Earth's geological history is punctuated by episodes of unusually protracted and large-scale volcanic activity, during which huge volumes of igneous rock are added to Earth's surface and crust. Humans have not witnessed this type of large-scale volcanic activity, known as large igneous province volcanism, but it is often temporally associated with profound environmental and climatic changes, such as mass extinction events. In order to understand what triggers these global changes, we need to consider the fluxes of particles and gas emitted by large igneous province-scale volcanic activity and match our projections with the signals left in the geological record. This is a challenging endeavour and this chapter discusses how evidence from today's active volcanoes can teach us not just about the present-day impact of volcanism, but also about these much larger volcanic eruptions that happened tens to hundreds of millions of years ago. The author argues that by peering into volcanoes, we can shed new light on enigmas surrounding the evolution of Earth's environment and biology over its deep geological history.