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Title: Ancient Landscapes of the Grand Canyon Region - The Geology of Grand Canyon, Zion, Bryce, Petrified Forest & Painted Desert
Author: McKee, Edwin Dinwiddie
Language: English
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CANYON REGION***
Transcriber’s note:
Text enclosed by underscores is in italics (_italics_).
[Illustration: THE GRAND CANYON—1. SCHISTS AND GRANITES (ARCHEAN ERA):
2. SANDSTONES, LIMESTONES, SHALES (ALGONKIAN ERA): 3. TONTO FORMATIONS
(CAMBRIAN PERIOD): 4. REDWALL LIMESTONE (MISSISSIPPIAN PERIOD): 5. SUPAI
SANDSTONE AND SHALE (PERMIAN PERIOD): 6. HERMIT SHALE (PERMIAN PERIOD):
7. COCONINO SANDSTONE (PERMIAN PERIOD): 8. TOROWEAP AND KAIBAB
FORMATIONS (PERMIAN PERIOD).
NATIONAL PARK SERVICE]
ANCIENT LANDSCAPES OF THE GRAND CANYON REGION
The Geology of Grand Canyon, Zion, Bryce, Petrified Forest & Painted
Desert
by
EDWIN D. McKEE, Asst. Director
Museum of Northern Arizona
Sketches and Charts by Louis Schellbach 3rd Park Naturalist, Grand
Canyon National Park, and Russell Hastings
Published by
Edwin D. McKee
1931
Copyright 1931
Edwin D. McKee
Thirteenth Edition, 1952
Printed by
Coconino Sun Co.
Flagstaff, Arizona
TABLE OF CONTENTS
PAGE
Introduction ix
Chapter I—The Archean Era 1
The Earth’s Oldest Rocks, Grand Canyon 2
Granite in Grand Canyon 4
Chapter II—The Algonkian Era 5
Algonkian Rocks in Grand Canyon 5
Formation of Mountains 6
Early Climates 6
Oldest Known Life 7
Chapter III—The Paleozoic Era 9
First Animal Life—The Tonto Rocks 9
The Missing Periods of the Third Era 11
The Age of Fish 12
Sea Life From the North—Redwall Limestone 12
Tracks in the Supai Sandstone 14
Landscapes of the Hermit Shale 15
Wind-blown Sand—The Coconino Sandstone 17
Warm Seas from the West—The Toroweap and Kaibab Formations 18
Chapter IV—The Mesozoic Era 21
Remnants of Younger Strata—Red Butte and Cedar Mountain 21
The Petrified Forest 22
Dinosaur Tracks—The Painted Desert 24
The Rocks of Zion Canyon and Rainbow Natural Bridge 26
From Seashells to Coalbeds 27
Chapter V—The Cenozoic Era 29
Bryce Canyon Formation 30
A Great Erosion Surface 32
Crustal Movement at Grand Canyon 33
Cutting the Grand Canyon 34
The Forming of Zion Canyon 37
Glaciers 38
San Francisco Mountain Volcanic Field 39
Elephants and Camels 41
Advent of Man in the Southwest 42
Bibliography 45
ILLUSTRATIONS
PAGE
The Grand Canyon Frontispiece
Diagrammatic Sections of Grand Canyon Region x
Rocks of First Era, Inner Gorge of Grand Canyon 1
Block Diagrams of Events of First Era 3
Tilted Rocks of the Second Era, Grand Canyon 5
Diagrammatic Section of Third Era Formations, Grand Canyon 8
Scene on Cambrian Sea Floor in Grand Canyon Region 10
Trilobites Preserved in Green Shale of Grand Canyon Walls 11
A Fresh-water Fish of Devonian Age (Sketch) 12
Sea Life from the Redwall, Grand Canyon (Sketches) 12
Havasu Falls in Redwall Limestone, Grand Canyon 13
Tracks of Short-legged, Prehistoric Animal, Supai Formation, Grand
Canyon 14
Landscape at Time Hermit Shale was Forming 15
Fossil Fern From the Hermit Shale, Grand Canyon 15
Wind-blown Sand, Coconino Formation, Grand Canyon 17
Tracks of Primitive Four-footed Animals, Coconino Sandstone, Grand
Canyon 17
Marine Life From the Kaibab Limestone, Grand Canyon (Sketches) 18, 19
Diagrammatic Section of Fourth Era Formations, Southern Utah and
Painted Desert Regions 20
Cedar Mountain 22
Red Butte 22
Petrified Forest, Arizona 23
Petrified Logs of Triassic Age 23
Dinosaur Tracks, Painted Desert 24
The Painted Desert 25
Zion Canyon, Navajo Sandstone 26
Rainbow Natural Bridge, Navajo Sandstone 26
Cretaceous Shells From Southern Utah (Sketches) 27
Coal Canyon, Painted Desert Country 28
Bryce Canyon 30
Map of Colorado River 31
A Great Erosion Surface 32
Diagrammatic Cross Sections of Grand Canyon 35
The Grand Canyon 36
Zion Canyon 37
Chart of San Francisco Mountains 39
San Francisco Mountain—Past and Present (Sketch) 40
Map of San Francisco Mountain Volcanic Field 40
San Francisco Mountain 41
Elephant and Camel Remains 42
Ancient Indian Petroglyphs, Head of Bright Angel Trail, Grand
Canyon 43
INTRODUCTION
Probably no place in the world of similar area has recorded a more
complete or a more interesting resume of the earth’s history than has
the high plateau country of northern Arizona and southern Utah. Although
many great events and some long intervals of time are not represented by
the formations of this region, yet of the five major chapters or eras
into which all of time has been divided by geologists, at least some
parts of each have left their traces in this area.
Whether on the brink of the mighty Grand Canyon, among beautiful logs of
the Petrified Forest, or beneath the lofty walls of Zion—the “Rainbow of
the Desert”—one looks upon rocks which are not alone curious or
colorful, but which are also records of the past inscribed and
illustrated in an intensely interesting manner. In one place is seen the
sand of ancient dunes, in another the border of an early sea, or perhaps
the floodplain of mighty rivers, and in all of these remain the
unmistakable evidences of life—plants and animals preserved to make a
reality of the living, moving past. Everywhere are found the evidences
of those great processes of nature—erosion of the high country, land
formation in the low country, and mighty crustal movements slowly
raising or lowering the land in both.
From the rim of Grand Canyon one not only looks down through tremendous
space, but also through time, glimpsing the record of vast ages,
measurable not in centuries but in millions and even hundreds of
millions of years. There in the bottom of that mighty chasm are found
rocks formed during the first and oldest era—rocks in which the original
structure has been entirely modified by great heat and pressure and in
which no evidence of life has been found. There in the Grand Canyon are
also seen two other great series of rocks, those of the second era which
are partially altered and which contain earliest traces of plants, and
those of the succeeding era in which are preserved primitive animals of
many types.
[Illustration: NORTH-SOUTH CROSS-SECTION OF THE GRAND CANYON REGION;
EAST-WEST CROSS-SECTION OF THE GRAND CANYON REGION]
Rocks of the fourth great era—the age of dinosaurs—lend color to the
Painted Desert, and to the sheer walls of Zion Canyon. Beautiful little
Bryce Canyon to the north boasts of some of the most recently formed
rocks in the region—those of the fifth and last era, the age of mammals.
The great volcanic mountains and the marvelous features of erosion, such
as the canyons and the desert cliffs, are also developments of this most
recent chapter. In brief, the Grand Canyon region affords some
wonderfully interesting glimpses of ancient landscapes during many
different parts of the earth’s history, and these make the past a
moving, living thing.
CHAPTER I
THE ARCHEAN ERA
[Illustration: ROCKS OF FIRST ERA. INNER GORGE OF GRAND CANYON]
THE EARTH’S OLDEST ROCKS
(THE ARCHEAN ERA)
Looking into the depths of Grand Canyon from any point within the Bright
Angel section, one is immediately impressed by the narrow V-shaped gorge
cut in the black rocks at the bottom. This is popularly termed the
Granite or Inner Gorge. Within its walls one is in another world, both
scenically and geologically. Their steep, bare sides, whose surfaces are
chaotic in the extreme, have a history—long and complex. The rocks of
which they are formed—some of the oldest known today on the surface of
the earth—partially tell the story of the first great era in geologic
history.
Other rocks of this, the Archean age, are found in the Rockies, in the
Adirondacks of New York, and to a very great extent in eastern Canada.
In the last named place they contain valuable deposits of iron, nickel,
cobalt, and copper. Rocks which probably also correspond in age occur in
Scandinavia, Brazil, China, India, and central Africa.
