Texas Dow Employees Credit Union Routing Number, Address, Swift Codes. By State: 41 branches found. A routing number is a 9 digit code for identifying a financial institution for the purpose of routing of checks (cheques), fund transfers, direct deposits, e-payments, online payments, and other payments to the correct bank branch.
Specific to layered sedimentary rocks, geologists long ago determined that studying such layers -- what is called the âsuperpositionâ of the rocks -- is the key to tracking the Earthâs evolution, including the ebb and flow of oceans, lakes and rivers, and the shifting of sands and other forms of sediment.
So to determine the age of sedimentary rock layers, researchers first have to find neighboring layers of Earth that include igneous rock, such as volcanic ash. These layers are like bookends -- they give a beginning and an end to the period of time when the sedimentary rock formed. By using radiometric dating to determine the age of igneous brackets, researchers can accurately determine the age of the sedimentary layers between them. Using the basic ideas of bracketing and radiometric dating, researchers have determined the age of rock layers all over the world. This information has also helped determine the age of the Earth itself. While the oldest known rocks on Earth are about 3.5 billion years old, researchers have found zircon crystals that are 4.3 billion years old [source: USGS]. Based on the analysis of these samples, scientists estimate that the Earth itself is about 4.5 billion years old.