Santa Cruz County History
HISTORY OF SANTA CRUZ COUNTY, CALIFORNIA.- E. S. Harrison, Pacific Press Publ. Co., San Francisco, 1891
CHAPTER VI.
GEOLOGY, OR THE ANCIENT HISTORY OF SANTA CRUZ.
BY C. L. ANDERSON.
I PURPOSE in this paper to attempt a translation of some of what might be called the ancient history of Santa Cruz. The records are abundant. If we do not read them aright, it is our fault, and not the want of material.
Beneath our feet are the leaves of a book more ancient than the church records of the mission Fathers, more lasting than the writings in our hall of records, and surely more reliable and consistent than some of the platforms of our modern politicians.
It is open to our eyes along our seashores, our rivers, and on the summits of our mountains. Every pebble, every grain of sand, every boulder, every fragment of animal or vegetable, whether preserved, or simply leaving its impression, has a history; and if we have the necessary wisdom, we may read it.
But, alas! there are many words in nature's great vocabulary that we do not understand. Even the wisest geologists do not agree on certain interpretations. Nevertheless, there are many things that we can all understand, without entering into speculations.
Now, for convenience in our study, I will outline, or tabulate, a classification of the earth's record at Santa Cruz, in the order in which it has been placed by the Great Author, beginning with the first or primitive rocks, as follows:—
SECTION OF THE EARTH'S CRUST AT SANTA CRUZ.
From fresh water and decay
7. ALLUVIUM AND SOIL.
All sedimentary and stratified
of organic matter.
From ice. 6. CONGLOMERATE OR DRIFT.
From the ocean. 5. SHALE.
4. SANDSTONE.
3. LIMESTONE.
2. METAMORPHIC.
From fire. 1. GRANITE. Unstratified.
This arrangement is more for convenience than absolute accuracy. While the relative position of each class is preserved in the main, these formations cannot always be distinctly identified. They run into each other, are intermingled, and at places are quite confusing. Sometimes a lower or older strata overlaps a newer. The binding has been broken, the leaves torn and misplaced, and fortunate is the geologist who is able to read a little "between the lines." The granite, for instance, may—and is in fact—folded back so as to cover the metamorphic, the limestone, and even the sandstone in some places. It must be remembered that all these formations (save the conglomorate and granite) were deposited in horizontal strata or layers, from aqueous solutions or mixtures. Each formation had its own conditions in a period of time differing more or less in its character from other periods. After the layers had been formed, there were earthquakes, and, the stratifications were disturbed, broken, uplifted, or depressed, so that now in many places they approach the perpendicular.
Each of these classes of rocks may be studied separately; and we may find it convenient to subdivide each great period into lesser periods.
Let us take the GRANITE of our vicinity. I have a bit before me from Blackburn's Gulch, a mile or two north of our city. It is composed of crystals of different colors and shapes. We are all familiar, doubtless, with what is called granite. There is plenty of it in the New England States, and no lack on this coast. Granite is of varying shades of color, red, pink, bluish, but chiefly gray. We remember that verse of Ben Bolt:—
"They have fitted a slab of granite so gray,
And sweet Alice lies under the stone."
If we look a little closer at this rock we will notice that it is made up of several kinds of minerals. The black shining crystals which we can easily pick into thin scales with a knife if we take it the right way, are called hornblende in this case, but in common granite mica. They are both of similar composition, only the mica contains more alumina, and the hornblende contains magnesia instead.
The white shining crystals presenting smooth sides, and which the knife can hardly scratch, are called feldspar. They resemble lime-rock crystals, but are much harder, and contain about fifty per cent of silica. Sometimes this feldspar is colored pink or red, affording a beautiful tint to granite when polished. The other kind of mineral in granite is quartz. A knife, unless of extra hard steel, will not scratch quartz. It fills the spaces between the crystals, and has a bluish, transparent look. It, in fact, is the cement, making granite so strong and useful.
Now there is one thing we can read with absolute certainty in the granite. Composed as it is of crystals and a cement, we know that at some time it was held in solution, for all crystals are formed out of solutions. As examples, we have the numerous and various kinds of salts from solutions. Water is the solvent, aided by heat. Our reading of granite then tells us that previous to its present condition it was in a state of solution, and out of that came the beautiful granite crystals.
