Teaching about Earth’s history is a challenge for all teachers. Time factors of millions and billions of years is difficult even for adults to comprehend. However, “relative” dating or time can be an easy concept for students to learn. Once they are able to manipulate the cards into the correct sequence, they are asked to do a similar sequencing activity using fossil pictures printed on “rock layer” cards. Sequencing the rock layers will show students how paleontologists use fossils to give relative dates to rock strata. Once students begin to grasp “relative” dating, they can extend their knowledge of geologic time by exploring radiometric dating and developing a timeline of Earth’s history. These major concepts are part of the Denver Earth Science Project’s “Paleontology and Dinosaurs” module written for students in grades
1.2: Geologic Time
We usually think in terms of a few tens of years, since that measures a lifetime. Hundreds or thousands of years are considered ancient history. But in geology, we must think in time spans of millions of years, hundreds of millions of years, even of billions of years. Geologists measure such tremendous spans of geologic time in a relative sense, that is, one event occurred after another and prior to a third event.
In that sense, a geologic time scale was developed in the ‘s to make handy “boxes” of relative time periods in order to think of events in an understandable manner.
Relative dating arranges geological events – and the rocks they leave The activity offers literacy opportunities as well as practice using the.
September 30, by Beth Geiger. Dinosaurs disappeared about 65 million years ago. That corn cob found in an ancient Native American fire pit is 1, years old. How do scientists actually know these ages? Geologic age dating—assigning an age to materials—is an entire discipline of its own. In a way this field, called geochronology, is some of the purest detective work earth scientists do.
There are two basic approaches: relative age dating, and absolute age dating. 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 is called the Rule of Superposition. This rule is common sense, but it serves as a powerful reference point. Relative age dating also means paying attention to crosscutting relationships.
Geologic dating exercise
UGA GEOL stratigraphy exercise Overview: This page presents an exercise to illustrate stratigraphic concepts to beginning geology students, with very preliminary considerations of biostratigraphy, lithostratigraphy, and chronostratigraphy. One of its goals is to answer the question “How can geologists claim to know the age of a rock or fossil without having a radiometric age for that specific rock or fossil?
The page presents materials for the project and directions about how to proceed, and then it presents the results, so that students can evaluate their work. The conceptual introduction required to complete the project is in Railsback’s GEOL lecture on “correlative and relative dating“. Materials for the project: The panel just below has nine very simple stratigraphic sections, or logs from observations of outcrops. The nine sections are arranged horizontally with their spacing proportional to the distances between outcrops.
Radiometric Dating. Web Exercise Go to Dating of Rocks and Minerals. Follow all of the directions given on the Web site. Submit your certificate of completion.
The amount of time that is involved in the carving of the landscape, the formation of rocks, or the movement of the continents is an important scientific question. Different hypotheses about the age of the earth can essentially change our perspective of the workings of geologic events that molded the Earth. Scientists studying rocks were able to piece together a progression of rocks through time to construct the Geologic Time Scale Figure 1.
This time scale was constructed by lining up in order rocks that had particular features such as rock types, environmental indicators, or fossils. Scientists looked at clues within the rocks and determined the age of these rocks in a comparative sense. This process is called Relative Dating , which is the process of determining the comparative age of two objects or events. For example, you are younger than your parents.
About the Book. Student Resources. Chapter 1. Chapter 2. Chapter 3.
Discusses how radiometric dating can provide an absolute age (date in number of years) to 16 Students take an informational tour to gain a basic understanding of geologic time, the evidence 2 Principles of Relative Dating Practice.
Requires Windows media Player. Deposition: land subsidence or rise in sea level, prevailing climate and geologic processes. Relative age dating entails placing events in sequential order, from oldest to youngest. In doing so there are a number of common sense principals or laws that are applied. List the events A-D in order of their relative age.
Remember the oldest first event is always on the bottom. Folded and faulted sediments. Before attempting this excercise locate and draw in any faults that you see. Feature Examples of possible events that may or may not be found: folding and uplift, faulting related to extention or compression , sedimentation, igneous activity related to convergence or extension , erosion, etc. Problem 4: Print out the following pages and practice your skills at relative age dating and critical thinking.
You may have to look up some terms. Absolute Age dating is determining the actual age of an event or feature in years. There are numerous methods of absolute age dating, such as counting tree rings, coring glacial ice, and counting sediment varves.
Geologic Dating Exercise
As many us work on developing online courses we have to ask ourselves how to implement lab activities. Listed below are some example lab activities that you might find useful as examples of others have used or even as lab activities to have your students do. Please make sure when using these activities to acknowledge the authors of the page. If you know of other sources of activities that you find useful for online courses, we encourage you to fill out an activity submission form or share them with the community.
There is also a growing collection of online lab activities identified within the Teach the Earth collections.
Name: Susana Bastos Section: ______ Lab 6 – Exercise on Relative Dating and Geologic Cross Sections 1. Describe the geologic history of the cross section.
Most sedimentary rocks are laid down in flat, horizontal layers. These can later tilt and fold due to tectonic activity, and river cuttings can cause gaps among the layers. Relative dating arranges geological events — and the rocks they leave behind — in a sequence. The method of reading the order is called stratigraphy layers of rock are called strata. In this activity, students observe rock layers located near Whanganui, watch an animation about how they were formed and use relative dating to work out the order in which rocks were created.
Scientists use diagrams and models to communicate information. Students need support and practice to become familiar with and know how to use these science communication tools. This activity is part of our collection on dating the past. The introductory article has links to related articles, activities and media.
Radiometric dating and geologic ages exercise 7
Geologists take advantage of decay of natural radioactive elements to determine the age of rocks, which can help us understand earth history. One example of this dating method is using volcanic ash layers to help determine the age of ash-bearing horizons in ice cores. Ice cores provide important records of past climate conditions because the chemical composition of the ice reveals past temperature, and tiny bubbles of air trapped between ice crystals can reveal past atmospheric composition.
Lab Exercise #7. Dating Sequences,. Observing Geologic Structures &. Reading the Grand Canyon’s Rock Record. If you are not enrolled in Geology at GCC.
Index fossils radiometric dating of parts to enable radiometric methods. Relative and allow age. Principles used way to determine radiometric dating is about the absolute age have been found in southern africa, they. This exercise radiometric dating. Exercise 8. Dates are radiometric dating, and half life work to calculate the same age dating laws, have been dated by these radioactive dating rocks 3.
Use the theory of radioactive isotope decay to calculate parent and daughter isotope abundances and determine the absolute age of geological materials. Determine relative geologic age sequences using the basic principles of relative age determination. Distinguish different types of unconformities in the stratigraphy of the Grand Canyon. There are two parts to this lab exercise A.
Dating Principles. Why is the Geologic Time Scale important? • Rocks record geologic and Applying Principles. Sequence of Events exercise.
Geologic Time. From the beginning of this course, we have stated that the Earth is about 4. How do we know this and how do we know the ages of other events in Earth history? Prior to the late 17th century, geologic time was thought to be the same as historical time. The goal of this lecture is come to come to a scientific understanding of geologic time and the age of the Earth.
In order to do so we will have to understand the following:. In order to understand how scientists deal with time we first need to understand the concepts of relative age and numeric age.