Geological Survey Bulletin 614 Guidebook of the Western United States: Part D. The Shasta Route and Coast Line

SHEET No. 6A (click on image for an enlargement in a new window)

From Watsonville Junction (see sheet 6A, p. 130) a branch line turns to the left (west) and makes a detour through Santa Cruz and other points, rejoining the main line to the north at San Jose. Passengers may take this route to San Francisco but will have to change cars. The Santa Cruz route affords an opportunity to see a fine group of "big trees" (Pl. XXXI, p. 125), the coast redwood (Sequoia sempervirens), which, although smaller than Sequoia gigantea of the Sierra Nevada, are still gigantic, the largest measuring 70 feet in circumference. This route, crossing the Santa Cruz Mountains at an altitude of more than 1,000 feet, passes through beautiful country. The geology is complicated, old crystalline rocks and later rocks of Jurassic (?), Cretaceous, and Tertiary age being much folded and faulted. The great rift or crack (San Andreas fault) along which occurred the earthquake of 1906 is crossed by this route west of Alma.

PLATE XXXI—BIG TREES (SEQUOIA SEMPERVIRENS) AT SANTA CRUZ, CAL.

North of Watsonville Junction the main Coast Line crosses a rich apple country, in which the orchards reach part way up the slopes of the bordering hills.

The hills to the right and left, gradually approaching as the valley narrows, are composed of Tertiary strata, with a narrow belt of Quaternary deposits along Pajaro River. Just beyond Aromas the train enters Pajaro Gap. Here a small fault, cutting across the range, has weakened the rocks and thereby enabled the river to wear its way through. On the left is the river, and on the right are bluffs of crumpled and crushed rocks, largely diorite (an igneous rock resembling granite, but containing little or no quartz), which are artificially further reduced by rock crushers for railroad ballast.

The country opens abruptly as the train crosses the bridge over the Pajaro near Chittenden; and the diorite of the gorge gives place to the Tertiary sediments of the Chittenden-Sargent oil field. This change is due to the fact that the Tertiary beds are much softer than the diorite and have been eroded out into a valley. Traces of the San Andreas fault, a slight recurrence of movement along which produced the earthquake of 1906, are here visible for the first time to the traveler from Los Angeles to San Francisco over the Coast Line, although the crack continues into southern California to the east of Los Angeles. The hillsides to the northwest (left) are scarred by the earthquake rift, and one-third of a mile beyond Chittenden, around a curve, on the left near the track, is a knoll blackened by the oil from a storage tank that was wrecked by the earthquake.

The Sargent oil field produces approximately 40,000 barrels a year, and some of the oil is shipped from Chittenden. The oil-bearing rocks—shales, sandstones, and conglomerates of the lower part of the Monterey group—cover a wide area. They are bent into anticlines and synclines and are covered by younger shales of the Monterey group and in part also by younger Miocene and Pliocene sediments. The rocks of the lower slopes near which the train passes just beyond Chittenden, on the right, are Pliocene (Merced formation). About 2-1/2 miles from Chittenden, near milepost 88, San Benito River and Llagas Creek join to form Pajaro River. The railroad turns to the left up Llagas Creek to Sargent.

West of Sargent, beyond the oil field, the Franciscan rocks form the higher portions of the range. Beyond Sargent the railroad soon passes out of the low hills into the southern portion of the broad Santa Clara Valley. This portion, a great alfalfa and stock country irrigated by electric pumps, is drained by Pajaro River to the Bay of Monterey. Across the valley in the distance can be seen Pacheco (pa-chay'co), Antimony, St. Anna, Mariposa (the highest), and other peaks of the Mount Hamilton division of the Diablo Range, which separates the Santa Clara Valley from the San Joaquin Valley.

The Santa Clara Valley extends from San Francisco Bay southeastward to and beyond San Benito, a distance of nearly 100 miles. It has a notable peculiarity in that it is divided transversely by a scarcely noticeable soil-covered divide. The southern portion is drained by Pajaro River, but the northern portion drains through Coyote River directly into San Francisco Bay, and the alluvial plain is continuous across the divide.