At the Grand Canyon, although we are impressed by the depth of the dark
Archean rocks, beneath the plateau surface approximately a mile, yet we
marvel even more when we contemplate their great age and the important
series of events whose history they partially record. Built up
originally as great horizontal deposits of sand and mud, they were bent
by mighty crustal movements until high mountains, probably comparable to
the present Alps, were formed. Pressures from the northwest and
southeast apparently folded them. The rocks themselves were greatly
compressed and heated, with the result that complete recrystallization
and the development of a banded structure were brought about. The
present vertical attitude of these ancient beds, together with their
dense crystalline character, is evidence of the great depth at which
they were formed and of the extreme pressures to which they were
subjected. In brief, the rocks that we see today in the Canyon bottom
represent merely the roots of once lofty mountains, and the flat surface
cut on these rocks is an old plain that resulted from the wearing down
of high country in this region.
[Illustration: BLOCK DIAGRAMS OF EVENTS OF FIRST ERA]
1 Sands and Muds accumulated to form rock strata.
2 The strata were folded into high mountains. Heat and pressure changed
both structure and composition of the lower rocks during the folding.
3 Molten masses were forced up into cracks from below. Upon cooling they
formed lavas on the surface and granites beneath.
4 During a tremendously long period of time the rivers and rains slowly
widened the valleys and wore down the ancient mountains to a great plain
near sea level.
As yet no definite traces of either plant or animal life have been found
in rocks of the Archean age in Grand Canyon. Though various forms of
life may have existed then, and may have been preserved in the original
rocks, their record has since been entirely removed by those extreme
pressures which altered even the composition and structure of the rocks
themselves.
GRANITE IN GRAND CANYON
(THE ARCHEAN ERA)
Within the black, crystalline rocks of the Inner Gorge may be seen many
large streaks, bands or irregular masses of a lighter color. From the
Canyon rim these appear white, but from nearby they are usually pink.
These light colored rocks are granites with a coarse crystalline
texture.
Granites derive their name from their granular texture. They are formed
by the slow cooling of molten masses that have been forced into older
rocks from the earth’s interior. From a similar source are formed lavas
and volcanic ash, but these flow out or are ejected on the surface of
the earth where they cool so rapidly that no crystals form.
Exceptionally fast cooling or chilling of molten masses, moreover, forms
volcanic glass or obsidian. It is by the application of this same
principle that crystal forming is prevented in the manufacture of common
glass.
The large size of the crystals forming the granite that fills cracks and
fissures of the Inner Gorge at Grand Canyon indicates the considerable
depth at which it was formed and is further evidence of the great
mountains that existed in this region during the first era in geologic
history.
CHAPTER II
THE ALGONKIAN ERA
[Illustration: TILTED ROCKS OF THE SECOND ERA. GRAND CANYON]
Rocks formed during the second great era of the earth’s history are
distinctive in several respects. They are not highly altered or
completely changed in form and structure as are those of the oldest era,
but are largely free from such changes and, for the most part, similar
to rocks which are seen in the process of formation today. Furthermore,
they are known to contain definite traces of plant life, though no
certain forms of animal life have yet been found in them. They represent
a period probably as great as all of subsequent time.
ALGONKIAN ROCKS IN GRAND CANYON
Along Bright Angel Canyon and in several other places in the Grand
Canyon, rocks of Algonkian age, representing accumulations of sediments
several thousand feet in thickness, are found. Below and to the north of
Desert View (southeast of Cape Royal on the North Rim) they form the
open floor of the Canyon. Everywhere the most conspicuous layer of this
series is a mud rock of brilliant vermilion color. However, the rocks
also include a conglomerate or pebble layer, a dark limestone formed
principally by plants, and a purple quartzite made by the consolidation
of the grains of a sandstone.
FORMATION OF MOUNTAINS
(THE ALGONKIAN ERA)
The Algonkian rocks of the Grand Canyon region were bent and broken into
mountains at an early date. In many places sloping layers showing the
steep angle at which they were tilted are easily visible, even from the
Canyon rim. Folded areas and strata which have been shattered are also
conspicuous features here and there. The mountains which they formed,
however, are now missing for they were worn away in large measure by
slow erosion. Today only remnants—small hills on a general level
surface—remain in the lower parts of Grand Canyon to tell the story.
EARLY CLIMATES
(THE ALGONKIAN ERA)
The rocks of Algonkian age are roughly estimated to be at least six or
seven hundred million years old, yet from all indications they were
formed under conditions of climate not unlike those of far later periods
of history. In several parts of the world traces of great ice
sheets—glaciers which scratched and eroded the surface—are found
preserved in Algonkian rocks. In other places, including the Grand
Canyon, ancient flows of lava are found where they gushed out upon the
surface of an old land mass. Among the rocks below Desert View (Navajo)
Point and bordering on the Colorado River may readily be seen several
black cliffs formed by the volcanic activity of this early age.
The brilliant red shales of Algonkian age found in the lower parts of
the Grand Canyon were formed as muds, accumulated probably by large
rivers. In these muds are found preserved great quantities of ripple
marks, indications of changing currents, also the moulds of salt
crystals, and large shrinkage cracks resulting from a very hot sun. In
brief, these criteria point toward a hot and probably arid climate in
this region during that chapter of history.
OLDEST KNOWN LIFE
(THE ALGONKIAN ERA)
The oldest forms of life represented in rocks of Grand Canyon are found
in strata of the Second, or Algonkian, Era. Certain layers of limestone
showing peculiar structural patterns on their surfaces are interpreted
as being the reefs built up through the activities of primitive
one-celled plants known as algae. Similar structures are being formed
today by plants of this type. Near Harper’s Ferry, West Virginia, for
example, algae are building up limestone layers almost identical to the
fossil ones found in the Algonkian rocks of Grand Canyon. In this
connection, it is interesting to note that because of this similarity of
the present to the past, the reality of the ancient plant structures was
recognized a few years ago. They were discovered at a place in the Grand
Canyon just west of the mouth of Bright Angel Creek.
[Illustration: Rocks of the Third Era in the Grand Canyon]
Rocks of the Fourth Era (Red Butte)
Rim of Grand Canyon
a~ Sandy limestone formed beneath the sea. In it are found corals,
sponges, sharks’ teeth and many sea shells.
Kaibab Formation 300 ft. Permian Age
b~ Red sandstone and gray limestone. Formed at bottom of a shallow
sea.
Toroweap Formation 250 ft. Permian Age
c~ Wind-blown sand which was piled in dunes. Contains the tracks of
many kinds of primitive reptiles or amphibians.
Coconino Sandstone 300 ft. Permian Age
d~ River mud in which are preserved many impressions of ferns and
cone-bearing plants, insect wings, raindrop pits and tracks of
salamander-like animals.
Hermit Shale 300 ft. Permian Age
e~ Ancient flood-plain deposits of sand and mud containing impressions
of fern-like plants and tracks of land animals.
Supai Formation 800 ft. Permian Age
f~ Sea deposits containing remains of shells, fish, sea-lillies and
related forms of life.
Redwall Limestone 550 ft. Mississippian Age
g~ Accumulations of sandy lime in which are preserved the remains of
some of the earliest fish.
Temple Butte Limestone Devonian Age
h~ Sand, muds, and limes representing ancient beach which was
gradually covered with water until finally the sediments were
at a considerable depth beneath the sea. The earliest definite
traces of animal life in the canyon found here.
Tonto Rocks Cambrian Age
_i and j rocks of the First and Second Era_
CHAPTER III
THE PALEOZOIC ERA
It was during the third or middle chapter in the earth’s history that
all of the apparently horizontal, upper layers in the Grand Canyon walls
were formed. As will be seen in the succeeding pages, some of these
rocks are sandstones formed from the sands of early beaches or sand dune
areas, others are shales—the hardened muds of ancient river deltas—and
still others are limestones built up by accumulations of plant and
animal remains on sea bottoms. All are rocks formed by the deposition of
sediments by wind and water during vast intervals of time. In them have
been hidden and preserved many forms of life. Seashells, footprints,
fern impressions, and various other traces of early plants and animals
remain to tell the story of these ancient times. It is of special
interest to note that in rocks formed during the earliest part of this
chapter are found the first definite traces of animal life, that in
other rocks of this chapter have been found evidences of primitive fish,
and that in the most recent rocks of this group occur the traces of
early reptiles, insects, ferns, and cone-bearing plants. In the walls of
Grand Canyon examples of all of these fossils have been found, and these
will be described in detail in the succeeding pages.
