Explaining The Causes Of Tectonic Hazards: Volcanoes Flashcards
What is a tilt meter
A device used to measure subsidence near a volcano as they may indicate an eruption is imminent
What is lava
Lava and magma are pretty much the same thing however lava is magma that has left the mantle and has been ejected onto the surface/ crust.
What do we mean by viscosity?
The viscosity of lava is determined by its chemical composition and temperature
What are the three types of lava and their properties?
Basaltic least viscous, highest temperature and silica content
Andesitic middle viscosity, middle explosively and middle silica content
Rhyolitic very vicious very explosive low silica content
Why is Rhyolitic lava so explosive
The high concentration of gas and air pockets allows explosions to be fuelled
What is a pyroclastic flow?
Primary hazard Super heated tephra - 1000*C High velocity- 700km/h From explosive eruptions For example, chances peak monserrat 1997 (captial destoyed)
What is a lahar?
Secondary hazard
Water mixed with volcanic deposits
Flows in existing valleys
Ash seeding can casue more percipitation. Leading to flooding.
Nevada del ruiz, 10% snow ice melted, 7 small lahars Armeo town 23,000 killed, more lahars inbiited evacuation
What is ash seeding?
When ash mixes with water vapour in the atmopshere this makes the water vapor condense and thus precipitate at lower altitudes increasing percipitation and cuold cause flooding.
What is volcanic ash?
Primary harzard
Solid and molten rock ejected into the air
Ligt articles have high ejection rate meaning planertary winds carry them across the globe.
Mainly falls in the local area causing roof collapse and breathing problems.
For example, eyjafjallajokull disrupted trans atlantic flight paths and 700people were evacuated.
What is volcanic gas?
Primaary hazard
Water vapor= 70-90% leads to heavy rainfall
Steam can escape with other gase form geyser fumaroles
Sulpher dioxide that reaches the startosphere relfect radiation like mini mirros having a global cooling effect.
What is a Jokulaup
Secondary hazard
Meltwater builds up at the base of a glacier
Volcano erupts melting ice forming a lake
There will eventually be enough water to lift the ice
Water bursts out carrying ise debris with it
Eyjaffjallajokull- anticipated roads closed and embankments made to mitigate damage
What are jet streams?
Ribbons of very strong winds which move weather systems around the worls
Found between 9-16km
Reach speeds of 200mph
What happened in 1996 in Iceland?
The Vatanajokull eruption and follwing glacial flooding
Where is the vatnajokull ice cap? (Boundary and country)
On a constructive plate margin with effusive eruptions, shield volcano
It is located in the south east of iceland and is about 100km wide
What happened in columbia in 1985
Nevada del ruiz eruption
Stratovolcano
Multiple enourmous lahars destroyed armeo