From Carnadero (car-na-day'ro) Junction, 4 miles beyond Sargent, a branch line runs southeast to Holster, in San Benito Valley, where it is said there is "silver in eggs" and "gold in apples." From the junction the main line continues northward through the Santa Clara Valley to San Francisco Bay, passing through one of the most productive fruit-growing regions in the world.

The town of Gilroy is the point of departure for the Gilroy Hot Springs, which lie 13 miles to the northeast. Oaks appear about Gilroy, and alfalfa begins to give way to grain and especially to fruits. Grapes, prunes, peaches, and apricots are grown in large quantities. The mountains on the right are markedly different in aspect from those on the left, although both are composed, at least in part, of rocks belonging to the Franciscan group, partly covered by Tertiary sediments. The mountains on the right have a nearly even crest line (Pl. XXXII, p. 126). Along their base, beyond the orchards, is a much lower even-crested ridge. Between this ridge and the mountains is Coyote River, which flows northwestward to San Francisco Bay. The valley in the foreground is drained to the southeast by Llagas Creek to Pajaro River and Monterey Bay.

PLATE XXXII—SANTA CLARA VALLEY NEAR GILROY, CAL. The green crest of the distant ridge of Franciscan rocks suggests a plain of erosion. The narrow valley between the two distant ridges is due to faulting and contains Coyote River. Santa Clara Valley, with its fine orchards, in the middle ground, is filled with alluvium that is continuous from San Francisco Bay to the Bay of Monterey. For explanation see page 124.

At Madrone the valley narrows. The rocky slopes on the left are near the railroad and several little cuts expose serpentine, which is a characteristic accompaniment to the Franciscan group. The summit of the transverse divide (elevation 345 feet) is reached near Perry, about 2 miles beyond Madrone, but there is no break in the continuity of the alluvial plain, and the traveler will probably not notice, unless his attention is called to it, that he is passing from the drainage basin of Pajaro River to that of Coyote River. The Coyote enters Santa Clara Valley from the mountains on the right (east).

It has been suggested that all the drainage that now finds its way into San Francisco Bay and thence to the ocean by way of the Golden Gate, once flowed southward through Santa Clara Valley to Monterey Bay. Those who maintain this view think that the submarine channel across Monterey Bay was cut by the more powerful stream that then flowed through Pajaro Valley. A striking resemblance that has been noted between the strictly fresh-water fishes and other forms of life inhabiting Sacramento and Pajaro rivers tends to confirm the conjecture that the two streams were formerly one. Later investigations by Dr. J. C. Branner, however, have suggested a different interpretation of this evidence.

A study of the material of the divide shows that it has the low conical form of an alluvial fan—that is, a deposit made by a stream where it issues from a canyon upon a plain. At such a place the velocity of the stream generally becomes less, and the water is compelled to drop much of the sand and gravel that it swept along with ease in the mountains. This particular deposit was made by Coyote River during a period (probably glacial) when the land stood at a higher level than now and the creek carried a large load of detritus. As the alluvial fan grew Coyote River shifted its position from time to time to lower parts of the conical slope, and thus flowed sometimes to San Francisco Bay and sometimes to Monterey Bay. In this way opportunity may have been given for fishes and other living things to pass over the divide by way of Coyote River. If this happened, it would of course not be necessary to account for the similar faunas of Sacramento and Pajaro rivers by supposing the streams to have been at one time directly united.

Six miles southwest of Coyote, in the hills composed of rocks belonging to the Franciscan group, is the New Almaden quicksilver mine, which has yielded more quicksilver than any other mine in the United States. At milepost 59 on the right may be had the first view of Lick Observatory, on Mount Hamilton (elevation 4,209 feet). The observatory may be visited from San Jose.

Just north of Coyote is the narrowest part of the valley. Serpentine occurs here on the left but is on the right at Edenvale, where the valley widens and a belt of Tertiary rocks forms foothills to mountains that are composed chiefly of Franciscan rocks.

At San Jose (ho-say'), which is by far the largest city in the Santa Clara Valley, the branch line running through Santa Cruz joins the main Coast Line. The New Almaden mine may be reached by a spur from this branch. Other railroad lines run from San Jose east of San Francisco Bay to Oakland and have connections across the Diablo Range, through Livermore Valley, with the several lines in San Joaquin Valley.