FIRST ANIMAL LIFE—THE TONTO ROCKS
(CAMBRIAN PERIOD)
Great highlands which were formed in the Grand Canyon region during the
Second Era of history were afterwards gradually worn away by erosion
until near the start of the next era a flat, almost featureless plain
existed. Here and there, however, isolated hills of dark, crystalline
rocks of the First Era stood above the general surface, as seen opposite
Yaki point. In other places, such as to the west of where Bright Angel
Creek now flows, small mountains of red Algonkian rocks (Second Era)
remained. Around and against these, sediments were then deposited.
Pebbles and sands accumulated, forming a thick layer which today appears
as the brown sandstone rim of the Inner Gorge. These represent the first
deposits of the Third Era. But the sea was encroaching upon the land
during this period, and gradually the sand deposited near shore was
covered by mud and this in turn by lime far out from the beach. Today
this series of sand, mud and lime is found represented in the rocks of
the Tonto Platform in Grand Canyon.
[Illustration: SCENE ON CAMBRIAN SEA FLOOR IN GRAND CANYON REGION
(RECONSTRUCTION. MUSEUM NORTHERN ARIZONA)]
Along the Tonto Trail a few hundred yards east of Indian Gardens
numerous primitive sea animals have been found buried and preserved in
layers of thin shale. Many of these are creatures with rounded shells
smaller than the nail of a person’s little finger, others are animals
related to the snail, and still others are crab-like creatures known as
trilobites. The trilobites undoubtedly were the rulers of that age for
they excelled not only in numbers but in size. Some specimens from Grand
Canyon have measured over three inches in length. Despite this size,
however, the trilobites and their associates from the Tonto Platform
represent some of the earliest known forms of animal life.
[Illustration: TRILOBITES PRESERVED IN GREEN SHALE OF GRAND CANYON WALLS
(ONE-EIGHTH NATURAL SIZE)]
THE MISSING PERIODS OF THE THIRD ERA
(ORDOVICIAN AND SILURIAN PERIODS)
The geologist has found that two long periods of history are lacking in
the great succession of ages represented by the strata in the Grand
Canyon walls. These missing periods which belong to the Third Era are
known as the Ordovician, the time when fish first appeared in the seas,
and the Silurian, the time when millipeds and scorpions became our first
air breathers. These ages immediately followed the Cambrian and involved
millions of years. The absence of the first of them is explained by some
geologists as the result of its rocks having been completely worn away
at a later time. It seems more probable, however, that the Grand Canyon
region was above sea level during these two ages so that no sediments
were accumulated and consequently no rocks formed.
THE AGE OF FISH
(DEVONIAN PERIOD)
[Illustration: A FRESH WATER FISH OF DEVONIAN AGE]
During that period of geologic time commonly known as the “age of fish,”
sands and limes were accumulated on the surface of the Grand Canyon
region filling in old river channels and burying the bodies of fish and
other animals. The deposits formed at this time were later eroded to a
large extent. The surface of the land was worn and washed away until
finally only isolated patches or pockets of limestone and sandstone
remained. These we find today exposed in the walls of the Grand Canyon
occurring just at the base of the great Redwall cliff in about fifteen
different localities.
Although fish were rulers of the age during Devonian times, they were of
primitive types and apparently depended for defense upon bony skin
armour rather than upon speed. The plates and scales of fresh-water fish
have been found preserved in the lavender rocks of this age in the Grand
Canyon.
SEA LIFE FROM THE NORTH—THE REDWALL LIMESTONE
(MISSISSIPPIAN OR LOWER CARBONIFEROUS PERIOD)
[Illustration: REDWALL FOSSILS (NATURAL SIZE)]
One of the most prominent and conspicuous features of the Grand Canyon
is the great red cliff of limestone about midway in its walls. This
cliff is the highest in the Canyon—averaging about 550 feet in the area
of Bright Angel Canyon. In most places it is almost vertical, and in
some it even overhangs to such an extent that a visitor once aptly said,
“The Washington Monument might be placed beneath it and kept out of the
rain.”
To the prospector this formation is known as the Blue Lime; to the
geologist it is the Redwall Limestone. Both are correct. Actually the
rock is a rather pure limestone of a grey or bluish color, but in most
places where seen, its surface has been stained a bright red by iron
oxides from above. It appears throughout the Grand Canyon as a wide band
or ribbon of red.
[Illustration: HAVASU FALLS IN REDWALL LIMESTONE. GRAND CANYON]
Large amphitheaters, many curving alcoves, caves, and solution tunnels
are all characteristic features of the great Redwall. It is composed of
relatively pure lime so rain and other waters have a chemical action
upon it—they leach and dissolve it. Waters all tend to drain toward
curving centers, and so increase this curving. Everywhere the rounding
off of corners takes place.
The origin of the Redwall Limestone is as interesting as its form. The
purity of the lime indicates that it was built up in a relatively wide
and quiet sea. Its composition represents a vast accumulation of the
skeletons of ancient plants and animals. Seashells are found in great
numbers, some of them preserved in delicate detail. These and other
forms of ocean life clearly indicate that a great sea connection then
existed between this region and that of western Canada to the north.
TRACKS IN THE SUPAI SANDSTONE
(PERMIAN PERIOD)
During that period in geological history known as the Permian, when some
of the beds of soft coal in eastern America were being formed, a large
area in northern Arizona was receiving red sediments from the east,
probably carried by rivers from the granitic highlands of that region.
Today these sediments appear in the Grand Canyon walls as alternating
layers of red sandstone and shale immediately above the great Redwall.
They are almost a thousand feet in thickness.
[Illustration: TRACKS OF SHORT-LEGGED PREHISTORIC ANIMAL. SUPAI
FORMATION. GRAND CANYON]
When the red beds were accumulating in this region, the climate probably
was more or less arid; the vegetation consisted principally of ferns and
other lowly plants; and the animal life included a group of large but
primitive four-footed creatures. Numerous tracks of the latter,
preserved in the walls of Grand Canyon, have provided one of the most
interesting discoveries of recent years. Some of these footprints are
several inches in length, and the number of toes varies between three
and five. They show no close relationship to the tracks of other
localities, and apparently represent a fauna new to North America.
LANDSCAPES OF THE HERMIT SHALE
(PERMIAN PERIOD)
[Illustration: LANDSCAPE AT TIME HERMIT SHALE WAS FORMING
(RECONSTRUCTION. MUSEUM NORTHERN ARIZONA)]
[Illustration: FOSSIL FERN FROM THE HERMIT SHALE (REDUCED)]
Concerning the conditions under which the topmost red formation of the
Grand Canyon (the Hermit Shale) was developed, and the nature of its
origin, we have today a rather definite and interesting picture. A
wealth of fossil plants and a number of tracks of animals have been
found excellently preserved in its muddy layers, and by means of these
and other indications the following conclusions have been drawn.
The Hermit Shale represents accumulations of mud and fine sandy material
deposited probably by streams flowing from the northeast. Here and there
are found evidences of pools and arroyos with wavy ripple marks on their
borders and a thin film of shiny slime covering the surface. The trails
of worms, the footprints of small salamander-like animals, and the
fronds of ferns, mostly mascerated or wilted, are found delicately
preserved in this slime. Raindrop impressions, the molds of salt
crystals and numerous sun-cracks also add to the picture. This region
has been described by Dr. David White as “the scene of showers, burning
sun, hailstorms, occasional torrents and periods of drought and drying
up of pools” during Hermit times.
Thirty-five species of plants are at present known from the Hermit Shale
of Grand Canyon. Many of these have not been found elsewhere in the
world, though some were representatives of European plants, and others
had their closest relations in central Asia, India, Australia, Africa,
and South America. This fossil flora consists principally of ferns and
small cone-bearing plants, all of which were relatively dwarfed in size
and appear less dense than those of corresponding age found in eastern
America. They apparently indicate a semi-arid climate with long dry
seasons, for the absence of moist-climate and swamp-loving types is
noticeable.
Several insect wings have been found in the Hermit Shale, one of which
was four inches in length. Numerous footprints of vertebrate animals
have also been found, and undoubtedly represent an interesting fauna.
