CAliFORNIA GEOlOGV slaff

DMG SEISMIC INTENSITY DISTRIBUTION MAPS 2181989 CALIFORNIA MINING REVIEW 219LIQUEFACTION AT SODA LAKE 225CALIFORNIA GEOLOGY WELCOMES NEW EDITOR 232BOOK REVIEWS 233TRANSPORTING MINING EQUIPMENT BY TRUCK 234MINERAL TRIVIA 236MAIL ORDER FORM 239CALIFORNIA GEOLOGY SUBSCRIPTION FORM 240CALL FOR PAPERS _ 240

Cover: Oblique aerial View of the Grelco Incorporated large diatorrute quarrynear lompoc. santa Barbara County. OIaIOOllte is a soh. light colored Siliceoussedtmentary rock used lor a variety of commercial products. Its name IS derivedfrom the diatom SkeIe10ns t1 IS composed 01 The diatomrte bearing zone In thismanne deposil exceeds 1.000 leet in thickness and ranges In age from 28 mil­lion years to 12 rYMIIion years o6d DIalomlle IS used as filters, insulabon maten­also fillers. line abrasive powders. adsorbents. catalysts, and in manulaetunngelploslVes

Diatoms are ooe-celled microscope water plants thai are found throughoutthe WOOd There are n'lOfe than 10.000 speaes 01 diatoms lI'lciuding both sat!water and fresh water vanebes. They play a Vital role in the food chain; WIthoutdiatoms most 01 the fISh ,n the wend would dl8. The ceM walls of diatoms arecomposed 01 SIlica Because Silica does not readily dissolve in waler. millionsof bny Silica skeletons from dead diatoms accumulate al the bottoms of seasand lakes. Over geologIC bme lhlCll. deposits 01 these skeletal remains amassed10 lorm commerCIally Importanl depoStts. Some crude Gil deposits were formedfrom lhe stored Oils of diatoms, Mosl 01 the large commercial depoSitS in Ca6for·rua occur pnmarily Within the central Coasl RaOQEls. An article about mineralm,mng In CalIfornIa starts on page 219. Photo courtesy of Craig Srmth. Grefco I........

Incorporated. I I

In This Issue I

DMG Seismic Intensity Distribution Maps

Don Cup..,Lena Tabibo

Lou.,. Huck4aby..leU Tambert

JAMES F DAVISStir. Gedog<st

GEORGE DEUKMEJIAN

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Al"UIklCATlON Of TtlII!DENRTIIElIfT Of COfQERVATlON0M!IICltt Of _S AND GEOI..OGY

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CAUFQANIA GEOI.OOY (ISSN 002tl4SSSI" publi&/le(Imonthly by t~ o.p••,mtnt or CoM_.tlon. Division 01MonH.1'Id GIOlog~ Th. Recordl Olll<:ell., ,n'·2OthSII"'. Sec:••",.nIO, CA 9$8'4 Second cl... post. 11p.id .1 S.c,.",."to. CA POltm••le, S."d .dd'e..chaOO-11O CALIFORNIA GEOLOGY (USPS 350 8401.80.2980. sacr........l<I, CA 95812-2980

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It has been a year since the magni­tude 7.1 Loma Prieta earthquake. Dueto the overwhelming demand for geo­logic and seismic safely information af­ter the quake. the Division of Mines andGeology (DMG) has for sale black-Hneprints of the seismic intensity distribu·tion maps taken from four DMG earth­quake plannin9 scenarios: (1) SpecialPublication 60 (SP60). Earthquake plan­ning scenario for a magnitude 8.3 earth­quake on the San Andreas fault insouthern California; (2) Special Publica­tion 61 (SP6l), Earthquake planningscenario lor a magnitude 8.3 earth­quake on the San Andreas fault in theSan Francisco Bay area; (3) Special Pub­lication 78 (SP78). Earthquake planningscenario for a magnitude 7.5 earth­quake on the Hayward fault in the SanFrancisco Bay area: and (4) Special Pub­lication 99 (SP99). Earthquake planningscenario for a ma}or earthquake on theNewport-Inglewood fault zone.

The seismic intensity distributionmaps show the expected distributionand intensity of seismic shaking andthe areas with a potential for liquefac­tlon. The maps from SP60 and SP99cover the 9reater Los Angeles area,the maps from SP61 and SP78 coverthe San Francisco Bay area. Pleasespecify the Special Publication num­ber for each seismic intensity distribu­tion map you order. The maps are$ 2.00 each (price includes sales taxand shipping). Payment must accom­pany your order. Make your check ormoney order payable to: Division ofMines and Geology. Address ordersto: Dale Stickney, Division of Minesand Geology. Geologic Informationand Publications. 660 Bercut Drive.Sacramento, CA 95814-0131.Please allow two to three weeks fordelivery. ~

CAlIFORNIA GEOLOGV ocroeEA 1990

1989 California Mining Review

JOHN L BURNETI. GeologIstMineral Resource Analysis Project

Division 01 Mines and Geology

Photo 1. Blasting gold ore at the open pit Mesquite mine. This large mine is located on the westernedge of the ChoCOlate Mountains near Glamis, Imperial County, Photos by author except as noted.

The October Issue of CALIFORNIA GE·OLOGY traditionally includes articles aboutmining actl.... ities In California, At the timethis issue went to press. mineral productiondata in California for 1989 were not yetcompiled. These statistics will be Includedin a luIure Issue. Every Californian is de·pendent upon mineral resources-they arethe building blocks 01 our society. Most ofthe mll'l9ral resources mined in Californiaare consumed here. A lew minerals minedhere, such as rare earths and borate miner­als. are used throughout the world. Morethan hall 01 the oil consumed in Californiais produced here: in 1989, 337 million bar·rels 01 oil were produced in this state whilenearly 706 mdUon barrels were consumedhere. Although Impressive amounts of !helT10fe ·glamorous· miMfals. such as gold.oil, and silver, are produced in CaUforma.SIgnificant amounts 01 industrial mineralssuch as limestone. gypsum, diatomite. zeo­~es. borates. and aggre;ate are also pro­duced K'I thiS state. PortlOOS of this ar!IClewere ooglnalty wntten by the author andpublished in the May. 1990 issue 01 MJningEngmeeflf'lg...editor.

INTRODUCTION

For the first time in many years Cali­fornia slipped to second place in the

production of non-fuel minerals during1989. according 10 U.s. Bureau ofMines preliminary statistics. After beingthe leading slate for several years, Cali­fornia dropped behind Arizona due toan escalation in copper production inthat slale which was spurred by sub­stantial increases in the price of copper.

The value of mineral commoditiesproduced in California increased 5 per­cent 10 $2.8 billion. California contin­ued to lead all other states in the pro­duction of boron minerals. portland ce­ment. gypsum. diatomite. sand andgravel. rare earth concentrates. andtungsten. California was second nation­w;de in the production of gokt (behindNevada). cakium chloride. feldspar.magnesium comlXlUf'lds from brine. andsodium compounds.

GOLD AND SILVER

Gold production in California con­tinued to increase and reached890.575 troy ounces in 1989. com­pared with 729.272 troy ounces in1988. Silver production moved upwardfrom 16.5 tons to 19.8 Ions. The twolargest producers of gold and silver. theMesquite mine in Imperial County andthe Mclaughlin mine in Napa County.led this increase (Photo 1). Mostsmaller gold and silver operationsshowed similar gains.

Open pit mining operations began atthe Royal/Mountain King mine nearCopperopolis. Calaveras County. Pro­duction at this mine is anticipated toreach 60.000 troy ounces of gokl peryear in the near future (Photos 2-5).TIle JamestO\All1 mine in TuolumneCounty increased production to morethan 100.000 troy ounces of gold in1989 (Photos 6-8).

CAliFORNIA GEOlOOY OCTOBeR 1990 ".

!-,-Io

Figure 1. Mine location map.

