The diagram below shows how 'Acid Rain' occurs.

The process illustrates how the acid rain is formed. Overall, the harmful precipitation is originated by two different causes: man-made and natural eruption of a volcano. Likewise, it is noticeable that the process has two types: ‘wet deposition’ which refers to rain, and ‘dry deposition’ is a term used to describe gaseous and particulate matters in the atmosphere. Initially, acid rains occur by two sources: man-made and natural vegetation. Man-made involves evaporation of various compounds of sulfur and nitrogen to the atmosphere layers, whilst the natural one is provoked by eruption of volcanoes, poisoned lakes and vegetation. Followed by the prevailing wind, evaporated chemicals with dust and ash particles from volcanoes are transferred to the clouds. Later on, these air masses with their specific wet percentage absorb these compositions of the abundance of elements and further mix with regular water droplets. Finally, depending on whether the temperature of the air is below 0 degrees Celsius or not, subsequent mass falls out in the form of acidic precipitations either the occurrence of ‘acid rain’ and ‘acid snow’.