WIND-BLOWN SAND—THE COCONINO
(PERMIAN PERIOD)
The light-colored formation which appears as a conspicuous ribbon-like
band around the upper part of the Grand Canyon has long presented a
puzzle concerning its origin. The grains of white sand of which it is
composed apparently were deposited at steep angles, for the many and
varied slopes which were formed may be readily seen today on the surface
of the rock. These slopes were probably once the lee sides of sand dunes
deposited by winds in an area bordering the sea. We find the only traces
of life in this formation represented by the trails of ancient worms and
insects, and by the foot-prints of early lizard, or salamander-like
creatures. Already the tracks of some 27 species of animals have been
discovered in this sandstone within the Grand Canyon, though strangely
enough no bones have yet been located.
[Illustration: WIND-BLOWN SAND. COCONINO FORMATION. GRAND CANYON]
[Illustration: TRACKS OF PRIMITIVE FOUR-FOOTED ANIMALS, COCONINO
SANDSTONE. GRAND CANYON
PHOTO BY E. W. ENSOR]
WARM SEAS FROM THE WEST—THE TOROWEAP AND KAIBAB FORMATIONS
(PERMIAN PERIOD)
[Illustration: SEASHELLS FROM KAIBAB LIMESTONE (REDUCED)]
Along both sides of Grand Canyon at the top, two buff and gray layers of
limestone stand out as massive cliffs separated by a tree-covered slope.
The upper of these limestones forms the plateau surface and may be seen
for a great distance in every direction. Both layers were formed as the
result of vast accumulations of organic and sandy materials on sea
bottoms, and in places are composed largely of the remains of marine
life—shells, corals and sponges. The teeth of sharks have also been
found in the upper limestone.
SEA LILY OR CRINOID (REDUCED)
HORN CORAL (NATURAL SIZE)
During the early stages of the period when these marine animals lived
and multiplied in the region, a great body of salt water extended over
its surface from far to the west, remained briefly, then retreated from
the area. Soon, however, marine waters advanced once more and another
sea was formed with its shoreline extending eastward even beyond the
region in which we now find Grand Canyon. Evidences of the second and
larger sea are found beyond Flagstaff to the south, in the Painted
Desert to the east, and almost to Zion Canyon to the north.
The presence of corals and sharks’ teeth not only indicates that this
region was covered on more than one occasion by marine waters, but also
suggests that these seas were warm and shallow. This is estimated to
have been some 200 million years ago.
FOSSIL SHARK’S TOOTH (NATURAL SIZE)
[Illustration: ROCKS OF THE FOURTH ERA
The Painted Desert and Zion Canyon Region]
CHAPTER IV
THE MESOZOIC ERA
The Fourth Chapter of the earth’s history is commonly known as “the age
of dinosaurs.” Large reptiles were the dominating forms of life all over
the world during this age. Landscapes and types of climate varied
considerably, and in the Grand Canyon region they changed completely
several times. During some periods ocean bodies covered the country; at
others desert winds piled up dunes on the surface. Again this region was
the flood plain of rivers, where pebbles, mud and great logs of pine
were washed in and deposited. At still other times coal was formed in
some quantity. All of these interesting features of the Fourth Chapter
will be briefly treated in the pages following. Their records as found
at Zion Canyon to the north, in the Painted Desert to the east, and at
the Petrified Forest to the south are such that a visitor to the region
can scarcely help but marvel and wonder at their meaning.
REMNANTS OF YOUNGER STRATA—RED BUTTE AND CEDAR MOUNTAIN
(MOENKOPI FORMATION: TRIASSIC PERIOD)
Two isolated hills of unusual interest rise above the plateau surface
near Grand Canyon. Looking east from Desert View (Navajo) Point one of
these, a flat-topped mesa called Cedar Mountain, may be seen. The other,
known as Red Butte, is a rounded hill about fifteen miles to the south
of Grand Canyon village. The most interesting feature of these hills is
found in the fact that they are composed for the most part of red
sandstones and shales which once formed a continuous layer over this
entire plateau region. These same rocks are found throughout southern
Utah to the north, and in the Painted Desert to the east. Except at Red
Butte and Cedar Mountain they have been completely stripped off and
eroded away from the vicinity of Grand Canyon. The time involved in this
erosion was tremendous and the consequences widespread. As a result the
present flat plateau surface was formed—a great plain high above sea
level. The persistence of Red Butte and Cedar Mountain against time and
the elements is easily explained, moreover, by the hard lava cap of the
former and the protecting layer of pebble-rock on top of the latter.
[Illustration: CEDAR MOUNTAIN]
[Illustration: RED BUTTE]
The red sandstones and shales found in Red Butte and Cedar Mountain were
formed from sands and muds accumulated during the early part of the
Triassic Age—the beginning of the fourth great era of history. Near
Flagstaff at the southernmost limit of the formation have been found
many tracks and trails left by small crawling animals which indicate a
shore environment in that section. In the same formation found in Utah
and other places to the north are many seashells of various types.
Gypsum, an indication of arid climate, is also found to a large extent
in the rocks of this group.
THE PETRIFIED FOREST
(SHINARUMP AND CHINLE FORMATIONS; TRIASSIC PERIOD)
The Petrified Forests of northern Arizona and southern Utah were formed
from trees which grew during a period known as the Triassic. The type of
environment in the Painted Desert region during that period makes a very
interesting speculation. The landscape of this ancient country, as
interpreted from the present rock formations found there, was that of a
low, flat area, perhaps a floodplain, where rivers and streams meandered
back and forth, depositing first large pebbles and sand, and later a
great thickness of finer material consisting of sand and much mud. It
was by these streams that a great quantity of logs of evergreen trees
was carried down probably from mountains to the south or southwest. Many
of the tree trunks were worn and battered on the way, and in this region
(from southern Utah to the vicinity of Adamana and Holbrook) they were
buried in great numbers among the depositing sediments. All four of the
Petrified Forests south of Adamana originated in this manner—and
probably represent old log-jams. Nine miles north of Adamana, however,
is the North Sigillaria Forest where the trees are found standing as
they grew.
[Illustration: PETRIFIED FOREST. ARIZONA]
[Illustration: PETRIFIED LOGS OF TRIASSIC AGE]
A large majority of the fossil trees in Petrified Forest National
Monument represent a pine-like species belonging to a group now extinct
in the northern hemisphere. Some individuals of this type have diameters
as great as ten feet and heights of more than 200 feet. Four or five
other varieties of tree occur but they are less common and rather
inconspicuous.
The process by which these trees were changed to stone took place a very
long time after they were buried beneath sands and silts. At a time
probably millions of years later, waters bearing in solution the mineral
silica passed through the rocks of this region. Particle by particle
wood was decayed, and almost simultaneously it was replaced by silica.
The brilliant colors found in much of it are due to small quantities of
iron and manganese which were introduced in a similar manner.
The wicked-looking upper jaw of a phytosaur—relative of the
crocodile—has been discovered buried in one of the colorful mounds of
mud out in the Petrified Forest. In nearby deposits are found still
other fossils including ferns preserved in delicate detail and clamlike
shells. These, together with the petrified logs of evergreen trees, make
the picture very much alive and real to one whose imagination allows him
to review these fascinating early pages in history.
DINOSAUR TRACKS
(WINGATE-KAYENTA; JURASSIC PERIOD)
Dinosaur means “terrible lizard.” Everyone has heard this name and
attaches to it at least a vague conception of a creature of peculiar
shape and tremendous size. In the dim far-away past these giant reptiles
lived, developed and died in many parts of this country, but to most of
us, they are only fantastic creatures in literature—not live or moving
animals.
[Illustration: DINOSAUR TRACKS. PAINTED DESERT]
The reality of the dinosaur should become apparent to those who travel
through the Painted Desert region of Arizona. In that country the grey
and red hills of clay, the cliffs of sand and the many brightly colored
layers of hardened mud represent a part of the ancient landscape in
which lived the “terrible lizards.” Furthermore, life definitely inserts
itself into this picture when a person sees in the rocks the very
three-toed tracks left by the dinosaur. Who can deny the story of life
when he can place his fingers in the foot impressions and measure the
strides of these animals—many of them—both large and small? Such is the
privilege of those who visit the Painted Desert just south of Tuba City.
The tracks of the dinosaurs are found in rocks which apparently were
formed from river deposits of sands and muds. In other rocks closely
associated have been found the bones of dinosaurs, other reptiles, and
animals related to the frog or toad. Some of these creatures apparently
were “largely if not entirely terrestrial in habit” while others
probably lived in either fresh water streams or swamps.
