Geological Time


Relative Dating Metamorphic Facies Outline

Why do engineers need to know about geologic time ?

Geolgical time is a method of ordering and measuring past events. The ordering of events uses a group of observational methods known collectively as:

Measuring techniques rely on looking at geological processes with a strong annual signature (eg. growth rings in various organisms) or on processes that occur at a constant and measureable rate (eg. radioactive decay). These methods comprise: The importance of "time" in engineering geology is in providing estimates of frequencies for rare events such as floods, volcanic eruptions, and earthquakes. Landslides can be dated and the rates of mass-wasting determined for studies of coastal erosion and valley slope recession.

Geological time periods have been given names that correspond to segments of the distant past. These names were appropriate when few absolute ages were known but relative ages could be assigned (mainly by analysis of the fossil record). The names are now part of the technical literature and popular culture (Jurassic Park).

As radiometric methods become increasingly refined, the "dates" associated with the names are modified so it is impractical to use the absolute dates in most cases.


Relative Dating Metamorphic Facies Outline
(c) Department of Civil and Geological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada, S7N 5A9