MINE LOCALITIES ~

1 Grey Eagle mIne2, $Iskon mmeJ, Hayden H'II mine4 McLal.l9hhn mine5 B'll Canyon, Vandalia mone6, Pacific Pearl mille7, RoyaVMounlam l<Jng minea. Jamestown mine9 LOI\{l Valley mine10.Crater m,ne11 United Ready MIJ quarry12. Fori Cady I11IIle13. Caslle Mountains mine14 Masqulle mine15,Padre/Madre mille16, locllao Rose ntln9

The company disclosed that the IndianRose ore deposit and the nearby Ocoti­llo gold zone are located between thePicacho mine and the Mesquite goldmine (Figure 1). A minable rese1V€ of5.1 million tons of ore averaging 0.023troy ounces of gold per ton has beenidentified in the Indian Rose deposit.Similar reserves are indicated in theOcotillo zone.

Hart District

Gold and silver exploration continuedin 1989 and many prospects ap­proached the point of beginning pro­duction. One notable prospect nearingcommencement of mining operations isthe Castle Mountain gold deposit (Fig­ure 1). The Castle Mountain deposit islocated in the historic Hart Mining Dis­trict about 20 miles southeast of Moun­tain Pass. California. This deposit iscomposed of 2.000 claims covering 65square miles of eastern San BernardinoCounty. Exploration drilling on six orebodies within this deposit indicates thainearly 26 million tons of 0.055 troyounces of gold per ton of minable oreexists. and that 13.5 million tons 01 orewith 0.046 ounces of gold per tonexists (Linder. 1989).

Production continued al the Padre/Madre mine in the Cargo MuchachoMountains of Imperial County and min­ing began at the adjacent Canyon Goldproject (Rgure 1), The combined un­derground and open pit operations fromthese two concerns is expected to proc­ess 8 million Ions of gold ore over a 10­year period with an annual productionof 60,000 troy ounces of gold. Thefirst gold from the nearby American GirlCanyon open pit mine was poured inSeptember 1989; the owner companyalso acquired the Oro Cruz propertyabout a mile from the American GirlCanyon pit.

New Gold Discovery

A new discovery was announced byGlamis Gold which operates the largePicacho gold mine in Imperial County.

,

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: ........... •

Photo 2. Distant view of mining operations at the Royal Mountain King gold mine.

220 CALIFORNIA GEOLOGY OCTOBER 1990

Photo 3. Front end loader IiIling a large dump truck with gold ore altha openpit Royal Mountain King mine near Copperopolis, Calaveras County.

The Hayden Hill deposit is a shallowepithermal ore body resulting from lateMiocene hot spring activity that occurredduring prolonged fault formation andcontemporaneous explosive volcanism.

The combined reserves of 2 millionounces of gokl in the ground will makethis deposit the third largest gold minein the state when full production isachieved. The deposit lies Vtlilhin agroup of rhyolite domes and plugs whichare cut by hydrothermal breccia lones.Preliminary results indicate that the min­eralization occurred 15 million years agoin mid·Miocene lime (Under, 1989).

Hayden Hill District

..- -----

----

_ -;00 -- ..~.-

Formation of the ore deposit was pre­ceded by the formation 01 a barren silicacap in middle Miocene volcanic rocks.Episodic fracturing of this cap providedspace for gold and silver to be depositedIn three different configurations; (1)quartz and potassium feldspar (adularia)veins, (2) stockworks or three-dimen­slonal ore deposits formed by networksof veinlets, and (3) breccia zones com­posed of angular broken rock fragmentsheld together by silica cement.

Long Valley

The Long Valley gold prospect nearMammoth Lakes in Mono County isbeing explored by a drilling and sam­pling program by Royal Gold, Incorpo­rated in a joint venture with StandardIndustrial Minerals, Incorporated (FtgureI). This prospect is located 2·1/2 milesnorth 01 the Mammoth Lakes Airportand 2 miles southeast of a kaolin pit thathas been operated by Standard IndustrialMinerals for many years. 1lle prospectIs an epithermal hot spring deposit withdisseminated free gold on the fracturesIn friable quartz veins and stringers.Proven ore reserves are placed at 1.8million tons containing an estimated50,000 troy ounces of recoverable gold.

The Hayden Hill District in LassenCounty has been drilled by Amax GoldIncorporated (Figure 1. Photo 9). Thisdistrict was first mined in the 18705 andIhe long·abandoned mine dumps werereworked by heap leach methods withinthe last len years. The present miningplan encompasses 6,000 acres and in­cludes virtually the entire Hayden HillMining District. Current reserves are es­timated to be 45.3 million tons of oreaveraging 0.032 ounces of gold per tonand 0.2 ounces 01 silver per ton. An­nual production is expected to be145,000 ounces of gold and 445,000ounces of silver. Amax Gold Inc. is cur­rently conducting environmental studieslor the necessary regulatory permittingprocess. Initial mine construction is ten­tatively expected to begin In 1991,

Photo 4. Close-up view of a drill rig at the Aoyal Mountain King mine.This rig is used to drill holes fOf placing explosive charges.

CAliFORNIA GEOLOGY OCTOBER 1990 '"

Photo 5. Milling plant al the Royal Mountain King mine where the gold ore is processed.

COPPER

The sustained high price of copperdUring the last few years has resulted inrefocusing the attention of mining com­panies on copper mines that may notcontain gold and silver values. Inactivemines in northwestern California andthe Foothills Copper Belt in the SierraNevada are being examined. Drilling,chemical sampling, and geochemicalwork are being performed on somecopper mineralized areas. Miningagreements and the necessary environ­mental negotiations are being consid­ered on others. Some of these coppermines can be expected to resume op­erations. For example, the WesternWorld Mining Company plans to de­velop a copper-zinc property about amile south of Smartville. Yuba County.

Smartville

Photo 6. Open pit of the Jamestown mine, Tuolumne County.The mineralized ore vein in the center 01 the hill dips steeply to the right.

Siskon Mine

American Gold Mineral Corporationis developing the gold reserves at theSiskon mine in western SiskiyouCounty. Recent sampling and drillinghas extended the strike and depth ofore zones. Before 1958 this depositproduced over 100,000 ounces of gold,over 1 million ounces of silver, as wellas base metals such as copper and lead.The are averaged 0.17 ounces of goldand 0.4 ounces of silver per ton.

Grey Eagle Mine

The Grey Eagle mine in SiskiyouCounty, which last operated from 1980to 1983, is being explored by Centu­rion Gold Ltd. (Figure 1). Closure ofthe mine in 1983 was caused by opera­tional problems centering aroundchemicals that leaked from the site.Significant ore reseJVes remain.

Big Canyon and Vandalia Mines

The Big Canyon and Vandalia minesin EI Dorado County were purchased byMother Lode Gold Mines Consolidated(Figure 1). These mines were exploredby Consolidated Goldfields in the early1980s and nearly $4 million was spent

to develop them. This area was the sub­ject of a recent U.S. Geological Surveyresearch effort that indicates substantiallow-grade gold ore may exist.

The Western World Company cop­per-zinc deposit occurs in an area thathas been mined for copper since 1849.This deposit occurs near the north endof a northwest-trending belt of meta­morphic rocks exposed along the west­ern margin of the Sierra Nevada. Rockformations in the metamorphic belt arecomposed of thick accumulations of

222 CALIFORNIA GEOLOGY OCToeER 1990

Photo 7. Distant view of the wof1ling face. Jamestown gold mine.

ways and concrete prOOucts. 1ne largestaggregate pit in the nation is the UnitedReady Mixed Concrete plant at Irwindalenear los Angeles (Figure 1). This singleplant produces 4.5 million Ions of sandand gravel per year. Nine of the tenlargest aggregate pits in 1988 were inthe Los Angeles basin, AlamedaCounty. and Sacramenlo County of Cali·fornia (Michard. 1989). Not only doesCalifornia prcxluce more sand and gravelaggregate than any other state. it is alsothe largest consumer of aggregate.

