1. The gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate. Most of the particles spewed from volcanoes cool the planet by shading incoming solar radiation. The cooling effect can last for months to years depending on the characteristics of the eruption.
2. a period of colder climate and increased glaciation occurring between warmer periods, in particular one such period which reached its peak during the 17th century. Scientists have figured out when past ice ages likely occurred by studying the geology of the land. Scientists also study the chemicals in rocks and fossil evidence to determine when ice ages have occurred.
