Introduction The ground beneath us is made up of rocks, some of which extend extraordinary depths into Earth. Venture deep enough and they are molten, moving, plastic-like substances. Rocks are not static and inert. They are constantly changing, shifting and rearranging their form and location. They can be melted, deposited, eroded and squeezed into new forms. These changes occur over vast periods of time. The pages of Earth's history are written in its rocks, minerals and fossils. Rocks and minerals provide evidence of events that took place in the distant past. They offer clues about the shifting, changing nature of the continents, mountain ranges, oceans and islands. They help us understand what Earth's climate was like billions of years ago, what elements the atmosphere contained, and how life may have evolved. When an animal or plant dies and its remains leave an impression in rock, the resulting fossil is a testament to life's history and its changing, evolving nature. Fossils reveal Earth's past lifeforms, among them long-extinct beasts, bizarre, alien-like beings and delicate marine creatures. Rocks are made up of minerals. It is among the minerals that the exquisite gemstones and ornamental stones are found. Sparkling diamonds, vivid green emeralds, multicolored tourmalines, clear crystal quartz and lacy agates are all minerals. Take a journey into Earth's history to discover what shaped its Excerpted from Rocks and Fossils: A Visual Guide by Robert R. Coenraads All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