SULFUR

The Crater mine in the Last ChanceRange of [nyo County is being exploredby the American Sulfur Prcxlucts Com­pany 10 develop sulfur and gypsum de­posits (Figure 1). The mine was first de­veloped in 1917 and operated intermit­tently until 1943.

Photo 8 Jamestown mine milling operation. II is Ihe largest gold flolation mitlin the United Slates.

Paleozoic and/or Mesozoic marine sedi­mentary and voIcank: rocks that havebeen deformed, intruded by plutonicrocks. and metamorphosed. Rock tex­lures throughout the metamorphic belt.such as bedding planes and foliation.normally trend northwest and dipsteeply 10 the east. The Westem WorldMining Company's copper-zinc depositoccurs within a sequence of mafic vol­canic rocks, sheeted mafic dikes. andlesser amounts of ultramafic rocks thatare probably Jurassic age (140 to 195million years old). Mafic rocks are com­monly dark colored and contain signifi·cant amounts of iron and magnesium.Ultramafic rocks are composed chieflyof iron and magnesium minerals.

1ne copper-zinc deposit occurs asabundant sulfide minerals. A voIcank:extrusive lava complex overlies it. 1nedeposit consists of two closely relatedlenses that have been separated by afault. The southern-most lens consistsof aOOut 900,000 tons 01 ore and thenonhem lens consists of about600.000 tons of ore. Exploratory drill­ing indicates that the ore from bothlenses averages about 2.81 percentcopper and about 0.95 percent zinc[raylor. 1990).

CONSTRUCTION AGGREGATE

California led the nalion in the pro­duction of sand and gravel. Sand andgravel is used extenstvely by the con­struction industry for aggregate in high-

1ne ore bo:ty is a fault controUed 001spring deposit with tabular beds of sulfurinterlaced with gypsum, rhyolite (a silicarich volcanic rock). and limestone. Thefirst ob;ectiw of the developer is to pr0­

duce agricultural sulfur and gypsum. A~on&ryru~moo~isw~~~

for epithermal disseminated gold.

CALIFORNIA GEOLOGY OCTOBER 1990

Photo 9. Oblique aerial view of the Hayden Hill Mining District, lassen County. Oldmine roads and abandoned shafts are common. Modern ore milling facilities are at themiddle foreground. Photo taken in July 1989. Courtesy of Amax Gold, Incorporated.

The most important market for bothsulfur and gypsum (hydrous calcium sul­fatel is in neutralizing the alkalinity indesert soils_ When sulfur or gypsum isspread on soils, a sulfate molecule(504 ) is created in the soil by irrigationand oxidation. The sulfate dissolves thecalcium, sodium, and potassium depos­its and increases the availabllity of phos­phate and other nutrients to plants.The utilization of sulfur and its com­pounds enables thousands of squaremiles of othelWise barren lands on thewest side of the San Joaquin Valley tobe used for valuable crops such as let­tuce, broccoli, and parsley.

SEA SHELLS

Oyster shell deposits on the floor ofthe San Francisco Bay continue to becollected by suction dredging methods.The largest deposits of native oysters (aspecies named OSfreo lurida Carpen­ter) occur offshore of Hayward and SanLeandro, Alameda County in the southSan Francisco Bay (Figure 1). Theyoungest shells collected are severalthousand years old and are buried inone to five feet of bay mud. The oys­ters originally grew over the entire floorof the bay but prevailing winds towardthe east transported the bottom sedi~

ments toward the eastern shore throughwave action,

The shells are gathered by a selfpropelled. wooden hulled barge withtwo trailing eight-inch suction pipes,The shells are washed and screened toremove mud and loaded onto a sepa"rate hopper barge.

The products. sold as Pacific PearlBrand Oyster Shell, include ground shellfor poultry and livestock feed, agricul­tural lime to neutralize acidic soils, andbam lime 10 neutralize livestock waste.This shell dredging operation is uniquebecause it is the only one on the PacificRim that supplies markets throughoutthis large region. Crushed shells areused as decorative stone and oystershell lablets are widely used as a foodsupplement by humans.

BORATE

An in situ solution mining operationis being planned by Fori Cady MineralsCorporation for a borate deposit southof the Cady Mountains, San BernardinoCounty (Figure 1). An estimated 147million tons of borate ore averaging 6.4percent boron oxide (B20 3l have beenlocated 1.350 feet below the desertfloor. A dilute hydrochloric acid solu­tion will be injected from the surfaceand, after reaction with the borate ore.the dissolved ore will be returned to thesurface as a boric acid solution. Crystal­line boric acid (H3BO) will then be pro­duced by evaporation in ponds. Thedeposit averages 118 feet in thicknessand extends over 384 acres.

REFERENCES

Linder, H" 1989, Hart Mining District, SanBernardino County, California: CALI·FORNIA GEOLOGY, v. 42, no. 6,p. 134-140.

Michard, Don, 1989, Top ten sand andgravel plants: Rock Products, May,p. 44-46.

Taylor, Gary C., 1990, Mineral land c1assifi·cation of the Western World MiningCompany copper·zinc deposit nearSmartville, Yuba County. California:Division of Mines and Geology Open­File Report90-1,12p. ~

'" CALIFORNIA GEOlOGY OCTOBER 1990

Liquefaction at Soda Lake:Effects of the Chittenden earthquake swarm of April 18, 1990

Santa Cruz County, California

By

C.J. WILLS and MW. MANSON, GeologistsDivision 01 Mines and Geology

INTRODUCTION

On the morning of Wednesday.April 18. 1990. the anniversary of

the great 1906 San Francisco earth­quake. a series of aftershocks of the Oc­tober 17. 1989 Lorna Prieta earthquakeoccurred near Chittenden ,md were feltthroughout the San Francisco Bay area.The largest of these earthquakes was amagnitude 5.4 event thai occurred at6:53 a.m. Pacific Daylight Time.

...Photo 1. View northeast over Soda Lake shoWing many sand bollstormed by Chinanden earthquakes of Apri118, 1990. Photos by theauthors except as noted.

.. Photo 2. Sand bolls from the Lorna Prieta earthquake 01 OCtober17,1989 and the Chlnar'lden earthquakes of Apnl 18, 1990 along aImear fissure near the edge of Soda Lake (view is 'rom center ofPhoto I toward top lell).

Landslides triggered by these earthquakes. which we infor­mally call the MChiltenden~ earthquakes. were reponed by thenews media on Highway 152 (Hecker Pass Road) and High­way 129 in the southern Santa Cruz Mountains (Hgure 1),Because earth scientists anticipated that significant after­shocks of the Lorna Prieta eanhquake could cause surfacerupture on the San Andreas fault. panicularly if the after~

shocks were shallow. and because of the reported landslides.we made a brief field reconnaissance to assess the amount oflandslide damage and search for surface fault rupture. AtSoda Lake. nonh of Chittenden. the Chinenden eanilquakescaused liquefaction of deposits that had also liquefied duringthe Lorna Prieta eanhquake (Photos I and 2).

CALIFORNIA GEOLOGY OCT08ER 1990 225

".

20

CHITTENDEN

Eplcenler 01April 18. 1990

Earlhquake

fl,l. */:~~NVIUE 0 Soda

Lake

SAH JOSE

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system and is the boundary bet\l.leen theNorth American plate and the Pacificplate. Crustal mowmenl along the SanAndreas fault in the Santa Cruz Moun­tains has a long-term average of about0.52 inches (13 mm) per year (Minsterand Jordan, 1987; Perkins and others,1989).

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GEOLOGY AND LANDSLIDES

The Chinenden earthquakes oc­curred along the San Andreas fault atthe southeast end of the Santa CruzMountains in the central Coast Rangesgeomorphic province (Flgures I and 2).The San Andreas fault is the majorcomponent of the San Andreas fault

..

