur a long plate boundaries (depends on which type)
- Form on Hot Spots
What is a hotspot volcano?
- Occur in areas where the earth’s crust is thinner.
- Magma rises from mantle and burns through the plate
What are the layers of the earth?
Inner Core: Solid, Temp up to 5500c, Made up of Iron and Nickel, 1220km thick
Outer Core: Liquid, Made up of iron and nickel, 2200km thick, Temp from 4500c to 5500c
Mantle: Thicket section of Earth (2900km), Made up of semi-molten rock, called magma. Temp from 1000c to 3700c
Crust: Solid rocks and minerals, Solid, 5km-10km thick, Temp from 200c-400*c
What was James Hutton’s plate theory?
The processes of erosion, deposition and uplift were connected and operated continuously- driven by the Earth’s internal heat.
What was Alfred Wegner’s plate theory?
Discovered a concept called continental drift
What was Harry Hess’ plate theory?
He proposed that ridges on the ocean floor were the result of molten rock rising from the asthenosphere
What was John Tuzo Wilson’s plate theory?
He proposed that volcanic island chains are created by fixed hotspots
What is seafloor spreading
Process of new crust pushing tectonic plates a part
Formed when hot magma is forced up from the asthenosphere and hardens, forming new oceanic crust
What is Mantle Convection
Heat produced by radioactive elements in the Earth’s core heats the lower mantle
This creates convection currents
Hot liquid magma currents move in circles in the asthenosphere, causing plates to move
Heat rises, cools and falls
What is paleomagnetism
Every 400,00 years or so, earths magnetic fields changes direction
Magnetic N and S swaps
When lava cools and becomes rocks, minerals inside rock line up with earths polarity at the time
Thus moving the plates
What is subduction
Process of a plate being destroyed
Two oceanic plates or oceanic and continent plate move towards each other, one becomes subducted, sliding into the mantle
This then melts
What is slab pull
Newly formed oceanic crust at mid-ocean ridges becomes denser and thicker as it cools
Causing it to sink into mantle under its own weight, pulling the rest of the plate down with it
What are primary ‘P’ waves?
- Body waves (travel through earth’s rock)
- 8km/sec (fastest)
- Travel in both solid and liquid
- Move in backwards and forwards motion
- Only damaging in the most powerful earthquakes
What are secondary ‘S’ waves?
- Body waves
- 4km/sec (medium)
- Only travel through solids
- Move in up and down motion, perpendicular to direction of travel
- Do more damage than P waves
What are love ‘L’ waves?
- Only travel on earth’s surface
- Slowest of three waves
- Move in side to side motion
- Large and cause the most damage
How do scientists predict earthquakes
- No method at accurately predicting one
- However, we can use knowledge of plate boundaries to forecast when one might occur
- Scientists often focus on precursors, e.g. foreshocks
What are the layers of the earth?
- Mantle
- Crust
- Inner core
- Outer core
What are the characteristics of the mantle?
- Thickest section of the earth
- 2900km thick
- Made up of magma (semi-molten rock)
- Temp 1000C to 3700C (near boundary to core)
What are the characteristics of crust?
- Made up of solid rocks and minerals
- 5km to 10km thick
- Temp 200C to 400C
What are the characteristics of inner core?
- Solid
- Made up of iron and nickel
- 1220km thick
- Temp up to 5500*C
What are the characteristics of outer core?
- Liquid
- Made up of molten iron and nickel
- 2200km thick
- Temp 4500C to 5500C
