Lecture 6 - Before the Eruption Flashcards
What are Hot Springs?
-Where water meets hot rock heated by magma
-Occur at the surface
-Vary in temperature (from warm bath to boiling)
-Potentially harboured life on early Earth
-Can quickly change temp./ chemistry which could warn of an eruption
What are New Thermal Areas?
-New hot spring activity
-Reactivation of old hot springs
-Suggest magma is moving
What are Geysers?
-Complex underground plumbing system comprised of underground cavities of water heated by magma or hot rock
-Water vaporises to steam which rapidly rises and displaces the water above it
-Can occur regularly so changes in behaviour could suggest an eruption
What is Acidified Water?
-Lakes near volcanoes become saturated with CO2 and SO2, producing carbonic and sulphuric acid
-These cause severe burns and even death
-Rapid changes in acidity could suggest an eruption
What are Fumeroles?
-Hazardous gases released from volcanic vents
-Can occur anytime, without an eruption
-Gasses are denser than air so condense and concentrate in valleys
-Causes asphyxiation, skin burns and crop death (and famine)
-Large gas release could be a sign of eruption
Describe the Lake Nyos Disaster
-1,746 dead after huge gas release
-Thousands injured with breathing problems and paralysis
-3,500 livestock animals dead
-Extended 25km from the lake and caused the water level to drop by 1m
-Since the event, a degassing station has been installed which penetrates the lake bed thus preventing gas build-up
What is Plant Dieback?
-Plants yellow and die due to increase in CO2 in the soil
-New areas of dying plantlife could be a sign of change in volcanic activity
What are Landslide?
-Volcanoes are weak structures
-Occur near the summit, especially if there is no other cause (i.e rain)
-Caused by movement of magma fracturing Earth’s surface or gas release
How does Soil Temperature indicate and Impending Eruption?
-Ground near volcanoes can be very hot
-Soil heating up/ cooling down indicates activity below ground
What is Ground Uplift?
-Could suggest magma/water is building up underground causing the ground above to rise
What are Volcanic Earthquakes?
-2 types; volcanic tectonic and long period
-VT are usually small, caused by regional tectonic forces or injection of new magma
-LP are caused by vibrations caused by movement of magma/ pressure build-up causing rocks to break thus generating an earthquake
What are Harmonic Tremors?
-Specific type of long-lasting rhythmic seismic waves
-Only associated with volcanoes
-Caused by magma moving through fractures in rock
-Very good indicator of an impending eruption
