Volcanoes

Question 1

Define a volcano

Answer 1

An opening in the Earth’s crust through which molten rock, ash and gases escape into the atmosphere or earths surface

Question 2

What is a active volcano

Answer 2

A volcano which has erupted in the last 10000 years and which is expected to erupt again. Eg mount Merapi

Question 3

What is a dormant volcano

Answer 3

A volcano which has not erupted in at least 10000 years but which has potential to erupt again eg Fourpeaked mountain, Alaska

Question 4

What is a extinct volcano

Answer 4

A volcano which cannot erupt angina as it has been cut off from a source of rising magma eg Edinburgh castle

Question 5

How do we measure volcanic eruptions

Answer 5

Using the volcanic exclusivity index. The VEI measures the magnitude of volcanic eruptions ranging from 1-8. It is based off the volume of ash emitted and the height that an eruption column reaches into the atmosphere

Question 6

What are the 7 main features of a volcano

Answer 6

Magma chamber, layers of compressed ash/lava, vent, secondary/ parasitic cone, lava flow, crater, ash cloud

Question 7

What is the magma chamber

Answer 7

A reservoir of molten rock within the earths crust beneath a volcano

Question 8

How are layers of compressed ash and lava made

Answer 8

The products from previous eruptions build up on the side of the volcano

Question 9

What is the vent

Answer 9

The pipe where the magma travels up from the magma chamber to the surface

Question 10

What is the secondary/parasitic cone

Answer 10

A smaller cone that develops on the side of the main cone. It can form if the main vent is blocked and magma travels along the secondary vent

Question 11

What is lava flow

Answer 11

Molten rock that flowers across the Earth’s surface from the vent

Question 12

What is the crater

Answer 12

A steep sided depression at a volcano’s summit created by the collapse of rock during eruptions

Question 13

What is the ash cloud

Answer 13

Fragments of rock ejected into the atmosphere during a eruption

Question 14

What are the characteristics of basic lava

Answer 14

Constructive margin, low silica content, low viscosity, hotter temp (1200 C), faster flowing, effusive eruption, shield volcano shape

Question 15

What are the characteristics of acidic lava

Answer 15

Destructive margin, high silica content, high viscosity, cooler temp (800 C), slower flowing, explosive eruptions, cone volcano shape

Question 16

What are shield volcanos

Answer 16

Shield volcanos are found on constructive margins (and the Hawaiian hotspot). They have a broad basal area and gentle sloping sides. They are formed by the effusive eruption of basic lava which has a low viscosity and high temperatures. Lava flows a long way from the vent before cooling and solidifying. Each eruption adds another layer to the volcano. 🌋 examples incluse Kilauea, Hawaii

Question 17

What are stratovolcanos

Answer 17

Stratovolcanos (cone) are found on destructive margins. They have a narrow basal area and steeply sloping sides. They are formed by the explosive eruptions of acidic lava which has high viscosity and low temperatures. This means lava does not erupt easily and often gets stuck in the vent. This can lead to the build up of pressure and the explosive eruption of ash. If lava erupts it is slow flowing and does not travel far before cooling. Over time layers of solidified lava and ash accumulated into a cone shape. Examples include mount Merapi

Question 18

What are five primary hazards of a volcano

Answer 18

Ash, pyroclastic flows, volcanic bombs, volcanic gases, lava

Question 19

What is volcanic ash

Answer 19

Rock which has been pulverised into a fine dust and ejected kilometres into the atmosphere during an explosive eruption

Question 20

What are pyroclastic flows

Answer 20

The deadliest volcanic hazard-a cloud of gas, ash and rocks that travel down the sides of the volcano erupting explosively at up to 300mph and 1000C

Question 21

What are volcanic bombs

Answer 21

Globs of lava or rock fragments ejected into the air during a eruption

Question 22

What are volcanic gases

Answer 22

Carbon monoxide and dioxide, sulphur dioxide can form a ground covering blanket which can asphyxiate anyone who gets trapped within it

Question 23

What is lava

Answer 23

Molten rock that flows down the sides of a volcano in a gentler eruption

Question 24

What are five secondary hazards of volcanos

Answer 24

Tsunamis, climate change, Jokulhlaups, Lahars, forest fires

Question 25

How are tsunamis formed by volcanos

Answer 25

Some eruptions of volcanos islands are explosive enough to trigger tsunami waves which can inundate costal areas

Question 26

How is climate change affected by volcanoes

Answer 26

Sulphur dioxide emitted into the atmosphere reflects sunlight back into space meaning than earth can cool down for several years following a major eruption 🌋