All these masses of granite rocks, of which a large part of the earth's crust is formed, have passed through nature's laboratory. Underneath miles of rock the granite has been manufactured out of clay, sand, and hot water, and, being dissolved, the solution was free in the process of cooling to form new combinations, according to the respective affinities. Hence the mica and feldspar (or hornblende, as the case might be) have formed crystals, and whatever of superfluous sand in the form of quartz remained has been used to fill in the spaces between the mica and feldspar. And thus we have granite in all its variations.
The heat contained in these great granite masses coming in contact with the surface rocks has changed them, metamorphosed, geologists say, by the heat pertaining to the fluid granite. We may say, then, that granite is not the primary crust of the earth. It is a product of the original mass, a secondary formation. The crust was formed and stratified many miles in depth before the granite appeared, and its appearance depended on a melting and solution of older deposits (as I have indicated), and then cooling and consequent crystallization.
I say many miles in depth; more definitely, it has been estimated that granite was consolidated at a depth of six to ten miles. Its appearance at the surface in our mountain ranges is due, of course, to upheaval, and, subsequently, the wearing away of the overt lying rock by rain, ice, waves, and currents of the sea. Granite only occurs in ponderous masses, lifting up, melting, penetrating, and covering great areas of the stratified rocks, and also being penetrated itself at places with material forming what are usually termed "trap rocks," "porphyries," "basalts," etc., formations too complicate to study and understand at present.
Only a few places in our vicinity show the granite deposits, and at such places there is an admixture so close and intimate of the various rock formations as to bewilder the wisest geologist.
Next to the granite come the METAMORPHIC rocks. They are abundant in our vicinity, and exceedingly variable. They all show signs of stratification; that is, they have been deposited from solutions or as sediment in regular layers, and afterwards changed by heat and eruptions. They run from the ordinary stratified rocks, by a gradation, to those of a crystalline structure. The fossils they contained, and even the stratification, have been in some cases entirely destroyed. We know they contained fossils by tracing the same strata from the metamorphic into the unchanged rocks. Suppose, for illustration, we take a pine board and place one end in a fire so as not to consume but to char it. The water, and the resin, and other materials have been consumed or driven out by the heat, leaving only the carbon. It has been metamorphosed. But by its continuing with the other end, we know that it once was of the same structure and composition. Thus we read the metamorphic rocks. Metamorphism is almost universal with the lower and older rocks, and less frequent as we approach the recent sedimentary rocks. Some places they are very thick, being estimated at forty thousand feet.
The metamorphic rocks of our vicinity and adjoining coast ranges are comparatively of recent date. The oldest rocks belong to the upper cretaceous and tertiary periods, the time of large reptiles and the beginning of the age of mammals. We find the same species of shells and other fossils as those now living in Monterey Bay. In the cliffs near our lighthouse, about Soquel and Aptos, back in the foothills, and even to the summits of our highest ranges, are remains of shells, whales, seals, sharks, etc., identical in species with those now living. In all probability, the strata that contained these fossils have been in many cases metamorphosed.
We read, then, in these rocks that there were periods and ages when our earth made its revolutions in quiet times and under genial influences of sunshine and heat. Succeeding these ages were stormy times, when the crust of the earth was broken and rendered uneven; when the heat was intense; and the rocks that were formed in horizontal strata were rent asunder by the thrusting upwards of igneous rocks through this crust. There were foldings and tiltings, and the elevation of mountain ranges. These ranges have generally a northerly and southerly direction. As I have said, these rocks are exceedingly variable. Perhaps the most common is what is called gneiss, which has the general appearance and composition of granite, except that stratification, where it occurs in large masses, is quite distinct. There are also many kinds of schists of both hornblende and mica, with abundant shining scales. The black sand so common along our beaches, containing a small per cent of gold, has its origin in these schists, which are made up of a variety of minerals, but chiefly sand, lime, iron, and magnesia.
In the ridge about half a mile south of the powder mill and adjoining the Italian vineyard are some fine specimens of these rocks.
Although metamorphism is going on to-day at great depth, doubtless, yet the period of greatest disturbance, so far as the history of our own locality is concerned, dates back to the times I have indicated, succeeding the cretaceous and tertiary periods.
Let us turn now to our LIMESTONE. This is also metamorphic, but it belongs to a later period, and was formed under different conditions. It is highly crystalline and is a very pure carbonate of lime. This quality is demonstrated every day in our limekilns. Broken into small pieces, it is placed in furnaces and subjected to a high heat. This heat does two things: it drives off the water, which is always necessary, as I have said, to crystallization, and it drives off the carbonic acid (an article so common and palatable in soda water and yet so deadly to breathe). We then have but one of the constituents of our limestone remaining, the water and carbonic acid having disappeared in transparent vapor, and only lime, or quicklime, as it is called sometimes, is left. Our rock, although in form the same, has lost a considerable portion of its weight, and it is very brittle, crumbling easily: Chemists call it oxide of calcium.
