L I T E~.~, .~,..,.~ "~ ~,,~..~,~.~.,..~,~

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A quarterly publication for educators arid the public-

contemporary geological topics~ issues and events

"[ spent too much time in thesame place in the back swampand the clanged concretion went and nucleated on me."

This Issue:Earth Briefs--how does Nature concealbombs and record ancient water-flowpathways?

Have you ever wondered... How has ourclimate varied in the past?

Reptiles’on the Rocks--some uniquephotos of homed lizards in NewMexico

Trips and worksl~ops for Earth scienceteachers (see page 10 and 12)

Winter 1995

New Mexico Bureauof ..............

Mines and MineralResources

(NMBM&MR)

Eadh Briefs" Concretions, Bombs, andGround WaterPeter S. MozleyDepartment of Earth and EnVironmental

Science,New Mexico Tech

Concretions are hard masses ofsedimentary and, more rarely, volcanicrock that form by the preferentialprecipitation of minerals (cementation)in localized portions of the rock. Theyare commonly subspherical, butfrequently form a variety of othershapes, including disks, grape-likeaggregates, and complex shapes thatdefy description (Figs. 1, 2, and 3).Concretions are usually very noticeablefeatures, because they have a strikingly.different color and/or hardness thanthe rest of the rock. In some areas thisis unfortunate, as the concretions haveattracted the unwanted attention oflocal graffiti artists.

Commonly, when you break openconcretions you will find that they haveformed around a nucleus, such as afossil fragment or piece of organicmatter. For a variety of reasons, thisnucleus created a more favorable sitefor cement precipitation than other sitesin the rock.

~erhaps the most unusual concretion.nucleiare found in a modem coastal’salt marsh in England. Siderite (FeCOa)concretions in the marsh formedaround World-War-II era militaryshells, bombs, and associated shrapnel,including some large unexplodedshells (AI-Agha et al., 1995). A British geologist studying these concretionsrealized this only after striking a largeunexploded shell repeatedly with hisrock hammer (yes, he lived to tell aboutit)! The concretions formedpreferentially around the militarydebris because it provided an abundantsource of iron for the siderite.

In shales, concr&ions often preserve

New Mexico Bureau of Mines and Mineral Resources 1 Lite Geology, Winter 1995

Figure 2--Complex elongete concretions in the Zia Formation (Miocene),NM. I.ens cap for scale.

Figure l~"Cannon ball" concretions in the ZiaFormatum (Miocene), NM. Photo courtesy of DaveI ,ove.

Figure 3--1 luge elongate concretions in the Zia Formation (Miocene), NM.

Figure 4---~,ptarian calcite concretion from the MancosShale, NM. Top concretior~ has been cut on a rock saw toreveal septarian fractures filled with several generationsof coarsely crystalline calcite cement. Top concretion is 10cm in diameter. Concretions courtesy of NMBM&MRMineral Muset,m.

Winter 19q5, I.ite Geolo£,tt 2 New Mexico Bureau of Mines and Mineral Resources

L

features of the original sediment--suchas burrows, fossils, and sedimentarylayering--that cannot be seen in the restof the rock. Preservation of primaryfeatures occurs because concretionsusually form relatively early, beforesediment compaction and otherprocesses disrupt the original sediment.Thus, cementation of the concretions"freezes" the early sediment structure,forming a rigid mass that resists lateralterations. Examining the concretionsis the only way of understanding theseearly features.

Septarian concretions are the mostcommon type of concretion found inrock and mineral shops. In theseconcretions the fine-grained concretionbody (usually composed of calcite,CaCO~) is cut by a radiating network offractures filled with coarsely crystallinecalcite and other minerals (Figs. 4 and5). The origin of the fractures is poorlyunderstood, but they may result frominternal shrinkage of the concretionbody (like the cracks found in seasonedfirewood). This shrinkage may berelated to dehydration ortransformation of a gel-like mineralprecursor in the concretion interior

(Raiswell, 1971; Astin, 1986).Alternatively, some authors havesuggested that they originate as tensilefractures produced in response toburial and compaction (Astin, 1986).The name septarian originates from theLatin word saeptum (enclosure or wall),referring to the raised cracks on theoutside of some septarian concretions.If you are interested in hunting for

septarian concretions in New Mexico,many are found in the Mancos Shale, amarine Cretaceous unit found innorthwest New Mexico.

