Frequently Asked Questions

Q. I'm confused about these "Colour Codes". Are they the same all over the world?

A. It's important to distinguish between local alert levels and aviation colour codes. For example, Indonesia has four alert levels:

Indonesia's Alert Code

Level I, green ("Aktif normal - Normal active")
Level II, yellow ("Waspada - Alert")
Level III, orange ("Siaga - Anticipation")
Level IV, red ("Awas - Ready to erupt")

These levels are designed to warn local populations, not aircraft. Where we quote colour codes in our advisories, we are extrapolating the information received to the code adopted by the International Civil Aviation Organisation:

Aviation Colour Code

Green Alert: Volcanic activity considered to have ceased and volcano reverted to its natural state.
Yellow Alert*: Volcano known to be active from time to time and volcanic activity has recently increased significantly, volcano not currently dangerous but caution should be exercised. *The code "yellow" may be used in cases or "regular" or "quasi-permanent" volcanic eruptions that do not normally reach FL250 and do not necessarily involve a "significant increase in volcanic activity".
Orange Alert: Volcanic eruption in progress but ash plume/cloud not reaching nor expected to reach FL250, or
Volcano dangerous, eruption likely but ash plume/cloud not expected to reach FL250.
Red Alert: Volcanic eruption in progress. Ash plume/cloud reported above FL250, or
Volcano dangerous, eruption likely, with ash plume/cloud expected to rise above FL250

(FL250 = appoximately 7.6 km above the mean sea level in height. Note that most ground-based volcanic height reports are given in metres above the volcano summit. It is also very difficult to estimate the height of a large eruption from the ground.)

It should be obvious that the surface-based and aviation colour codes above for a volcano will not always be the same, although 'red' generally means 'red'. Unless a code is quoted explicitly as 'Aviation colour code', it should be assumed to relate only to the surface-based code.

Note further that a revised version of the Aviation Colour Code will probably become applicable on 22 November 2007.

Q. I'm confused about the difference between NOTAMs, ASHTAMs, SIGMETs and Volcanic Ash Advisories....

A. NOTAMs are issued by Area Control Centres to advise of, amongst other things, hazards. They may include information such as route closures. ASHTAMs are a special series of NOTAM specifically for volcanic hazards. SIGMETs are meterological warnings issued by Meteorological Watch Offices. In the case of volcanic ash, the SIGMETs would usually give information about the extent of ash cloud. Volcanic Ash Advisories are messages issued by the Volcanic Ash Advisory Centres to inform Area Control Centres, Meteorological Watch Offices, and other parties. The Volcanic Ash Advisories do not have warning status, but may provide useful information in cases where SIGMETs or NOTAMS are not up to date.

Q. Where can I find out more infomation about the Galunggung 747 encounters in 1982?

Q. Is the Australian Bureau of Meteorology responsible for predicting earthquakes and volcanic eruptions in Australia?

A. No, Geoscience Australia is responsible for those areas, particularly earthquake monitoring. Their web site contains a wealth of information. Our interest is confined to the aviation hazard of volcanic ash once an eruption has taken place (or when authorities advise that an eruption is imminent).

Q. Is VAAC Darwin responsible for predicting a tsunami generated from a volcanic eruption in Australia?

A. No, tsunami warnings are issued by the Joint Australian Tsunami Warning Centre operated by Geoscience Australia and the Australian Bureau of Meteorology. National warnings and bulletins, along with other information on the Australian Tsunami Warning System can be found at http://www.bom.gov.au/tsunami/index.shtml

Q. Are there any active volcanoes in Australia?

Q. Do you take graduate students?

Q. I run an airport near an erupting volcano. How do I keep my runways clear of volcanic ash?

"Basic techniques include:

• Wet ash with water trucks
• Blade into windows,
• Pick up with belt or front-end loaders,
• Haul to dump areas, and
• Sweep and flush residue.
• Sweep/vacuum ash first, then flush with water (best for ramps, etc.).
• Push ash to runway edge and plow under or cover with binder such as Coherex or lignin.
• Install sprinklers along edges of runway to control resuspension of ash from aircraft engine blast or wing-tip vortices.
• Keep residue wet on taxiways and ramps."

from J.R. Labadie, 1994, 'Mitigation of Volcanic Ash Effects on Aircraft Operating and Support Systems', in 'Volcanic Ash and Aviation Safety: Proceedings of the First International Symposium on Volcanic Ash and Aviation Safety', edited by Thomas J. Casadevall published as US Geological Survey Bulletin 2047

The full text of the article is highly recommended.

Q. Volcanic ash is a very useful material in industry and agriculture. Where can I buy some in bulk?

Q. I have a more general question about volcanoes. Where should I start looking?

A. If you like reading the 'Frequently Asked Questions' type format (and since you've got this far we assume you do), then look no further than the excellent 'Top 101 ask a volcanologist questions' on the 'Volcano World' site. Failing that, try some of the other sites under our 'links' page, or try an advanced search on a good search engine.