Describe the secondary effects of volcanic eruptions [4]

Volcanic eruptions can result in a wide variety of secondary effects, which are effects which happen some time after the eruption itself. Most commonly, these are negative, for example, travel can be disrupted. After the Mt St Helens eruption of 1980, traffic was unable to flow for 3 days in the area, due to a build up of ash. Additionally, there can be widespread homelessness if, for example, lava or pyroclastic flows reach settlements. This loss of housing can result in further economic damage, since the poverty resulting from the loss of possessions would prevent people from spending in local businesses, leading to their closure. This is also known as the multiplier effect. Looking at a larger scale, changing climate is a secondary effect of volcanic eruptions. The release of aerosols and volcanic ash from eruptions causes more incoming solar radiation being reflected and blocked, resulting in overall cooling. Although this is not an effect of every eruption, it has occurred in the past, for example the 1883 eruption of Krakatoa resulted in global cooling. However, the effects of volcanic eruptions are not always negative: ash deposits can often result in increased soil fertility, enabling improved agricultural production in subsequent years. Furthermore, tourism can be increased in areas where volcanic eruptions have occurred, for example a visitor centre has opened near Mt St Helens for tourists to learn about the eruption of 1980.