Lascar, a volcano located in northern Chile, erupted on April 19, 1993. Eruptions such as this can send large amounts of fine ash particles high into the atmosphere, where they sometimes remain for years. The ash particles scatter incoming sunlight, shading and slightly cooling Earth's surface. Some very large eruptions can have a measurable effect on climate worldwide.
Image courtesy University Corporation for Atmospheric Research; photo by Caspar Ammann.