Volcanoes and Earthquakes - Exam

Question 1

Types of eruptions

Answer 1

Effusive / Explosive

Question 2

Effusive eruption

Answer 2

Less violent than explosive, due to free-flowing basic lava such as basalt

Question 3

Explosive eruption

Answer 3

Violent due to the build-up of pressure within the volcano / Tend to have viscous lava such as andesite, which can block the volcano vent.

Question 4

Characteristics of explosive eruptions:

Location, Type of lava, Style of eruption, frequency, materials erupted, Shape.

Answer 4

Location:
Convergent

Type of lava:
Acidic, high viscosity

Style of eruption:
Bursts of gas bubbles when magma reaches surface, highly explosive and can explode vent + top of cone leaving caldera

Frequency:
Low frequency, doesn’t occur often.

Causes:
Gas, Dust, Ash, Lava bombs, Tephra, pyroclastic flow.

Shape:
Steep sided stratovolcanoes, caldera volcanoes.

Question 5

Characteristics of effusive eruptions:

Location, Type of lava, Style of eruption, Materials erupted, Shape.

Answer 5

Location;
Divergent plate boundaries

Type of lava:
Non-acidic, low viscosity

Style of eruption:
Gas bubbles can expand freely, limited explosive force.

Material erupted:
Gas, lava flows, minimal ash

Frequency:
Tend to be more frequent than explosive, may continue erupting for months / years

Shape:
Gently sloping sides, Shield volcanoes, due to the lava plateauing from the multiple fissures and cooling

Question 6

Super-volcano:

What it is,
Example and size.

Answer 6

Super-volcanoes are volcanoes which erupt more than 1,000km^2 in a single eruption event. They tend to exist in calderas formed from past explosions, such as that of Yellowstone.

Question 7

Yellowstone:

Answer 7

VEI = 8 (heighest)

Last eruption = 70,000 years ago

Size / scale of eruption = Deposits found as far away as the gulf of Mexico, ash spread across the world.

Type of volcano - Super-volcano lying on a caldera, 30miles wide, 1,000 feet deep

Location = NA plate, Pacific plate, convergent.

1% chance of erupting in the next 100 years

Question 8

Montserrat CS

Answer 8

VEI 4

Size:
Small-sized stratovolcano

Last explosion date:
June 15, 1995

Distance of farthest deposits:
Up to 10 miles

Fault type:
Convergent

Plates:
Caribbean Plate / Atlantic plate.

Timeline:
The eruption began at 10:00 a.m. local time on June 15, 1995.
The eruption lasted for about 12 hours.
The eruption produced a plume of ash and gas that reached up to 20 miles high.
The eruption caused widespread damage on the island of Montserrat, including the destruction of homes, businesses, and crops.
The eruption forced the evacuation of more than 10,000 people from the island.
There were 19 deaths as a result of the eruption.

Question 9

Eyjafjallajokull CS

Answer 9

VEI 4

Size:
Medium-sized stratovolcano

Last explosion date:
April 14, 2010

Distance of farthest deposits:
Up to 2,000 miles
8km high ash, lower stratosphere, caught by jet stream

Type of explosion:
Phreatomagmatic eruption
First effusive, then explosive
Under the Eyjafjallajokull glacier, which blocked volcanic vents, meted, then fell into vent, causing explosive eruptions.

Fault type: Divergent (constructive)
Plates: Eurasian Plate, Atlantic plate
Located at the mid-atlantic ridge

Question 10

Montserrat, who was effected?

Answer 10

Inhabitants, 10,000 evacuated;
The city of Plymouth was destroyed, and the entire Island had to evacuate up north. During the period of eruption, the area of plymouth and the lower half of the island was no-go zone. As after the evacuation at first there was no direct threat, people went back into the city, which proved deadly; 19 people were killed by the pyroclastic flow.

Question 11

Eyjafjallajokull, who was effected?

Answer 11

100,000 flights delayed / cancelled globally.
In the UK, approx. 1000 from Heathrow cancelled / delayed
Cost industry £1.1 Billion.

The state funeral of President of Poland Lech Kaczyński and his wife Maria Kaczyńska on 18 April 2010 was affected as some national leaders were unable to attend, including Barack Obama, Stephen Harper, Angela Merkel, and Nicolas Sarkozy.

