Chapter 14, Problem 15STP

Summary Introduction

To explain:

The way paleontologists use geological principles for relative dating of fossils

Introduction:

A fossil is any preserved evidence of an organism. Plants, animals and even bacteria can form fossils. More than 99 percent of the species that existed have become extinct. Only a small percentage of these organisms are preserved as fossils. A paleontologist is a scientist who studies fossils.

Answer to Problem 15STP

Paleontologists use geological principle of law of superposition for relative dating of fossils. This law states that younger layers of rock are deposited on top of older layers. Hence the older fossils will be at the bottom of the layers and youngest fossil will be on the topmost layer.

Explanation of Solution

Nearly all the fossils are formed in sedimentary rocks. The organism dies and gets buried in sediments. The sediments build up and cover the remains of the organism. The sediments later on harden to become rocks. When geologists studied the different strata of rocks in different parts of the world, they found that layers of same age tended to have same kind of fossils. This led to relative dating of rocks.

Relative dating is a method used to determine the age of rocks by comparing them with those in other layers. Relative dating is based on the geological principle of law of superposition. This law states that younger layers of rock are deposited on top of older layers. The sedimentary rocks are formed from bottom to top. Hence, fossils found in bottom strata represent oldest form of life in that era of rock formation.