CAl.IFORNIA

AF.gure 1. Map of the San Franasco BaylIfea showtng faults thai make up the SanAndreas lauh system and epcenters 01 thelorna PrIeta and Chittenden earthquakesModified from Wagner, 1990

'" CAliFORNIA GEOlOGY OCTOBER 1990

'-,-.:'

--'- ,-Figure 2. Active faults of the Watsonville-Chittenden area (adapted from Sryanl andotl'lers, 1981). Epicenter 01 M 5.4 earthquake, largest of the Chittenden earthquakes(from Undh and Lester, 1990). t.. landslide or rockfalilriggered by Chittendenearthquakes of April 18, 1990.

both, and locally have been cut off anddisplaced by fault movement (Allen,1946; Dibblee and Brabb, 1978; Wag­ner, 1990).

Landslides triggered by the Chitten­den earthquake swarm were minor, Ashallow slump of poorly consolidatedsand buried one lane of Highway 129east of River Oaks in San BenitoCounty. This slump and several verysmall debris avalanches occurred in theTertiary Etchegoin(?) Formation (Agure3). The debris consisted of light-brownsandy soil. bedrock blocks or fragments.brush and trees. Similar shallow slumpsoccurred along the banks of the PajaroRiver in the same area. lhere werealso minor rockfalls onto Highway 129at Chittenden and in Chinenden Pass.and onto Highway 152 west of HeckerPass. All of these minor slides on theroads, with the exception of the largestone on Highway 129. were cleaned upby California Department of Transpor­tation crews by noon on the day of theearthquakes.

Bedrock units in the S<x:Ia Lake areaare quite different on either side of thefault (FIgure 3). Northeast of the faultthe units are dominantly line-grainedmarine sedimentary rocks of Tertiaryage. Southwest of the fault, bedrockconsists of Mesozoic hornblende quartz­diorite overlain by Quaternary and Ter­tiary eolian sand, and both marine andnon-ma.t\ne. sand and gravel. Theseunits have been fractw"ed or folded or

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LEGEND

alluvium

landslide debrisolder alluviumAromas sandPaso Robles Formation

Elchegoln Formation

Purisima Formationshale of Mt. Pajaro area

hornblende quartz.gabbro

geologic contact

active faultdike around margin

01 Soda lake

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Figure 3. Geologic map 01 the Soda Lake area ((rom Dibblee and Brabb, 1978)with traces 01 active raults (by Bryant and others. 1981).

CAlIFOFlNIA GEOlOGY OCT08ER 1990

•

..

exceeded a threshold value (Holzer andothers, 1989), The Imperial Countysite did not undergo liquefaction duringearlier earthquakes with measured peakaccelerations of less than 18 percent ofthe force of gravity {gravitational accel­eration is 32 feet per second per sec·ond}, but did so when the triggeringearthquake had a peak acceleration of21 percent gravity. The unexpecteddelay in recorded onset of liquefaction(until after the strong motion ended)was attributed by the researchers to re­distribution of pore pressures through­out the deposit.

Liquefaction occurred in many placesat the time of the Loma Prieta earth,quake. It was extensive along MontereyBay, Soda Lake. and the Pajaro Riverand caused severe damage to the MossLanding Marine Laboratory of the Cali­fornia State Universities and Colleges.Farther away from the epicentral area.the Marina District of San Francisco.Treasure Island, the eastern approachto the San Francisco-Oakland BayBridge, and the Port of Oakland wereheavily damaged, partly as a result ofliquefaction (Earthquake EngineeringResearch Institute. 1989; Plafker andGalloway, 1989).

Simultaneous measurements of seis­mically induced pore pressure changesand ground accelerations at a site in Im­perial County thai was undergoingliquefaction during an earthquake indi­cated that total pore pressures ap­proached the weight of overlying sedi­ments after most of the strong motionceased, and excess pore pressures weregenerated once horizontal acceleration

..•

Photo 3. "Flowing" sand boil. At about noon on April 18, 1990 several sand boils were stillactive. When this photo was taken. water was still issuing 'rom the central crater o! thissand boil and t10wing evenly over all sides 01 the volcano-shaped mound (note ripples onthe sides of the sand boil).

quakes or volcanic eruptions) or artifi­cial (vibrations from heavy equipment orblasting). Vibration of a saturated, po­rous sand or silt causes pore water tomigrate toward the direction of leastconfinement. If pore water cannot es­cape. pore pressures can approach thelithostatic pressure (the weight of theoverlying sediment). When liquefactionoccurs. the saturaled sediment nolonger acts as a solid but becomes a liq­uid with suspended mineral grains.Such material loses its internal resis­tance to defomlation by shearing (or~shear strength'") and can no longersupport a load. The excess pore pres­sure may be relieved by rapid ejectionof water and sediment in suspension tothe ground surface to form sand boils(also knov.m as sand blows or sand vol­canoes). or by lateral spreading or hy­draulic fracturing.

The stresses that produce liquefactionmay be natural (shaking from earth-

FAULT RUPTURE SEARCH

LIQUEFACTIONAND RELATED EVENTS

Uquefaction is defined by Youd(1973) as the transformation of a granu­lar material from a solid state into aliquefied state as a consequence of in­creased pore pressure (pressure exertedby groundwater within the voids amongmineral grains in soil, alluvium, and bed­rock). It is a relatively common earth­quake-related phenomenon in Holocenesediments (Youel and Hoose. 1977). Itcan be induced by rapid application ofstresses that result in increased porepressure by pore water migration.

The San Andreas fault cuts throughthe southern Santa Cruz Mountains,where it has formed a series of right­laterally offset drainages, side-hillbenches. and scarps. Following the Chit~

tenden earthquakes, we checked asmuch of the fault in the quake epicentralarea as possible for surface rupture.State Highways 129 and 152, MountMadonna Road. and Green Valley Roadall cross the San Andreas fault east ofWatsonville. All of these roads weredamaged in the Loma Prieta earthquakeby slumping of road fill and pavementcracking that was commonly perpendicu­lar to the roadway. The cracks onMount Madonna Road in October 1989suggested right-lateral faulting, althoughthey may have been due to down-slopemovement of the road fill (Hart and oth­ers, 1990). The Chittenden earthquakescaused some longitudinal cracks in thepavement of Highway 152 to re-openslightly but no new cracks were obselV€dalong the trend of the fault at any of theroad crossings.

Following the reconnaissance of thepaved roads, a section of the San An­dreas fault that crosses pasture land eastof Watsonville was examined. This seg­ment of the fault is well defined by a se­ries of tectonically produced geomorphicfeatures such as fault scarps. offset drain­ages, and sidehill benches, There weresome minor shaking cracks in a dirt roadwithin the fault zone, but no cracks thaiindicated right lateral faulting.

"8 CALIFORNIA GEOLOGY OCToeER 1990

Photo 4. Sand boil lormed by the Lorna Prieta earthquake(cenlral lissure in foreground) with two sand boils that wereerupted on April 18, 1990, possibly from the same tissure.

SODA LAKE

The Loma Prieta earthquake caused sand boils 10 eruptfrom the dry bed of Soda Lake. The volcano-shaped (conical)sand deposits were as large as 10 feet in diameter by 1 foothigh. Water continued to flow from several sand boils for fourdays after the main shock. The sand boils tended to be clus­tered along fissures. some of which paralleled the edge of thelakebed. Violent shaking from the Loma Prieta earthquakealso caused the entire lakebed to subside: fissures and scarpsalong the edge of the lake indicated that the lakebed sank asmuch as four feet during the earthquake (Manson and others.in progress). The loose sandy sediment consolidated, becom­ing both denser and more compact. This permanent consoli­dation of the sandy material reduced the amount of porespace and should have made the deposit less prone to futureliquefaction.