[Illustration: THE PAINTED DESERT]
THE ROCKS OF ZION CANYON AND RAINBOW NATURAL BRIDGE
(NAVAJO SANDSTONE; JURASSIC PERIOD)
The lure of a desert with its drifting sands, its scattered oases, and
its broad extent has ever been great. Today in the Southwest, cut off
from the moist ocean breezes of the west by the lofty Sierra Nevadas and
further isolated by the Rocky Mountains to the east, is America’s great
desert region. Here the winds and the rains are constantly at work
tearing down and sculpturing the great land masses, while in places the
wind is piling up the sand and debris to form dunes and new lands.
Far back in history, probably in what is known as the Jurassic Period,
southwestern United States witnessed conditions of climate and
environment which were perhaps somewhat comparable though probably far
more desert-like than those which exist today. The land which had been
raised in the preceding period to form a great flood-plain remained
above sea level. Lofty mountains were formed to the west and like the
Sierras of today, they robbed the east-travelling winds of their
moisture. These mountains were very high and furnished a vast supply of
sediment which was carried down into the arid basin to the east, worked
and reworked by the wind, and finally deposited as a great layer of
sand.
[Illustration: ZION CANYON. NAVAJO SANDSTONE]
[Illustration: RAINBOW NATURAL BRIDGE. NAVAJO SANDSTONE]
The beautiful Vermilion Cliffs and the White Cliffs of southern Utah
which together form the walls of Zion Canyon, the red sandstone out of
which is carved Rainbow Natural Bridge, and the jagged Echo Cliffs seen
to the northeast of Desert View (Navajo) Point at Grand Canyon are all
monuments of the Jurassic Age. These high walls are of sandstone—formed
from sand steeply piled at varying angles. They have been aptly called
“cliffs of fossil sand dunes.”
While desert winds and a burning sun were playing a prominent part in
the Grand Canyon region, during the Jurassic Age, other sections of the
country were favored with a moist climate and luxuriant vegetation.
Dinosaurs and other reptiles waded about in swamps and developed to
tremendous sizes. The country teemed with life, very different from that
of today, yet none the less interesting.
FROM SEASHELLS TO COAL BEDS
(DAKOTA. MANCOS, MESA VERDE; CRETACEOUS PERIOD)
[Illustration: CRETACEOUS SHELLS FROM SOUTHERN UTAH]
During the last part of the “Age of Dinosaurs,” in that period of
history known as the Cretaceous, much of northeastern Arizona, southern
Utah, and northwestern New Mexico apparently was submerged beneath a
sea. Mollusks abounded, and various other types of water animals swam or
crawled in this region. Their shells were buried and preserved among the
muds and limes which were accumulating, and today many of them are found
in the rocks of this age.
As time went on, the Cretaceous seas were expelled from their basins in
the Southwest. Low-lying coastal plains—two hundred and more miles
wide—with luxuriant vegetation and perhaps swamps, replaced them, and
these new conditions were the means of much coal formation. Great
accumulations of vegetable matter, buried beneath sediments brought down
by streams, eventually formed the many layers of coal which today are
found in various places in Utah, Arizona, and New Mexico. In the last
named state some extensive and valuable coal beds are found in rocks of
this age near Gallup. Impressions of leaves and pieces of fossil wood
are also numerous among these rocks and they indicate that there was a
warm, moist climate during that period in which they grew.
The Cretaceous Period ended with a general change of conditions or a
revolution, the world over. Many of the seas were changed into lands,
new mountains were formed and the dinosaurs and giant reptiles were
largely replaced by mammals and other modern varieties of life.
[Illustration: COAL CANYON. PAINTED DESERT COUNTRY
AERIAL PHOTO COPYRIGHT FRED HARVEY]
CHAPTER V
THE CENOZOIC ERA
Although chapter five is the most recent in the earth’s history and
lasts up to the present day, evidences of its life and its happenings
are extremely meager in the Grand Canyon region. With the exceptions of
the fresh water deposits formed during the very early part (Bryce Canyon
formations) and of the many volcanoes built in the later stages, no
rocks were formed here during that chapter. This region was then above
sea level and erosion was working continuously. The great level plain
which today forms the plateau surface at Grand Canyon was created by the
wearing away of overlying rocks. The Grand Canyon itself and also Zion
and Bryce Canyons were sculptured. In fact, all of the features of
erosion which today make this desert region so picturesque and fanciful
owe their origin to the various agents of erosion which have been at
work during this most recent chapter of the world’s history.
The “Age of Mammals” is a name often applied to the last era. Creatures
not unlike some of the most advanced forms of life found today lived
even in the early parts of this age. As the era progressed,
nevertheless, a development was noticeable until finally in the very
last part man himself appeared. Though few remains of this interesting
and comparatively recent life have been found in northern Arizona and
southern Utah, still a few elephant tusks, some camel teeth and the more
recent remains of early cliff and pueblo dwellers give evidence of a
thrilling history during parts of this era.
In the following pages will be found brief sketches of some of these
interesting features represented in the Grand Canyon region. The many
activities of erosion such as canyon-forming, the eruption of volcanoes,
influences of the great ice sheets of the north, crustal movements,
fragmentary evidences of early mammals, and lastly early man himself are
all introduced.
BRYCE CANYON FORMATION
(WASATCH: EOCENE EPOCH)
The formation found at Bryce Canyon and at Cedar Breaks in southern Utah
has the distinction of being composed of the most recently formed
sedimentary rocks in this plateau region. It was during the early part
of the last great chapter of history that lime and some sand were
accumulating here in fresh water. They are believed by most geologists
to represent the deposits of ancient lakes and in them are found
freshwater mollusks. Rivers and other agents of deposition probably also
took a part in the forming of these strata as is indicated by the great
irregularity and variety of sand and other sediments. Truly the origin
of these rocks presents an interesting problem.
[Illustration: BRYCE CANYON
AERIAL PHOTO COPYRIGHT FRED HARVEY]
[Illustration: MAP OF THE COLORADO RIVER]
The delicate and beautiful colors of Bryce are due to the white
limestone which in many places retains its creamy color, but in others
has been stained a vivid pink by the drainage from upland washes. The
Canyon itself is almost entirely the result of running water which has
carved and etched its pattern during geologically recent times. Just as
the Grand Canyon and Zion Canyon were made possible by a great elevation
of the land in this region, so also was Bryce affected. The small
streams of the Paunsagunt Plateau were given power to cut into the
sandstones and limestones which form the Pink Cliffs, and due to the
peculiar nature of these rocks the many spires, promontories, and
pinnacles were formed as remnants of erosion in the valleys.
A GREAT EROSION SURFACE
(CENOZOIC AGE)
The level, flat and almost featureless skyline of Grand Canyon is an
outstanding characteristic of the plateau of northern Arizona. This
surface is fascinating to some; monotonous to others. To all, it is one
of the most striking features of the region. The history which it
represents, moreover, is of extreme interest and impressive length. Here
on the top of the great plateau is seen the result of vast erosion. Long
periods of work by water, wind, and other elements have gradually worn
away strata that were once above. Just as erosion is forming the Grand
Canyon today, so it has accomplished this much greater task. Several
thousand feet of materials have been removed from the surface over much
of this entire region.
[Illustration: A GREAT EROSION SURFACE
NATIONAL PARK SERVICE]
South of Grand Canyon, at Red Butte, east in the Painted Desert, and
north in Utah are found remnants of those rocks which once formed a
continuous layer over the present plateau. Red sandstones and shales
representing former sands and muds of shallow water and beach,
pebble-rocks and marls deposited by rivers and containing the remains of
cone-bearing trees, crocodiles, and dinosaurs—all these rocks and
probably others once gave color to this area just as today they lend
brilliance to the Painted Desert and to southern Utah. In those places
high cliffs mark the lines of recession—the stages of the constant
retreat of the rocks from the Grand Canyon region before ever-working
forces of erosion. Red Butte to the south of Grand Canyon, on the other
hand, has been preserved as an isolated remnant of the same rocks by its
hard, resistant cap of lava. Thus we have mute evidence of a
tremendously large and wonderful story of former lands, and of their
later wearing away to leave the great plain which now forms the surface
of the plateau about Grand Canyon.
CRUSTAL MOVEMENT AT GRAND CANYON
(CENOZOIC AGE)
Many visitors to the Grand Canyon are distinctly surprised when they
find numerous seashells, corals, and sponges, beautifully preserved in
the limestone layer upon which they are standing. The idea immediately
occurs that this region was once beneath the sea. Obviously then either
the land has risen or the ocean has receded.
A careful study of the region shows that the rock strata which form the
great plateau of northern Arizona have been bent into a huge arch or
dome. The Santa Fe railway travels steadily up grade to the south rim of
Grand Canyon which is 7,000 feet above sea level. The north rim is a
thousand feet higher, while fifteen miles farther north a high point of
9,000 feet is attained. In southern Utah the limestone layer which forms
the top of Grand Canyon passes beneath the surface at 4,000 feet.
