Two status systems, not one colour scale
The USGS alert-level explanation distinguishes volcano alert levels from aviation colour codes. The ground-oriented status and aviation-oriented code have different purposes. A volcano can therefore have a combination that does not appear to match if the reader expects one shared scale. Read both labels and the accompanying explanation rather than collapsing them into a single eruption score.
A volcano marker identifies a location or record. It does not describe the shape, height or movement of an ash cloud. In particular, a historical volcano entry should not be captioned as a current ash plume. Begin by asking whether the selected product is a reference location, an observatory update or an atmospheric advisory.
Read the observatory message and ash advisory separately
USGS Volcano Observatory Notices for Aviation provide source messages concerning activity and aviation status. Preserve the volcano name, issuing observatory and message time. An early message with limited observations is not equivalent to a later complete assessment. If uncertainty is stated, keep it visible in the summary instead of translating it into a confirmed absence of ash.
The Alaska Aviation Weather Unit ash-product page separates advisory information used in the aviation context. Read the product's observation time, forecast time and altitude labels. A forecast cloud position is not a measured boundary at the same time as an older observation. Do not assume that a surface map describes conditions at every flight level.
Keep atmospheric and ground questions apart
The USGS ash aviation overview explains why airborne ash is a specialist concern. This article does not provide flight-planning advice, a safe route or an operational aviation briefing. Nor does an airborne-ash product establish the amount of ash deposited at a particular street address. Use the responsible authority's appropriate product for the question being researched.
The PocketWorld volcano overview provides geographic context and source-labelled records. Some entries are reference information, not current alerts. It does not reproduce all VONA messages, aviation advisories or altitude-resolved ash forecasts. A clear-looking globe around a volcano cannot establish that an ash advisory is absent.
For a reproducible explanation, record the volcano identity, product type, issue time, observation or forecast time, and altitude reference where shown. Link the source message and retain its uncertainty. When comparing maps across Alaska and the wider North Pacific, also check which advisory centre issued each product. This preserves the difference between an observatory's status assessment and the mapped evolution of an atmospheric cloud.
Data sources
References are linked beside the explanations above. This evergreen guide does not report current incidents.