Hazardous Environments

Question 1

Definition of a hazard

Answer 1

A physical event that may potentially cause damage to people

Question 2

Definition of risk

Answer 2

Exposure of people to a hazardous event

Question 3

Disaster

Answer 3

The realisation of risk

Question 4

Vulnerability

Answer 4

The susceptibility to loss

Question 5

Describe and explain a divergent plate boundary and the hazards associated (draw diagram)

Answer 5

DIAGRAM draw correctly
- shallow, weak and narrow belt of earthquakes due to weak volcanic activity (basaltic lava, low silica content)
=> harmless at oceanic boundary
- little risk to humans

Question 6

Describe and explain a conservative plate boundary and the hazard associated

Answer 6

DIAGRAM
- shallow and powerful earthquakes
- relatively narrow belt
=> hazardous to human life because human settlements may be in close proximity + they are powerful

Question 7

Describe and explain a destructive convergent plate boundary and associated hazards

Answer 7

DIAGRAM
- deepest and most powerful earthquake
- broader belt of earthquakes
- highly explosive volcanoes(andesitic volcanic eruptions)
=> although there are mountains which may reduce population density, associated risk of landslides and there are likely to be human settlements on the coast

Question 8

Describe and explain a collision plate boundary and associated hazards

Answer 8

DIAGRAM

- shallow, broad zones of seismic activity

Question 9

Types of waves

Answer 9

Body waves: P-waves (fastest and longitudinal) & S-waves (slowest and transverse)
Surface waves: Love waves and Raleigh waves

Question 10

Two seismic scales

Answer 10

Modified Mercalli scale: subjective & qualitative, measure of intensity
Moment Magnitude scale: calibrated measure of energy release, logarithmic scale

Question 11

Three secondary hazards earthquakes + brief explanation

Answer 11

1. Soil liquefaction - loose sand and silt that is saturated with water can behave like a liquid when shaken by an earthquake. Pore water pressure increases so sand grains lose contact with each other. Soil loses its ability to support structures.
2. Mass movements - may be triggered by earthquakes, reducing the shear strength of the slope for a short time period
3. Tsunami - when a large volume of water is instantaneously displaced vertically du to upward or downward movement of the sea bed -> becomes especially hazardous once in increases in height as it approaches the shore with a shallowing sea bed

Question 12

6 types of volcanoes with brief description

Answer 12

1. Fissure volcano - gentle basaltic slope
2. Shield volcano - gentle slope of basaltic lava flows
3. Dome volcano - steep convex slope from thick and fast-cooling lava
4. Ash-cinder volcano - cinder, fine ash
5. Composite volcano - branch pipe (stratovolcano)
6. Caldera volcano - old cone, new cone -> highly explosive

Question 13

7 types of volcanic eruption

Answer 13

1. Pelean eruption - highly viscous magma -> explosion out of weakness in the side of volcano
2. Plinian eruption - very violent explosion resulting in narrower cloud e.g. Mt Pinatubo
3. Icelandic eruption - fluid basalts issue quietly from fissures and mid-oceanic ridges
4. Hawaiian eruption - fluid basalts issue from vents in volcanoes. Gases escape easily and quietly with occasional spurts of gases form lava lakes causing lava fountains.
5. Strombolian eruption - less fluid lava and gases escape with moderate explosions in which lava bombs are ejected
6. Vulcanian eruption - eruptions more violent as more viscous lava solidifies more quickly and traps gases. Tephra released + ash-laden clouds in mushroom shape
7. Vesuvian - high gas content, long periods of inactivity, wide and dark ash cloud

Question 14

Nuees ardentes

Answer 14

Dark glowing, fast-moving, incandescent mass of gas - enveloped particles that is associated with certain types of volcanic eruptions (contain dense lava fragments derived from a growing lava dome) e.g. Martinique 1902

Question 15

Lava flows

Answer 15

Streams of molten rock that poor or ooze from an erupting vent. with speed depending on the… type of lava, viscosity, steepness, width of flow, rate of lava production

Question 16

Lahar

Answer 16

A hot or cold mixture of water and rock fragments that flows down the slopes of a volcano

Question 17

Pyroclastic flows

Answer 17

80/100 km/hr, between 200-700 degrees celcius

Contains a high density mix of hot lava blocks, pumice, ash and volcanic gas

Question 18

Ash fallout and tephra

Answer 18

Fragments of rock that are produced when magma or rock is explosively ejected;
ashes < 4mm, cinders 4-5mm, lapilli are pebble sized, volcanic block are large fragments

Question 19

Steam and poisonous gas emission

Answer 19

Magma contains dissolved gases which provide the driving force that causes most volcanic eruptions - Mt Pinatubo released 250 megatons of gas

Question 20

Characteristics of basaltic lava

Answer 20

Low viscosity, hotter (up to 1200 degrees), lower silica content, associated with frequent but gentle eruptions, found at constructive margins and hotspots

Question 21

Andesitic

Answer 21

High viscosity, less hot (900 degrees), higher silica content, pyroclastic flows likely, destructive margins, infrequent but violent eruptions

Question 22

Aa lava

Answer 22

Free chunks, lava flows rapidly, viscosity increases as heat is lost quickly, up to 10m thick

Question 23

Pahoehoe lava

Answer 23

Smooth surface, slow flow, flows far

Question 24

Factors contributing to increased sheer stress

Answer 24

Undercutting/slope steepening (erosion)
Loading of slope - weight of water, infrastructure etc.
Lateral pressure - water in cracks, subsequent freezing
Transient stress - earthquakes or winds

Question 25

Factors contributing to reduced shear strength

Answer 25

Weathering
Changes in pore-water pressure
Changes of structure
Organic effects - decay of roots, burrowing

Question 26

Scale to measure hurricane magnitude

Answer 26

Saffir-Simpson scale - looks at damage done, working back to estimate wind speeds and height of storm surge

Question 27

Explain the formation of a hurricane

Answer 27

Diagram with detailed annotations
N.B. low pressure area has to be far enough away for the equator so that the coreolis force creates rotation in the rising air mass.
Conditions must be unstable

Question 28

Factors affecting the impact of tropical storms

Answer 28

1. Unpredictability - e.g. Hurricane Charley (2004) hit Florida’s Punta Gorda unexpectedly
2. Strongest storms do not always cause the greatest damage
3. Population distribution
4. Hazard mitigation effectiveness
5. Levels of development

Question 29

4 conditions needed for tornado formation + explanation of formation

Answer 29

DIAGRAM
Moisture, instability, lift, wind shear
- elongated funnels of cloud that descend from the base of a well-developed cumulonimbus cloud
- for a vortex to be classified as a tornado, it must be in contact with the ground and that cloud base
- pressure gradients can reach 25mb per 100m
- wind speeds can exceed 300mph
- most destructive and deadly tornadoes develop from supercells, which are rotating thunderstorms with a well-defined low-pressure system called a mesocyclone

Question 30

Scale to measure size of volcanoes

Answer 30

Fujita scale: F5 = 261-318 mph & 1-3 mile path width

Question 31

Hazards associated with tornadoes

Answer 31

Strength of winds
Strong rotational can twist objects from their fixings
Strong uplift can left debris to great heights
Pressure gradient can result in explosions of walls and glass
Precipitation - hail stones/heavy rainfall is common

Question 32

How many deaths and injuries caused by tornadoes every year in the US

Answer 32

80 deaths, 1,500 injuries