The average temperature in the Northern Hemisphere was about 0.2 degrees Celsius cooler than average during the months following the eruption.

Tourism increased following the eruption; 559,000 in 2010, 1.39 million in 2015.

Farmers in the area received more bountiful crops due to mineral rich deposits from the volcanic ash on their land.

Tourist centre was open from 2011-2017;
Displayed video footage from the explosion
Displayed volcanic rocks / geology
visitor tour around the volcanic area
Educated visitors of the history of volcano
Also increased local economy due to visitor spending

Question 12

Hazards posed from volcanoes

Answer 12

Lava flows
Pyroclastic flows
Tephra
Toxic gasses
Lahars
Floods
Tsunamis

Question 13

Lava flows

Answer 13

Basic lava (basaltic) can run for several kilometers.

Acidic lavas, are thick, rarely flowing far.

Lavas destroy everything in their way, although slow moving, so mainly infrastructure / property destroyed, mot many killed.

Question 14

Pyroclastic flows

Answer 14

Hot gas (500*c+), ash and rock fragments travelling at high speed (100km/h+) following the shape of the ground.. Devastating anything in their path.

Caused the death of 19 in Montserrat in Plymouth.

Question 15

Tephra

Answer 15

Any material ejected from a volcano, ranging from a fine ash to large volcanic bombs (6cm across), potentially very hazardous.

Question 16

Toxic gasses

Answer 16

Causes breathing problems; Gases released during eruption, such as sulfur dioxide, carbon monoxide, co2. Also causes acid rain, crop failure and pollution in soil and water.

Question 17

Lahars

Answer 17

Mud flows often including larger rocks and boulders with the consistency of wet concrete. Can travel up to speeds of up to 50km/h. Destroys everything in its path.

Question 18

Floods

Answer 18

Floods can be caused due to phreatomagmatic eruptions, like in Iceland 2010

Question 19

Tsunamis

Answer 19

Very rare to have been caused by a volcano… Reach up to speeds of 500-600mph

The 1883 eruption of Krakatoa in Indonesia: The eruption of Krakatoa caused a series of tsunamis that reached heights of up to 135 feet (41 meters). The tsunamis killed over 36,000 people and destroyed coastal towns and villages in Indonesia, Malaysia, and Singapore.

&

The 1991 eruption of Mount Pinatubo in the Philippines: The eruption of Mount Pinatubo caused a tsunami that reached heights of up to 65 feet (20 meters). The tsunami killed over 800 people and destroyed coastal villages in the Philippines.

Question 20

Types of hazards generated by Earthquakes

Answer 20

Ground shaking / Land Displacement
Landslides
avalanches
liquefaction
Tsunamis

Question 21

Effect of Ground shaking / Land displacement as consequence of earthquake

Answer 21

Dependent on:

Distance from epicentre
Severity of earthquake
Geology in the area

In Nepal 2015, 300,000 homes were destroyed by the shaking; Over 22,000 injured overall and 8,000 killed.
This was due to the non-earthquake proof buildings in Nepal, which were not resistant to the Earthquake; 80% homes destroyed.

Question 22

Effect of landslides as a consequence of earthquake

Answer 22

Landslides occur when loose sediment falls from a steep relief caused by the displacement of ground during an earthquake.

This caused 300,000 houses to be destroyed in Nepal 2015.

In addition, this can worsen the effects of the earthquake, as it destroyed / blocked roads leading to remote villages, which prevented aide from reaching those effected in rural areas faster, exacerbating the effects of the earthquake; This caused many to die from sustained injuries, as well as starvation, de-hydration etc.

Question 23

Liquefaction

Answer 23

If the unconsolidated sediments, such as fine-grained sands, alluvium or even landfill, has a high water content, then earthquake vibrations can cause it to behave like a liquid.

This therefore can cause the destruction of many building seemingly built on stable material, such as in the 6.9 1989 San Fransisco Loma Prieta earthquake which caused the destruction of the Bay area, specifically the marina district, which was built on landfill waste.

This resulted in the death of 42 people on the cypress freeway, which was a double decker freeway that collapsed.

The earthquake caused $6 billion in damage.

