volcanism - lecture 1 Flashcards
why study volcanic gases?
- they are a direct signal for underground activity
- degassing drives activity e.g. seismic, eruptions
- impact climate system and atmospheric chemistry
- important to understand what volcanos
what is volcanic gas comprised of?
water vapour, CO2 and acidic gases
what is magma (multi phase material) made of?
molten rock
crystals
gas
what can gases tell us?
- elevated emissions can indicate an eruption
- decreasing emissions may signify the end of an eruption
- increase in gas ratios can indicate an eruption
problems with gas interpretation?
- emission rate decrease doesn’t always signify end of an eruption, can in fact mean the opposite
example of secondary data
- geophysical data e.g. seismic and deformation
gas measurement approaches
- direct sampling
- remote sensing
- measuring dissolved volatiles in rocks/minerals
- Grocke et al 2010
what is direct sampling?
- trapping gases in a bottle
- provides the most detailed information
- dangerous, time resolution poor, can only measure chemical compositions not emissions
what is remote sensing?
- safer than direct sampling
- allows fingerprint identification of gas absorption
- good for observing atmospheric impacts
ground vs space platforms
- ground based = better for monitoring
- space/satellite = good for atmospheric impacts
3 steps of UV imaging
- contrast absorbing / non-absorbing images
- sum concentrations over plume width
- find plume speed and multiply by this to get emission rate
problems with measurements?
- sensors are bulky, 1970’s tech expensive to maintain
- low sampling frequency
- large error - wind speed at summit
handheld spectrometer
- smaller, lighter, cheaper
- now used as standard internationally
what is passive degassing?
gas which is released at all times from a volcano, even when no eruption is occurring
why is understanding driving mechanisms limited?
1 - poor time resolution data
2 - models for underground gas flow previously not related to field degassing data
