Volcanic eruptions

Question 1

How many volcanic eruptions are there globally every year?

Answer 1

There are 60 globally a year

Question 2

How many people on average do volcano’s kill a year?

Answer 2

500 people a year

Question 3

What are volcanic eruptions?

Answer 3

Openings of the crust through which magma erupts as lava, occurring mainly at plate margins

Question 4

What allows the magma to rise?

Answer 4

Plate movement at constructive and destructive boundaries but not conservative

Question 5

What are hot spot volcanoes?

Answer 5

Volcanoes that occur at intra-plate locations such as the Ring of Fire in the pacific e.g. Kilauea, Hawaii 1983 to today

Question 6

Is lava flow a secondary or primary hazard?

Answer 6

Primary

Question 7

Is a Pyroclastic flow a secondary or primary hazard?

Answer 7

Primary

Question 8

What are lava flows?

Answer 8

Lava flows are streams of lava that have erupted from a volcano onto the earths surface, however they are generally not a threat to human life as they move so slowly

Question 9

What are Pyroclastic flows?

Answer 9

Pyroclastic flows are one of the greatest threats to life. They are a mixture of dense hot rock, lava, ash and toxic gases ejected from a volcano which move very quickly across the earths surface, they destroy everything they touch

Question 10

What are Tephra and ash falls?

Answer 10

Tephra are pieces of volcanic rock and ash that blast into the air during volcanic eruptions, these can be deadly when large pieces fall close to the volcano, however they can spread great distances causing widespread disruption

Question 11

What are gas eruptions?

Answer 11

Magma contains dissolved gasses that are released into the atmosphere during an eruption, some of which can be hazardous to people, animals and structures and can travel for thousands of kilometres

Question 12

What are Lahars?

Answer 12

Lahars are masses of rock, mud and water that travel very quickly down the slope of the volcano and can flow at tens of metres a second, caused when an eruption melts surrounding ice and snow or when there is heavy rainfall during an eruption

Question 13

What are Jokulhlaup’s

Answer 13

The heat of the eruption can melt snow and ice in a glacier causing heavy and sudden floods that can damage structures and kill

Question 14

What is an example of a Lahar?

Answer 14

Armero, Colombia where 25,000 people died in 1985 as a result of a Lahar

Question 15

What is the Volcanic Explosivity Index? (VEI)

Answer 15

It measures eruption magnitude and ranges from 0 to 8, with 0 being non-explosive and 8 being extremely explosive

Question 16

What type of scale is the VEI?

Answer 16

It is a logarithmic scale

Question 17

Where does Basalt magma occur?

Answer 17

It occurs at constructive boundaries and hotspots

Question 18

What is basaltic magma like?

Answer 18

It is non-viscous and gas escapes freely

Question 19

How do basaltic eruptions usually behave?

Answer 19

They are usually effusive (gentle) therefore a low risk

Question 20

Where does Andesite magma occur?

Answer 20

Destructive boundaries

Question 21

What is Andesite magma like?

Answer 21

It is viscous and traps gases underground

Question 22

How do Andesite eruptions usually behave?

Answer 22

Eruptions are usually explosive therefore a high risk

Question 23

What factors does the VEI look at?

Answer 23

• The amount and height of the volcanic material
  ejected
• How long the eruption lasts
• Qualitative descriptive terms

Question 24

What changes are looked at to predict an eruption?

Answer 24

• Small EQ’s as magma rises to the surface it breaks rock creating small EQ’s
• Changes to the surface of the volcano as the magma rises it may swell
• Changes to the tilt of the volcano

Question 25

Can volcanic eruptions be predicted?

Answer 25

Unlike EQ’s they can be predicted with some accuracy

Question 26

What happened in Montserrat in 1995?

Answer 26

The island volcano began to erupt huge clouds of ash, over the next 5 years these eruptions continued with pyroclastic flows also affecting much of the island

Question 27

What social impacts did the Montserrat eruption have?

Answer 27

• Dozens of people lost their lives and more than 7000 moved to other countries, over half of the original residents
• A top heavy population pyramid was created as the younger generations moved away as they saw no economic future on the island

Question 28

What economic impacts did the Montserrat eruption have?

Answer 28

• The capital, Plymouth was destroyed
• Unemployment rose as the islands main industry of tourism collapsed
• A lot of farmland was destroyed further damaging the economy