Question 24

Tsunami

Answer 24

Tsunami caused by underwater earthquakes which cause the sea bed to rise (displacing the water). This can cause large waves of high speed.

As seen in the 2011 Sendai earthquake, which reached speeds of 440 mph and up to 40m in height.

This caused approx. 90% of the over 18,500 deaths were caused by the tsunami, which was exacerbated due to the fact that the original warning for the tsunami was only 3m tall, not 40m. People didn’t have time to move, and it hit an area of elderly retirees. The tsunami also cost approx $200 billion to the Japanese economy in damages.

Question 25

Reasons why people in Montserrat have emotional attachment

Answer 25

1) They grew up on the island, have strong memories of the place.

2) They have economic attachment to the island, e.g. House / business / employment etc.

3) Attachment to the shared culture of the area, unique to Montserrat

Question 26

Reasons why people in Iceland have emotional attachment

Answer 26

1) They have economic attachment to the area; For instance the multi-general farm on the foot of the volcano, which benefits from the mineral and nutrient rich soil.

2)

Question 27

Earthquake in an LIDC - Nepal

Answer 27

The 7.8 magnitude earthquake destroyed infrastructure needed to reach Nepal, meaning that it was difficult to deliver aid to affected areas in April 2015

There were several aftershocks of up to magnitude 7.3 in early may which destroyed already partially ruined buildings

Thousands of homeless people had to sleep outside. 22,000 people were injured and 9,000 people were killed. $10 billion of damage was caused.

80% of homes destroyed in Kathmandu

More than 600,000 homes destroyed

Approx. $7.3 billion in damages
reduced tourism by 25% in the following years

Question 28

Earthquake in an AC - Japan

Answer 28

A magnitude 9.0 earthquake struck off the coast of Japan on March 11, 2011

The Epicenter of the earthquake was located off the coast of Tohoku, Japan, at a depth of 29 kilometers (18 miles), and effected the region of Sendai.

The earthquake triggered a massive tsunami that reached heights of up to 40 meters (130 feet) and devastated coastal areas of Japan.

16,000 killed, 6,000 injured

Approx 90% of deaths caused by tsunami, as most buildings were earthquake proof

330,000 IDP

Economic cost of $235 billion
Additionally, caused the Fukushima meltdown, which was due to tsunami flooding the nuclear plant.
Fukushima cleanup cost ET. by JCER think tank to be around 450-600 billion USD
1 worker died of lung cancer after radiation exposure

Question 29

Strategies to modify a hazardous event

Answer 29

Volcanoes:
Lava diversion channels; Lava diversion channels built out of steel / concrete can be used to create channels for lava to flow down, and not into populated areas, decreasing the damage done. This is done in Hawaii:

1960, a lava diversion channel built to protect the town of Kapoho from Kīlauea volcano; Channel was successful in diverting the lava flow, saving town from destruction.

Spraying lava with water / pouring sand on lava can slow it down by cooling it; This was also done in 1960 eruption of Kīlauea by U.S army corps spraying with fire hoses.

Concrete blocks can also be dropped to slow down lava flows.

Earthquakes:
Trick question, can’t prevent an earthquake.

Question 30

Modify peoples vulnerability

Answer 30

Education:
Teach population in hazardous areas how to respond to an event; e.g. run to a volcano proof centre / zone which will be unaffected, or during an earthquake to crawl under table / stand in the street, as seen in Japan.

Infrastructure:
Flood defences for areas in tsunami risk location; 15m high in Taro, japan, to prevent a repeat of 2011.
Mass dampers in buildings, cross-lattice design for aseismic building designs.
Shelters which are resistant to earthquakes / volcanoes.

Monitering & forecasting:
JMA & ERI in Japan
NERMA in Nepal

Question 31

Modify people’s lossess

Answer 31

Emergency aid:
Governments can train and prepare aid for emergency situations; However, in certain situations (e.g. Nepal Apr. 2015) it can be hard to deliver aid.
Nepal - WFP 2 million, Red cross 100,000 medical care
Japan - USAID 1 million fed and hydrated, World bank loans for rebuild

Disaster response:
Have helicopters and heavy lifting machinery available for countries which are most vulnerable to tectonic hazards.