The city is built on the fertile plain between Guadalupe and Coyote rivers, 11 miles southeast of the head of San Francisco Bay. Its delightful climate, beauty of surroundings, fertility of soil, and consequent profusion of flowers and fruits make San Jose a favored spot even in California.

From San Jose automobile stages run to Mount Hamilton (26 miles). All the sedimentary rocks seen on this trip belong to the Franciscan group. Some beautiful drives may be enjoyed in the suburbs and in the country around the town. During the rose season the drive along Alameda Avenue from San Jose to Santa Clara, about 3 miles, is particularly recommended. This trip may also be made by trolley car.

At College Park, on the left as the train leaves San Jose, is the College of the Pacific. Well-kept orchards of prunes, apricots, peaches, pears, and cherries, as well as vineyards, lie on both sides of the railroad throughout this part of the valley. Acres of sun-drying prunes are a common sight in August.

Santa Clara College, the white building of which may be seen on the left near the center of the town of Santa Clara, was founded in 1851 by the Jesuits. The chapel is one of the old mission buildings erected in 1777 and is well preserved. Several large canneries may be seen along the railroad and are kept busy for most of the year by the wide range of fruit and vegetable products which the Santa Clara Valley affords. Two miles beyond Santa Clara on the right, barely visible in the distance across the broad fields of barley hay and between groves of oak and eucalyptus, is Agnew Asylum for the Insane, a State institution.

The Santa Clara Valley widens northward and the fertile bottom land grades near the south end of the Bay of San Francisco into extensive salt marshes. The railroad bears to the west from Santa Clara, toward the mountains which form the backbone of the peninsula of San Francisco.

Although fields of hay with scattered oaks predominate near Sunnyvale, there are large tracts devoted to orchards and market gardens. The climate and soil of the lower Santa Clara Valley between San Jose and Sunnyvale, like that of Lompoc Valley (p. 111), are such that seeds mature well, and there are several large seed farms near Sunnyvale and Santa Clara.

Near Mountain View the railroad runs nearer to the foothills of the Santa Cruz Range. The lowest hills are composed of sandstone belonging to the lower part of the Monterey group. Black Mountain (elevation 2,787 feet), the culminating point of Monte Bello Ridge, is the most prominent peak of this part of the range. Just behind it lies the San Andreas fault or rift. (See pp. 89-90.). The upper slopes of Black Mountain are mainly sandstone with some lenticular masses of limestone, several thousand tons of which are crushed annually and shipped to beet-sugar factories. Some of the best red wine made in California is produced near Mountain View.

From Castro, about a mile beyond Mountain View, is visible on the right the Dumbarton Bridge on the railroad freight route from Oakland to San Francisco.

At milepost 33 on the left, ahead and more than a mile away, may be seen among the trees the red-tiled roofs of the Stanford University buildings. The entrance to the university grounds is on the left, near the Palo Alto station, and the university buildings, a mile away, hidden from the station by trees, may be reached by a trolley line. Leland Stanford Junior University, founded by Senator and Mr. Stanford and opened in 1891, has nearly 2,000 students, both men and women. The medical department is in San Francisco and the biological laboratory at Pacific Grove. The buildings of the other departments are on the Stanford University tract, 8,400 acres. The buildings (see Pl. XXXIII, A), designed originally by H. H. Richardson, take their architectural motif from the cloisters of the San Antonio mission, and the combination of buff sandstone with red tiled roofs gives striking color effects. The buff sandstone came from the quarries at Graystone, about 10 miles south of San Jose, and is of early Miocene (Monterey) age. The San Andreas fault, the line of the San Francisco earthquake, lies 4 miles southwest of Stanford University and is easily reached from that point. The university suffered much from the earthquake but has completely recovered.

PLATE XXXIII—A. THE ARCHES, STANFORD UNIVERSITY, CAL. The displacement of the capitols of the small columns supporting the arches is an effect of the earthquake of 1906. B. FURROW A MILE NORTHWEST OF OLEMA, CAL., MADE BY THE MOVEMENT WHICH CAUSED THE EARTHQUAKE OF 1906. On the left Is the rift valley, which extends from Bolinas Lagoon to Tomales Bay and is a result partly of earlier movements, partly of erosion along a cone of crushed rocks.

