Geology: the Science of the Earth's Crust

Volume Three

P. F. COLLIER & SON COMPANY NEW YORK

Copyright 1922 By P. F. Collier & Son Company

MANUFACTURED IN U. S. A.

GEOLOGY

The Science of the Earth's Crust

WILLIAM J. MILLER Professor of Geology, Smith College

P. F. COLLIER & SON COMPANY NEW YORK

PREFACE

In the preparation of this book the author has attempted to present, in popular form, the salient points of a general survey of the whole great science of geology, the science which deals with the history of the earth and its inhabitants as revealed in the rocks.

The use of technical and unusual terms has been reduced to a minimum compatible with a reasonable understanding of the subject by the layman. Each of the relatively few scientific terms is explained where first used in the text, and a glossary of common geological terms has been appended.

The matter of illustrations has received very careful attention, and only pictures, maps, and diagrams are used which actually illustrate important features of the text. A special point has been made to introduce only cuts of simple construction comparatively free from technicalities. Nearly every illustration is accompanied by a really explanatory title.

A number of the pictures are from the author's collection of photographs, and many of the line-cuts have either been made or considerably modified by the author. Among the numerous sources of illustrations, special mention should be made of the United States Geological Survey, the New York State Museum, the American Museum of Natural History, the University of Chicago Press, and various individuals, full credit being given wherever due.

William J. Miller.

Northampton, Mass.

CONTENTS

CHAPTER PAGE

I. Introduction 9

II. Weathering and Erosion 22

III. Stream Work 30

IV. The Sea and Its Work 51

V. Glaciers and Their Work 59

VI. The Action of Wind 71

VII. Instability of the Earth's Crust 76

VIII. Volcanoes and Igneous Rocks 99

IX. Waters Within the Earth 113

X. How Mountains Come and Go 130

XI. A Study of Lakes 142

XII. How the Earth May Have Originated 158

XIII. Very Ancient Earth History 164

XIV. Ancient Earth History 179

XV. Medieval Earth History 208

XVI. Modern Earth History 221

XVII. Evolution of Plants 249

XVIII. Geological History of Animals (Excluding Vertebrates) 259

XIX. Geological History of Vertebrate Animals (Including Man) 281

XX. Mineralogy 307

XXI. Economic Geology 342

Glossary of Common Geological Terms 377

LIST OF ILLUSTRATIONS

Ledge of Rock with Nearly Vertical Strata Frontispiece

PLATE FACING PAGE

1 Granite Weathering to Soil Leaving Residual Cores of Joint Blocks (Upper picture) 32

Looking-Glass Rock, Utah. Stratified Sandstone Sculptured by Wind Erosion (Lower picture) 32

2 Grand Canyon of the Yellowstone River. A Channel Worn by Erosion 33

3 Gorge of the Niagara River Below the Falls. A Sample of Recent Erosion 64

4 Winding Stream in the St. Lawrence Valley with Flood Plain (Upper picture) 65

Davidson Glacier, Alaska, Showing Action on the Valley's Walls and Floor (Lower picture) 65

5 Swift Current Valley in Glacier National Park, Formed by Stream and Glacier Action 96

6 Yosemite Valley from Western Entrance. The Result of Glacial Action 97

7 An Upbend Fold or Anticline in Maryland 128

8 Ledge of Igneous Rock Showing Joints (Upper picture) 129

Fault Fracture in Limestone Formations (Lower pictures) 129

9 Molten Lava Flowing Over a Cliff in Hawaii (Upper picture) 160

Dikes of Granite Cutting Old Rock (Lower picture) 160

10 Lassen Peak, California, in Eruption (Left picture) 161

Devil's Tower, Wyoming, Once a Mass of Molten Rock Forced Through Strata (Right picture) 161

11 Mammoth Hot Springs Terrace in Yellowstone National Park (Upper picture) 224

Crater Lake, Oregon, Formed by the Subsidence of a Volcano (Lower picture) 224

12 Archeozoic Rock, Oldest Known Rock Formation on Earth (Upper picture) 225

Twisted Mass of Stratified Limestone, Surrounded by Granite (Lower picture) 225

13 Paleozoic Rock, Covered with Oldest Known Animal Remains 256

14 "Stone-Lily" Stems in Ordovician Strata (Upper left picture) 257

Various Brachiopods in Ordovician Strata (Upper right picture) 257

Stratified Limestone of Middle Ordovician Era Containing Fossils (Lower picture) 257

