Stratigraphy – Annika Sturgeon

Stratigraphy is an area of study within the science of geology that analyzes the layers found in rocks, their positionings to each other, and their relation to the geographic time scale. Generally, rock layers are built by sediment deposition. This sediment is compressed over long periods of time, forming layers —or “strata”— of sedimentary rock. In the 17th century, Danish scientist Nicolas Steno investigated this occurrence and documented his discoveries, earning the reputation as the pioneer of stratigraphy. Steno also explained that the oldest layer of rock is found the farthest from the surface of the Earth, while the newest is the closest.

The differing properties, compositions, and materials —such as fossils— that are found in each layer of sedimentary and volcanic rock has allowed scientists to understand the geological makeup of the Earth at different times in the past and divide its four-billion-year history into distinct geological periods. Not only does stratigraphy relate to geological periods, but it also relates to human understandings and experiences of time. Typically, human understandings of time revolve around our lifespan, or a few generations. This span is but a fleeting moment when compared to geologic time. The vast timescales involved in stratigraphy are difficult to comprehend because they far exceed our personal experience and historical accounts.

This vastness of stratigraphy is exemplified by iconic geological formations such as the Grand Canyon, where millennia of sediment deposition has sculpted intricate layers —each representing how the Earth has changed throughout time. Over millions of years, the Colorado River carved a path through the rock known as the Colorado Plateau. As the river carved deeper, more layers of rock were exposed, revealing the passage of time. To see millions of years of history in front of you in a canyon is a feeling like no other.

References:

BBC News. (2023, March 26). The man who discovered the “abyss of Time.” YouTube. https://www.youtube.com/watch?v=esqxYO5vsEI

PBS Eons. (2017, November 6). A Brief History of Geologic Time. YouTube. https://www.youtube.com/watch?v=rWp5ZpJAIAE