There are no reports of liquefaction in Soda Lake causedby the April 18, 1906 San Francisco earthquake. althoughsevere ground shaking in the surrounding area was docu-

mented (Lawson and others, 1908; Youd and Hoose, 1978).At Chittenden, several buildings were shifted off of their foun­dations and the Southern Pacific Railroad bridge over the Pa­jaro River was shifted three feet away from one of its abut­ments. A large landslide was triggered at the mouth of a can­yon just west of the Jake, and there was severe liquefactionand fissuring in the Pajaro River and the Salinas River. SodaLake was probably full of water during the 1906 earthquake,which followed a winter of above normal rainfall (Lawson andothers, 1908. p. 399).

Extensive liquefaction occurred at Soda Lake as a result ofthe Chittenden earthquakes (maximum magnitude 5.4).Much of the 66'acre lakebed was covered by fissures andsand boils (Photos 1-4). The lakebed area affected by thisepisode of liquefaction was as extensive as that resulting fromthe Lorna Prieta earthquake (magnitude 7.1). There havebeen no reports of renewed liquefaction from other localitieswhere it occurred in October 1989. Apparently. the rela­tively small earthquakes of April 1990 were strong enough tocause liquefaction only in the immediate epicentral area andthe deposits in Soda Lake may be especially susceptible toliquefaction.

Soda Lake was originally a natural lake in an abandonedmeander bend of the Pajaro River (Jenkins, 1973). The surfi­cial deposits and the material that formed the sand boils(Photo 5) appear to be tailings from the Granite Rock Com­pany's Wilson quarry 0.6 mile west of the lake (for a descrip­tion of this quarry see Higgins, 1989). The material beingquarried by Granite Rock Company is hornblende quartz-dio­rite (Dibblee and Brabb. 1978). Capacity of the natural lakewas increased by the construction of dikes along part of itsshoreline and the lake was used as a tailings pond for veryfine-grained quarry tailings from 1968 to the mid-1980s(Bruce Woolpert, Jr., Granite Rock Company. personal com·munication, 1990).

Grain-size analysis of the material erupted from the sandboils shows that the material that liquefied is a well-sortedsandy silt. with an average of 87 percent passing through a200-mesh screen. Screen mesh numbers indicate the num'bers of wires per inch for woven wire screens, particles pass­ing through a 200-mesh screen are less than 0.074 mm indiameter (Table 1, Photo 6). An average of about 10 percentfine sand was also erupted from the sand boils, along with avery small percentage of clay.

If the effects of liquefaction can produce denser deposits,why has Soda Lake undergone repealed (at least two) epi­sodes 01 liquefaction? There are numerous reported instancesof repeated liquefaction at many sites and in the laboratory(Borchardt and Kennedy, 1979, p. 217). It is not unusual fora sand sample to have a cyclic reaction to applied strain: thesample liquefies then solidifies in less than one second. Aslong as pore water drainage is blocked, the sample (or naturaldeposit) can liquefy again and again (Youd, 1973, p. 3).

The sediments at Soda Lake are probably susceptible toliquefaction for the following five reasons:

CALlFOONIA GEOLOGY OCTOBER 1990 '29

I

Photo 5. Cross section of a sand boil formed at Soda lake by the Lorna Prietaearthquake. Nole "feeder dike" 01 line sand below vent and line layering withinthe sand boil. Photo by W.A. Bryant.

flows caused by liquefaction have oc­curred in areas with intensities of M-MV to M-M Xl, with the greatest propor­tion (9 of 22 events, or 41 percent)lying within M-M VII zones (Keefer.1984). The lower peak accelerationand shorter duration of strong shakingassociated with a M 5.4 earthquake,compared to a M 7.1 earthquake, pre­sumably is much less likely to causeliquefaction.

Keefer (1984) constructed a chartbased on data from several hundredearthquakes showing the distance ofliquefaction effects from the source faultrupture lones. From Keefer's chart, amagnitude 5.4 earthquake should causeliquefaction no farther than 3.7 milesfrom its hypocenter. Soda Lake isabout 3.7 miles from the hypocenter ofthe largest Chittenden earthquakes(hypocenter data from Lindh andLester. 1990).

Grain size (mm)

Figure 4. Grain size distribution of the average of three samples taken from Sodalake sal'ld boils ploned on chart sllowing "most liquefiable" al'ld "potentiallyliquefiable" soil. By Tsuchida, 7970, as reprinted in Hausner and others, 7985.

101.0

(5) Shaking from the Loma Prieta earth­quake may have caused uneven consoli­dation of the sediments, compactingportions of the deposit but not affectingothers. A model for repeated liquefac­tion of a deposit due to partial compac­tion has been proposed (Finn and oth­ers, 1970) and is summarized as: ~Aseries of small previous shakings eithertoo weak to cause liquefaction or justbarely strong enough to cause [initialliquefaction!. allows the soil to densify

Sand

0.10.01

0

~/A rage of ~7/ 1//0sa d bollsI,

m SOda!yBoundaries

7 /for mostliquefiable soil

0

II I /0I

Boundaries

II /for potentielly

/liquefiable soil0

// / / V0

10Silt

may be just below the surface of thelakebed. Any addition of rainwater andthe water expelled by liquefaction seepsback into the deposit.

(4) Soda Lake lies within the ModifiedMercalli (M-M) VII intensity zone for theLoma Prieta earthquake (plafker andGalloway, 1989). Lateral spreading or

E•o:f 2

(I) The deposits have a uniform grainsize and almost total lack of cohesivedays that would tend to bind the par­tides together. The grain-size analysis(F19ure 4) shows that these sedimentsplot within the range of ~potentially

liquefiable soil" though not within the~most liquefiable soil" range.

(2) They were emplaced as a ~hydraulic

fill" that was deposited in and settledout of a still body of water. Prior to theLorna Prieta earthquake this fill had notbeen compacted. In this way, the fill atSoda Lake is similar 10 the fill thaI un­derlies much of the San FranciscoMarina District. The hydraulic fill under­lying the Marina Disrtict also under­went extensive liquefaction during theLoma Prieta earthquake, which contrib­uted to the wide-spread damage tobuildings. The Marina District fill iscoarser than the material at Soda Lakebut similar in its uniform grain size andlack of cohesive days (Bonilla, 1990).

(3) The Soda Lake deposits are proba­bly saturated, even when the lake ap­pears dry, because it is a natural basin.The level of the water table (depth togroundwater beneath the land surface)

230 CALIFORNIA GEOLOGY OCTOBER 1990

uniformly and increases subsequentresistance to liquefaction. However, avery strong shaking may cause unevendensification, leaving a topmost looserlayer with increased susceptibility toliquefaction~ (Hausner and others,1985, p. 58).

CONCLUSIONS

The earthquakes of April 18, 1990occurred on the anniversary of the1906 quake and six months after theLama Prieta event. They were a dis­tinct reminder to the people of the SanFrancisco Bay area of the earthquakehazards associated with the San An­dreas fault system. No surface ruptureand relatively little landsliding occurredduring the April 18 event, but theearthquakes did cause liquefaction of asandy silt deposit in Soda Lake that hadalso liquefied as a result of the LomaPrieta event in October. 1989.

The liquefaction of this deposit froma relatively small earthquake with a rela­tively short period of strong shakingshows that the hydraulically emplaceddeposits of Soda Lake are especiallysusceptible to liquefaction. even afterlhey were made more dense by lique­faction during the October 17. 1989earthquake. This repeated liquefactionof a hydraulic fill at Soda Lake suggeststhat repeated liquefaction of similar hy­draulic fills around the margins of SanFrancisco Bay is also possible. Futureearthquakes in the San Francisco Bayarea could cause repeated liquefactionof the deposits that the Loma Prietaearthquake showed to be susceptible toliquefaction. such as those underlyingthe Marina District and along the east­ern margin of San Francisco Bay.

