Clearly, Sedimentary Rocks A were deposited and deformed before the Volcanic Dyke intruded them.These were then eroded and Sedimentary Rocks B were deposited.For example, a geologist may examine a cutting where the rocks appear as shown in Figure 1.Here he can see that some curved sedimentary rocks have been cut vertically by a sheet of volcanic rock called a dyke.
Uranium is present in many different rocks and minerals, usually in the form of uranium-238.
Following this introduction, there are several links to different sites concerning the methods scientists use to assist them in estimating the age of the Earth.
You will investigate Steno's Laws, radiometric dating, and then visit an interactive site that will help you better understand how to tell time - with geology! As you proceed through Assignment 4, be sure to compare your answers from "If Scientists Think. ." to the actual methods scientists use to estimate the age of prehistoric objects.
In Assignment 3, we began exploring the age of the Earth. Through presentation and discussion of individual ideas, the class reached agreements as to the best way to complete each of the prompts.
You worked in small groups and as a class to complete the "If Scientists Think. Today's assignment will allow you to compare and contrast your ideas to some of the actual methods scientists used to develop an estimation of the age of the Earth.