The accompanying cross section from Palo Alto to the summit of Santa Cruz Mountains (fig. 15, p. 128) shows the general geologic structure of the region.

FIGURE 15.—Section from Palo Alto, Cal., to the summit of the Santa Cruz Range, showing the folds and faults of the several formations about the San Andreas rift. Qal, Alluvium; Tsc, Santa Clara formation (Tertiary); Tp, Purisima formation (Tertiary); Tm, Monterey shale (Tertiary); Tv, Vaqueros formation (Tertiary); db, diabase and basalt; Kc, Chico formation (Cretaceous); fc, Franciscan formation (Jurassic?). (click on image for an enlargement in a new window)

By looking ahead from the Palo Alto station the traveler may see on the right of the track the tall tree (Spanish, palo alto) for which Senator Stanford's estate was named. It is the only redwood (Sequoia sempervirens) near the main line of the railroad. It stands on the bank of San Francisquito Creek, and the Southern Pacific Co. has built a wall of concrete to protect it from floods.

In Menlo Park, a village of beautiful parks and grounds, reside many well-to-do business and professional men who pass their working days in San Francisco. On the right, near the bay beyond Menlo Park, is a large tannery, and far out in the marsh a station for drying Alaskan codfish.

The town of Redwood was formerly the center of the redwood lumber industry of the Santa Cruz Range, then completely forested. Most of the redwood trees are gone, but a few of them can be seen scattered along the crest of the distant range The trees in view, however, are largely a second growth. On the left, near Redwood, is a factory where magnesite is ground.

Between Redwood and San Carlos there is a good view to the left (west) of an even-crested ridge well clothed with forest. This is Cahill Ridge. Between it and the rounded oak-strewn foothills that lie nearer to the railroad is the narrow, rectilinear valley of the San Andreas rift. Two lakes, San Andreas and Crystal Springs, have been formed in this part of the valley by damming and supply much of the water used in San Francisco.

Just beyond San Carlos, on the left (west), is an iron standpipe forming part of the water supply system of San Francisco, and below it, near the railroad, is one of the pumping stations. Here the oak-crowned hills composed of sandstones and other rocks of the Franciscan group come close to the bay and leave only a narrow belt of alluvium between the foothills and the salt marshes.

Soon after leaving Belmont the train passes through a shallow cut in sandstones and cherts of the Franciscan group. The chert is quarried for use on roads. Half a mile beyond Belmont there is an extensive view to the right across the marshes and bay to the white salt fields of the Union Salt Works, where salt is obtained by solar evaporation of water from the bay. Along this portion of the salt marsh bordering the bay fresh water is obtained from wells of various depths up to 400 feet. This water evidently lies below the salt water. Generally the fresh water can be obtained from these wells only by pumping, but at high tide, when the flats are covered by salt water, which is heavier than fresh, the hydrostatic pressure of the salt water on the deeper fresh water makes some of the wells overflow.

At Leslie there are artificial ponds (vats) in which the water of the bay is evaporated for salt. In the mill close by the salt is refined and prepared for market at the rate of about 8 carloads there so a day. The bay water contains only about half as much salt as an equal volume of ocean water, but are many more bright days in this locality than there are along the coast that it is more profitable to use the weaker brine.

San Mateo (ma-tay'o) is a pretty town noted for its beautiful live oaks and handsome suburban residences. Here the road crosses San Mateo Creek, which, at the point where it issues from the San Andreas rift valley, about 3-1/2 miles southwest of San Mateo, has been dammed by a high concrete structure that holds back the waters of Crystal Springs Lake.

A daily stage plies between San Mateo and Pescadero (pes-ca day'ro, Spanish for fishmonger), near Pebble Beach on the coast, a distance of 33 miles. This stage ascends the valley of San Mateo Creek and crosses Crystal Springs Lake on a dividing dam, made of earth, which was cut and displaced by the movement along the fault at the time of the San Francisco earthquake but was soon repaired. The road to Pescadero passes near the interesting old village of Spanishtown and reaches the coast at Pebble Beach, noted for its agate pebbles. The trip from Pescadero to San Mateo may be conveniently taken in connection with one from San Francisco to Pescadero by the Ocean Shore Railroad.

