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About the pagination of this eBook Due to the unique page numbering scheme of this book, the electronic pagination of the eBook does not match the pagination of the printed version. To navigate the text, please use the electronic Table of Contents that appears alongside the eBook or the Search function. For citation purposes, use the page numbers that appear in the text. ROCKS AND MINERALS Britannica Illustrated Science Library Encyclop?dia Britannica, Inc. Chicago ? London ? New Delhi ? Paris ? Seoul ? Sydney ? Taipei ? Tokyo © 2008 Editorial Sol 90 All rights reserved. Idea and Concept of This Work: Editorial Sol 90 Project Management: Fabi?n Cassan Photo Credits: Corbis, ESA, Getty Images, Graphic News, NASA, National Geographic, Science Photo Library Illustrators: Guido Arroyo, Pablo Aschei, Gustavo J. Caironi, Hern?n Ca?ellas, Leonardo C?sar, Jos? Luis Corsetti, Vanina Far?as, Joana Garrido, Celina Hilbert, Isidro L?pez, Diego Mart?n, Jorge Mart?nez, Marco Menco, Ala de Mosca, Diego Mourelos, Eduardo P?rez, Javier P?rez, Ariel Piroyansky, Ariel Rold?n, Marcel Soc?as, N?stor Taylor, Trebol Animation, Juan Venegas, Coralia Vignau, 3DN, 3DOM studio, Jorge Ivanovich, Fernando Ramallo, Constanza Vicco, Diego Mourelos Composition and Pre-press Services: Editorial Sol 90 Translation Services and Index: Publication Services, Inc. Portions © 2008 Encyclop?dia Britannica, Inc. Encyclop?dia Britannica, Britannica, and the thistle logo are registered trademarks of Encyclop?dia Britannica, Inc. Britannica Illustrated Science Library Staff Editorial Michael Levy, Executive Editor Core Editorial John Rafferty, Associate Editor Earth Sciences William L. Hosch, Associate Editor Mathematics and Computers Kara Rogers, Associate Editor Life Sciences Rob Curley, Senior Editor Science and Technology David Hayes, Special Projects Editor Art and Composition Steven N. Kapusta, Director Carol A. Gaines, Composition Supervisor Christine McCabe, Senior Illustrator Media Acquisition Kathy Nakamura, Manager Copy Department Sylvia Wallace, Director Julian Ronning, Supervisor Information Management and Retrieval Sheila Vasich, Information Architect Production Control Marilyn L. Barton Manufacturing Kim Gerber, Director Encyclop?dia Britannica, Inc. Jacob E. Safra, Chairman of the Board Jorge Aguilar-Cauz, President Michael Ross, Senior Vice President Corporate Development Dale H. Hoiberg, Senior Vice President and Editor Marsha Mackenzie, Director of Production International Standard Book Number (set): 978-1-59339-797-5 International Standard Book Number (volume): 978-1-59339-799-9 Britannica Illustrated Science Library: Rocks and Minerals 2008 Printed in China www.britannica.com ROCKS AND MINERALS Contents Dynamics of the Earth's Crust Page 6 Minerals Page 18 Formation and Transformation of Rocks Page 40 Classes of Rocks Page 60 Use of Rocks and Minerals Page 76 PHOTOGRAPH ON PAGE 1 A stone with a blue opal in its center is a product of time, since it forms over millions of years. Memory of the Planet Rocks, like airplane flight recorders, store in their interior very useful information about what has happened in the past. Whether forming caves in the middle of mountains, mixed among folds, or lying at the bottom of lakes and oceans, stones are everywhere, and they hold clues to the past. By studying rocks, we can reconstruct the history of the Earth. Even the most insignificant rocks can tell stories about other times, because rocks have been around since the beginning of the universe. They were part of the cloud of dust and gases that revolved around the Sun over four billion years ago. Rocks have been silent witnesses to the cataclysms our planet has experienced. They know the cold of the glacial era, the intense heat of the Earth's interior, and the fury of the oceans. They store much information about how external agents, such as wind, rain, ice, and temperature changes, have been altering the planet's surface for millions of years. For ancient civilizations, stones symbolized eternity. This idea has persisted throughout time because stones endure, but they are recycled time and again. Fifty million years from now, nothing will be as we now know it—not the Andes, nor the Himalayas, nor the ice of Antarctica, nor the Sahara Desert. Weathering and erosion, though slow, will never stop. This should free us from any illusion of the immortality of the Earth's features. What will everything be like in the future? We don't know. The only sure thing is that there will be rocks. Only stones will remain, and their chemical composition, shape, and texture will provide clues about previous geological events and about what the Earth's surface was like in the past. In the pages of this book, illustrated with stunning images, you will find invaluable information about the language of rocks and natural forces in general. You will also learn to identify the most important minerals, know their physical and chemical properties, and discover the environments in which they form. Did you know that the Earth's crust and its oceans are sources of useful and essential minerals for human beings? Coal, petroleum, and natural gas found in the crust allow us to travel and to heat our homes. Furthermore, practically all the products that surround us have elements provided by rocks and minerals. For example, aluminum is used to produce beverage cans; copper is used in electric cables; and titanium, mixed with other durable metals, is used in the construction of spacecraft. We invite you to enjoy this book. It is full of interesting and worthwhile information. Don't miss out on it! Dynamics of the Earth's Crust MOUNTAINS OF SAND Corkscrew Canyon in Arizona contains an array of shapes, colors, and textures. The sand varies from pink to yellow to red depending on the sunlight it receives. TRAVERSING TIME 8-11 UNDER CONSTRUCTION 12-13 A CHANGING SURFACE 14-15 BEFORE ROCK, MINERAL 16-17 The Earth is like a blender in which rocks are moved around, broken, and crumbled. The fragments are deposited, forming different layers. Then weathering and erosion by wind and rain wear down and transform the rock. This produces mountains, cliffs, and sand dunes, among other features. The deposited material settles into layers of sediment that eventually become sedimentary rock. This rock cycle never stops. In 50 million years, no single mountain we know will exist in the same condition as it does today. 