TECTONICS - everything else

Question 1

what is a divergent plate margin?

Answer 1

• divergent plates move apart
• make new land
• cause holes where magma spits through the crust
• gentle volcanic eruptions which have runny lava rather than explosive lava

Question 2

what is another name for a divergent plate margin?

Answer 2

constructive

Question 3

how are divergent plates formed?

Answer 3

convection currents cause the plates to move apart

- as they move the magma wells up from the mantle to form new plate

Question 4

Explain the processes that take place at divergent plate boundaries (4)

Answer 4

Divergent plate boundaries are when two plates move away from each other. The plates move due to convection currents in the mantle. The movement can cause a gap called a mid-oceanic ridge. Magma rises to fill the gap, thus creating new land. Where magma builds up above the surface of the ocean, volcanic islands form. If a constructive (divergent) margin is found on the land a rift valley will be formed.

Question 5

what is a destructive plate margin for continental and oceanic and how is it formed?

Answer 5

• dense oceanic plate subjects under the continental plate (becomes subduction zone)
• magma rises due to convections currents and heat
  then rises through the cracks in the continental crust
• pressure builds and may cause volcanic eruption
• as plates such together continental is squashed and forced upward
• creates fold mountains
• lava solidifies to create volcano

Question 6

what is a destructive plate margin for continental and continental and how is it formed?

Answer 6

• When continental plates collide head on with other continental plates, the result is upheaval!
• Similar densities – neither plate is subducted
• Gradual forward movement of each plate creates extreme pressures= earthquakes
• Over time, the rock strata (layers) become folded, and rise to create mountain ranges

Question 7

what is the conservative plate margin and how is it formed?

Answer 7

when plates move oppositely or at different paces/angles
• As the plates slide horizontally past each other pressure builds up in the rocks either side of the fault
• Fault surface often rough – friction creates large strains along the faults
• An earthquake happens when the built up pressure and energy are released in a sudden, jerky movement

Question 8

how do you define what type of volcano it is?

Answer 8

activity levels

   - Active: have erupted in the last 80 years
- Dormant: resting but may erupt in the future 
- Extinct: dead and will not erupt again

Question 9

what are characteristics of a shield volcano?

Answer 9

• broad peak
• wide long slopes
• runny lava
• gentler eruptions
• gentle slopes
• on a constructive plate boundary

Question 10

what are characteristics of a composite volcano?

Answer 10

• cone shape, steep sides
• has main vent and secondary vents
• big lava flow of andesitic sticky magma
• volcanic bombs, so flying rock etc
• ash cloud
• has alternate layers of ash and lava
• violent eruptions

Question 11

difference between andesitic and basaltic magma

Answer 11

• andesitic is lower in temp, more acidic and very sticky

- basaltic is high in temp, non-acidic and very runny and fluid

Question 12

what is another name for a composite volcano ?

Answer 12

stratovolcano

Question 13

where are shield volcanoes found?

Answer 13

divergent plate boundaries

Question 14

where are composite volcanoes found?

Answer 14

convergent, where oceanic plate subducts

Question 15

what is another name for convergent plate boundary?

Answer 15

destructive - oceanic and continental

Question 16

what is an earthquake?

Answer 16

• a violent shaking of the earths crust

Question 17

how are earthquakes measured?

Answer 17

• They are measured by something called the Richter scale, this is based on the energy levels or the strength (table to the side)
  
  • The Mercalli scale measures how much damage is caused by the earthquake based on observations, it basically measures its impact on people.

Question 18

how is The Richter scale used?

Answer 18

Open ended scale indication the strength of an earthquake measured by a seismograph, its an actual scientific measurement.

Question 19

how is the Mercalli scale used?

Answer 19

• A scale from roman numerals 1 -12, used to indicate the impact and effects of an earthquake.

Question 20

why do earthquakes and volcanoes cause more damage in LEDC’s than MEDC’s?

Answer 20

• LEDC’s dont have resources to cope
• bad buildings and infrastructure
• no buildings regs
• poverty
• government has little money to deal with it
• MEDC’s have more resources, more stable government etc
• have building regs and better things

Question 21

what is the focus of an earthquake?

Answer 21

• point at which the rock moves

Question 22

where do the seismic waves of an earthquake start?

Answer 22

start at the focus

Question 23

what is the epicentre of an earthquake?

Answer 23

directly above the focus on the earth’s surface

Question 24

what are management techniques for volcanoes and earthquakes?

Answer 24

prediction and preparation

Question 25

how do they predict a volcano?

Answer 25

volcanologists

• seismometers
• thermal imaging
• gas samples and sensors

Question 26

how do they prepare for a volcano?

Answer 26

detailed planning

• exclusion zones
• evacuation
• basic provisions
• good communication systems

Question 27

how do they predict earthquakes?

Answer 27

they aren’t easy to predict

- they can measure the vibrations and plate movement but its still not super reliable

Question 28

how do they prepare for an earthquake?

Answer 28

• training people, earthquake drills
• emergency kits
• earthquake proof buildings
• roads and bridges that are earthquake proof

Question 29

what increases as the river progresses?

Answer 29

discharge
channel width 
channel depth 
velocity 
load quantity

Question 30

what decreases as the river progresses?

Answer 30

load particle size
bed roughness
gradient of the river