At Burlingame (pronounced locally bling'um), a place of residence in favor with people of wealth and leisure, there is a country club, with golf links and polo grounds. (See sheet 13, p. 90.) In this vicinity, as elsewhere in California south of San Francisco, there are three trees which figure characteristically in the landscape—the Australian eucalyptus, the Peruvian pepper tree, and the sturdy native oak. The eucalyptus, a tall, slim tree that is rather untidy about its bark, grows rapidly and is much used not only along the roadsides but as windbreaks. The pepper tree, which has pendant plumose foliage, is highly ornamental and is largely used in cities as a street tree and in parks and gardens. But of all the trees that adorn the fertile bottom lands of the great interior valleys the native valley oak (Quercus lobata) is by far the most important.

The large hay ranch on the left (west) near Millbrae belongs to the estate of the late D. O. Mills, a well-known capitalist and philanthropist. On the right in the bay are the oyster beds of the Morgan Oyster Co. The native oyster is small and of coppery flavor, and although esteemed by epicures for oyster cocktails is generally inferior to the eastern oyster. Attempts to establish colonies of eastern oysters on the Pacific coast have been unsuccessful. The young oysters, or spat, however, are brought from the Atlantic seaboard and are matured on the western coast.

Ahead is San Bruno Mountain, beyond which lies San Francisco. On the left are some parallel ridges running northwest. The nearest is Buriburi Ridge (elevation 700 feet), composed of sandstones and shales of the Merced formation (Pliocene), underlain by Franciscan sandstones and igneous rocks, which form the mass of the ridge. Beyond is Sawyer Ridge (1,100 feet), consisting of Franciscan rocks. In the valley between them, 1-3/4 miles southwest of Millbrae, is San Andreas Lake.

At San Bruno the railroad branches. The main line (a cut-off), built only a few years ago and now used for the through traffic, bears to the right along the bay shore around the east end of San Bruno Mountain and through five tunnels reaches the station at Third and Townsend streets in San Francisco. The old line bears to the left up Merced Valley and round the west end of San Bruno Mountain and by a heavier grade and greater distance reaches the same station.

The San Francisco Peninsula, at whose northern extremity is the city of San Francisco, is divided into two parts by the northwestward-trending Merced Valley. Each of these parts is a block of the earth's crust with a fault along its southwest side, upheaved along that side so that it has a gentle slope to the northeast. Both fault blocks have been much carved and worn by erosion so that their original blocklike character has been in great part lost. Both are composed of pre-Tertiary rocks, and the valley between them is filled with the Merced formation (Pliocene), covered for the most part by alluvium. The fault which limits the San Bruno fault block on the southwest is concealed by the alluvium. North of San Bruno Mountain, between it and the Golden Gate, is an irregular group of hills composed of Franciscan rocks and dune sand. On and between these hills is the city of San Francisco.

South San Francisco is a manufacturing town, whose chief industry is the refrigeration and preparation of meats. Here also there are steel, glazing and terra-cotta, brick, paint, pipe, and ice works.

The five tunnels between South San Francisco and San Francisco are from 1,088 to 3,547 feet in length. All are in rocks of the Franciscan group. The first, through Sierra Point, is in sandstone, of which there is a line exposure in an open cut beyond the tunnel. The second, the longest tunnel, penetrates a complex ridge of sandstone, radiolarian chert, and diabase. The large railroad traffic near San Francisco is indicated by the great freight yards in Visitation Valley, between the second and third tunnels. As the train emerges from the third tunnel, which is in sandstone, Hunter Point appears ahead. Beyond Hunter Point, on the left (west), across the salt marsh of Islais (ees-lah'ees) Creek, is the city garbage incinerator. The last two tunnels are in serpentine. Near the new terminal station a sugar refinery and the Union Iron Works, where the famous battleship Oregon and many other warships have been built, are to be seen on the right.

A short description of San Francisco is given on pages 86-87.