Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old.
To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones. This rule is common sense, but it serves as a powerful reference point.Geologists draw on it and other basic principles ( to determine the relative ages of rocks or features such as faults.By carefully digging, we have found that each trash pit shows a sequence of layers.Although the types of trash in each pit is quite variable, each layer has a distinctive kind of trash that distinguishes it from other layers in the pits.Free 5-day trial Discover how geologists study the layers in sedimentary rock to establish relative age.
Learn how inclusions and unconformities can tell us stories about the geologic past.Work on only a small part of the cross-sections geologic history then find the next higher unconformity and work on the events between the two unconformities.You will join the unconformities by linking them with periods of uplift and erosion followed by ocean rising and deposition of sedimentary rocks (if the rocks are marine in origin.The chemical composition of Earth's crust has similarities with other stony planets, with silicate-rich rocks being dominant in most locations on the surface.In addition, basic geologic principles can be applied to resolving the order of events leading to the formation of rocks and landscape features. Cross Sections - interpretations of vertical views of geologic features below the surface.Usually this exercise is associated with a cross section or profile in which there are a series of stacked rock units composed of sedimentary, igneous, and/or metamorphic rocks as well as structures such as faults and folds (anticline, syncline) and unconformities (nonconformity, angular unconformity, If you have subsequent deposition of marine sediments (limestone, shale and sandstone) then the land mass must subside or the oceans rise to cover the surface by water before you can have deposition of sediments.