This analogy highlights the relative length of each geologic time period. Spread your arms wide. With the span of your arms representing all geologic time, look at one hand; your fingertips represent the formation of Earth and the beginning of geologic time. Now look at your other hand; the Cambrian Period begins in the wrist area of this hand, and the Permian extinction is at the other end of the palm. The Cenozoic Era is in a fingerprint, and with a single stroke of a nail file, you eradicate human history (McPhee 1998). From the American Geosciences Institute comes Big Idea 2: Earth is 4.6 Billion Years Old. Watch Earth form, and learn about Earth's history and the events of deep time. See what processes shaped the Earth we know today. Fossils Through Geologic Time. Fossils are found in the rocks, museum collections, and cultural contexts of more than 260 National Park Service areas and span every period of geologic time from billion-year-old stromatolites to Ice Age mammals that lived a few thousand years ago. Visit the parks that preserve fossils from each major time period. Geologic Time - Geology (U.S. National Park Service)
n/a
n/a