Many scientists believe that public anxiety over the pollution of foods is often unjustified. They argue that it is absurd for smokers, or heavy drinkers, to make much of this comparatively minor threat to their health. However pollution is a problem, and one which is still increasing, as more and more contaminants enter the environment and the food chain.

The word volcano comes from Vulcan, the Roman god of fire. It applies to openings in the Earth’s crust that spew out molten lava, ash, steam and gas, and to the cone of ash and lava that builds up around the opening.

Movement in the Earth’s crust, caused by an earthquake or volcano, can create a depression in an area of coastline Land surrounding a river sinks and floods, becoming a bay with a narrow opening to the sea. San Francisco Bay and the St Lawrence Estuary formed this way.