He served on the Geological Survey from 1862 until 1882, when be succeeded his brother as Murchison professor of geology and mineralogy at the University of Edinburgh. He took as his special subject of investigation the origin of surface-features, and the part played in their formation by glacial action. His views are embodied in his chief work, The Great Ice Age and its Relation to the Antiquity of Man (1874; 3rd ed., 1894). He was elected F.R.S. in 1875, his candidacy xitation reading " Author of "The Great Ice Age and its relation to the Antiquity of Man" "On the Changes of Climate during the Glacial Epoch" "On the Glacial Phenomena of the Outer Hebrides" (Quart Journ Geol Soc) and of various papers on Palaeozoic, Glacial and Post-Tertiary Geology in the Transactions of the Royal Society of Edinburgh; the Quarterly Journal of the Geological Society of London; the Transactions of the North of England Institute of Mining and Mechanical Engineers; the Journal of the Iron and Steel Institute; the Transactions of the Glasgow Geological Society; and the Geological Magazine; District Surveyor on the Geological Survey in Scotland for years, during which time he has surveyed, and drawn many sections through, large areas in the Central and Southern districts of Scotland which he has described in the published "Explanations" issued by the Geological Survey." 
Geikie became the leader of the school that upholds the all important action of land-ice, as against those geologists who assign chief importance to the work of pack ice and icebergs. Continuing this line of investigation in his Prehistoric Europe (1881), he maintained the hypothesis of five inter-Glacial periods in Great Britain, and argued that the palaeolithic deposits of the Pleistocene period were not post- but inter- or pre-Glacial. His Fragments of Earth Lore: Sketches and Addresses, Geological and Geographical (1893) and Earth Sculpture (1898) are mainly concerned with the same subject. His Outlines of Geology (1886), a standard textbook of its subject, reached its third edition in 1896; and in 1905 he published an important manual on structural and field geology.
In 1887 he displayed another side of his activity in a volume of Songs and Lyrics by H. Heine and other German Poets, done into English Verse. From 1888 he was honorary editor of the Scottish Geographical Magazine.
- "Library and Archive catalogue". Royal Society. Retrieved 7 January 2011.
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.
1913. Mountains, Their Origin,Growth and Decay.