volcanos

Question 1

what is ash?

Answer 1

dust sized particles of rock produced by an eruption

Question 2

what is a composite volcano?

Answer 2

a large steep sides volcano formed by alternating layers of lava flow, ash and blocks.

Question 3

where are composite volcanos found?

Answer 3

destructive plate boundaries

Question 4

what are lahars?

Answer 4

mudflows composed of pyroclastic flow and water

Question 5

what is a pyroclastic flow?

Answer 5

a rapidly moving dense flow of volcanic gases, ash and larger material

Question 6

what is tephra?

Answer 6

rock fragment which is ejected from a volcano

Question 7

what are volcanic bombs?

Answer 7

material over 5mm which is ejected from a volcano

Question 8

what is the volcanic explosive index?

Answer 8

a logarithmic scale of 1-8 which measures the explosivity of a volcano

Question 9

where are shield volcanos found?

Answer 9

constructive plate margins

Question 10

give 4 features of shield volcanos

Answer 10

1. gently sloped
2. low viscosity
3. basaltic lava
4. gentle but frequent eruptions

Question 11

give 4 features of composite volcanos

Answer 11

1. steep sloped
2. high viscosity
3. andesitic lava
4. less frequent but violent eruptions

Question 12

how do composite volcanos form?

Answer 12

1. subduction occurs, melting the desner plate into magma.
2. the less dense andesitic lava exploits cracks in the crust and climbs to the top
3. the magma cools and forms volcanos

Question 13

how are shield volcanos formed?

Answer 13

1. as plates separate basaltic magma is forced up and cooled into a volcano
   or
2. hot spots force magma up through the crust, causing it to cool into a volcano

Question 14

give 3 features of pyroclastic flow

Answer 14

1. 800 degrees C
2. high velocity
3. gas charged

Question 15

give 3 primary effects of volcanos

Answer 15

1. pyroclastic flow
2. tephra
3. lava flow

Question 16

give 3 secondary effects of volcanos

Answer 16

1. lahars
2. flooding(glaciers melt)
3. tsunamis(displacement of water)

Question 17

what is acid rain?

Answer 17

when volcanic gases such as sulphur combines with moisture forming acid rain

Question 18

what is climatic change in eruptions?

Answer 18

when huge amounts of debris blocks solar radiation, cooling the earth

Question 19

what are 3 signs a volcano may erupt

Answer 19

1. an increase in the release of volcanic gases
2. a rise in the level of lava lakes in the crater
3. the buldging up of surrounding land due to pressure

Question 20

what are 3 physical actions that can be used during an eruption?

Answer 20

1. digging to divert viscous lava
2. pour water on lava flows
3. evacuations