Vapours of sulphur escaping from a volcano often form a crust on the rocks. The process involved is an example of

The correct answer is deposition.

Key Points

Deposition:

• Vapours of sulphur escaping from a volcano have a gaseous state. The crust on the Rock has a Solid state.
• Here, Gas is directly converted into a solid.
• The deposition is the process in which phase conversion takes place from a gaseous state to a solid state without passing via the liquid phase.
• It is a type of thermodynamic process.
• It is the reverse process of sublimation thus, it is also called desublimation.

Example of Deposition:

• Frost is a common example of deposition because water vapours from humid air are directly deposited on the solid and crystalline frost pattern on windows or on a leaf, without ever being altered into a liquid phase.
• Soot is another example of deposition, as soot is deposited on the walls of chimneys, Soot is black powdery molecules that arise due to the burning of things that are collected in chimneys.