ACKNOWLEDGMENTS

TABLE 1. GRAIN SIZE ANALYSIS OF THREE SAMPLES FROM SODA LAKESAND BOilS. Adapted from F.H. Chin and J D Rogers written communication, 1990

Screen % Retained on screen (Cumulative % passing"size'

sand Boil 1 Sand Boil 2 Sand Boil 3 Average

No. 10

No. 20 0.04199.95 0.02199.98 0.03199.97 0.03199.97

No. 40 0.02/99.93 0.12/99.86 0.40/99.57 0.18/99.78

No. 60 0.04199.89 0.83/99.03 0.92/98.65 0.60199.19

No. 140 3.19/96.70 8.59/90.44 5.05/93.60 5.61193.58

No. 200 5.09/91.61 7.64/82.80 5.24/88.36 5.99/87.59

PO' 91.61 82.80 88.36 87.59

• Screen size indicates the number 01 wires per inch for woven wire mesh.•• Totals may not equal 100% due to rounding.

Photo 6. Electron micrograph of sit! grains that erupted from a sand volcano atSoda Lake. Bar scale is in microns. Photo taken al the U.c. Davis Facility forAdvanced Instrumentalion.

REFERENCESWe wish to thank Mark Molinari, ofDames and Moore, Jne., who broughtthe liquefaction at Soda Lake to our at­tention following the Lorna Prieta earth­quake. We also wish to thank J. DavidRogers of Rogers-Pacific Inc., PleasantHill. California for test data and reviewof this article. Analyses were per­formed by F.H. Chin of Rogers-PacificCompany on samples collected by per­sonnel of the Division of Mines and Ge­ology and Rogers-Pacific Inc.

Alten. J.E., 1946, Geology 01 the San JuanBaullsta quadrangle, California: CaliforniaDivision Of Mines Bulletin 133, p. 75, 2plates, scale 1:62,500.

Borchardt. G.A. and Kennedy, M.P., 1979,Liquefaction potential in urban San Diego:A pilot study: CALIFORNIA GEOLOGY, v.32, no. 10. p. 217-221.

Bonilla, M.G" 1990, Natural and artificial de­posits in the Marina District, in U.S. Geo­logical SUNey. Effects 01 the Lorna Prietaearthquake on the Marina District, San

Francisco. California: U.S. GeologicalSUNey Open File 90-253.

Oibblee. T.W., Jr., arn::l Brabl>, E.E., 1978,Preliminary geologic maps of the Chit­tenden, Los Gatos. and Watsonville eastquadrangles. California: U.S. GeologicalSUNey Open File Report 78-453, 3sheets, scale 1:24,000.

Earthquake Engineering Research Institute.1989. Lorna Prieta earthquake--Octooor17, 1989: Preliminary reconnaissancereport: EI Cerrito, California. 51 p.

CALIFORNIA GEOlOGY OCT06ER 1990 '"

Finn, W.D.L., Bransby, P.l., and Pickering,D.J.. 1970. Effects 01 strain history onliquefaction or sands: Journal of the SoilMechanics and Foundations Division,American Society of Civil Engineers, 96(SM6). p. 1917-1934.

Hart, EW.• Bryant, W.A., Wills, C.J., andTreiman. J.A.. 1990. The search for sur­face faulting and signilicance of ridgetopfissures, in S. McNutt and R.H. Sydnor,editors. The Loma Prieta earthquake ofOCtober 17, 1989: California Department01 Conservation, Division 01 Mines andGeology Special Publication 104, inpress.

Higgins, C.T., 1989, Anhur R. Wilsonquarry-where nature gives man abreak: CALIFORNIA GEOLOGY, v. 42,no. 11, p. 256·259.

Holzer, T.l., Youd, T.l.. and Hanks, T.C.•1989. Dynamics of liquefaction duringthe 1987 Superstition Hills earthquake,California. SCience. v. 244, p. 56-59.

Housner. G.W. and the Committee onEarthquake Engineering. National Re­search Council. 1985. Liquefaction ofsoils during earthquakes: National Acad·emy Press. Washington, D.C., 240 p.

Jenkins. O.P.• 1973. Pleistocene Lake SanBenito: CALIFORNIA GEOLOGY. v. 26.no. 7, p. 15"'63.

Keeler, O.K., 1984. Landslides caused byearthquakes: Geological Society 01America Bulletin, v. 95. p. 406-421.

Lawson, A. C., and others, 1908, The Cali·lornia earthquake 01 April 18, 1906: Re·port of the State Earthquake Investiga­tion Commission: Carnegie Institute 01Washington Publication 87, 2 volumes,452 p.

Lindh. A. and Lester. R., 1990. Weeklyearthquake report for the San FranciscoBay area, 16--23 April, 1990: U.S. Geo­logical Survey, 5 p.

Manson. M.W., Keeter, O.K., andMcKittrick. M.A.. compilers. Landslidesand other geologic features in the SantaCruz Mountains, California, resultingfrom the Loma Priela earthquake ofOCtober 17. 1989: Calilornia Departmentof Conservation, Division ot Mines andGeology Preliminary Report 29, inprogress.

Minster, J.B., and Jordan. T.H.. 1987. Vee·lor constraints on western U.S. deforma­tion from space geodesy. neotectonics,and plate motions: Journal of Geophysi­cal Research, v. 92, no. B6. p. 4798­4804.

Perkins, J.A., Sims, J.D., and Sturgess,5.5.,1989, Late Holocene movementalong the San Andreas fault at MelendyRanch: Implications for the distribution01 fault slip in central California: Journal

of Geophysical Research, v. 94, no. 68.p. 10,217-10,230.

Plafker, G. and Galloway, J.p.. editors,1989. Lessons learned from the LomaPrieta. California. earthquake of October17,1989: U.S. Geological Survey Circu­lar 1045. 48 p.

Tsuchida. H.. 1970, Predicfion and counler­measure against the liquetaction in sanddeposits: Abstract of the Seminar in thePort and Harbor Research Institute. p.3.1'3.33 (in Japanese).

Wagner, D.l., 1990. Geologic and tectonicsetting of the epicentral area of the LomaPrieta earthquake. Santa Cruz Moun­tains, centra! California. in S. McNutt andR.H. Sydnor, editors. The Loma Prietaearthquake of October 17, 1989: Califor­nia Department of Conservation. Divisionof Mines and Geology Special Publica·tion 104, in press.

Youd, T.l., 1973, Liquefaction, flow. and as·sociated ground failure: U.S. GeologicalSurvey Circular 688. 12 p.

Youd, T.L.. and Hoose. S.N.. 1977. lique­faction susceptibilily and geologic setting:Proceedings of Ihe Sixth World Confer·ence on Earthquake Engineering. v. 3. p.2189·2194, Prenlice Hall, Inc.

Youd, T.l., and Hoose, S.N" 1978, Historicground failures in northern California trig­gered by earthquakes: U.S. GeologicalSurvey Prolessional Paper 993, 177 p. ~

CALIFORNIA GEOLOGYWelcomes New Editor

CAUFORNIA GEOLOGY ispleased to welcome Lena Tabilio toits staff. Lena. a graduate of the Uni·versity of San Francisco, will assistthe Technical Editor in researching,editing, and writing articles.

Lena comes to State seruice after13 years of priuate industry andfreelance technical and promotionalwriting experience. She also has anextensive marketing and publicrelations background. ~

232 CALIFORNIA GEOLOGY OCTOBER 1990

Book Reviews

•

Regional Geology

VOLCANISM AND TECTONISM in the Columbia River Rood­Basalt Province. SpeCial Paper 239. Edited by Stephen P. Reideland Peter R Hopper. Available from the Geological Society ofAmerica. PO, Box 9140. Boulder. Co 80301. 400 p .. paper cover.1 plate. $52.50 postpaid.

The geologic history and structural evolution of the ColumbiaRiver Plateau has long intrigued geologists and other scientists. h isan area that has been shaped in part by catastrophic nooding. aod bytectonic events. occurring and re-occurring on a grand scale. How­ever. these events often occurred Oller a very short period 01 lime.