Recently hydrologists have becomeinterested in elongate concretions.These concretions range in size frompencil- and cigar-like bodies to thosethat resemble large fallen logs (Figs. and 3). They are thought to form fromflowing ground water, with the longaxis of the concretion oriented parallelto the ground-water flow direction(McBride et al., 1994). In formationswhere such concretions are common,measuring concretion orientation canprovide a direct measurement of thepast ground-water flow orientation overa large area. Such concretions arecommon in the Santa Fe Group, New

Mexico’s most important aquifer(Mozley and Davis, 1996). Elongateconcretions have even been found infaults cutting the Santa Fe Group, wherethey record the past flow orientation ofground water in the fault zone (Mozleyand Goodwin, 1995).

AcknowledgementsThanks to Stuart Burley for relating his

hair raising encounter with’the LinconshireWash concretions. This article benefittedfrom the comments and suggestions of VirgilLueth.

References

AI-Agha, M. R., Burley, S. D., Curtis, C. D.,and Esson, J., 1995, Complex cementationtextures and authigenic mineralassemblages in Recent concretions fromthe Linconshire Wash (east coast, UK)driven by Fe(0) Fe(lI) oxidation: Journalof the Geological Society, London, v. 152,pp. 157-171.

Astin, T. R., 1986, Septarian crack formationin carbonate concretions from shales andmudstones: Clay Minerals, v. 21, pp’. 617-632.

McBride, E. E, Picard, M. D., and Folk, R.L., 1994, Oriented concretions, IonianCoast, Italy--Evidence of groundwaterflow direction: Journal of SedimentaryResearch, v. A64, pp. 535-540.

Mozley, P. S., and Davis, J. M., 1996,Relationship between oriented calciteconcretions and permeability correlationstructure in an alluvial aquifer, SierraLadrones Formation, New Mexico:Journal of Sedimentary Research, v. 66,pp. 11-16.

Mozley, P. S., and Goodwin, L., )995,Patterns of cementation along a Cenozoicnormal fault: A record of paleofloworientations: Geology, v. 23, pp. 539-542.

Raiswell, R., 1971,The growth of Cambrian and Liassicconcretions: Sedimentology, v. 17, pp.147-171.

Figure 5--Moeraki boulders, Moeraki Formation, Paleocene, South lslanct,New Zealand. These huge septarian calcite concretions were exposedwhen the shale host rock was eroded by wave action. Photo courtesy ofJames Boles.

New Mexico Bureau of Mines and Mineral Resources 3 Life Geology, Winter 1995

Have you ever wondered...... How our climate hasvaried in thepast?

Part 1: The El Nifio effect

Charles E. ChapinDirector and State Geologist, NMBM&MR

Many of us have listened .tograndparents and elderly neighborstell of how when they were youngthe climate was different. Smallstreams were bigger then and hadmore fish in them, or winters weremore severe, etc. Such stories areusually received with politeinterest and considerableskepticism. But how variable is ourclimate.., and how can we fiodout?

Widely publicized worries aboutthe buildup of carbon dioxide inthe Earth’s atmospl~ere, as a resultof burning fossil fuels, and thepossibility of global warming, withthe melting of ice caps and rise ofsea level, etc., have elevatedresearch on past climates to seriousbusiness. Climate change is now amajor field of interdisciplinaryresearch and a voluminousliterature has developed around thesubject. In fact, there is so much ""research being done, on such awide variety of subjects, by such adiverse group of scientists, that it isreminiscent of the excitement andcontroversies during the platetectonics revolution of the 1960sand 70s.

