During large volcanic eruptions, tremendous amounts of ash and gases are spewedinto the atmosphere, where they reflect incoming solar radiation and reduce atmospherictemperatures.【】We know that small droplets of sulfur gases remain in the atmosphere for yearsand can have a significant effect on climate. 【 】 Several large-scale volcanic events have beenrecorded, such as the 1815 eruption of Tambora and the 1991 eruption of Pinatubo, and are knownto have had climatic effects.【】However, no relationship between periods of volcanic activity andperiods of glaciation has yet been established.【】9. Look at the four squares【】that indicate where the following sentence could be added tothe passage.The former decreased global temperatures by as much as three degrees Celsius, causing thefollowing year to be known in places as the year without a summer.