hazards resulting from tectonic processes

Question 1

causes of tsunamis

Answer 1

displacement of water triggered by tectonic activity (earthquake or volcanic eruption) or a submarine landslide

Question 2

how do tsunamis rapidly increase in height?

Answer 2

when shallow water is reached, the water is pushed upwards and can reach heights of 25m

Question 3

What changes the impacts of tsunamis?

Answer 3

Height of the waves
distance travelled
Length of source event
warning or no warning
physical geography of the coastline
Coastal land use & population density

Question 4

Distribution of tsunamis?

Answer 4

90% are generated in the Pacific Ocean

Question 5

factors affecting
landslides

Answer 5

moisture content of the land
topography of the land
geology of the land
climate

Question 6

cause of earthquakes

Answer 6

friction along plate boundaries builds up in the lithosphere and when this strength is overcome, they fracture along faults sending a series of seismic shockwaves to the surface

Question 7

types of seismic shockwaves

Answer 7

P-waves
S-waves
L-waves
R-waves

Question 8

Which seismic waves always occur

Answer 8

P-waves
S-waves

Question 9

how do L-waves cause the most damage?

Answer 9

with a side to side movement across the surface

Question 10

why do R-waves need loose material?

Answer 10

for rolling motions to occur from the low frequency

Question 11

measuring the magnitude of earthquakes

Answer 11

Richter scale
Moment magnitude
Mercalli

Question 12

impacts of seismic activity, shaking, can depend upon

Answer 12

population density
magnitude
depth of earthquake
distance from epicentre
design and strength of buildings
education/preparation

Question 13

secondary impacts of earthquakes

Answer 13

flooding
fires
landslides
tsunamis

Question 14

is predicting earthquakes possible?

Answer 14

no, but monitoring is

Question 15

what do you monitor for an earthquake?

Answer 15

Foreshocks - series of minor shocks
Radon gas - decrease sharply before
Groundwater levels - rises before

Question 16

spatial distribution of volcanic hazards

Answer 16

75% on the pacific ring of fire
5% on hotspots

Question 17

hazards and their tectonic boundaries

Answer 17

earthquakes at all
no volcanoes at transform
volcanoes are linear to the boundary, earthquakes have a larger spatial distribution

Question 18

classification of volcanic eruptions

Answer 18

Icelandic
Hawaiian
strombolian
vulcanian
vesuvian
Plinian
pelean

Question 19

features of an Icelandic eruption -

Answer 19

fluid basalt magma
eruption from fissures and mid-ocean ridges

Question 20

features of a Hawaiian eruption -

Answer 20

fluid basalt magma
from single vents in volcanoes

Question 21

features of Strombolian eruption -

Answer 21

less fluid magma and gasses 1km
moderate explosion
frequent activity

Question 22

features of vulcanian eruption -

Answer 22

viscous magma which solidifies fast turning into ash and cinders
violent
ash cloud 5km high and shaped like a cauliflower

Question 23

features of a vesuvian eruption -

Answer 23

viscous magma with a high gas content
violent eruptions sends a wide, 25km tall ash cloud into the stratosphere

Question 24

features of a Pelean eruption -

Answer 24

highly viscous magma
erupts out of weaknesses in the geology
15km ash cloud
pyroclastic flows down the side

Question 25

features of a Plinian eruption -

Answer 25

gas ash and pumice ‘magma’
violent gas explosion
narrow cloud 30km into the stratosphere

Question 26

types of magma flow

Answer 26

Pahoehoe
A’a
Blocky
Pillow

Question 27

how are volcanic eruptions classified

Answer 27

VEI
Volcanic
Explosivity
Index

Question 28

products of eruptions

Answer 28

Nuees ardentes
lava flows
mudflows
pyroclastic flows
ash fallout
gasses/acid rain
tephra

Question 29

what are Nuees ardentes

Answer 29

a dense rapidly moving cloud of hot gasses ashes and lava fragments. a type of pyroclastic flow

Question 30

what is tephra

Answer 30

rock fragments ejected during the eruption

Question 31

how to manage volcanic risk

Answer 31

evacuation
hazard mapping
trenches and walls
observation of gas, temp, deformations, melting of snow % ice, magnetism

Question 32

type of monitoring on the white island volcano

Answer 32

careful as it is capable of erupting violently and frequently
is a tourist destination - day trips
digital cameras are pointing into the crater, which are connected to satellites

Question 33

how is predicting volcanic eruptions not always successful

Answer 33

insufficient action from authorities
lack of compliance with evacuation
unexpected/early
wind direction change

Question 34

Hotspots occur…

Answer 34

due to the radioactive decay in the Earth’s core generating hot spots, which heat the lower mantle and create localised thermal currents where mantle plumes of magma rise vertically

Question 35

how are super volcanoes formed?

Answer 35

when hotspots occur under continents, as the magma gets stuck and pools, melting the rock around for thousands of years. Over thousands of years the pressure builds up and when the eruption eventually happens it drains the magma lake and the land above collapse down over, creating a caldera