IT'S ALL RELATIVE

The image below is a photo of the exhibit panel. Following it is a transcript of the panel.

Photo of the panel from the exhibit.

Photo of the panel from the exhibit.

Rocks can be dated in relation to other fossil-bearing rocks.

Relative Geologic Time
Most fossils are found in sedimentary rocks, which form in layers at the Earth's surface as mineral grains are deposited by water, air, or ice. In a sequence of undisturbed rock layers, older fossils are found in lower layers; newer fossils are found in higher layers.

Because life forms appear, evolve, and become extinct at different times, distinctive fossils characterize different eras and rock layers. Rocks that contain the same kinds of fossils are assumed to be the same age, even if they are found in areas that are far apart.

PICTURE CAPTIONS:
Vertical Images

  • 5,000 years ago to present bottles, cans, roots
  • 6,000 years ago volcanic ash
  • 650,000 to 10,000 years ago human skull & jaw bone, spear points, potsherds
  • 1.8 million years ago to 40,000 years ago mammoth tusks
  • 6 to 4 million years ago fish
  • 15 to 5 million years ago oysters, scallops, barnacles, sand dollars, shark teeth, whale bones
  • 35 to 25 million years ago petrified wood
  • 35 to 25 million years ago mammal skulls, rhinoceros teeth, saber-toothed cat skull, turtle, seeds
  • 55 to 45 million years ago insects, fishes, bat
  • 85 to 65 million years ago ceratopsian dinosaur bone, petrified wood
  • 85 to 65 million years ago
    • ammonites, clams, oysters, shark teeth, fish vertebrae
  • 15 to 100 million years ago ammonites, belemnites, snails, clams, sea urchins

Horizontal Images

  • 208 to 204 million years ago therapod dinosaur
  • 240 to 255 million years ago ammonites, belemnites, scallops
  • 285 to 265 million years ago mesosaurs
    • (small aquatic amniotes)
  • 285 to 265 million years ago amphibian relatives
  • 285 to 265 million years ago tetrapod trackway
  • 320 to 290 million years ago ferns, horsetail relatives
  • 320 million years ago coal
  • 320 to 290 million years ago crinoids, ammonoids, snails, clams, corals, brachiopods, bryozoa, phytoplankton
  • 390 to 360 million years ago trilobites, brittle stars
  • 390 to 360 million years ago sponges, corals, snails, nautiloids, trilobites, brachiopods
  • 430 to 410 million years ago nautiloids, snails, corals, trilobites, bryozoa, trace fossils (burrows & trails)
  • 430 to 410 million years ago graptolites (multi-celled colonial animals)
  • 480 to 440 million years ago nautiloids, snails, brachiopods, bryozoa, trilobites
  • 540 to 520 million years ago trilobites, brachiopods
  • 570 to 540 million years ago trilobites, trace fossils (burrows & trails)
  • 590 to 570 million years ago small conical shells
  • 600 million years ago Ediacaran animals
  • 900 million years ago stromatolites