Lecture 11 - Mitigating Volcanic Hazards Flashcards
How does Town Planning help to mitigate the impacts of a Volcanic Eruption?
-Best approach
-Plan towns outside the path of the volcano
-Build infrastructure on high points and ridges
-Valleys are more prone to lahars, lava flows and PDCs
What are the Evacuation Logistics in the event of an Eruption of Mt. Vesuvius?
-Naples lives in the shadow of Vesuvius (active)
-Moving large amounts of people quickly is very difficult
-Naples would take 72 hours to fully evacuate in the best case scenario (more than 1 million people live there)
Describe the Eruption of Mt. Etna in 1669 and the Response
-Effusive eruption
-Lava flows were moving towards the city of Catania
-Local Catania expedition was led by Diego Pappalardo (a local chaplin)
-The party wore cow hides drenched in water to protect them from the heat, whist carving channels into the side of the volcano
-This was successful but diverted the flow towards Paterno (so it was then diverted back the other way and 20,000 died in Catania)
What Lessons were learned from the 1669 Mt. Etna eruption?
-Prioritise people first, not property
-Laws were written which prohibited anyone (except royalty) from interfering with volcanoes
Describe the 1992 Eruption of Mt. Etna
-Lava flows heading towards the town of Zaffarena Etnea
-Locals built an earthen barrier 234m long and 21m high to divert the flow
-This contained the lava for a month, but it eventually overflowed
-Additional barriers were built to divert the flow and concrete plugs were emplaced to block a lava tunnel (this was somewhat successful)
-A map of the lava flows afterwards showed that the lava wouldn’t even reached Zaffarena anyway
Describe the Heimaey Eruption on Iceland, 1973
-Long fissures erupted on the flanks of Helgafell
-Lava flows threatened to close the bay which would prevent trade
-People were evacuated and seawater was pumped onto the lava flows which stopped them before they cut off the bay
-This meant the town could continue trading and fishing
Describe the profile for Mt. Ruapehu, New Zealand
-Lahar risk from crater lake
-Ski resort is potentially in the path of the volcano
-A bung has been installed to protect the town and resort, however this has not been tested yet
Describe the Eruption and Response to Mauna Loa, November 1935
-Lava flows threatened to engulf the town of Hilo
-Volcanologists Thomas A. Jagger and Guido Giacometti had a plan to bomb the lava tunnel and block them from letting the lava flow further down hill
-2 squadrons of bombers from Pearl Harbour dropped 20 bombs on the exposed lava flows (14 missed, 1 was a dud and 5 hit)
-Lava from the explosions splashed up into the air and hit the aircraft behind, nearly setting them on fire
The lava did eventually slow and stop, but only a week after the bombing
Describe what Carbonatite Volcanoes are
-Coldest type of lave (around 500C)
-Carbonate mineral-rich (like what shells are made out of)
-Only form in continental rift settings
-Only active volcano is in Tanzania
They form from either:
-Incredibly low partial melting
(low Si content)
-Melt immiscibility (separating)
between carbonate and silicate
melt
-Peculiar extreme crystal
fractionation
-Very low viscosity (low Si content)
-Produces relatively fast lava flows
-Economically important because rare earths are found in abundance here (these rare earths are used in pretty much all modern technology)
Describe what Komatiite Volcanoes are
-Hottest magma (around 1600C)
-So hot that lava erodes into the the ground by melting the bedrock
-They only erupted between 4-2.5 billion years ago during the Archean period
-Earth’s mantle is no longer hot enough to produce them
They are formed by:
-Incredibly high partial melt
(>50%)
-Very Mg rich ultramafic rocks
-Mostly made of olivine
-Many are supercooled which
produces a spinifex texture in the
crystals
