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?

Answer: (d) All four

Eruptions throw out pyroclastic debris, ash and dust, and gases including nitrogen and sulphur compounds (NCERT).

The idea

An eruption can release solid fragments, molten rock and gases together. Expanding gas can break magma and older rock into pieces of different sizes. Do not restrict volcanic products to the glowing lava visible in photographs.

Magma rises → Pressure falls → Dissolved gases form bubbles → Gas expands and may fragment magma → Fragments and ash are expelled → Gases spread while lava may flow

Why the others are wrong

(a) Keeps only pyroclastic debris — thinking of a volcano as just rock and lava. Much of an eruption is gas and fine ash.

(b) Keeps the solids (debris, ash) and drops the gases. Volcanic gas includes sulphur and nitrogen compounds.

(c) Usually drops nitrogen compounds. Sulphur is remembered for its smell; NCERT lists nitrogen too.

The trap

Everyone remembers sulphur (the rotten-egg smell) and forgets nitrogen. NCERT lists both.

Also know

Tephra is the collective name for airborne volcanic fragments: ash is finest, lapilli are larger, and blocks or bombs are larger still. A pyroclastic flow is a hot mixture moving rapidly along the ground; a lahar is a water-rich volcanic mudflow. Sulphur dioxide reaching the stratosphere can form sunlight-reflecting aerosols; this differs from the warming effect of carbon dioxide.