14.1: What is Geologic Time?

What Is Geologic Time?

The amount of time involved in carving a landscape, forming rocks, moving continents is an important scientific question. Different hypotheses Links to an external site. about the age of the Earth offer drastically different perspectives of the workings of geologic events that formed and shaped the planet. For example, if geologic time is relatively short (less than a 100 million years) then catastrophic events would have been required to form the features we see on the surface of Earth; whereas vast amounts of geologic time (more than 100 million years) could have produced the slow, steady rate of change we observe around us today.

Examining geologic time, or deep time Links to an external site., can be challenging for humans, as it is difficult for us to imagine hundreds of millions or billions of years. Geologists have used a variety of methods to map major geologic events and their duration to reconstruct Earth’s history Links to an external site. during the last 4.54 billion years. Early geologists (naturalists) were able to piece together a progression of rocks through time to construct the original Geologic Time Scale Links to an external site., and geologists continue to update and make the timescale more accurate (Figure 14.1). Interested in more GTS? Visit this interactive time scale Links to an external site. for more information!

Those who study geologic time can be associated with a variety of disciplines within geology, including sedimentology, paleontology, geomorphology, petrology, structural geology, and many others. Like many other geoscientists, working with other disciplines is common, with a heavy influence from both math and technology. Many are employed by universities where they teach and/or do research, and state and federal agencies, including geological surveys, like the California Geological Survey Links to an external site. or United State Geological Survey (USGS) Links to an external site.. Additional career pathways are available in the private sector including in mining and natural resource extraction. Many of these career options require a college degree and postgraduate work. If you are interested, talk to your geology instructor for advice. We recommend completing as many math and science courses as possible (chemistry is incredibly important for mineralogy). Also, visit National Parks Links to an external site., CA State Parks Links to an external site., museums, gem & mineral shows, or join a local rock and mineral club. Typically, natural history museums will have wonderful displays of rocks, including those from your local region. Here in California, there are a number of large collections, including the San Diego Natural History Museum Links to an external site., Natural History Museum of Los Angeles County Links to an external site., Santa Barbara Museum of Natural History Links to an external site., and Kimball Natural History Museum Links to an external site.. Many colleges and universities also have their own collections/museums.