8 DYNAMICS OF THE EARTH’S CRUST Traversing Time Geologists and paleontologists use many sources to reconstruct the Earth's history. The analysis of rocks, minerals, and fossils found on the Earth's surface provides data about the deepest layers of the planet's crust and reveals both climatic and atmospheric changes that are often associated with catastrophes. Craters caused by the impact of meteorites and other bodies on the surface of the Earth also reveal valuable information about the history of the planet. 2 COLLISION AND FUSION Heavy elements migrate. Complex Structure THE FORMATION OF THE INTERIOR Cosmic materials began to accumulate, forming a growing celestial body, the precursor of the Earth. High temperatures combined with gravity caused the heaviest elements to migrate to the center of the planet and the lighter ones to move toward the surface. Under a rain of meteors, the external layers began to consolidate and form the Earth's crust. In the center, metals such as iron concentrated into a red-hot nucleus. Age in millions of years ERA PERIOD EPOCH Climate 4,600 Hadean Pregeologic Consolidation begins under a rain of meteors. The Earth cools and the first ocean is formed. Life Ca 3.6_ Na K 2.8_ 2.6_ ELEMENTS PRESENT ACCORDING TO THE TABLE Existing in different combinations, the crust of the Earth contains the same elements today as those that were present when the planet was formed. The most abundant element in the crust is oxygen, which bonds with metals and nonmetals to form different compounds. Mg 2.1_ Al Fe 8.1_ 5.0_ Si 27.7_ Small bodies and dust accumulate to become the size of an asteroid. The oldest minerals, such as zircon, form. The oldest rocks metamorphose, forming gneiss. 2,500 Proterozoic Precambrian 1,100 Rodinia, an early supercontinent, forms. A meteorite falls in Sudbury, Ontario, Canada. O 46.6_ Metals Transition metals Nonmetals Noble gases Lanthanide series Actinide series 2,500 Glaciations: White Earth The Earth undergoes the first of its massive global cooling events (glaciations). 800 Second glaciation 600 Last massive glaciation THE FIRST ANIMALS Among the most mysterious fossils of the Precambrian Period are the remains of the Ediacaran fauna, the Earth's first-known animals. They lived at the bottom of the ocean. Many were round and reminiscent of jellyfish, while others were flat and sheetlike. 3 METALLIC CORE The light elements form the mantle. ROCKS AND MINERALS9 THE CORE The Earth's core is extremely hot and is made mostly of iron and nickel. Mountains are external folds of the crust produced by extremely powerful forces occurring inside the Earth. 542 The supercontinent Panotia forms, containing portions of present-day continents. North America separates from Panotia. OROGENIES Geological history recognizes long periods (lasting millions of years) of intense mountain formation called orogenies. Each orogeny is characterized by its own particular materials and location. The first major orogeny (Caledonian folding) begins. Gondwana moves toward the South Pole. Laurentia and Baltica converge, creating the Caledonian range. Gneiss forms on the coast of Scotland. 542 488.3 Paleozoic THE ERA OF PRIMITIVE LIFE Cambrian Ordovician 443.7 Silurian 416 Devonian Ключевые слова: north america, metamorphic rock, magma, fragment, black stone, compound, chemical perspective, organic, chemical substance, ultraviolet ray, basic component, surface, constituent element, porous consistency, upper mantle, composition, volcanic, chemical action, south america, electric current, formed, upper layer, rocks minerals, construction, organic material, erosion weathering, thicker grain, property, group, produce, petroleum, canyon, sand, optical property, granite, salt, rock, mineralogical composition, volcanic ash, metal, high pressure, three-dimensional network, gold, redwall limestone, marine animal, wall erode, material extracted, soil, wa, energy, fossil, force, foot, ton, environmental impact, size, mineral, rocks, water, mass, united, olivine pyroxene, type, chemical composition, fugitive slave, rock cycle, outer shell, large area, body, artificial canal, park, atom, level, volcanic activity, quartz, compacted, layer, valley, long, high mountain, grain, substance, organism, living organism, chemical process, material, shape, sedimentary rock, cementation material, cave, silica content, dense, earths core, pressure, minerals, successive layer, organic matter, stone, rise, organic origin, limestone, younger rock, area, water basin, sacramento river, changing surface, sulfuric acid, process, tetrahedron share, positively charged, karst cycle, earths surface, geologic process, characteristic, raw material, nuclear energy, dark, earth crust, light pass, oxidized mineral, great extent, lose electron, form, igneous rock, fine grain, change, crystalline structure, cretaceous period, crystalline, oceanic crust, air, component, giant sequoia, scratched, mantle, sodium potassium, coal oil, earths crust, year, extracted, transformation, recognize minerals, century, heat, element, erosive action, history, crystal, composed, conveyor belt, tectonic plate, temperature, time, cut, deposit, peat bog, earth, deposited, glacial cirque, high, mile, physical property, geologic history, diamond, coal, plant root, igneous metamorphic, wind, native element, nuclear reactor, located, outer core, great, fracture, river, large, ion, network, ha, feldspar quartz, large mass, gas, sedimentary, national, inch, depth, crust, light, common minerals, high content, solid, metamorphic, igneous, rock formation, sediment, mineral composition, carbon, electric cable, formation, hardness, structure, main shaft, unaided eye, percent, fine, copper, chemical, period, glacier, silicon, metamorphism, san juan, organic remains, ancient time, erosion, iron, oxygen, green pond