“The Grand Facts of Stratigraphy”: Ives’s Strata Map

When you look at a map, what do you see? If you’re looking at a road map, you’re likely seeing things on top of the earth’s surface – or a symbolized depiction of them – like streets, buildings, or whole cities. If you want to see the surface of the earth itself, you have to look at a physical map, a satellite photo, or maybe a soil map. Want to see what’s below the soil? Try a geological map, which shows the bedrock underlying the soil and the built environment.

But what if you want to know what’s under the bedrock? To visually delve deep into the earth’s crust to see the layers of geologic time laid out before you?

One map in the Geography and Map Division that can help you out. The Strata map of part of the United States of America, together with a portion of the Dominion of Canada, published around 1888 by James T. B. Ives, is a unique geological map, which demonstrates the stratigraphy of the eastern US in three vivid dimensions.

The strata map is essentially an oversized flip book. Ten plates are bound together, with a cloth hinge connecting them along the south edge. Each plate represents a layer of rock under the surface of the eastern United States which was deposited during a particular geological period. Laid one by one on top of each other, they build up the structure of the land.

When the topmost plate, representing the recent Quaternary deposits, is in place, the strata map shows the geology underlying the surface of the eastern US in all its multicolored glory.

Ives’s strata map was designed as an educational tool for schools, colleges, and a science-hungry public. The map emphasizes that layers of rock are exactly that – layers, superimposed on top of each other, with newer rocks generally occurring on top of older rocks. Per the pamphlet which accompanies the map, “that the formations, or strata, do thus run under one another is constantly proved in mining, a shaft often passing through several successively.” The idea that different types of rock simply occur next to each other, with each type extending from the earth’s surface to its core, is “a very mischievous conception,” resulting from uncritical observations of standard geological maps, which don’t show depth.

The accompanying pamphlet includes a page of statements from geology experts at various universities, museums, and geological survey agencies. “Wherever American geology is taught your map should be part of the apparatus,” said President D. C. Gilman of Johns Hopkins University. Professor R. P. Whitfield of the American Museum of Natural History described it as “In the direction of a want long felt by teachers of geology.” Perhaps the most prestigious review comes from Major John Wesley Powell, then the director of the U.S. Geological Survey:

After examination I am able to state that the work has been executed with care and fidelity, and I believe will be a valuable aid to teachers.

The pamphlet goes on to provide “an introduction to geology by means of the strata map.” It is explained that the different layers of rock are distinguished and classified by the inclusion of fossils, which vary depending on the time period in which the animals and plants lived, and by the makeup of the land at the time of fossilization. Geological terms such as “outcrop,” “escarpment,” “dip,” and “strike” are defined, and ways to illustrate those terms by holding the atlas in different ways.

The map in G&M’s collections is accompanied by a wooden template used for cutting out portions of the map, giving some insight into how it was made.

The science of geology has evolved since the late 19th century: we’ve learned better ways of dating rock layers beyond seeing which fossils they contain, and our picture of the geologic past has become much richer. But the fundamental principles conveyed through Ives’s strata map remain true. And it’s hard to argue with the visual and tactile impact of peeling back layers of time and rock as a tool for understanding earth’s history.

Learn more:

• Learn how to read a geologic map from the Wisconsin Geological and Natural History Survey
• How Geology Shapes History explores the geology of the eastern US and its impact on cities and society
• Explore more geologic maps in our online collections
• Find modern geologic mapping in the National Geologic Map Database