Assertion (A): The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil and thus create fertile soil.

Reason (R): Agricultural fields are covered with layers of volcanic ash and dust making them unsuitable for cultivation.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R does not explain A.
3. A is true but R is false.
4. A is false but R is true.

Both A and R are true but R does not explain A.

Explanation — Lava and volcanic ash break down over time to form mineral-rich fertile soil, which is a constructive effect of volcanoes. Hence, Assertion (A) is true. Volcanic eruptions may also cover agricultural land with ash and dust, damaging crops and making the land unsuitable for cultivation, which is a destructive effect of volcanoes. Therefore, Reason (R) is also true. However, the destructive effect stated in Reason (R) does not explain the constructive effect mentioned in Assertion (A).