Adam Sedgwick was born on 22 March 1785 in the vicarage at Dent, Yorkshire, the third of seven children of Richard Sedgwick (1736-1828), the local vicar, and his second wife and cousin, Margaret (nee Sturgis). Sedgwick first attended the grammar school at Dent and then between the ages of eight and sixteen was under the instruction of his father. In 1801 he was sent to the grammar school at Sedbergh conducted by the Revd William Stevens.

In 1804 Sedgwick entered Trinity College, Cambridge, as a sizar, a position which allowed poorer students to pay reduced fees in exchange for carrying out a number of duties. Despite a near-fatal attack of typhoid in 1805 Sedgwick was elected to a college scholarship in 1807, and graduated fifth wrangler in the following year. He took private pupils and read for a Trinity fellowship, which he obtained in 1810. In 1813 he burst a blood vessel and his health broke down completely. Sedgwick recovered during the next few years, but suffered thereafter from poor health. He became an assistant tutor in mathematics at Trinity in 1815, and was ordained a year later, when he also travelled for several months on the continent.

In 1818 Sedgwick was elected to the Woodwardian Professorship of geology at the University of Cambridge, a post which he held for the next fifty-five years. He had previously attended the mineralogical lectures of Edward Daniel Clarke and read a few works on the subject. He undertook his first geological excursion in that summer and became a fellow of the Geological Society of London. In 1819 he delivered his first course of lectures, and joined with John Stevens Henslow and others to encourage scientific pursuits within the university by founding the Cambridge Philosophical Society.

Sedgwick was concerned to build up the geological collections of the university. He collected rocks and fossils during systematic tours in the British Isles and elsewhere in Europe, and also purchased rare specimens, either with his own funds or through public appeals for the then Woodwardian Museum from collectors such as Mary Anning and by the acquisition of complete collection such as that of Georg Graf von Munster. He acquired about 40,000 to 50,000 specimens by the 1840s.

The collection however outgrew its original accommodation, and in 1841 spacious new quarters were made available. The Woodwardian had a reputation as one of Europe's outstanding geological museums.

Sedgwick became an accomplished field geologist, learning much from Henslow and William Daniel Conybeare. His earliest papers, read in 1820 before the Cambridge Philosophical Society, discussed the structure of the ancient rocks of Devon and Cornwall.

In 1828 Sedgwick accompanied Roderick Murchison, whom he had met at the Geological Society, on a tour of Scotland. Opposing the work of John MacCulloch, they concluded that the ancient sandstones of the north-west highlands could be correlated with the Old Red Sandstone to the east.

Two presidential addresses to the Geological Society in 1830 and 1831 expressed his theoretical views. Discussing Charles Lyell's Principles of Geology (1830-33), Sedgwick agreed that geologists had demonstrated the need for a vastly expanded time-scale. He abjured his support for fellow cleric William Bucklands attempt to find empirical evidence for a universal flood, and attacked those, like Andrew Ure and William Cockburn, who interpreted geology in the light of scripture. However, Sedgwick rejected what he saw as Lyell's gratuitous assumption that geological processes had been uniform in intensity throughout all time. He argued that the empirical record of the strata bore witness to catastrophic events without parallel in forces currently shaping the face of the earth.

From the late 1820s, Sedgwick's chief goal in geology was to complete a big book on the strata below the Old Red Sandstone. Most of his papers over the next two decades were progress reports on this project, as Sedgwick toured the Lake District, Wales, and the southern uplands of Scotland to add to his knowledge of the older rocks.

In 1831 he entered north Wales with a young Charles Darwin, who thereby gained his first training in the field. Sedgwick, with his grounding in mathematics, had an ability to work out the complex geological structures characteristic of these strata. Particularly important was a distinction, which he emphasized from the late 1820s, between stratification, jointing, and slaty cleavage. Sedgwick was also guided by Leonce Elie de Beaumont's theory of the elevation of mountain chains, which he believed would provide a key to unravelling the older rocks.