Determination of past climates(beyond historical records)generally requires two things: 1) material, landform, or event whoseage can be accurately measured,and 2),a characteristic or ]:n’operty ofa material that can be reliablyrelated to a climate variable, suchas temperature or precipitation. Awide variety of opportunities existto gain insight into past climates,both local and global. Beginning

¯ with this article, I will attempt tosummarize where some of this

Winter 1995, Lite Geology

research is leading and point out someexamples pertinent to New Mexico.

Oceans and atmospheric currentsFirst-order effects on climate are the

circuJation patterns in the oceans andatmosphere. The two are stronglyinterrelated as has been graphicallyillustrated by the El Niflo effects inrecent years. The El Nifio or ENSO (ElNifio--southern Oscillation) is warming of surface waters in the easternPacific near the Equator (Fig. I). It caused by a weakening of the tradewinds that normally blow westwardacross the equatorial south Pacific. Asthey weaken, warm Pacific surfacewaters that usuallybuild up near Asiabegin flowing eastward.t0ward Centraland South America (Fig. 1A) bringingunusually warm currents to the region.Why the trade winds weaken is notknown.

The build up of warm surface waters,thousands of miles across, in the easternPacific causes the globe-circling,

weather-shaping, upper-level windscalled jet streams to alter their course(Fig. 2). The effects are often droughtsin Australia, India, and Africa; floods inSouth America and California; and col,d,wet winters in New Mexico. For ’example, the Albuquerque Journal onDe~:ember 17, 1992 (an El Nifio year)reported that November was thecoldest in Albuquerque since 1938(average,temperature 39.7 °F versusnormal average of 44 °F) and thesnowiest since 1946 (5.9 inches versus0.38 inches). Of(icial snowfall Albuquerque up to December 17th was19.6 inches, making 1992 the fifthsnowiest year of the past 100 years.What a contrast with 1995!

The El Nii’lo-Southern Oscillation isactually a cycle with both warm andcold extremes. The warm extreme (ElNifio) is driven by an eastwardpropagating, broad wave ofdownwelling warm surface water thatdepresses the therm0cline (the thinlayer of steep temperature gradient

1982 El Ni~o

North America

A

B

IllusZration by Becky TitusModified from an original illqstration by Szeven Davis, Earth,

Figdre t--Map of the equatorial Pacific showing sea surface temperatures (A)during the 1982 El Nifio event (when slackening of the westward-blowing trade winds allowed warm surface waters to "slosh" eastward toward Central and SouthAmerica) and one year later (B) during the westward return flow (La Nifia).Modified from Knox, 1992.

4 New Mexico Bureau of Mines and,Mineral Resources

i

separating warm surface watersandcold deeper waters) and inhibits thenormal upwelling of cold deep waters

¯ along the west coast of South America.The disappearance of the cold, nutrient-laden watersaround Christmas timeand its negative impact on fisheries ledfishermen to call the phenomenon "ElNiPto," after the Christ child. During theother half of the cycle, the rejuvenatedtrade winds blow the warm surface.waters westward away from SouthAmerica so that they again accumulatein the western Pacific. The cold half ofthe cycle was called La Nit~a by thefishermen, meaning "the girl". Butsome scientists prefer the term El Viejo,meaning "old man."

How are El Ni~o-SouthernOscillation events defined andmeasured? The JapaneseMeteorological Agency considers an ElNitro (the warm extreme) to underway when sea surfacetemperature in the tropical PacificOcean is a minimum of 0.5°C (0.9°F)warmer than normal for at least sixconsecutive months. Alternatively, an El

Ni~o can be said to be und.erway whensea level at the Galapagos Islands inthe eastern Pacific is 2 centimeters (0.8inches) above its normal height for sixor more consecutive months. As youcan see, these waves of warm or cQldwater are very broad and of lowamplitude, requiring sensitivemeasurements to detect them. It wasthe advent of satellites carrying verysophisticated instruments during thelast 20 or 30 years that allowedscientists to gain an understanding ofthe El Ni~o-Southern Oscillationeffect.

