Assignment 8: The Dating of Rocks, Fossils and Geologic Events

Introduction

Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale. Development of the geologic time scale and dating of formations and rocks relies upon two fundamentally different ways of telling time: relative and absolute.

Relative dating places events or rocks in their chronologic sequence or order of occurrence. It is a qualitative way of describing the sequence of events. The sequence orders the events but provides no information on the amount of time passed or between events. To determine the sequence of geologic events, several principles must be followed.

Absolute dating places events or rocks at a specific time. If a geologist claims to be younger than his or her co-worker, that is a relative age. If a geologist claims to be 45 years old, that is an absolute age. The nuclear decay of radioactive isotopes is a process that behaves in a clock-like fashion and is thus a useful tool for determining the absolute age of rocks. Radioactive decay is the process by which a “parent” isotope changes into a “daughter” isotope. Rates of radioactive decay are constant and measured in terms of half-life, the time it takes half of a parent isotope to decay into a stable daughter isotope.

Directions: 

1) This assignment is designed to assist you in learning the concepts of this module as well as assess your understanding and application of the content. 

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3) This assignment must be completed by the due date assigned or the course late policy will be applied. 

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