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Volcano Traffic Light Alert System

Similarly to the color-coded four-level alert system used by the USGS, the Mexican government uses the Volcano Traffic Light Alert System (VTLAS) to designate the current level of volcanic hazard (DeLaCruz-Reyna and Tilling, 2007).

This image, from DeLaCruz-Reyna and Tilling, 2007, shows an example of a poster that could be used to educate people about the VTLAS and volcanic hazards. Below is an explanation of the alert levels (DeLaCruz-Reyna and Tilling, 2007):

Green is divided into two subsets.

Phase 1:
little to no activity,

Phase 2:
low levels of seismicity and minor fumaroles.

Yellow is divided into three subsets.

Phase 1:
Increased seismicity, fumaroles

Phase 2:
Eruptive activity <VEI-2; minor explosions and ash   ejection; minor pyroclastic flows and lahars that would not threaten humans

Phase 3:
Increased eruptive activity; phreatic explosions;             evidence of magma injection (dome growth, deformation); significant ash fall hazards; larger pyroclastic flows and lahars but not ones that threaten humans.

Red has two subsets.

Phase 1:
Large eruption (VEI 3-4); major explosions; ash fall in     surrounding area (enough to cause roof collapses); pyroclastic flows that threaten humans; significant air travel hazard.

Phase 2:
It's basically the end of the world. In all seriousness,        though, Phase 2 describes a VEI-5 or greater eruption, which could have pyroclastic flows and lahars reaching multiple populated areas, an ash column tens of kilometers in altitude (creating international aviation hazards), significant
ashfall up to 100km away, debris avalanches caused by sector collapse, and overall widespread devastation.