The Columbia Plateau occupies an area large enough to containthe six New England slales ilnd is approximately 62.320 squaTemiles. During Miocene and early Pliocene time. lava welled up frombeneath the continental plate and inlennitlently poured 001 creatingwhat today is the Columbia Plateau. The process may have beensimilar to what is happening today on ocean floors on both sides ofoceanic rifts. Extrusive events produced enough layered flow rock to

Photo 2. This spectacular panorama shows the Grande RondeRiver meandering through a valley which has been cut into thelayered basalt plateau. The erosive 'orces 01 the river haveexposed more than a dozen individual Ilows. The river isapparently approaching base level. The rate of down cutting issubsiding as evidenced by the meandering course. The layercake form of rocks which make up the flood-basalt province isvery evident. Basalt flows are often easily eroded by fast movingwater In streams due to characteristic Joint patterns. Courtesy ofWashington Srare Division of Geology and Earth Resources.

Books reviewed in thIS sectIon ale not available for purchase hom DMG.

Photo 1. This is a view of one wall of Frenchman Springs coulee.A coulee is a long. steep-walled, trench-like gorge or valley. Thephoto was taken trom Highway 90 at a point between Vantageand George, Washington. Several flat·lying basalt layers ot vary­ing thickness deposited by different tlow events can be seen inthe vertical 'ace 01 Ihe coulee wall. Weathering has caused disin·tegration of the wall and deposits 01 talus at its base. Courtesy ofWashington Srare Division of Geology and Earth Resources.

cover approximately one half of Oregon and one quarter of Washing­ton. a large portion of western and southern klaho, and parts of Cali­fornia. and Nevada. Totalll'Olume of these flow basalts is approxi­mately 41.520 cubic miles. Some individual IIows are less tnan 50feet thick however. aggregate average fhickness of the flood basalts isoolieved to be a lillie over 3.200 feet on fhe average. Basaltic Iavilproduced during individual eruptions was apparently not very viscous.hence it did oot form cones around vents and traveled great distances{I 00 miles or more) before solidifying completely.

Speciill Paper 239 is a compilation of 25 papers resulting from acomprehensive invesfigafion of fhis region. These studies stress theoverall importance of an adequate stratigraphic framework in under­standing this continental flood basalt province. Interpretations arebased on knowledge of flow strafigraphy acquired through field pe­trography. magnetic polarity. and chemical analyses. Striltigraphyprovides the basis for current understanding of the morphological andstructural evolution of the province. Investigafors subdivided the pla­teau info individual eruptions and. at the same lime. characterized thelarger packages of nows by using related chemical and/or physicalcharacferistics that act as common stratigraphic indicators in theirevolufion.

In addition to an increased knowledge of the stratigraphy of theColumbia River Plateau, there now exists greater knowledge andunderstanding of the infernal feafures of flood-basalt flows and thephysical processes of flow emplacemenf and cooling. Even simpleflows are now known to result from a complex series of processes.Analysis of relationships bel\veen individual eruptions has enabled in­vestigators to create a flow-by-f1ow record of the morphological andstructural evoluliOll of the province. Dating and analysis of individualfolds and faults on the Columbia Plateau yield accurate mcxIels of thetectOllic evolution in this part of fhe Pacific Northwest.

Individual eruptions have produced flows 1.Vith volumes of up to480 cubic miles. In addition to volume. several factors induding rapidextrusion rates. linear vent systems. and the absence of collapsecalderas, indicate there are large magma reservoirs at or near the baseof the crus/. However. the origins of various magmas which formedthe Columbia River basalt province are complex and remain contro­versial. Reviewed bV Richard Boylan.

(... mor8 books on pagB 238)

CALIfORNIA GEOLOGY OCTOBER 1990 233

I ndustry and consumer alike depend upon commodities deliv­ered by truck because it is often the most expedient fOnTI of

transport. California is the leading trucking stale in the na­tion. Of the 39 million trucks in the United States. Californiahas more than 4.3 million or about 11 percent. More than 98percent of all commodities in California are transported viatruck. In 1987 the trucking industry in this state provkled725,000 jobs with earnings of over $16 billion. Nearly 70percent of the 10\4II'IS and cities in California are solely depend­ent on trucking to deliver needed supplies.

Trucks are also important 10 the mining industry and ena1»eremote mines to operate economically. Occasionally the mosteffkient way to haul very heavy mining equipment is by truck.Photos 1 and 2 show large pieces of ore processing equip­ment being transported by trucks to mines. While this mayappear costly and time consuming, moving such equipmentoften saves lNI?eks or months of expensive tear-down and re­assembly at the mine site. Other benefits of moving largeequipment intact include minimizing damage and shortenedproduction schedules.

Photo 1 shows ill mammoth 425,000 JX>llIld autoclavebeing moved 275 miles to a gold mine north of Flko. Nevada.Although autoclaves have been used extensively since the 17thcentury. their use in the mining industry is relatively recent.Large autocla\JE!$ are used to extract gold from sulfide ore.

TransportirrcJ

CALIFORNIA GEOLOGY OCTQ8EA 1990

A.fining Equipment By Truck

- - -..

Photo 1. A gigantic 425,000 pound autocla....e being transported275 miles along pUblic roads 10 a gold mine north of Elko, Ne­vada in June 1989. The entire unit includes two specially modi­tied tractors: the Iront traclor as a 'poller" and the rear traclor asa ·pusher." The entire load was 262leetlong. 21 feet wide, 18leet tall, al1d grossed 704,500 pounds. All 164 tires made con­tact with the road. This was the heaviest, largest. and longestload ever moved on a freeway. Due to the extreme weight andlength. this shipment was limited to 40 miles per hour on thefreeway. The lull cooperation 01 slale and local authorities wasobtained, and the route was carefully planned. Photos courtesyof Jake's Crane, Rigging, and Transpor1lnternational.

... Photo 2. Transporting a 170.000 pound. 20-'oot diameter. 14­tool high grinding milt 600 miles to a mine site in northern Ne­vada. The "pusher" tractor has a 15 1001 push bar and carries25.000 pounds of ballast for traction on its drive wheels. Trans­porting large pieces 01 mining equipment by truck saves costswhile increasing the efficiency 01 mining operations.

The process involves cooking the ore at high temperatureunder high pressure in the autoclave. Large autoclaves likethe one in Photo 1 are effectively utilized in Califomia goldmines.

Photo 2 shows a 20 foot diameter ore grinding mill beingmoved from Kingman. Arizona to a mine site in northemNevada. Previously. such large pieces of equipment had tobe either disassembled for transport or simply could not betransported at all and had to be fabricated in the field at themine site. ~

CALIFORNIA GEOLOGY OCTOBER 1990 235

[~ M_in_e_ra_'_1i_r_iv_ia__~J

(l) What is the difference in mean­ing between the words "karat"ana ~caral~?

(2) When and where was the firstproducing oil well in California?

(3) What is the largest oil field inCalifornia?

(4) How deep. was the deeoest oilwell drillea in California'?

POOla 2, Called the ·Parller Aig No. 162,­this rig is capable of drilling to 25.000 teet.II is one of the largest land-based drillingrigs in the wortd. The height from groundlevel to the lop is over 200 feel. Electricalpower lor the rig is supplied by banks 01large diesel engines with pistons the size of5-gallon buckets-the same type 01 enginesused on modern diesel electric trains.

CALIFORNIA GEOLOGY

Photo 1. Large exploratory oilrig when il was used to drililhe22,735-1001 test hole for theDepartment 01 Energy at theElk Hills Naval Reserve, KernCounty. The accompanyingphotos depict the sophisticatedtechnology of this rig andillustrate the progress in oilexploration since Ihe first oitwells were drilled In Californiaduring the 1860s. Photos byMike Glinzak, courtesy of theDivision of Oil and Gas.

PholO 3. Drill pipe slacked next to fhe rig. Called "joints: eachlenglh of pipe is about 40 feet long and weIghs aboul 1,000pounds. When these pipes are used on the rig. Ihree joints of pipeare screwed togelher inlo a lenglh at pipe called a ·sland: Standsare stacked venically on lhe rig tloor unlillhey are used to drill.Every time a drilling bit is worn down, the entire length of pipecalled the "drill string" is pulled out ollhe hole by 12O-loot standsections. Pulling 22,000 leet 01 drilling pipe oul of the hole.replacing the drill bit. then returning lhe entire drill string into thehole is a tedious and arduous process thaI requires most of a day.

