Modifiers matching depression:

• major,
• volcanic,
• geriatric,
• clinical,
• topographic,
• regular,
• severe,
• chronic,
• moist,
• mental,

Simple categories matching volcanic:

• rock,
• eruption,
• depression,
• material,
• emanation,
• stone,
• structure,
• deposit,
• domain,
• substance,
• centre,
• precursor,
• stratum,
• cone,
• feature,
• product,
• phenomenon,
• flow,
• episode,
• system,
• action,
• component,
• substrate,
• activity,
• marker,
• process,
• hazard,
• unit,
• island,
• lava,
• condition,
• mineral,
• sediment,
• form,
• event,
• formation,
• sand,