rates of increase of atmospheric carbon dioxide on a yearly basis based on the time of the article, the lightning-biota climatic feedback once again showed a cooling effect on global average temperatures, given an initial perturbation. Given the simplified nature of the model, several parameters (ozone produced by lightning, etc.) and other feedback mechanisms were neglected, so the significance of the results is still an area of discussion. Lightning in the geologic record Indicators of lightning activity in the geologic record are often difficult to decipher. For example, fossil charcoals from the Late Triassic could potentially be the result of lightning-induced wildfires. Even though lightning strikes are, for the most part, instantaneous events, evidence of lightning activity can be found in objects called fulgurites. Fulgurites Fulgurites (from the Latin fulgur, meaning "lightning") are natural tubes, clumps, or masses of sintered, vitrified, and/or fused soil, sand, rock, organic debris and other sediments that sometimes form when lightning discharges into ground. Fulgurites are classified as a variety of the mineraloid lechatelierite. Fulgurites have no fixed composition because their chemical composition is determined by the physical and chemical properties of material struck by lightning. When lightning strikes a grounding substrate, upwards of 100 million volts (100 MV) are rapidly discharged into the ground. This charge propagates into and rapidly vaporizes and melts silica-rich quartzose sand, mixed soil, clay, or other sediments. This results in the formation of hollow and/or branching assemblages of glassy, protocrystalline, and heterogeneously microcrystalline tubes, crusts, slags, and vesicular masses. Fulgurites are homologous to Lichtenberg figures, which are the branching patterns produced on surfaces of insulators during dielectric breakdown by high-voltage discharges, such as lightning. Fulgurites are indicative of thunderstorms; the distribution of fulgurites can hint at patterns of lightning strikes. Sponholz et al. (1993) studied fulgurite distributions along a north–south cross section in the south central Saharan Desert (Niger). The study found that newer fulgurite concentrations increased from north to south, which indicated not only a paleo-monsoon pattern, but also the demarcation for thunderstorms as they progressed from a northern line to a southern location over time. By examining the outcrops in which the fulgurite samples were found, Sponholz et al. (1993) could provide a relative date for the minerals. The fulgurite samples dated back approximately 15,000 years to the mid to upper Holocene. This finding was in agreement with the paleosols of the region, as this period of