The roots of El Ni~o research,however, date back much earlier. Thecoast of Peru is normally bathed bycold waters of the Humboldt currentthat flows northward toward theEquator. Peruvian sailors who navigatethese waters in small boats noticedlong ago that a warm counter-current,flowir/g from north to south appearedimmediately after Christmas someyears. It was actually this current thatwas named El Nitro by the fishermen.In 1891, Dr. Louis Carranza, President

of the Lima Geographical Society, drewattention to the El Ni~o current in ashort paper in the bulletin of theSociety. And in 1895, Sei~or FedericoPezet of the Lima Geographical Society"described the El Ni~lo current and itseffects ir~ ah address to the SixthInternational Geographical Congress.The appearance of the warm counter-current coincided with heavy rains inarid regions where it seldom rains.

Prediction and measurement of ElNiflo

Early in this century, Britishmeteorologist Sir Gilbert Walker, theDirector-General ol~ Observatories inIndia, began studying tropical climatefluctuations after the 1899 disastrousfailure of the monsoon rains in India.The El Ni~to years of 1877 and 1888 alsosaw widespread famine in India andheavy loss of life.’Walker’s goal was topredict variations in the northward flowof moisture-laden air from the IndianOcean that provides the summermonsoon rains so necessary to India’sContinued on page 8 ~"

+Stronglow-pressure

J.ANUARY ’ area; recordAmplified storm track rains and

tloodlng

Normal PacificJet Stream

,,J ANUAR,YPowerful Jet .~tream

well south of normal directs i~i~major storms and moisture

into California ) ",,

D~c~a~n/JA.uARYPolar Jet Stream shlTted

well north of normal;, warm in easternNorth America

polarJet Stream J

Figure 2--Map showing typical effects of an El Ni~o on winter weather patterns in the United States. The northern and easternstates enjoy unusually warm, dry weather because a displaced polar jet stream keeps cold Arctic air from reaching as farsouth as it normally does during winter. In the west, the Pacific jet stream is south ’of its usual route, driving El Ni~o-fedstorms directly into Californih. The El Niflo effect enhances Pacific storminess but other, unrelated weather patterns also helpdetermine the paths of the jet streamS. Drawing modified from National Oceanic and Atmospheric Administration/ClimatePrediction Center data, (Monastersky, 1995).

New Mexico Bureau of Mines and Mineral.Resources 5 Lite Geology,. Winter 1995

Reptiles on the Rocks

Here are some horned lizards t~f New Mexico photographed in various geologic settings. Descriptions of the horned lizardsare by Gary Stolz, National Interpretive Specialist, U.S. Fish and Wildlife Service. Photos are by Dave Love, NMBM&MRSenior Environmental Geologist.

Photo AmShort-horned lizard Phrynosoma douglasslThe short-horned lizard is the widest ranging of seven species of these curious reptiles native to the United States. Found fromsouthwestern Canada to northern Mexico, short-horns are more cold-tolerant than other species. Short-horned lizards haveadapted by giving birth to live young to help survive cooler temperatures and limited incubation seasons found withinlatitudes and altitudes of their home range (all other U.S. species lay eggs). Throughout the diverse range of native habitats,horned lizards depend on camouflage to escape predation. Over generations, natural selection gives a survival advantage tothose that blend best with their surroundings. Here we see an individual from the Magdalena Mountains with colorationmatching rocks and lichens on which it dwells, while the disruptive coloration of the dorsal stripe helps break up arecognizable body line.

Winter 1995, Life Geology 6 New Mexico Bureau of Mines and Mineral Resources

Photo B--Short-horned lizard Phrynosoma douglaulThe short-horned lizard, like the individual shown here, can grow to four inches. It can be recognized by relatively short hornson its head with a U-shaped separation in the center, a single row of fringe scales on its sides, and light dorsal mid-line stripe.Note the different coloration of this specimen, blending well with its habitat of Cretaceous sandstones of Sand Canyon, east ofEl Malpais. Short-horns, like other horned lizards, spend much of their time hidden just below the ground surface where theyfind protection from predators and extremes in temperature.

