volcanic hazard assessment IV

Question 1

can volcanism be influenced by climate change?

Answer 1

probably in some places (young field of study)

Question 2

what is a glacial pump?

Answer 2

volcanism increases in response to deglaciation ad isostatic rebound
water melts rock, increasing temperature, decreasing pressure

Question 3

what is isostatic pressure?

Answer 3

decreasing the pressure (2 - 3km thick ice sheet pushing down on the crust and depressurizing the mantle)

Question 4

what are subduction zone (arc) climate volcano interactions?

Answer 4

arc volcanoes comprise most of subaerial volcanism
more subdued response

Question 5

if you have multiple eruptions, what can happen during volcanic-climate interactions?

Answer 5

positive feedback

Question 6

how frequent were eruptions in the cook inlet region?

Answer 6

consistent patterns of tephra deposition at the 13 different sites: deglacial peak subdued, then large peak (sulphate)

Question 7

quaternary glacial-interglacial transitions are paced by?

Answer 7

milankovitch cycles

Question 8

what are milankovitch cycles?

Answer 8

changes in earth’s obliquity (tilt), precession and eccentricity control the solar energy distribution (amount) on earth’s surface

Question 9

are milankovitch cycles strong enough to push earth in and out of glaciation alone?

Answer 9

no! these energy changes cause a series of positive feedback that start the actual transition into/out of glaciation

Question 10

what are positive feedbacks?

Answer 10

reinforce each other, enhancing the initial change, and many feedbacks encourage CO2 cycling, must remove CO2 to counteract

Question 11

what happens as glaciers grow on land?

Answer 11

sea level drops, which makes it easier for hot spots to reach surface

Question 12

what is the evidence of milankovitch cycles?

Answer 12

enhanced volcanic eruption frequency (flux) at ocean spreading centers and hotspots during and/or after glaciation

Question 13

what is opposite to terrestrial volcanism?

Answer 13

volcanism timed slightly differently (peak after deglaciation rather than prior)

Question 14

what are some volcanic challenges?

Answer 14

• lots of people live within 100km of an active volcano
• some countries deal with volcanic hazards regularly
• many countries with the highest population exposure to volcanic hazards are also developing nations that struggle to address hazard mitigation
• challenges with prediction, planning, and funding
• populations increase and people occupy more space around volcanoes

Question 15

what is the problem with volcanoes?

Answer 15

low probability, high consequence

Question 17

how can we manage the risk of volcanoes?

Answer 17

1. study geological record
2. monitoring
3. modelling and experimentation

Question 18

how do we establish eruption histories?

Answer 18

mapping tephra, pyroclastic flows, lahars and lava flows

detailed mapping of tephra is the most critical in determining eruption frequency and magnitude

Question 19

how is the volume of erupted tephra calculated?

Answer 19

isopach maps

Question 20

what does reconstruction of past volcanic activity provide information on?

Answer 20

likely hazards of any one volcano, how active the volcano has been, and may be going forward

Question 21

what are some typical signs that magma is moving at greater depths include?

Answer 21

1. elevated CO2 emissions (CO2 exsolves from magma at depth and can ascend faster than parent magma)
2. deep long period earthquakes
3. aseismic inflation caused by magma accumulation
4. changes in water chemistry and thermal output

Question 22

what are some signs that magma has entered shallow storage areas only a few km beneath the surface?

Answer 22

1. inflationary ground deformation increases (as magma accumulates in an underground reservoir before an eruption, the ground surface typically swells)
2. volcano-tectonic seismicity (frequency of earthquakes caused by magma)
3. ground cracking, glacier melting, increased spring discharge and thermal output
4. significant sulfur degassing (removal of dissolved gas from liquids)
5. at “wet” volcanoes sulfur gases may change from hydrogen sulfide, to sulfur dioxide emissions (groundwater driven off by rising magma and other soluble gas species like halogens are detected)
6. phreatic explosions (steam-driven explosions that occur when water beneath the ground or on the surface is heated by volcanic activity. water, once heated, begins to boil or can even flash straight to steam, causing an explosion.)

Question 23

what are some of the key monitoring equipment?

Answer 23

seismometers, tiltmeters, GPS, gas monitoring stations, airborne surveys, remote space and aircraft sensing

Question 24

why is modeling of volcanic phenomena critical?

Answer 24

limited observed events to learn from
need computer modeling, AI, machine learning and probabilistic

Question 25

what are computer models fundamental for mapping out?

Answer 25

ash-fall modelling

Question 26

what are event trees?

Answer 26

data and various models combined together to increase out ability to make informed predictions

Question 27

what are some features of emergency plans that are in place?

Answer 27

1. escape routes
2. warning systems (sirens)
3. downloadable maps

Question 28

mount st. helens eruption showed us the importance of?

Answer 28

understanding how the landscape will respond to disaster