While Sedgwick was in north Wales, Murchison independently began examining the younger and more fossiliferous strata of south Wales and the Welsh borders. Together, their work provided the foundations for a new classification of the oldest rocks with fossils: Sedgwick's strata were called the Cambrian, while Murchison's became the Silurian. This amicable arrangement was threatened when Henry De la Beche discovered Coal plants in rocks which appeared to be of the same age as those which the two friends had been studying. The resulting controversy, in which the two friends collaborated closely, bore fruit in their 1839 announcement of the Devonian system as a distinctive period in earth history.

The creation of the Devonian, however, also removed any distinctive fauna from Sedgwick's Cambrian. The problem was exacerbated when John Eddowes Bowman, Daniel Sharpe, and finally the official Geological Survey extended its work into Sedgwick's territory during the early 1840s; most of the strata which had been identified as being older than the Silurian proved to be of the same age. Almost all geologists followed Murchison in wiping the Cambrian off the map. Sedgwick believed that the question involved nothing less than the foundations of proper scientific method.

By the 1850s Sedgwick argued the case for the Cambrian, cutting off links not only with Murchison, but also with the Geological Society (whose Wollaston medal he had been awarded in 1851) and the metropolitan geological community more generally. The controversy was settled only after Sedgwick's death. The discovery of a fauna below that of Murchison's oldest Silurians, first in Bohemia and then in Wales, became the basis for a redefined Cambrian. The uppermost strata of Murchison's expanded system were called Silurian, and the strata in between were termed Ordovician.

Throughout his life, Sedgwick was an advocate of the moral basis of scientific enquiry. His Discourse on the Studies of the University (1832), originally delivered as a sermon in Trinity College chapel, argued for the place of geology within natural theology, opposing what he condemned as the misuse of the science by scriptural literalists.

Sedgwick opposed all attempts to explain the origin of new species through natural laws. He was particularly concerned about Robert Chambers's anonymous best-seller, Vestiges of the Natural History of Creation (1844), which introduced an evolutionary cosmology to a wide public. By the time Darwin sent him a copy of the Origin of Species in 1859, Sedgwick's reaction was one of dismay.

Sedgwick's lectures, like all those in the natural sciences at Cambridge in the first half of the century, were extracurricular and aimed to make geology an appropriate study for the Christian gentleman. When Sedgwick set his first examination questions in 1851 after the introduction of the natural sciences tripos, he asked students to show that the fossil evidence does not support evolution.

Sedgwick was a major performer at the British Association for the Advancement of Science (BAAS), serving as president at its third meeting in 1833 at Cambridge. In this capacity he voiced his belief that science should be extended to working-class audiences. He gave lectures throughout the country, serving as an example of the compatibility of truths of religion and science. In 1820 he became a fellow of the Royal Society of London, which awarded him its Copley medal in 1863 as part of an anti-Darwinian campaign.

Sedgwick was active in university politics and administration. He was appointed senior proctor in 1827, and in 1847 he served as secretary to Prince Albert in his capacity as university chancellor. In politics Sedgwick strongly supported reform of the ancient universities and the abolition of religious tests, and for two years from 1850 he sat on the royal commission appointed to investigate the affairs of the university.

His income from his chair was supplemented by his college fellowship at Trinity and by his appointment in 1825 to the vicarage of Shudy Camps, Cambridgeshire. In 1832 the whig government offered Sedgwick the valuable living of East Farleigh, which he turned down. Two years later he accepted a prebendal stall at Norwich, which required absence from Cambridge for only two months of each year. Sedgwick had strong evangelical views and opposed innovations in Anglican ritual.

Sedgwick never married. He died in his rooms at Trinity College on 27 January 1873, and was buried in the college chapel on 1 February. The Sedgwick Museum in Cambridge was established by his successor, Thomas McKenny Hughes, as a memorial to house the collections he had brought together. He is memorialized in the Sedgwick prize, given at Cambridge for a student essay; the Sedgwick Club, the undergraduate geological society; and by a granite memorial fountain in Dent.