Abstract Chalk flows are flow slides that develop under certain circumstances from falls in chalk slopes. They are characterized chiefly by the mobility of the debris, which can run out over near-horizontal surfaces for as much as five to six times the slope height. After a brief account of the stratigraphy and extent of the Upper Cretaceous exposures of northwest Europe, chalk flows are described in outline, classified, and set in context with other types of flow slides. The relevant morphological parameters are defined. The incidence of chalk flows on the coasts of northwest Europe is outlined. Such failures occur in England, to a small extent in Sussex but predominantly in southeast Kent, in France from just north of Cap de la Hève to Ault in Haute-Normandie, in Denmark at Møns Klint, and in north Germany at Jasmund, in the northeast of the Isle of Rügen. It is shown that these flows occur only in soft chalks of high porosity (>~40%), in cliffs higher than ~30 m. Their mobility is inferred to derive principally from high excess pore-water pressures generated by a process of impact collapse in the saturated or near-saturated metastable soft chalk as it impacts onto the shore platform. Where earlier saturated colluvium is present on this platform, its undrained loading by the falling debris probably also plays a role, as does the presence or absence of seawater. Desirable further research is outlined, and the hazards posed by chalk flows are described.

Abstract Volcanic eruptions represent a significant source of volatile gases that are harmful to human health. This chapter reviews and develops current understanding of the human health response to volcanogenic pollution and dry fog events; in particular it explores the health impact of the gases from the Laki fissure eruption, and presents data that point to a significant increase in the national death rate in England coincident with the early phases of the eruption. It is noted that many common symptoms of severe exposure to air pollution can be linked to the dry fog of 1783; these included difficulty in breathing, eye and skin irritation, headaches, loss of appetite and tiredness.