Why crustal movements occur is not definitely known though many theories
have been advanced to explain them. It is significant, nevertheless,
that such movements have gone on in all parts of the world many times in
history, and that in many regions they are taking place today. Parts of
the California coast are known to be rising, while some other parts of
the country are sinking slowly.
The question of whether or not the Grand Canyon region is still rising
today cannot be answered with assuredness, but certain it is that it has
been both above and below sea level at many different times in history.
It is the slow sinking of the region which has made possible great
accumulations of sediments and the building up of rock layers. It is the
rising of the land which has brought about great cycles of erosion such
as apparently have occurred several times in the history of the
Southwest. Since today this region is high above sea level, erosion is
rapid. Not only does this elevation give the Colorado River and its
tributaries speed and power to erode downward, but also it gives them
unusual depth through which to cut and to carve the canyons which are
their valleys. Without the rising of this plateau region, the colossal
gorges, the weird, sculptured forms of erosion, all of the fascinating
and picturesque features of this region could not be.
CUTTING THE GRAND CANYON
(PLIOCENE AND PLEISTOCENE EPOCHS)
“WHAT FORCE HAS FORMED THIS MASTERPIECE OF AWE?
WHAT HANDS HAVE WROUGHT THESE WONDERS IN THE WASTE?
O RIVER, GLEAMING IN THE NARROW RIFT
OF GLOOM THAT CLEAVES THE VALLEY’S NETHER DEEP,
FIERCE COLORADO, PRISONED BY THY TOIL,
AND BLINDLY TOILING STILL TO REACH THE SEA.
THY WATERS, GATHERED FROM THE SNOWS AND SPRINGS
AMID THE UTAH HILLS, HAVE CARVED THIS ROAD
OF GLORY TO THE CALIFORNIA GULF.”
—HENRY VAN DYKE
Very difficult is it for the average human fully to realize, to
comprehend the tremendous power of running water. One does not question
the origin of a wayside gulch cut out by recent storms, nor is it hard
to visualize the formation of some steep-walled glen where a
fast-rushing stream is found at work in its bottom. The vast Grand
Canyon, however, an extreme example of erosion, seems a bit too
large—too wide and deep—to be attributed alone to the power of any river
such as exists today. But the Grand Canyon—the greatest of chasms—is
nothing more than the result of the work of running water over a long
period of history.
[Illustration: CROSS SECTIONS OF GRAND CANYON]
NEAR THE WESTERN END OF NATIONAL PARK. ROCKS OF THE THIRD ERA ALONE HERE
FORM THE CANYON WALLS. THOSE OF THE FIRST ERA ARE PROBABLY NOT FAR BELOW
THE RIVER BED.
CENTRAL OR BRIGHT ANGEL AREA. THE INNER GORGE IS CUT IN HARD VERTICAL
ROCKS OF THE FIRST ERA (ARCHEAN). THE UPPER CANYON WALLS ARE FORMED OF
HORIZONTAL ROCKS OF THE THIRD ERA. THE TILTED STRATA OF THE SECOND ERA
WERE HERE WORN AWAY EXCEPT TO THE LEFT OF THE GORGE.
EASTERN END (DESERT VIEW, CAPE ROYAL). THE FLOOR OF THE CANYON IS HERE
FORMED OF TILTED ROCKS OF THE SECOND ERA. THE UPPER WALLS ARE OF
COMPARATIVELY HORIZONTAL ROCKS OF THE THIRD ERA.
[Illustration: THE GRAND CANYON]
Those who have been to the rocky shores of the Colorado River in Grand
Canyon, who have heard its wild roar, and seen its mad waves rush along
their course, need no further introduction to the power of this stream.
It is a mighty river! In the open stretch above the mouth of Bright
Angel Creek its speed varies between two and a half and ten miles an
hour. Its width at the same place is over one hundred yards and its
depth between twelve and forty-five feet. But the Colorado River alone
would have made but little progress were it not for the many
rocks—boulders, pebbles, and sand grains—all of which act as tools and
are constantly gouging and cutting as they move. Just as sandpaper
rubbing over the same place continuously leaves its groove, so this
combination of power and tools is ever carving its course. The Colorado
River during a vast period has cut almost a mile vertically through all
of the great rock layers now exposed in the walls of Grand Canyon.
The width of the Grand Canyon, an average of about ten miles, has been
brought about by the wearing and washing-in of its sides by natural
processes of erosion. Rain, wind, frost, temperature changes and plant
action have all combined to break down the Canyon walls. The soft rocks
on the slopes are continually being broken and removed; the more
resistant ones in the cliffs are undermined so in time fall down. While
the river has been cutting deeper, the Canyon’s sides have been steadily
receding. The Grand Canyon itself is the valley of the Colorado, and its
narrowness rather than its width is the remarkable feature when compared
with the valleys of other rivers. This present canyon profile has been
brought about as the combined effects of an arid climate and a rapidly
downward cutting river.
Even a distant view of the Colorado River in the Grand Canyon bottom is
sufficient to convince one of the tremendous transporting power of this
stream. Thus it not only does the work of cutting downward, but also
carries off the vast load of sand and silt which is continually emptied
into its waters. It has been aptly described as being “too thick to
drink but too thin to plow.” In this region the river known at its
headwaters as the “Silvery Colorado” bears even a higher percentage of
sediment than does the muddy Mississippi-Missouri. It has been found
from carefully made tests by the United States Geological Survey that
the Colorado River carries past any given point in the Grand Canyon an
average of nearly a million tons of sand and silt every day. Thus has
the Grand Canyon been excavated!
THE FORMING OF ZION CANYON
(PLIOCENE AND PLEISTOCENE EPOCHS)
“A Yosemite Valley in colors” is a very apt description which has often
been applied to Zion Canyon in southern Utah. Sheer-walled with a
beautiful flat valley floor, this canyon is not unlike California’s
glacier-carved fairyland in general size and shape, but in formation it
has a very different history.
[Illustration: ZION CANYON]
The brilliant Vermilion Cliffs which form the bottom two thousand feet
of Zion’s walls and the contrasting White Cliffs which rise an
additional thousand feet are hard, resistant sandstones. Wherever these
rocks are found, they form conspicuous perpendicular cliffs because of
their hardness, yet even they show the results of the constant attacks
of weather and erosion over long periods. From once continuous layers,
they have in many places gradually been cut and dissected by running
water until now numerous canyons expose their secrets.
It was relatively late in the last chapter of the earth’s history
(Cenozoic Era) that the cutting of Zion and associated canyons was made
possible by gradual though tremendous crustal movements in the region.
The then broad, low-lying country was raised several thousand feet to
about its present altitude. This was the means of giving power to the
streams, including the masterstream—the Virgin River. Steadily and
relentlessly these active agents of erosion, heavy-laden with their
tools, the muds, sands, and pebbles, have been cutting notches and then
canyons. Zion Creek itself, which is one of the largest tributaries of
the Virgin River, has cut downward through all of the layers now exposed
in the walls of its canyon, and the rock fragments derived from these
have been the means of grinding and gouging. As the stream has struggled
in its course, these sides have slowly but surely receded through the
combined efforts of rain, wind, frost and plants. They have been
undermined and otherwise attacked, but as yet represent comparatively
little progress in widening. Beautiful Zion Canyon, therefore, has been
created as the result of crustal movements bringing into action the
effective cutting power of running water, assisted by all the
ever-working forces of disintegration and decay.
GLACIERS
(PLEISTOCENE EPOCH)
“What part did glaciers play in cutting the Grand Canyon?” This is a
question asked almost daily on the rim of that great chasm. Everyone has
heard of the mighty ice sheets which somewhere back in geologic history
covered a large part of eastern and midwestern United States. Many
people have seen beautiful Yosemite Valley in the far west, and have
been told how it was carved by the action of glaciers. It is not
altogether strange, therefore, that visitors to the Grand Canyon should
associate the cutting power of ice with that tremendous gash in the
earth’s surface. But geologists agree that the glaciers of the Ice Ages
had no direct part in the story of Grand Canyon. No scratches or gouges
made by ice are to be found on the canyon walls, no great rock piles
formed at a glacier’s front are in evidence, and lastly, the very
V-shape of the canyon itself is vastly different from the usual
flat-bottomed valley scooped out by moving ice.
