Hilltops surrounded by farmland in southern Wisconsin turn out to be the eroded remnants of an ancient archipelago. An island in the Yellow Sea where Korean tourists flock is the peak of a flooded mountain rising from a drowned continental shelf. From a mountaintop shrine to Genghis Khan in Inner Mongolia, the silhouette of a Silurian seascape can be spotted. On the shores of Hudson Bay, where polar bears patrol the Arctic tundra, a close look unveils what was a tropical coastline encrusted with corals nearly 450 million years ago.

The geologist Markes E. Johnson invites readers on a journey through deep time to find the traces of ancient islands. He visits a dozen sites around the globe, looking above and below today’s waterlines to uncover how landscapes of the past are preserved in the present. Going back 500 million years to the Cambrian through the Pleistocene 125,000 years ago, this book reconstructs how “paleoislands” appeared under different climatic conditions and environmental constraints. Finding vestiges of prehistoric ecologies, Johnson emphasizes the complexity of island ecosystems and the importance of preserving these significant sites.

Inviting and accessible, this book is a travelogue that takes readers through time as well as space. Islands in Deep Time shares the adventure of exploring striking locations across geologic eras and issues a passionate call for their conservation.

Islands in Deep Time is a deep dive into the logic of geology: how vanished land- and seascapes can be conjured back into existence from the raw rock record. All geologists collect old rocks, but Markes Johnson collects entire ancient islands. This book is an exhibit of a dozen particularly fine specimens, which Johnson holds up and rotates so they can be viewed from multiple perspectives. -- Marcia Bjornerud, author of Geopedia: A Brief Compendium of Geologic Curiosities and Timefulness: How Thinking Like a Geologist Can Help Save the World
Using his lifetime of experience in geology, Johnson illustrates how a landscape can be read as the results of millions of years of geological, biological, and climatological processes. A fascinating and imaginative work. -- Henry Hooghiemstra, emeritus professor in the Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam
Islands in Deep Time takes readers on hikes to ancient shorelines, featuring possibly the best descriptions and visualizations of field locations I have ever read. -- Gordon Chancellor, coeditor of Charles Darwin's Notebooks from the Voyage of the Beagle
[A…] geological tour de force. * Deposits Magazne *
Each of the twelve chapters includes a topographic map of the island's physical structure paired with a global map showing its location in the context of the geography unique to that time. The accompanying narrative offers a guided tour of each island, illustrated with images of fossil finds and geologic features. * Outrider Books & Travel *
Very much an enjoyable, informative, and relatable text that will serve well both the serious student of geology and the engaged lay reader alike. * H-Environment *
[Islands in Deep Time] is a little geological tour de force. * Outrider Reading Group *

Markes E. Johnson is the Charles L. MacMillan Professor of Natural Science Emeritus at Williams College. His most recent book is Baja California’s Coastal Landscapes Revealed: Excursions in Geologic Time and Climate Change (2021).