15 A Landscape of the Coal Age (Upper picture) 288

Fossil Fern on a Piece of Shale (Lower picture) 288

16 Restoration of Huge Animals of the Mesozoic Era 289

17 Skeleton of Two-Legged Carnivorous Dinosaur (Large picture) 320

Earliest Known Bird Form (Insert) 320

18 Skeleton of Large Flying Reptile (Upper picture) 321

Skeleton of a Swimming Reptile of the Mesozoic Era (Lower picture) 321

19 Appalachians Along New River, Peneplain Upraised Again 352

20 Glacial Bowlder Left by Ice Sheet (Upper picture) 353

Esker, Deposited by a Stream in the Great Glacier (Lower picture) 353

CHAPTER I. Introduction

INTRODUCTION

Earth features are not fixed. The person of ordinary intelligence, surrounded as he is by a great variety of physical features, is, unless he has devoted some study to the subject, very likely to regard those features as practically unchangeable, and to think that they are now essentially as they were in the beginning of the earth's history. Some of the most fundamental ideas taught in this book are that the physical features of the earth, as we behold them to-day, represent but a single phase of a very long-continued history; that significant changes are now going on all around us; and that we are able to interpret present-day earth features only by an understanding of earth changes in the past.

Geology, meaning literally "earth science," deals with the history of the earth and its inhabitants as revealed in the rocks. The science is very broad in its scope. It treats of the processes by which the earth has been, and is now being, changed; the structure of the earth; the stages through which it has passed; and the evolution of the organisms which have lived upon it.

Geography deals with the distribution of the earth's physical features, in their relation to one another, to the life of sea and land, and human life and culture. It is the present and outward expression of geological effects.

As a result of the work of many able students of geology during the past century and a quarter, it is now well established that our planet has a definitely recorded history of many millions of years, and that during the lapse of those eons, revolutionary changes in earth features have occurred, and also that there has been a vast succession of living things which, from very early times, have gradually passed from simple into more and more complex forms. The physical changes and the organisms of past ages have left abundant evidence of their character, and the study of the rock formations has shown that within them we have a fairly complete record of the earth's history. Although very much yet remains to be learned about this old earth, it is a remarkable fact that man, through the exercise of his highest faculty, has come to know so much concerning it.

The following words, by the late Professor Barrell, admirably summarize the significance of geological history. "The great lesson taught by the study of the outer crust is that the earth mother, like her children, has attained her present form through ceaseless change, which marks the pulse of life and which shall cease only when her internal forces slumber and the cloudy air and surf-bound ocean no more are moving garments. The flowing landscapes of geologic time may be likened to a kinetoscopic panorama. The scenes transform from age to age, as from act to act; seas and plains and mountains of different types follow and replace each other through time, as the traveler sees them succeed each other in space. At times the drama hastens, and unusual rapidity of geologic action has, in fact, marked those epochs since man has been a spectator upon the earth. Science demonstrates that mountains are transitory forms, but the eye of man through all his lifetime sees no change, and his reason is appalled at the conception of a duration so vast that the milleniums of written history have not accomplished the shifting of even one of the fleeting views which blend into the moving picture."

Central Connecticut in the Geologic Past, pp. 1-2.

Or in the words of Tennyson:

There rolls the deep where grew the tree. O, earth, what changes hast thou seen! There where the long street roars, hath been The stillness of the central sea. The hills are shadows, and they flow From form to form, and nothing stands; They melt like mist, the solid lands, Like clouds they shape themselves and go.

The following statement of some of the more definite important conclusions regarding earth changes may serve to make still clearer the general scope of the science of geology. The evidences upon which these conclusions are based are discussed in various parts of this book. For untold millions of years the rocks at and near the earth's surface have been crumbling; streams have been incessantly sawing into the lands; the sea has been eating into continental masses; the winds have been sculpturing desert lands; and, more intermittently and locally, glaciers have plowed through mountain valleys, and even great sheets of ice have spread over considerable portions of continents. Throughout geologic time, the crust of the earth has shown marked instability. Slow upward and downward movements of the lands relative to sea level have been very common, in many cases amounting to even thousands of feet. Various parts of the earth have been notably affected by sudden movements (resulting in earthquakes) along fractures in the outer crust. During millions of years molten materials have, at various times, been forced into the earth's crust, and in many cases to its surface. Mountain ranges have been brought forth and cut down. The site of the Appalachian Mountains was, millions of years ago, the bottom of a shallow sea. Lakes have come and gone. The Great Lakes have come into existence very recently (geologically), that is to say, since the great Ice Age. A study of stratified rocks of marine origin shows that all, or nearly all, of the earth's surface has at some time, or times, been covered by sea water. Over certain districts the sea has transgressed and retrogressed repeatedly. Organisms have inhabited the earth for many millions of years. In earlier known geologic time, the plants and animals were comparatively simple and low in the scale of organization, and through the succeeding ages higher and more complex types were gradually evolved until the highly organized forms of the present time, including the human race, were produced.

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