It is very difficult to read the history of our limestone. The fossils once contained in it have almost entirely disappeared in its metamorphism. Only slight traces remain, and I know of no place where the strata can be traced to the condition it once had before metamorphism.
Geologists, however, commonly agree that our limestones and quartz rocks, in most cases when stratified, have been secreted by living organisms. They have obtained the lime and silica from the water where it is held in solution, to build the framework of their bodies—the houses in which they live—such as sponges, corals, diatoms, shells, etc. Such was the structure of our limestone in all probability. During the periods of quiet that reigned over the earth's surface when the metamorphic rocks were deposited, vegetable and animal life of the small microscopic forms, as well as the larger kinds, increased to an enormous extent. We should endeavor to comprehend the wonderful fact that in some cases there are deposits of limestones occupying hundreds of square miles, and attaining perhaps a thousand feet in thickness, which are essentially composed of the calcareous envelopes of animals and the silicious cells of plants, so small as to be invisible to the naked eye.
This superabundance of living organisms probably accounts for the deposit of so much pure limestone following the other material so plentiful in the older metamorphic rocks which we have already considered.
Our limestone gradually runs into the gneiss beneath and the sandstone above. Hence we will consider next the period of SANDSTONE deposits.
Sand and sandstone result from the rubbing of all kinds of rocks to a fine powder. This powder accumulates in heaps, by the agency of water and winds, forming our beaches and sand hills. In many places it is cemented into hard rocks, and other places loose and shifting.
This was a period when the sea was troubled and the winds were tempestuous. The sea was over all; and there are many remains of marine life, both vegetable and animal, scattered through our sandstone. Petrified bones of whales, seals, sharks, and immense beds of mollusks and starfish abound, especially in the upper and softer portions. Sometimes these fossils are changed to lime, or silex, and sometimes the shelly and bony structures are so well preserved as to appear to have been laid away only a year or two. And yet countless ages have elapsed since these sand hills were elevated above the sea and a longer time still in their deposit. There are many curious as well as valuable things in our sandstones. Jutting out from our cliffs we frequently notice long branching forms resembling trees, or some monstrous animals. These are concretionary sandstones. They are very hard, and of many odd and fantastic shapes. Usually there is a nucleus of shell, bone, or pebble around which certain particles of sand collect, moved by an attractive force.
In some places petroleum has come in contact with ridges of sandstone, and has percolated or been absorbed by the sand strata, forming what we call bituminous rock, now extensively used in covering our streets and sidewalks.
We also have golden sand—sand that contains a small quantity of finely-powdered gold—which has been derived from quartz rocks, the main source of our white sand. Lately I have seen some iron sands containing a large per cent of magnetic iron, about sixty per cent, I am told.
The next formation above the sandstone is the SHALE. This has a history similar to the sandstone. It belongs to a similar age, and has resulted from the same causes. It is also of marine origin. During the disturbance of the waters the material found in the sandstones and shales was intimately mixed. But as the agitations subsided, the sands of gold, quartz, iron, etc., being of greater specific gravity, settled first, and the finer and lighter sediment of our clay and shales rested on top. The classes of rocks which belong to the shales differ widely in composition, structure, hardness, color, etc., from each other.
It abounds in the debris of organic matter, such as the shelly parts of starfish, mollusks, the spicula of sponges, and the frustules of diatoms. Of course when the shales have been metamorphosed nearly all traces of fossils have been destroyed.
It is sometimes called bituminous shale, from the fact that carbonaceous material seems to be disseminated throughout the whole system in the form of lignites and bitumen, or tar-like oozings.
And now we come to another and very interesting period in our history, which we may designate the CONGLOMERATE. In this we include the glacial, bowlder and drift deposits.
If we examine the deep cuts made by our creeks, and some of the hills and even level lands in our vicinity, we will find masses of smooth-worn, round-like bowlders from the size of a marble up to those a foot or more in diameter. In some places they are loosely piled together, in other places slightly cemented. Looking along the sides of the valley margins we will notice that the basins, or depressions, in the underlying strata are frequently filled with these bowlders. The question arises, Whence came they? and by what agency have they been ground, polished, and rounded into these shapes? We plainly read that rivers and ordinary streams could not have done this work. They are not in the course, even, of old river beds. And yet water in some way has ground them out. They are not the result of the ocean's tides, or even of salt water; for the remains found in this drift are not of marine life. They are above the ocean's waves, and always have been so.
