Eruption columns with heights of over break through the tropopause and inject particulates into the stratosphere. Ashes and aerosols in the troposphere are quickly removed by precipitation, but material injected into the stratosphere is much more slowly dispersed, in the absence of weather systems. Substantial amounts of stratospheric injection can have global effects: after Mount Pinatubo erupted in 1991, global temperatures dropped by about . The largest eruptions are thought to cause temperature drops down to several degrees, and are potentially the cause of some of the known mass extinctions.