During the last epoch of geologic history, climatic conditions the world
over altered very materially. Upon five different occasions snow
accumulated in the north to form extensive ice sheets which advanced
steadily toward the equator and then retreated with a later change in
conditions. These were not the only ice ages in history, but they were
of such a comparatively recent date that their influence is strongly
felt today in many parts of the world. At the time of greatest expansion
the glaciers reached New York in the east, Missouri in the mid west, and
Washington in the far west. Contemporaneous with these main ice sheets,
furthermore, were large glaciers throughout the Rocky Mountains and the
Sierra Nevadas. In the mountains of Utah and even in the San Francisco
Peaks, just south of the Grand Canyon, are found evidences of glaciers
of this period. Evidently then, climatic conditions in the Southwest as
elsewhere were greatly different from those of today. It is believed
that there was much more rainfall and less evaporation, as shown by the
extensive lakes which existed in this region at that time. Furthermore,
the later melting of the glaciers must have supplied a vast quantity of
water to the Colorado River causing it to be far larger and more
powerful than today.
SAN FRANCISCO MOUNTAIN VOLCANIC FIELD
(PLIOCENE AND PLEISTOCENE EPOCHS)
[Illustration: VIEW OF VOLCANOES FROM NORTH]
Over a large part of the great plateau of northern Arizona are found
sheets of hard lava and cone-shaped craters. The center of this volcanic
activity is located in the San Francisco Peaks just north of the town of
Flagstaff, but lavas and cones are found westward beyond Williams and to
a considerable extent in every other direction. Looking south from Grand
Canyon these peaks may be seen to rise high above the plateau and are a
very beautiful sight. From Flagstaff and Williams not only the mountains
but also great sheets of lava resting on the limestone surface are
conspicuous.
[Illustration: SAN FRANCISCO MOUNTAIN—PAST AND PRESENT]
It was during the last great era in geological history, and for the most
part after the Colorado River had already started to cut the Grand
Canyon, that molten masses broke through and flowed out on the northern
Arizona plateau. Three great periods of such volcanic activity are
represented by the rocks of this region and they range in age from
probably at least a million to relatively recent years.
The first general period of eruption in the San Francisco Volcanic Field
was characterized by a predominance of lava flows which formed a black
rock known as basalt. These flows had an average thickness of about 50
feet and covered an area of 3,000 square miles. Accompanying them was
the formation of about a hundred small cinder cones.
[Illustration: _San Francisco Mountain Volcanic Field_]
It was during the second period of volcanism that six isolated cones of
large size and a somewhat greater number of small cones were formed by
the eruption of lavas widely ranging in composition. San Francisco Peak,
the largest of these cones and a dominant feature of the region reaches
an elevation of 12,611 feet above sea level, or about 5,000 feet above
the plateau surface. It is composed of five different types, of
lava—mostly red or light colored—which represent a corresponding number
of distinct stages in eruption. Since the termination of its
building-up, the crest of this cone has been eroded and worn away to the
extent of 3,000 feet as estimated from restored cross-sections. Other
large volcanic craters of this period are Bill Williams (9,090 feet),
Kendrick (10,418 feet), O’Leary (8,925 feet) and Sitgreaves (9,240
feet).
Two hundred small cones and about twenty cubic miles of lava were
produced in this same general region during a third and relatively
recent period of volcanic activity. Much of this material overlies that
of the two preceding periods. Probably the most interesting feature of
these cones and flows is their age, at least one cone being so recent
that ash from it buried numerous pithouses built by Pueblo Indians
during the eleventh century, A. D.
[Illustration: SAN FRANCISCO MOUNTAIN]
ELEPHANTS AND CAMELS
(PLEISTOCENE EPOCH)
It was during the fifth and last great era in the earth’s history that
mammals developed and that man made his appearance on earth. In many
places in the world the remains of animals that lived during various
parts of this age have been preserved. In the famous asphalt pits of
California literally hundreds of the bones of large mammals—tigers,
mastodons, wolves and many others—have been brought to light. In the
receding ice of northern Siberia, large mammoths—elephant-like animals
representative of the last era, but unknown today—have come to the
surface with even their skin and flesh preserved. But in the Grand
Canyon region few fossils of the more recent times remain to tell the
story of the life that then roamed over this surface. For long ages this
region has been above the level of the sea, erosion has been continuous,
so sediments have not accumulated and consequently few records of life
have been made.
Recently near the western Navajo Indian agency at Tuba City, Arizona,
however, the remains of several extinct animals were discovered. In a
spring, hidden in a sandstone crevice, were found the tusks of a mammoth
and some teeth which belonged to camels and bison. These were creatures
native to this country not far back in history. They give but a very
fragmentary insight into the more recent geologic history of the region,
but they open up a field for interesting speculation to the imaginative
person.
[Illustration: ELEPHANT AND CAMEL REMAINS]
ADVENT OF MAN IN THE SOUTHWEST
(PLEISTOCENE HISTORIC)
After reviewing the chapters of the earth’s history and witnessing the
procession and the slow but steady development of life through the ages,
it is very natural that one should wonder when man came upon the scene.
Compared with the hundreds of millions of years which have elapsed since
the time of the first plants, or the millions of years following the
first appearance of vertebrate animals, the age of man is as nothing. In
the Old World there is evidence that humans existed before the last
great Ice Ages, more than a million years ago, but in the Americas human
occupation is measured in terms of thousands of years only.
Numerous recent discoveries in widely scattered parts of the Southwest
indicate that man first occupied this region at a time when it was still
inhabited by such animals as the ground sloth, the mammoth and the
camel. Artifacts of stone and bone have been found associated with the
remains of these animals. Early man’s camp sites are located along the
margins of former extensive water bodies that existed throughout this
region at a time when the climate was far more humid than now. Little is
known about the nature or habits of these men, but it is supposed that
they were hunters with no knowledge of agriculture.
In the Grand Canyon region, the earliest human history with a clear,
detailed record goes back only to about 300 A. D. From that time up to
the present, however, the story of a flourishing and rapidly changing
civilization is well recorded. Although no written documents have been
left, abundant reliable information is available as a result of
archeological excavations. Even the dates of many important events have
been accurately determined through an ingenious method of calculating
years on the basis of growth rings in the trees used for house
construction.
[Illustration: ANCIENT INDIAN PETROGLYPHS, HEAD OF BRIGHT ANGEL TRAIL,
GRAND CANYON]
Two distinct cultures are represented in the people who have inhabited
the Grand Canyon region for the past 1,600 years. The earlier and more
primitive was that of a long-headed type of man known as the
Basketmaker. This culture was replaced at about 700 A. D. by another,
probably the result of new people entering the area, mixing with the
older inhabitants and introducing new ideas. A broad-headed type of man
who lived in pueblos and made pottery was the result. In the earliest
stages he built only small one-roomed houses and made relatively crude
pottery, but by 1,200 A. D. his architecture and crafts had developed to
a very high stage as witnessed in the largest cliff-dwellings and
pueblos of the region. Since then the culture has declined. The Hopi
Indians of today who live near the Painted Desert Country to the east of
Grand Canyon are considered to be modern representatives of this group.
In numerous localities throughout southern Utah burials of the early
Farmer Basketmaker period and also pithouses of the later Potter
Basketmaker period have been found. One of the latter has also been
discovered near Clear Creek in Grand Canyon. The remains of
cliff-dwellings and surface houses built by the later Pueblo Indians are
common everywhere throughout the region and show all stages of
development. Those at and in the Grand Canyon are typical of the
intermediate periods and, judging from pottery fragments in them, were
made by the ancestors of the modern Hopi.
GEOLOGICAL BIBLIOGRAPHY OF GRAND CANYON REGION
Including Zion, Bryce, Painted Desert, and Petrified Forest
Allen, V. T., Triassic Bentonite of the Painted Desert: Am. Jour.
Sci., vol. xix, April, 1930.
Baker, A. A. and others, Notes on the Stratigraphy of the Moab Region,
Utah; Bull. Am. Assoc. Petrol. Geol., vol. 11, 1927.
—— and Reeside, J. B., Correlation of the Permian of southern Utah,
northern Arizona, northwestern New Mexico, and southwestern Colorado:
Bull. Am. Assoc. Petrol. Geol., vol. 13, no. 11, Nov., 1929.
——, Dane, C. H., and Reeside, J. B. Jr., Correlation of the Jurassic
Formations of Parts of Utah, Arizona, New Mexico and Colorado: U. S.
Geol. Survey Prof. Paper 183, 1936.
——, Geology of the Monument Valley—Navajo Mountain Region, San Juan
County, Utah: U. S. Geol. Survey Bull. 865, 1936.