New Mexico Bureau of Mines and Mineral Resources 7 Lite Geology, Winter 1995

agriculture. (New Mexico is alsodependent on northward flow of moistair for most of its summer rainfall.)Walker noticed that the barometricpressures recorded by land-basedstations between 1905 and 1937 on theeastern and western sides of the PacificOcean tended to seesaw back and forth.He called this periodic variation ofatmospheric pressure the SouthernOscillation and linked it to manyclimatic variables around the world.Unfortunately, he was not able to use itto accurately predict monsoon failures;other factors apparently are involved.

Water TemperaturesTl~e large body of warm water that

straddles the Equator northeast ofAustralia (Fig. 1B) is called the WesternPacific Warm Pool (WPWP), whichcovers an area lal"ger than thecontinental United States. The WPWP

"has a tempe’rature consistently higherthan 28°C (82°F) about 2°C to 5°C (3.6 9°F) higher than that of other equatorialwaters, and is the largest singleexpanse of warm water on Earth.Between El Nii~os, the westwardblowing trade winds dragwarm ’surface waters into the western Pacificraising sea level there as much as 16inches (40 cm) higher than sea levelsnear South America. When the tradewinds .weaken, the pool of warm waterbegins to drift eastward, which startsanother El Nifio. The position of thewarmest water may vary from oneoscillation to another and lead todifferent effects in separate El Ni~os,possibly chusing floods one time anddroughts the next.

Warm surface waters heat theoverlying atmosphere, stimulatingevaporation and pumping moistureand energy high into the atmosphere.When the moisture condenses into rain,

¯ it gives off heat, further warming theatmosphere. This fountain of heat andmoisture provides a major engine forglobal atmospheric circulatiom A seriesof low- and high-pressure cells radiatefrom the air overlying the pool of. warmwater. Variations in the pattern of these

’Winter 1995, Lite Geology

,highs and "lows" at mid-latitudesmay cause storms to divert from theirnormal paths and lead to unusualweather conditions in some locations.That the world’s oceans should havesuch major influence on the atmosphereand weather patterns is notsurprisingwhen you consider the high capacity ofwater to store heat (a property of waterutilized in many solar heated homes inNew Mexico). The upper three meters(9 f.eet) of ocean water hold as much.heat as the entire atmosphere!

Effects Of El Ni/IoE! Nittos usually occur every three to

seven years and last one to two years,but the latest El Nii~o was a doublecycle that lasted from January 1991 tomid-1994 (Fig. 3), and some say it lasted until mid-1995. Weather aroundthe globe was unusually severe duringthis interval. For example, heavy rainsthrough the winter’and spring of 1992caused major flooding in Texas(remember the earlier description ofwhat that winter was like in NewMexico). In December 1992 "nor’easter" of hurricane velocitypounded the east coast from Virginia to

Maine with waves up to 30 feet high.The summer of 1993 saw relentlessrains inundate the Midwest/forcingthousands from their homes andflooding 23 million acres of farmland.The following winter saw a recordblizzard with hurricane force windsthat churned up the eastern seaboard,killing 270 people. Meanwhile,

, Australia was suffering a majordrought. On the plus side, scientistshave found that there are noticeablyfewer Atlantic hurricanes during ElNifio years.

