Consider the following: 1. Pyroclastic debris 2. Ash and dust 3. Nitrogen compounds 4. Sulphur compounds How many of the above are products of volcanic eruptions?

All four items are products released during volcanic eruptions. Pyroclastic debris (hot rock fragments) and ash and dust are obvious solid ejecta. Volcanic gases include large amounts of water vapour, carbon dioxide, sulphur compounds (such as SO2 and H2S), and nitrogen compounds (including N2 and nitrogen oxides). Sulphur compounds are particularly important as they form sulphate aerosols affecting climate, while nitrogen and its compounds are also released in significant quantities.