OCTOBER 1990

Photo 4. Workers screwing drill pipe. To change a drill bit, eachstand is unscrewed as the drill string is lifted, then reconnectedwhen the new bit is in place. Drilling is rigorous work and is done24 hours a day, 7 days a week in all types 01 weather. A drillcrew requires good teamwork: safety is emphasized at all times.

Answers

Photo 5. Powerful mud pumps located next to the rig. No deepwell could be drilled wilhout drilling mud for several reasons. Onereason why drilling mud is essential is because it is the onlymeans available for controlling the extreme physical forces thatoccur in the drill hole thousands of feel beneath the ground sur·lace: without the weighl of the drilling mud to hold the hole open,the hote would implode at depth. Another reason is because mudlubricates the drilling processes. Without mud the friction betweenthe drill string. the drill bit, and the rock it penetrates would be­come overwhelming. Drill mud is also used to condition the holeand to carry out the rock cuttings. Much care is devoted to clean,monitor, and precisely combine various mineral additives, such asbarite and bentonite clay. into the mud.

Photo 6. The vertical metallic column(commonly referred to as the "stack") inthe center of this photo shows blowoutprevention equipment that is located be­neath the drill lloor and above the groundsurface. A blowout is an uncontrolled flowof drill hole lIuids: it is extremely danger­ous and can seriously deplete the totalamount of oil recovered from a lield.Blowout prevention is critical when drillingdeep exploratory oil wells. The diNerenttypes of blowout prevention equipmentshown in the stack allow the drill string tofreely pass through Irom the drill lloor intothe ground. When the drill bit enters arock formation that is under extreme pres·sure with natural gas or lIuids at depth,combinations of these blowout preventiondevices are used in conjunction with thedrilling mud to stabilize the pressures.

(1) Karat is used to Indicate the purityo! gold. One karat is equal to 1124th thetotal amount 01 pure gold in an alloy.Pure gold is 24 karats. Gold With a lowerkarat number, such as 18-karat gold,indicates that the gold cont3Jns 18 parts01 gold mixed with 6 parts of anothermetal, usually copper or silVer. Carat isused as a measure of weight in preciousgems such as diamonds, emeralds. andrubies. Five carals are equal to 0.035ounce (one carat is 200 milligrams). So agemstone weighing 1 ounce would beabout 142 carats. Both lerms karat andcarat are derived from the Greek word"keration," meaning "carob bean." Carobbeans were used in arlClent Greece asweight standards.

(2) The lirst producing oil well in Cali­fornia was drilled in1861, only two yearsalter the first oil well in the United Stateswas drilled near TItusville, Pennsylvania.It was located on the north lork 01 theManole River near Petrolia, HumboldtCounty. "Petrolia" IS derived from theword petroleum.

(3) The largesl oil lield in Calilomia isthe Elk Hills Naval Petroleum Reserve,Kern County. It is an oval-shaped areaaboul 14 miles by 8 miles and has oilreserves estimated at 742.5 million bar­rels (one barrel is equal 10 42 gallons).At 21,600 acres in area. Elk Hills edgesout nearby Midway Sunset oil field by amere 340 acres.

(4) The deepest oil well drilled in Cali­fornia was 22,735 feet deep at Elk HillsNaval Pelroleum Reserve west 01 Bak­erslield (Photos 1-6). In contrast. theaverage ell well in California is about4,400 feet deep and the deepest produc·ing oil well in CaHlornia is at 14.680 leeltn the Rio Viejo oilliald, Kern County.The deepest exploratory oil well dnlled inIhe United States was in Oklahoma andreached 31,444 leel. 'X'

CALIFORNIA GEOLOGY OCTOBER 1990

[~._._._m_o_r_e_B_o_o_k_R_e_v_ie_w_s~J

Earthquake

COLOR PHOTOGRAPHS (35mm)SUDES SHOWING EXAMPlES OFSTRUCT1JRAL DAMAGE AND SURFl­CIAL EFFECTS OF THE M7.1 ocro­BER 17, 1989. LOMA PRIETA, CAU­FORNIA EARTHQUAKE. Compiled byCynthia C. Ramseyer. Specify U.S,Geological Survey Open-File Report89-687. 1989. Books and Open-FileReports Section. Brdflch of Distribution,U.S. Geok::agkal Survey. Box 2545.Federal Center. Denver. CO 80225. 36color slides. $72.00. make checks pay­able to: Department of Imerior-USGS.

Collapsed section of the Cypress 1-880 freeway structure,Oakland, California. Photo by M. Rymer/USGS.

Highway 1 bridge collapse, Struve Slough, Pajaro Valley. Calilornla.Photo by J. Tinsley/USGS.

The 36 slides in this set were takenby geologists of the M7.1 Lorna Prietaearthquake effects during the week fol­lowing the temblor. This slide set willbe of interest to teachers and otherprofessionals concerned with inform­ing others about the damaging effectsof earthquakes. Although the strongshaking associated with the quakelasted less than 15 seconds. it caused67 deaths. more than 3.500 injuries.and dose 10 $6 billion in propertydamage. This U.S. Geological Surveyslide set shows damage caused by thequake to a variety of structures includ­ing; unreinforced masonry. olderwooden houses. the San Francisco-

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Collapsed section 01 the SanFrancisco-Oakland Bay Bridge. ....Phoro by H. Wilshire/USGS.

Oakland Bay Bridge. the Cypress 1-880freeway overpass in Oakland, and theHighway 1 bridge collapse at StruveSlough. Pajaro Valley. In addition tostructural damage, this slide set showsexamples of surface expression on theground surface caused by the quakeand includes; extension cracks, land­slides. rock falls, ground deformation,collapse of coastal bluff. and sand boils.

In 1974 the Cordilleran Section 01 theGeological Society of America held its 70thannual meeting in Las Vegas. Significantchanges in the geological interpretation ofthe Mojave Desert and the southwesternGreat Basin have occurred in the succeeding14 years. Factors accounting for the evolu­tion of this interpretation include renewedinterest by young geologists, better geologicmapping. beller analytical tools such as reomote sensing and geochronology. and con­tinuing exploration by a cadre of geologistslong associated with the area.

Tectonism is the focus of the 18 fieldexcursions covering an area from Utah toCalifornia to nonhern Mexico. The mecha~

nism for this tectonic activity is emphaSizedin this volume. GeologiC problems discussedin this book include the recognition 01 Ceno­zoic low-angle. listric-normal faults that occurwithin the major Mesozoic thrust belts, thetiming and amount of regional extension.<Inc! the rel<ltion between extensional tecton­ism <100 regional volcanism. Other geologicproblems include (I) the genesis and geo­chemistry of major gold deposits throughoutNevada. Arizona. and California; (2) theinterpretation of the Paleoroic depositionalenvironments using ichnofOSSils (trace fos­sils); (3) the techniques appropriate for deter­mining the <lge 01 well-eemented alluvial fandeposits; and (4) the interpretation of sedi­ments deposited in Mesozoic arcs thatformed from Utah to nonhem Ba}a Califor­nia. Reviewed by Sy/vlo Bender-Lomb. ~

Structural Geology

THIS EXTENDED LAND: GeologicalJourneys in the Southern Basin and Range.Geological Society of America, CordilleranSection Meeting. Field Trip Guidebook. LawVegas. Nevada. 1988. Edited by David L.Weide and Marianne L. Faber. 1988. Avail·able Irom, Depa"ment of Geoscience, Uni­II(!rsity of Nevada, Las Vegas. Las Vegas,NE. 330 p. $22.00. soft cover.

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2.. CALIFORNIA GEOlOGY OCToec:R 1990