The ground beneath our cities is rarely as stable as it appears. Beneath every road, foundation, and drainage system lies a complex landscape shaped by millions of years of geological processes—processes that continue to evolve long after the first brick…
Stratigraphy is one of geology’s most foundational disciplines—a systematic framework for reading Earth’s history as it is preserved in rock. By studying the order, composition, and age of rock layers, or strata, geologists can reconstruct past environments, track the movement…
The story of Earth is written in its rocks. Layer by layer, sediment accumulates, hardens, and preserves a record of life, climate, and geological events spanning billions of years. Understanding how to read that record begins with one of geology’s…
The Principle of Original Horizontality, formulated by Nicolas Steno in 1669, states that sedimentary rock layers are deposited in flat, horizontal sheets due to gravity. Any tilting or folding observed in rock strata today is the result of geological forces…
The history of Earth is written in stone—literally. Millions of years of geological activity have left behind a complex record of events, layered and interlocked in ways that can seem impossible to decode. Yet geologists have long relied on a…
Beneath every mountain range, canyon wall, and ocean floor lies a record of Earth’s history—written not in ink, but in stone. For geologists and paleontologists, deciphering that record depends heavily on a discipline known as biostratigraphy: the science of using…
The rock record is not a complete book. It is, more accurately, a book with chapters torn out—some pages missing entirely, others smudged beyond recognition. These gaps, known in geology as unconformities, represent spans of time during which sediment was…
Unconformities are gaps in the geological record caused by erosion or non-deposition. The three main types—angular unconformities, disconformities, and nonconformities—each reflect distinct tectonic and depositional histories. Identifying them helps geologists reconstruct Earth’s past environments and timelines with greater accuracy. Few…
Beneath every mountain range, river valley, and ocean floor lies a record of Earth’s history written in stone. Lithostratigraphy is the scientific discipline that deciphers this record—systematically classifying, describing, and correlating rock layers based on their physical and compositional characteristics.…
Billions of years of Earth history are recorded in rock. The challenge, for centuries, has been learning how to read it. Chronostratigraphy is the scientific discipline that makes this possible—translating the physical sequence of rock layers into a coherent timeline…