Brady, L. F., Preliminary Note on the Occurrence of a Primitive
Theropod in the Navajo: Amer. Jour. Sci., vol. 30, 1935.
Branson, E. B., and Mehl, M. G., Triassic Amphibians from the Rocky
Mountain Region: Univ. Mo. Studies, vol. 4, no. 2, 1929.
Butler, B. S., The Ore Deposits of Utah: U. S. Geol. Survey Prof.
Paper 111, pp. 619-620, 1920.
Bryan, Kirk, Discussion of rock-fill dam, Lees Ferry, Arizona: Am.
Soc. Civ. Eng., Proc., vol. 48, pp. 1615-1627.
——, Wind Erosion near Lees Ferry, Arizona: Am. Jour. Sci., vol. 6, p.
291, 1923.
Camp, Charles L., A Study of the Phytosaurs: Memoirs, Univ. Calif.,
vol. 10, Univ. Calif. Press, 1930.
—— and VanderHoof, V. L., Small Bipedal Dinosaur from the Jurassic of
Northern Arizona: Proc. Geol. Soc. Amer., abstract, pp. 384-5, 1934.
Campbell, Ian, and Maxson, J. H., Some Observations on the Archean
Metamorphics of the Grand Canyon: Proc. Nat. Acad. Sci., vol. 19, no.
9, pp. 806-809, 1933.
Campbell, M. R., and Gregory, H. E., The Black Mesa coal field,
Arizona: U. S. Geol. Survey Bull. 431, pt. 2, 1909.
Carpenter, Frank M., A Fossil Insect from the Lower Permian of the
Grand Canyon: U. S. National Museum Proc. No. 2695, 1927.
Colton, Harold S., Sunset Crater—The Effect of a Volcanic Eruption on
an Ancient Pueblo People: Geogr. Review, vol. 22, no. 4, 1932.
—— Basaltic Cinder Cones and Lava Flows of the San Francisco Mountain
Volcanic Field: Mus. Northern Arizona, Bull. 10, 1937.
Cross and Howe, Redbeds of southwestern Colorado and their
correlation: Geol. Soc. Am. Bull., vol. 16, pp. 486-487, 1905.
Dake, C. L., The pre-Moencopi unconformity of the Colorado Plateau:
Jour. Geology, vol. 28, pp. 61-74, 1920.
Darton, N. H., Reconnaissance of parts of northwestern New Mexico and
northern Arizona: U. S. Geol. Survey, Bull. 435, 84 pp., 17 pls.,
1910.
—— Guidebook of the western United States: Part C, the Santa Fe Route
with a side trip to the Grand Canyon of the Colorado: U. S. Geol.
Survey Bull. 615, pp. 123-131, 1915.
—— A Reconnaissance of parts of northwestern New Mexico and northern
Arizona: U. S. Geol. Surv. Prof. Paper 131, 1922.
—— Resume of Arizona geology: Arizona Bu. of Mines, Bull. 119, 1925.
Daugherty, Lyman H., New Fossil Plants from the Petrified Forest:
Proc. Geol. Soc. Amer., abstract, p. 389, 1934.
Davis, W. M., Notes on the Colorado Canyon district: Am. Jour. Sci.,
4th ser., vol. 10, pp. 251-259, 1900.
—— An excursion to the Grand Canyon of the Colorado: Harvard Coll.
Mus. Comp. Zool., vol. 38, pp. 107-201, 1901.
—— The lessons of the Colorado Canyon: Bull. Am. Geogr. Soc., vol. 41,
1909.
Diller, J. S., Asbestos in 1917: U. S. Geol. Survey Mineral Resources
of U. S. 1917, Pt. 2, pp. 198-199, 1918.
Dutton, E. C., The physical history of the Grand Canyon District: U.
S. Geol. Survey Second Ann. Rept., pp. 47-166, pls. X-XXV, and map,
1882.
—— Tertiary history of the Grand Canyon District: U. S. Geol. Survey
Mon. 2, 264 pp., folio atlas, 1882.
Frech, F., Section in Congress Canyon opposite Point Sublime: Compt.
rend. 5th Sess. Cong. geol. internat., pp. 476-81, 1893.
Gilbert, G. K., Report on the geology of portions of Nevada, Utah,
California, and Arizona, examined in the years 1871, 1872, and 1873,
Report U. S. Geog. Surveys W. 100th Mer. vol. 3, pp. 17-187, 503-567,
1875.
Gilmore, Charles W., Fossil Footprints from the Grand Canyon:
Smithsonian Misc. Collections 77 No. 9, 80 No. 3, 80 No. 8, 1926-7-8.
Gregory, H. E., Geology of the Navajo Country: U. S. Geol. Survey
Prof. Paper 93, 161 pp., map, 1917.
—— The Shinarump conglomerate: Am. Jour. Sci., vol. 35, pp. 424-438,
1913.
—— Reconnaissance of a portion of the Little Colorado Valley: Am.
Jour. Sci., 4th ser., vol. 38, pp. 491-501.
—— Igneous origin of the glacial deposits of the Navajo Reservation:
Am. Jour. Sci., 4th ser., vol. 40, pp. 97-115.
—— The Navajo Country: U. S. Geol. Survey Water-Supply Paper 380, 219
pp., map, 1916.
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Paper 164, 161 pp. 31 pls., 1931.
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Guidebook 18, Excursions C-1, C-2, 1933.
Hager, Dorsey, Stratigraphy—northeast Arizona—southeast Utah: Mining
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1935.
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Huntington, Ellsworth and Goldthwait, J. W., The Hurricane Fault in
the Toquerville district, Utah: Harvard Coll. Mus. Comp. Zool. Bull.,
vol. 42, 1904.
Iddings, J. P., Pre-Cambrian igneous rocks of the Unkar terrane, Grand
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petrographic character of the lavas by Iddings U. S. Geol. Survey
Fourteenth Ann. Report, Part 2, pp. 520-24, 1895.
Johnson, D. W., A geological excursion in the Grand Canyon district:
Proc. Boston Soc. Nat. Hist., vol. 34, pp. 135-161, pls. 17-22, 1909.
Knowlton, F. H., The Fossil Forests of Arizona: Amer. For., vol. 9,
1913.
—— A Catalogue of the Mesozoic and Cenozoic plants of North America:
U. S. Geol. Survey Bull. 696, 1919.
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Longwell, C. R., Geology of the Muddy Mountains, Nev., with a section
to the Grand Wash Cliffs, in western Arizona: Am. Jour. Sci., 4th
ser., vol. 50, pp. 52-54, 1921.
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1-23, 1923.
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5th ser., vol. 10, pp. 93-106, 1925.
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Virgin Range to the Grand Wash Cliffs, Arizona: U. S. Geol. Survey
Bull. 798, 1928.
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vol. 47, pp. 1393-1476, 1936.
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Amer. Jour. Sci., vol. 45, 1918.
Marcou, Jules, Resume and field notes: U. S. Pacific Railroad Expl.
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Matthes, F. E., Bright Angel Quadrangle. U. S. Geol. Survey topo. map
text.
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Utah, to Gila River, Arizona, examined in 1871: U. S. Geog. Survey W.
of 100th Mer., vol. 3, 1875, pp. 189-225, maps.
Maxson, J. H., and Campbell, Ian, Archean Ripple Mark in the Grand
Canyon: Amer. Jour. Sci., vol. 28, 1934.
McKee, Edwin D., Climates of the Age of Mammals in the Grand Canyon
Region: Museum Notes, Museum of Northern Arizona, Flagstaff, 1932.
——, Arizona Through the Ages: Scientific Monthly, 1932.
—— The Coconino Sandstone—Its History and Origin: Carnegie Institution
Publ. 440, vii, 1934.
—— A Study of the Light-colored, Cross-bedded Sandstones of Canyon de
Chelly, Arizona: Am. Jour. Sci., 5th Ser., vol. 28, pp. 219-233, 1934.
——, Occurrence of Triassic Sediments on the Rim of Grand Canyon: Jour.
Wash. Acad. Sci., vol. 25, no. 4, 1935.
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9, no. 5, 1935.
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——, The Environment and History of the Toroweap and Kaibab formations
of Northern Arizona and Southern Utah: Carnegie Inst. Washington,
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ser., vol. 29, pp. 369-386, 497-528, 1910.
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Geol. Survey Bull. 549, 100 pp., 18 pls., 1914.
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* * * * * *
Transcriber’s note:
--Obvious typographical errors were corrected without comment.
--Non-standard spellings and dialect were not changed.
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