<P> The 1815 eruption of Mount Tambora created global climate anomalies that became known as the "Year Without a Summer" because of the effect on North American and European weather . Agricultural crops failed and livestock died in much of the Northern Hemisphere, resulting in one of the worst famines of the 19th century . </P> <P> The freezing winter of 1740--41, which led to widespread famine in northern Europe, may also owe its origins to a volcanic eruption . </P> <P> Sulfate aerosols promote complex chemical reactions on their surfaces that alter chlorine and nitrogen chemical species in the stratosphere . This effect, together with increased stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which destroys ozone (O). As the aerosols grow and coagulate, they settle down into the upper troposphere where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance . Most of the hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud and quickly fall to the ground as acid rain . The injected ash also falls rapidly from the stratosphere; most of it is removed within several days to a few weeks . Finally, explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles . </P> <P> Gas emissions from volcanoes are a natural contributor to acid rain . Volcanic activity releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year . Volcanic eruptions may inject aerosols into the Earth's atmosphere . Large injections may cause visual effects such as unusually colorful sunsets and affect global climate mainly by cooling it . Volcanic eruptions also provide the benefit of adding nutrients to soil through the weathering process of volcanic rocks . These fertile soils assist the growth of plants and various crops . Volcanic eruptions can also create new islands, as the magma cools and solidifies upon contact with the water . </P>

Which type of plain forms near a volcano