Humboldt, (Friedrich Wilhelm Heinrich) Alexander (1769–1859)

German geophysicist, botanist, geologist, and writer who, with French botanist Aimé Bonpland (1773–1858), explored the regions of the Orinoco and Amazon rivers in South America 1800–04, and gathered 60,000 plant specimens. He was a founder of ecology.

Humboldt aimed to erect a new science, a ‘physics of the globe’, analysing the deep physical interconnectedness of all terrestrial phenomena. He believed that geological phenomena were to be understood in terms of basic physical causes (for example, terrestrial magnetism or rotation).

One of the first popularizers of science, he gave a series of lectures later published as Kosmos/Cosmos 1845–62, an account of the relations between physical environment and flora and fauna.

Humboldt was born in Berlin and studied at Göttingen and the Mining Academy, Freiburg. He travelled widely in Europe before the expedition to South and Central America. Surveying, mapping, and gathering information, Humboldt covered some 9,600 km/6,000 mi. The accounts of his travels were written over the next 20 years.

In meteorology, he introduced isobars and isotherms on weather maps, made a general study of global temperature and pressure, and instituted a worldwide programme for compiling magnetic and weather observations. His studies of American volcanoes demonstrated they corresponded to underlying geological faults; on that basis he deduced that volcanic action had been pivotal in geological history and that many rocks were igneous in origin. In 1804, he discovered that the Earth's magnetic field decreased from the poles to the Equator.