Hazard maps can be classified into two main categories based on the length of the intended time-scale of the map: background or crisis hazard maps.
Background (Long-term) Hazard Maps
Background, or long-term, hazard maps are usually created in advance of volcanic unrest and are intended to show the possible distribution of volcanic hazards over long (years to decades) time frames. They are often based on a combination of methods that incorporate eruptive history, geologic records, and/or modeling; and may be based on either specific scenarios (e.g. most likely, worst-case) or on all possible activity. Because of the long timescales of these maps, low-likelihood but high-impact hazards may be included (e.g. lateral blasts at Kanaga, USA 2002). Background hazard maps are the most common map timescale (93% of maps in the database), often accompany long-term hazard assessments produced by geological surveys, and are most suited to general hazard awareness and land-use planning purposes . They are often used during volcanic crises, but may not be well-suited to this purpose, unless scenarios relevant to the crisis were included on the map.
Examples of background hazard maps include: Baker, USA (1995), Nevado del Huila, Colombia (2007), and Osorno, Chile (1999).
A full list of background hazard maps in the database can be found here.
Crisis (Short-term) Hazard Maps
Crisis, or short-term, hazard maps are usually created at the start of volcanic unrest or during an eruption. They are usually intended for crisis-management purposes and show the likely distribution of hazards based on current conditions over short (days to months) or very short (hours to days) time frames. Crisis hazard maps are often also based on eruptive history and geologic records, but they incorporate more information about the current state or specific conditions of the volcano. They are also commonly based on modeling, with many modeling-based crisis maps serving as forecasts with very short (hours to days) time frames (e.g. Holuhraun, Iceland 2014 gas distribution forecast; see more here). Crisis hazard maps are best-suited to managing volcanic crises and may be presented in non-traditional formats such as interactive web-maps (e.g. Fuego, Guatemala 2018) or smart phone applications. About 7% of the maps in the database are crisis, or short-term, maps.
Some examples of crisis hazard maps include: Tongariro, New Zealand (2012), Nevados de Chillan, Chile (2018), Holuhraun, Iceland (2014), and St. Helens, USA (1980).
A full list of crisis hazard maps in the database can be found here.