strata

Examples of strata in the following topics:

• The Fossil Record as Evidence for Evolution

  • The observation that certain fossils were associated with certain rock strata led 19th century geologists to recognize a geological timescale.
  • The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record.
  • The development of radiometric dating techniques in the early 20th century allowed geologists to determine the numerical or "absolute" age of various strata and their included fossils.

• Carbon Dating and Estimating Fossil Age

  • Stratigraphy is the science of understanding the strata, or layers, that form the sedimentary record.
  • Strata are differentiated from each other by their different colors or compositions and are exposed in cliffs, quarries, and river banks.
  • The layers of sedimentary rock, or strata, can be seen as horizontal bands of differently colored or differently structured materials exposed in this cliff.
  • The deeper layers are older than the layers found at the top, which aids in determining the relative age of fossils found within the strata.

• Biodiversity Change through Geological Time

  • Paleontologists have identified five strata in the fossil record that appear to show sudden and dramatic losses in biodiversity known as mass extinctions.
  • The transitions between the five main mass extinctions can be seen in the rock strata.