This formation has long been a difficult chapter for geologists to understand. They have been obliged to travel all over the world, and even now only the general outlines can be read. It is so full of notes and queries that I can only state the general facts, leaving you to read Agassiz, Geikie, and other voluminous writers.
After a long period of "warm weather"—extending through centuries, incalculable ages—when redwood trees grew in Alaska and Siberia, and magnolias in Greenland, when the mammoth and the mastodon of the elephant family found a congenial home north of the Arctic Circle, when cycads and other curious trees grew at the foot of Monte Diablo and Loma Prieta in our vicinity, plants now only found in tropical regions, there came a "cold snap," colder than the "oldest inhabitant" had ever known. It came not in one night—a mere frost—but it was ages coming, getting colder and colder each year. The air was full of snow and ice. Ice was piled up ten, twenty, one hundred, probably one thousand feet deep on our mountains. The higher the mountain, the deeper the snow
This great ice age was not confined to this Santa Cruz Mountain Range alone. There was a belt of ice all around the globe. It was the period of glaciers, which carried the drift and spread it out over North America as far south as the mouth of the Ohio River. Europe and other countries received their share, rocks being transported by glaciers and icebergs hundreds of miles. There were rivers and seas of ice on the land, moving from the higher peaks and ridges towards the sea level, moving under a pressure of thousands of feet in places, not in direct lines but with zigzag and wave-like motions, wearing, grinding, chiseling, rolling, crushing, tossing,—slowly but surely rounding the tops of the granite and metamorphic peaks and ridges, and rounding the great and the small bowlders and pebbles into the shapes you see them now.
In regard to this glacial period, James Geikie, who has so thoroughly studied Scotland, that country so interesting to the geologist, remarks: "It is no exaggeration to say that the whole surface of North America from the shores of the Arctic Ocean to the latitude of New York and from the Pacific to the Atlantic, has been scarped, scraped, furrowed, and scoured by the action of ice."
If we should visit the Alaskan shores that lie between latitudes fifty-five degrees and sixty-five degrees, including Sitka and the inland passages, we would see striking illustrations of the conditions that once existed on the shores of Monterey Bay and northward to the Bay of San Francisco. On those Alaskan coasts are thousands of islands which are but the emerging peaks of what may possibly some day become a coast range of mountains. At Icy Bay the glaciers come down to the very edge of the sea and discharge their icebergs continually. Twenty-nine miles back from this bay stands Mount St. Elias, a "pyramid of eternal ice," sixteen thousand or seventeen thousand feet high, with craters that sometimes open as volcanoes.
Alaska has not
yet recovered from her ice age. The rainfall, the snow, the fog, the glacier are
all reminders of the condition of our mountains and shores in ages long ago.
Looking from the Sierra Nevada
Mountains, we could see the ocean rolling up to their foothills. The coast
ranges were just emerging from the sea. The Bays of Monterey and San Francisco
were connected by a deep and wide channel. Outside of this were a thousand
"inland passages" between the islands.
Again we look, and the coast ranges are from one thousand to fifteen hundred feet above the sea. Whether they came up gradually or suddenly our history tells, but we as yet cannot read it. Whether volcanoes existed or not our knowledge is at fault.
Then came the "cold snap." There was a heavy precipitation of moisture on these mountains. One hundred and twenty inches per annum (the amount at Boulder for the season of 1889 to 1890) was but a drop in the bucket. But it did not run off as rapidly as it fell. It accumulated, on account of freezing, until the pressure became so great it moved as icy lakes and rivers towards the sea. An increase of temperature, which doubtless took place in the course of time, brought this great accumulation more rapidly forward, forcing cuts through the ranges and helping to form our valleys.
And thus we have the bowlders, and the clays, and the gravel, and the sand, of our drift or conglomerate formations.
And now we come to the last chapter in this wonderful history,—the ALLUVIUM and the SOIL. This chapter is unfinished—it is continued day after day, and year after year; and we see how it is done. From it we derive our bread, our meat, our fruits. No better soil exists in the world than that of Santa Cruz, so far as variety of constituents is concerned. It is derived from nearly all classes of rocks and sources, from the igneous through the metamorphic, the limestones, the sandstone, the shales, the clays, to the rich vegetable molds of dense forests and productive fields. Portions of our city rest upon the alluvium brought in by the mountain streams and the waves of the sea. There are trees from the forest and whalebones from the sea under our houses. And doubtless there would be wrecks of ships had ships been sailing these seas when all this region called "the flat" was an estuary. But the mountain streams, aided by the occasional floods, have been gaining on the sea; and now where large ships once might have anchored in safety, this basin is filled with the wearings from the mountain, and the business portion of the city of Santa Cruz stands thereon.