Question 27

What are Jokulhlaups

Answer 27

If a volcano erupts beneath a glacier or ice sheet a meltwater flood or Jokulhaup can be formed

Question 28

What are Lahars

Answer 28

Volcanic ash mixes with water to create a mudflow that can travel down the volcanos sides at 40mph

Question 29

How are forest fires cause by volcanos

Answer 29

Lava flows and hot ash and gas can result in major forest fires

Question 30

What are four physical factors which affect the impacts of volcanic eruptions

Answer 30

Magnitude of eruption, explosivity or eruption, eruption products, local physical environment

Question 31

How does the magnitude of a eruption affect the impacts of a volcanic eruption

Answer 31

The greater the volume of material erupted (higher on the VEI) the higher the risk of significant impacts

Question 32

How does the explosivity of a eruption affect the impacts of a volcanic eruption

Answer 32

More explosive eruptions tend to produce more dangerous eruption products resulting in a higher loss of life

Question 33

How do the eruption products affect the impacts of a volcanic eruption

Answer 33

Fast moving pyroclastic flows and Lahars are often the deadliest eruption products. Slow moving lava is not as deadly but causes great damage to buildings, infrastructure, farmland

Question 34

How does the local physical environment affect the impacts of a volcanic eruption

Answer 34

If eruption products interact with the local physical environment in a certain way, dangerous and damaging secondary hazards can be produced e.g Lahars

Question 35

What are four human factors which affect the impact of eruptions

Answer 35

Exposure, ability to predict, managing eruption products, response and modifying loss

Question 36

How does response and modifying loss affect the impacts of a eruption

Answer 36

Well trained and equipped e regency services play a crucial role in reducing negative impacts. These are most likely to be found in developed countries. While developed countries may be self sufficient in their response, developing countries may be reliant on international air to respond and recover

Question 37

How does managing eruption products affect the impacts of a eruption

Answer 37

It is not possible to manage all eruption products eg pyroclastic flows. There has been some success with the use of dams to slow and re direct lava flows however the ability to do so depends on the country’s development

Question 38

How does the ability to predict affect the impacts of a eruption

Answer 38

The ability to predict an eruption before they occur enables prior evacuation of people at risk potentially saving thousands of live. However an effective volcano monitoring system is expensive and developing countries may not have the necessary resources. Even in developed countries some reactions catch volcanologists out

Question 39

How does exposure affect the impacts of a eruption

Answer 39

Impacts will be greater if there is a higher population density in the affected area as more people will experience the hazard and there is more infrastructure to damage

Question 40

Name the volcano case study

Answer 40

Mount Merapi, Indonesia 2010

Question 41

What were 5 short term impacts of mount Merapi

Answer 41

-rapid spread of disease in overcrowded and unsanitary refugee camps -disruption to education as schools in evacuation zone closed -loss of crops already in field and death of livestock meant loss of income for farmers -contamination of lakes and rivers with volcanic ash reduced access to clean water -damage to crops led to reduction in food supply and increased food prices

Question 42

How many deaths were cause by the mount Merapi eruption

Answer 42

353 dead and 577 injuries

Question 43

What were 5 long term impacts of the mount merapi eruption

Answer 43

-2682 people were unable to return to their homes after the eruption and had to be permanently relocated -destruction of key infrastructure creating significant rebuilding costs -burial of fertile farmland under ash and Lahars meant loss of income for farmers -vegetation loss and contamination of water courses -final cost of disaster estimated $600 million

Question 44

What are two physical factors that make Indonesia more vulnerable to volcanic hazards

Answer 44

-Indonesia is an archipelago of more than 13000 island between the pacific and Indian oceans. It is found at the western edge of the pacific ring of fire, a belt of destructive plate margins -the lava associated with Indonesia volcanoes is acidic meaning that eruption tend to be infrequent but highly explosive generating dangerous hazards such as pyroclastic flows

Question 45

What are two economic factors which make Indonesia more vulnerable to hazards

Answer 45

-31% of Indonesians are employed in agriculture which is very vulnerable to volcanic ash, pyroclastic flows and Lahars which can destroy crops. -few people in Indonesia can afford the luxury of insurance against volcanic hazards making rebuilding and recovery a long struggle

Question 46

What are two social factors which make Indonesia more vulnerable to hazards

Answer 46

-Indonesia has a very high exposure to volcanoes with a population of 260 million -for some Indonesian volcanoes like merapi have sacred significance. This meant that in the build up to the eruption some villages refused to evacuate creating more fatalities