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Earth's volcanoes and earthquakes

Earth's volcanoes and earthquakes. Map of the Earth, centred on the American continents, showing the location of earthquakes (yellow dots) and volcanoes (red triangles). These are concentrated along the boundaries (red lines) of the tectonic plates that make up the Earth's crust. These tectonic plates move over the molten rock below them, colliding with and moving past, under and over each other. Immense pressures can build up, which are released during an earthquake. Where a plate is being destroyed under another one (seen around the Pacific Ocean), volcanoes form as the molten rock rises to the surface. Volcanoes can also form at isolated hotspots, such as Hawaii

© GARY HINCKS/SCIENCE PHOTO LIBRARY

Ripe cashew nut

Ripe cashew nut. Image 2 of 2. Native to South America, the cashew (Anacardium occidentale) is now widely cultivated throughout the tropics. Cashew trees produce a fruit, known as an 'apple' (centre), and a nut (lower centre). The nut forms before the fruit swells and ripens, which takes two months. Once harvested, the fruit is often discarded in favour of the nut, although it can be used to make jellies, jams and juice. The nut must be removed from its shell with care, as the shell contains an allergen that can cause dermatitis. Cashew nuts are used in a variety of sweet and savoury recipes. Photographed in Grenada. See B790/237 for an unripe cashew nut

© DAVID NUNUK/SCIENCE PHOTO LIBRARY

1812 Sloth skeleton by Cuvier

Skeleton of a three toad sloth, or 'Ai', copperplate engraving from Cuvier's "Ossamens Fossiles" 1812. Cuvier saw that the key to understanding fossils was to relate their bones to animals currently known. In this he was the father of comparative anatomy - a field that was to be crucial to the founding of modern biology. Here a modern sloth provides reference for the even larger bones of the extinct ground sloth megatherium that had been discovered in South America and displayed in Spain. Cuvier was among the first to realise the reality of extinction

© PAUL D STEWART/SCIENCE PHOTO LIBRARY