Figure 13 – The 110,000-year GISP2 record of volcanic SO42-, compared to the GISP2 Ca2+ record (higher calcium reflects colder climatic conditions, lower calcium reflects warmer climatic conditions). All of the eruptions represented by the signals shown here probably were of sufficient magnitude to have perturbed climate. The number of eruptions recorded in the GISP2 core is fewer than the number of northern hemisphere or equatorial eruptions that actually occured over the last 110,000 years because of the decreased temporal resolution of individual samples with depth and age. Also shown are glaciochemical signals believed to be from the equatorial Toba eruption (T) and the high-latitude Icelandic eruptions that produced the Z2 tephra layer in North Atlantic marine sediment cores. Tephra found in the the Z2 layer of the GISP2 core matches that found in marine sediments (Zielinski et al., 1997), thereby providing an example of one absolute means of establishing a distinct time line for correlation among ice core, marine, and terrestrial records. Modified from Zielinski et al., 1996a.