Abstract The HOTSAT multiplatform system for the analysis of infrared data from satellites provides a framework that allows the detection of volcanic hotspots and an output of their associated radiative power. This multiplatform system can operate on both Moderate Resolution Imaging Spectroradiometer and Spinning Enhanced Visible and Infrared Imager data. The new version of the system is now implemented on graphics processing units and its interface is available on the internet under restricted access conditions. Combining the estimation of time-varying discharge rates using HOTSAT with the MAGFLOW physics-based model to simulate lava flow paths resulted in the first operational system in which satellite observations drive the modelling of lava flow emplacement. This allows the timely definition of the parameters and maps essential for hazard assessment, including the propagation time of lava flows and the maximum run-out distance. The system was first used in an operational context during the paroxysmal episode at Mt Etna on 12–13 January 2011, when we produced real-time predictions of the areas likely to be inundated by lava flows while the eruption was still ongoing. This allowed key at-risk areas to be rapidly and appropriately identified.

This paper presents a review of recent progress on the theory of orographic precipitation and a discussion of the role of preexisting atmospheric disturbances, especially their strong water vapor fluxes. I also introduce the basic elements of stable moist airflow dynamics and cloud physics, and a new linear theory of orographic precipitation. The theory is tested against two types of data: a single event of Alpine precipitation and the annual climatology of the Oregon coastal ranges. Different methods are used to determine the free “cloud-delay” parameters in the theory, including a statistical analysis of data from conventional rain gauges and isotope analysis of stream samples. The surprising threshold behavior of nonlinear accretion-dominated cloud physics is displayed. Finally, I consider the impact of scale-dependent precipitation patterns on erosion and terrain evolution.

Sediments containing components produced by accretionary events should contain sufficient geochemical evidence to constrain several of the variables involved in modeling the environmental consequences of such events. We consider the geochemical record expected for 3 modes of accretion: accretion from an interstellar cloud, non-impacting accretion of weak materials subjected to tidal and atmospheric disruption, and the impact of dense asteroidal or cometary materials. To constrain an accretionary event, it is important to determine: 1) the siderophile abundance patterns; 2) the duration of the event; 3) the geographic extent of the anomaly; 4) the physical nature of the extraterrestrial materials and their siderophile concentrations; and 5) the source of the terrestrial component. In attempting to constrain the Cretaceous-Tertiary and the Antarctic Basin late-Pliocene events we find that the necessary evidence is only partially available. It seems clear that the Cretaceous-Tertiary event generated fallout on a worldwide basis, and that its duration was ⩽1 ka, but other features are not yet well defined. The siderophile pattern is generally chondritic, but variations from site to site (and even sample to sample) indicate differing geochemical fractionations during deposition and make it impossible to associate the projectile with a specific group of meteorites. Future studies of unusually well-preserved basal layers at Caravaca and DSDP 465A may improve the precision with which the siderophile patterns are determined. Magnesium concentrations and isotopic studies argue against a mantle ejecta component in the boundary layer, and thus against the oceanic impact of a dense projectile.

Two independent calculations suggest that temperate marine zooplankton would starve to death relatively quickly if phytoplankton photosynthesis were to cease. A sudden atmospheric darkening, blocking 99% of sunlight, as might accompany the impact of a large meteor, would be sufficient to stop global photosynthesis. An equation derived from basic principles, solved using North Sea plankton data, gives 9–41 days as the duration of the shortest atmospheric darkening needed to initiate a zooplankton starvation crisis during the spring season. An adaptation of a simple plankton model gives outer limits ranging from 104 days in January to 33 days in July and August for critical blackout durations. The durations and severity of critical atmospheric darkenings are well within the plausible limits established by other workers, and such an event cannot be discounted as a cause of the widespread terminal Cretaceous plankton extinction.