Thus I have but briefly noticed the contents of chapters in this our ancient history, and have wandered along down to a time "within the memory of those now living." Here and there we have been able to read a word or a sentence. A very large part of this history remains for translation by some future student of the geology of this region.
Professor Whitney, in his geological survey of California, complains of two difficulties which constantly beset him and his corps of geologists in these Coast Ranges. First, the similarity in character of rocks of different geological ages. Second, the scarcity of fossils by which different sets of strata might be identified.
Geologists depend on these two things to determine the ages of deposits. Looking, for instance, at our sandstone, without seeing its fossils, we might conclude that it belonged to the oldest fossil-bearing rocks, the Silurian or Cambrian of Wales or the "old red sandstone" of Scotland, in which all the fossils are of extinct species. But when we come to see the fossils of our sandstone, we find but very few of extinct species; and we therefore determine that it is of comparatively recent times.
A similar mistake is doubtless often made in another branch of study, that of archaeology. Stone axes and other stone implements have been referred to ages long past, when the human race universally were supposed to be savages. But the fact is there are savages to-day making stone axes and arrowheads and spears.
So the condition that existed in Scotland when the old red stone was deposited was the condition that existed on our shores countless ages subsequently, and that now exists in part on the Alaskan shores of our own country.
I may add also that in the bottom of Monterey Bay, were it elevated into a mountain range, the deposits that are going on to-day, and that have been going on in ages past, would not be very unlike those we find now on our plateaus, mountain sides, and summits. There would be some changes in species. But in the long periods that have existed between the Silurian formations and the present times, animal and vegetable forms have undergone very marked transformations. In those days the sea was universal. In these times it holds dominion over but two-thirds of the earth.
In regard to the extremes of climate and the causes that changed the land from one of genial warmth to a frigid temperature, belting the temperate zone with a deep crust of snow and ice, we have at present no time to speculate; for, as yet, much is but speculation.
I once had the pleasure of sitting on a redwood stump some ten feet in diameter, and, with Professor Asa Gray, the botanist, counting the rings of growth. I do not remember how many there were, but this is what Professor Gray afterwards wrote: "It is probable that close to the heart of some of these living trees may be found the circle that records the year of our Saviour's nativity. A few generations of such trees might carry the history a long way back. But the ground they stand upon and the marks of very recent geological change and vicissitude in the region around testify that not very many such generations can have flourished just there, at least in an unbroken series. When their site was covered by glaciers, these Sequoias must have occupied other stations, if, as there is reason to believe, they then existed in the land."
I think, perhaps, since Professor Gray wrote these sentences, cumulative proofs have come to light that the Sequoias grew in Washington and Alaska previous to the glacial or ice age. Since their introduction to this, our locality, we may read the climatology back some two thousand years in the rings of growth in these trees; and there has been no great variation. We can see that there have been wet seasons and dry seasons, cold seasons and warm seasons; that there have been many years following each other in succession when but little growth has been made; and then again the rings are thick and vigorous—the tree has made rapid growth. Possibly there are other qualities of seasons that may be learned from these trees.
In like manner, but probably with more complications, may we study the facts as they are written in the circles about the earth.
It matters but little where we begin. But as we advance, we will find there is need of knowledge in many directions. There is a diversity and a uniformity. And, like the rings of a tree (although there are many breaks), or the leaves of a book that has been badly handled by some library borrower, we may have trouble in reading all we might desire to read. But, by gathering information from every source, in time we may be able to trace the different rings which certainly exist around the earth.
Travelers go to Egypt, and Greece, and Rome, and the Holy Land, looking for relics of the past. The older, the more valuable they are esteemed.
But here are relics in these rocks older than the pyramids, older than the creation of man; and yet I find but few persons who value them; notwithstanding, they have histories exceedingly aged and interesting, and we walk over them every day, with but little emotion or feelings of wonder at their great age or curious forms.
And now, as the reader has been so patient in passing through this outline of the ancient history of Santa Cruz, I will close with the admonition of Job, given three thousand four hundred years ago, but just as applicable to-day as then: "Speak to the earth and it shall teach thee."
Transcribed by Kathy Sedler