1. Volcanic ashes covers earth’s atmosphere reducing the sunlight on earth.
2. Sulphur dioxide from volcanic eruption reacts with water vapour in upper atmosphere and becomes sulphuric acid. This sulphuric acid droplets acts as mirrors, which reflects sun’s energy back into space cutting down sunlight.
One of the automatic natural feedbacks that help to moderate the temperature extremes of the Earth–so even if we have a major rise in sea-level (7 metres from the loss of Greenland’s ice, for example)the extra mass of seawater creates more volcanic eruptions because of more pressure on the crust.