Where urban planners and architects in Chicago, London, and Tokyo saw in their fires an opportunity for more modern cities, in volcanic eruptions such as Laki, Krakatoa, and Vesuvius scientists have seen an opportunity to better understand the natural world itself. In their violent explosions, volcanoes reveal the secrets below the surface of the earth. In turn, by distributing matter into the air, they reveal global weather patterns and the warming and cooling effects of particulate matter in the air. And, in their ash and lava, they can turn a whole city into a fossil. The scientific allure of volcanic disaster, for instance, drove Alexander von Humboldt to climb every volcano in the Andes and, in 1803—thirty years after the eruption at Laki—to try to delay his return to Europe when he heard that Cotapaxi had just erupted two hundred miles away.  The enormous scale of volcanic disasters, that is, allows scholars from Benjamin Franklin and Humboldt to contemporary environmental scientists to understand the interconnectedness of the world.