Since the El Nifio of 1991-94 ended,New Mexico has experienced twounusually warm and dry winters, arecord-breaking summer heat wave in1994, a partial failure of our summermonsoonal rains, and major problemsfor ranchers and the ski areas, whichbrings us to the subject of weatherprediction and its importance.Understanding the El Nifio-southernOscillation and detecting the changes inits cycle early can help reduce theeconomic devastation and loss of lifethat often accompanies extremes ofweather. A speaker at a geological

-.

i

® -10m

-2o

1960 1970 .1980 1990

El Nitro ~ La Nii~a (El Viejo)

’Figure 3--Graph showing the Southern Oscillation from 1963 to’ 1994. The dark-shaded regions indicate ̄ El Nil’to events; the light-shaded regions indicate La Ni~ut(El Viejo) events. The solid line indicates the sea level anomalies in the GalapagosIslands near the South American coast. Note that sea level in the Galapagos ishigher during El Nil’to events because of the arrival 6f a broad wave of warmsurface waters from the western Pacific. Modified from Meyers and O’Brien, Dec. 5,1995 issue of Eos, Transactions of the American Geophysical Union.¯

8 New Mexico Bureau Of Mines and Mineral Resources

k.

k.,

meeting in Denver has even correlatedvariations in the price of natural gaswith El Nifio events; he suggests thatthe El Nifio cycles can be useful instrategic planning by both energyproducers and large consumers. DuringEl Nifio years, the populousnortheastern United States andsoutheastern Canada are unusuallywarm and dry. During El Viejo years,the southwestern United States is warmand dry and the northeast gets itsnormal cold and snowy winter, as it hasthis year.

Further ReadingCane, M. A., 1986, Et Nifio: Annual Review

of Earth and Planetary Sciences, v. 14, pp.43-70.

Canby, T. Y., 1984, El Nifios’ ill wind:National Geographic, v. 165, pp, 144-183.

Knox, E N., 1992, A current catastrophe: ElNifio: Earth, v. 1, no. 5, pp. 30-37.

Monastersky, R., 1995, Tropical trouble: Twodecades of Pacific warmth have fired upthe globe: Science News, v. 147, pp. 154--155.

0.

Life ~ology evolvm.Lite Geology began as a small Earth-science publication designed aladscaled for New Mexico. Oursubscription list now includes a largenumber of out-of-state readers. In orderto keep up with the demand for thispublication from outside of NewMexico, we will charge $4.00 per yearfor out-of-state readers, which coversthe cost of printing and mailing. Thesubscription year begins with the Fallissue, and ends with the Summer issueto correspond with the academic year.If you reside outside Of New Mexicoand wish to keep your subscriptionactive, please return this form with acheck for $4.00. If you have questions,please call Theresa Lopez at (505) 835-5420.

t

Fun for kids...Falcon Magazine is for kids who arewild about wildlife: This bi-monthlypublication is filled with fun stories,pictures, and amazing facts aboutwildlife, conservation, and theenvironment. To order .FalconMagazine, call i-(800) 582-2665.

Fun for Earth scienceteachersApril 19, 1996; AlbuquerqueNational Association of Geology Teacherswill present Geology and Earth Scienceworkshops for teachers at the NewMexico Museum of Natural History inAlbuquerque. The emphasis is on fun,geology, samples, and curriculumideas. Staff from the Museum, N.MBureau of Mines,. UNM College ofEducation and Department of Earth andPhinetary Sciences, and other agencieswill conduct sessions on a variety oftopics. For more information, please.contaqt Chris Whittle, Southwest IndianPolytechnic Institute (SIPI), at (505)897-5380; or fax (505) 897-5713.

Free trip for a NewMexico teacherJune 19-22, 1996; Scottsdale, ArizonaThe 5th National Minerals EducationConference is an opportunity forteachers to gather information andresources to help teach mineral science.The Central New Mexico Section of theSociety for Mining; Mineral, andExploration (SME) will send a NewMexico teacher to the conference With

To apply, call GeorgeAustin, SME, GEM Committee Chair,c/o New.Mexico Bureau of Mines(505) 835-5230; fax (505) 835--6333.Applications are due May 1st, 1996.

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Lite GeologyD **($4.00 enclosed for out-of-state subscribers)

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*For in-state subscribers, please send in this form only once**Beginning with the Fall 1994 issue, out-of-sta’t6 subscribers will

be charged $4.00 per year to cover printing and mailing costs.

