What is Stratigraphy?

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  • Written By: Felicia Dye
  • Edited By: Heather Bailey
  • Last Modified Date: 20 January 2020
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Strata is a term that refers to layers of rock. Stratigraphy is the study of those layers of rocks. This branch of geology is believed to have developed from attempts to determine the Earth’s age. A scientist who specializes in this field is called a stratigrapher.

There are many places around the world where a person can view stratification, or layering of rocks. This is often evidenced when a body of rock appears to have bands running around it. These bands are actually sediments that have been compacted over time.

Stratigraphers believe that each of those bands represents a period. They believe those bands contain information about the past. Consequently, stratigraphers believe that studying those bands can provide many answers.

The study of stratigraphy can be used to do more than determine the age of the planet. It can also reveal information about environmental changes. To determine what they need to know, stratigraphers study rock samples called cores. These are slices of Earth composed of numerous strata.

At one time stratigraphy was considered an observational science. There was not much innovation involved. Now, scientists use modern methods such as seismic technology to obtain information about the Earth’s core. Seismic technology employs the use of waves that vibrate through Earth’s inner layers.


Stratigraphy not only studies the layers of rocks but also the fossils that are found in those layers. Fossils are remnants of the past that can provide a great deal of information to those trained to study such items. Impressions of animal skeletons and preserved vegetation are examples of fossils.

The study of stratigraphy is based on numerous theories developed by scientists throughout time. James Hutton, a Scottish geologist, was one of the first scientists to express the theory that the Earth is millions of years old. Before his theory, it was commonly held that Earth was only a few thousand years old. It is believed that Hutton’s theory helped prompt others to question whether ideas about Earth’s age were correct.

Later, Charles Lyell developed the law of superposition, which says that the lowest layers of soils are the oldest. William Smith developed a similar theory called the principle of faunal succession. His principle says that the fossils in the highest layers of rock are the youngest. Most stratigraphers today still believe that the youngest parts of this planet are those closest to the surface.


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I had the privilege of traveling to the Philippines with an undergraduate group of students from a course called sedimentology stratigraphy. I was invited along to acquire video footage for the geology departments Earth and Planetary science lab at my university.

The group conducted seismic stratigraphy and limestone analysis at the site of the Chocolate Hills in Bohol. It was a fascinating expedition to be on.

There's over seventeen hundred perfectly domed shaped hills covering a range of twenty square miles (fifty square kilometers). The formation of these brown grass covered limestone hills is still under speculation ranging anywhere from volcanism to simple weathering to the uplifting of the seafloor.

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