From 1980 to 1984, he was a graduate student at the Institute of Geology at the Estonian Academy of Sciences, defending his degree in geology with a dissertation "Formation, composition and use of glaciofluvial deposits in Estonia" (his supervisor was Anto Raukas) in 1984.
Kalm had worked since 1981 in the Institute of Geology at the Faculty of Biology and Geography of the University of Tartu (since 2008 at the Institute of Ecology and Earth Sciences at the Faculty of Science and Technology), first as an assistant, from 1986 to 1988 as a lecturer, from 1988 to 1992 as a docent, and, from 1992 until his appointment as rector, as a professor of applied geology.
In 2007, he applied twice to be the rector of the university; the first time in 2007 was a failure, losing the position to Alar Karis who was ahead of him in other elections.
Kalm was chosen rector of the University of Tartu on 31 May 2012, ahead of Mart Ustav and Toivo Maimets.
Kalm has published studies on the mineralogy of lithology and stratigraphy, clay and archaeological ceramics in Estonia and the paleogeography of the Baltic, Scandinavian and Andean glaciers.