volcanoes

Question 1

primary hazards

Answer 1

lava flow = up to 1170 degrees and can take years to cool completely
destroy everything in path but move slow

pyroclastic flow = hot dense rock, lava, ash, and gases ejected - move very quickly (100km/h) - up to 700C
destroy everything they touch

tephra and ash falls = pieces of volcanic rock and ash that blast into air during eruptions - larger pieces fall nearer to volcano and ash can travel for 1000 of kms
ash causes slippery roads, poor visilbity, collapse roofs from weight, stop engines working

gas eruption = magma has dissolved gases that are released e.g. water vapour, CO2, sulphur dioxide
can travel for 1000s km

Question 2

secondary hazards

Answer 2

jokulhhlaup = heat of eruption melt snow/ice in glacier, causing sudden floods (glacial flood outbursts)
water, rock, gravel, and ice can catch people unaware and damage land
-iceland = evacuation

lahars = masses of rock, mud, and water that travel quickly down volcano side
vary in size and speed but too quick to outrun (10sm/s and can be 100m wide or more
caused when eruption quickly melts snow or heavy rainfall during or after eruption erodes/loosens rock/soil

Question 3

meausure volcanoes

Answer 3

VEI = volcanic explosivity index
0-8 logarithmic scale
-factors amount/heihgt of volcanic material ejected, how long eruption lasts, and qualative descriptive factors

Question 4

predicting

Answer 4

-small earthquakes = magma rises to surface, it breaks rock)

changes to surface of volcano = pushes upwards as magma builds pressure

changes to til of volcano = magma moves inside, it changes slope

Question 5

types of lava

Answer 5

basaltic

andesitic

rhyolitic

Question 6

basaltic lava

Answer 6

-hottest ( 1000-1200C)
-low silica, high CO2
-low gas content (0.5%-2)
-low viscocity (runny) so gases escape
-ocean hot spots, mid ocean ridges, shield volcanoes
-gentle and effusive explosion

Question 7

andesitic lava

Answer 7

800-1000C
-medium silica
-medium gas content (3-4%)
-intermediate viscocity = slow, traps gasses
-composite cone volcanoes, subduction zones
-violent and moderatly explosive

Question 8

rhyoltic lava

Answer 8

• coolest ( 650-800C)
  -high silica and gas content
  -thick and stiff lava
  -very violent eruptions
  -supervolcanoes or composite cones