Tectonics 3.1.2

Question 1

name the three types of lava

Answer 1

Basaltic, Andesitic and Rhyolitic

Question 2

Name the lava that has a medium silica content

Answer 2

Andesitic lava

Question 3

Name the lava that has a low silica content which means it has low viscosity

Answer 3

Basaltic lava is runny due to the low silica content and low viscosity

Question 4

Name the lava that has a high silica content meaning it has high viscosity

Answer 4

Rhyolitic lava is really thick due to the high silica content which makes means it has high viscosity

Question 5

describe the characteristics of where Basaltic lava occurs

Answer 5

Basaltic lava occurs in an effusive eruption from a shield volcano. The magma is fluid and allows pressure release so it’s less explosive

Question 6

Describe the characteristics of where Rhyolitic and Andesitic lava occurs

Answer 6

Both types of lava occur at explosive eruptions at composite or cinder cone volcanoes. It is highly explosive due to the high silica content, which means it solidifies on the way to the surface, building up the pressure as the gas is trapped in air pockets

Question 7

list 5 features of a composite volcanoes

Answer 7

1. Occurs at convergent boundaries where there’s subduction zones
2. very high and consist of many layers from hardened lava, tephra, ash and pumice
3. steep gradient of up to 30
4. High silica and water content
5. Explosive eruptions

Question 8

list 4 characteristics of a shield volcano

Answer 8

1. occurs at divergent boundaries experiencing ridge push or at hotspots
2. fluid lava as it is Basaltic
3. Effusive eruptions, low viscosity
4. gentle slopes 2-10

Question 9

List characteristics of a cinder cone volcano

Answer 9

1. Found on the sides of a composite or shield volcano
2. it is a steep conical hill of tephra that has accumulated around a vent
3. medium to high viscosity
4. explosive and only last one eruption as they are weak

Question 10

name the 4 primary volcanic hazards

Answer 10

1. Tephra
2. Lava flow
3. Pyroclastic flow
4. Volcanic gases

Question 11

name the 2 secondary volcanic hazards

Answer 11

1. Lahars
2. Jokulhlaups

Question 12

explain features of tephra

Answer 12

Tephra is combination of ash and volcanic bombs, which is ejected out as fragmented material

Question 13

explain features of pyroclastic flow

Answer 13

Pyroclastic flows are hot rock fragments (lava and ash) which glows as it surges downhill rapidly, it is red hot up to 1000 degrees c

Question 14

explain features of volcanic gases

Answer 14

volcanic gases is dangerous because they are denser than air, so sinks
Lake Nyos is an example of how dangerous it is, as it suffocated a town of 1,700 people (where 1747 people in total died from this eruption)

Question 15

Explain features of a lahar

Answer 15

A lahar occurs when ice and snow melts or when ash is washed down by rainfall turning it into a mudflow of sediment and ash, that rapidly runs down the volcano

Question 16

Explain the features of a Jokulhlaup

Answer 16

It is the same as a lahar, but it is a full glacier that melts and rushes down the volcano

Question 17

name the two primary impacts of volcanic hazards

Answer 17

1. Social impacts- 91,000 deaths due to suffocation and thermal injuries from major hazards between over just a century- shows how regions are affected
2. Environmental impacts- local/regional scale impact due to landslides and lahars reshaping the landscape, destroying vegetation in the process

Question 18

name the three secondary impacts of volcanic hazards and in what scale

Answer 18

1. Economic- a regional scale impact is significant due to the financial loss estimated $65 million a year due to clean ups and repairs
2. Environment- Large global impact due to the GHG emissions being released
3. Social- average of 15,000 people left homeless every year is a local scale impact

Question 19

When comparing eruptions case studies you must remember these 7 characteristics

Answer 19

1. date- if they are similar or not
2. measure of eruption using VEI
3. Characteristics of the eruption
4. what precautions have been taken
5. death toll
6. homelessness
7. other factors and the scale of those impacts

Question 20

E15 is a good eruption to compare to, as Iceland is a HIC and prepared
List the 7 features for E15

Answer 20

1. 2010, Iceland one month
2. VEI 4
3. Ash plume 30km high, composite, subglacial, so vaporised the glacier in the crater
4. 700 evacuated, given 30 min warning of floods
5. 0 deaths
6. 0 homeless
7. Ash plume was blown southeast to Europe, led to airspace shutting down for 6 days
   - 95,000 flights cancelled, leaving 1 mill people stranded
   - $5 billion economic loss to European’s economy

Question 21

Name two eruptions that are ideal to compare against E15

Answer 21

1. Lake Nyos 1986- 1,746 people died, mainly due to suffocation of a a whole town as 100,000 tons of carbon was released, lake chemistry altered
2. White Island, NZ 2019- 22 deaths, pyroclastic flow, phrenic eruption (steam blast eruption)