New Mexico Bureau oFMines and Mineral Resources 9 Lite Geology, Winter 1995

Reptiles on the Rocks

Photo CmRoundtall horned llzard Phrynosoma modestumLooking like just another basalt pebble, near a volcanic crater in the northern portion of Jornada del Muerto, this roundtailhorned lizard is barely visible to predators or prey. As fascinating and beloved creatures, horned lizards have long capturedhuman curiosity and imagination. These harmless and beneficial reptiles have been celebrated by Native Americans on theirpottery and rock art and by Hollywood in movies. Today horned lizards are faced with threats to habitat destruction, overcollection, and the introduction of exotic species such as fire ants. Horned lizards have survived on the Earth for millions ofyears, yet like all wildlife species, they now depend on Our stewardship of a shared planet for their future.

Winter 1995, l.ite Geolagy 10 New Mexico Bureau of Mines and Mineral Resources

Teacher training on earthquakesis coming soonleismic Sleuths: May 6--8, 1996

The first in a series of four workshops for teacherson earthquakes will be held in Socorro at the NewMexico Bureau of Mines and Mineral Resources(NMBM&MR). Seismic Sleuths features hands-on

activities to integrate math, science, and social studiesconcepts as applied to earthquakes. The curriculum was ,developed for Federal Emergency Management Agency(FEMA) by the American Geophysical Union (AGU). Mexico Seismic Sleuths curriculum will contain a specialvolcanic hazards section developed by NMBM&MR. Theworkshops are free, and travel and per diem are available if

participants travel more than 30 miles to attend. For moreinformation, or to register, call Bob Redden, New Mexico

Department of Public Safety at (505) 827-9254; or call SusanWelch, NMBM&MR, at (505) 835-5112.

Ne~v Mexico/Princeton Earth Physics Project(NM/PEPP): July 8--12, 1996

Travel and per-diem funding are available for 20 NewMexico middle school, high school, and college science teachers to participate inan NSF-funded.national program to develop and teach a series of curriculummodules focused on seismology. For a selected subset of workshop participants,NM/PEPP will purchase and install in schools Internet-linked, high-qualityseismographs to facilitate teaching and collaborative research projects with othermembers of the academic community. For more information, contact Dr. Rick Aster,Dept. of Earth and Environmental Sciences, New Mexico Tech, by phone at (505)

-835-5924; e-mail at aster@nmt.edu; or call Susan Welch.

i

L I T E.gy

is published quarterly by New MexicoBureau of Mines and Mineral Resources(Dr. Charles E. Chapin, Director and StateGeologist), a division of New Mexico Tech(Dr. Daniel H. Lopez, President).Purpose: to build Earth science awarenessby presenting educators and the publicwith contemporary geologic topics, issues,and events. Use Life Geology as a sourcefor ideas in the classroom or for publiceducation. Reproduction is encouragedwith proper recognitioo of the source. Allrights reserved on copyrighted © materialreprinted with permission within this issue.

Lite Geology Staff InformationEditor: Susan J. WelchGeological Editors: Dr. Dave Love, Dr.

Charles Chapin, and Gretchen"Hoffman

Educational Coordinator: Barbara PoppGraphic Designer: Jan ThomasCartoonist: Jan Thomas with inspiration

from Dr. Peter MozleyEditorial Assistant: Toby ClickCreative and Technical Support:

NMBM&MR Staff

Mailing AddressNew Mexico Bureau of Mines and MineralResourues, 801 Leroy Place, Socorro, NM87801. Phone (505) 835-5420. Forsubscription information, please call orwrite. Lite Geology is printed on recycledpaper.E-mail: nmbmmr@mailhost.nmt.eduWWW: http’J/geoin fo.nmt.edud

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Winter 1995, Lite Geology ~12 "New Mexico Bureau of Mines and Mineral Resources