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The Dynamic Earth

by: Cathrine Hoeger

The Dynamic Earth ESCI 401

Cathrine Hoeger
GPA 3.67


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This 85 page Class Notes was uploaded by Cathrine Hoeger on Thursday October 29, 2015. The Class Notes belongs to ESCI 401 at University of New Hampshire taught by Staff in Fall. Since its upload, it has received 40 views. For similar materials see /class/231682/esci-401-university-of-new-hampshire in Earth Sciences at University of New Hampshire.

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Date Created: 10/29/15
CLASS 42 HOT SPOTS AND MANTLE PLUMES INTRODUCTION We have seen that many volcanoes in the sea and some on land form chains with clear and obvious age progression In other words as we travel along a chain such as the Hawaiian Islands we encounter older and older islands In some cases the evidence for age progression is so overwhelming that Darwin Dana and other geologists of the nineteenth century easily recognized it EVIDENCE FOR AGE PROGRESSION The most obvious evidence is the degree of volcanic activity Hawaii has very active volcanoes Maui had eruptions within the period of European exploration and Oahu has a few Holocene volcanic cones Punchbowl Diamond Head The others islands are inactive The degree of erosion and weathering also provides strong evidence Hawaii is composed of ve cones none deeply eroded Oahu is deeply dissected by steep ravines and the older islands even more so The beaches and reefs tell the sane story Hawaii has blacksand beaches weathered from basalt with no reefs In contrast the older islands like Oahu have carbonate sand coral beaches and prominent reefs Midway the oldest island is an atoll it s all reef with the basalt foundation sunk beneath the sea A recent study develops another line of evidence On Hawaii the Polynesian inhabitants practiced dry land farming on the young fertile soil Sweet potatoes were the main crop On the older islands the soil became less fertile with time and the farmers shifted to growing taro poi in coastal paddies THE WILSONMORGAN HYPOTHESIS Before the plate tectonic revolution the dominant explanation for the age trends was that a fault zippered or propagated through the lithosphere thus releasing pressure on the rocks below and permitting pressurerelease melting to form magma As the crack opened at the front of the chain it also closed behind leading to a systematic age progression As part of the then new concept of plate tectonics it was proposed by Tuzo Wilson Toronto and Jason Morgan Princeton that the age progression in volcanic island chains was due to motion of a plate over a magmatic source hot spot below the plate Early radiometric measurements of island ages were interpreted to mean that the hot spots don t move with respect to one another they form an absolute reference frame for describing plate motions This appeared to be a big advance because other data only gave relative or platetoplate motion The hot spots were then explained as manisfestations of hot plumes of mantle rock rising like thunderheads all the way up from the coremantle boundary Subsequent collection of more and better radiometeric age data has convinced many geologists that the WilsonMorgan story is wrong It now appears that there are three main hot spot clusters within which there is little relative motion The clusters Paci c AfricaIndia North Atlantic are in relative motion on the order of one centimeter per year This is less than most plate velocities but certainly not zero These three mesosphere clusters are bounded by subduction zones as the plates are too but not by ridges unlike the plates In some chains including the Hawaiian paleomagnetic measurements indicate that the latitude of the hot spot has changed with time That is the hot spot has moved with respect to the rotational poles For a long time geologists have noted subtle differences in the lavas erupted along the midocean ridges and those on hot spot islands The island basalts apparently form by partial melting of the mantle at greater depths than the ridge basalts do Thus it was natural to conclude that the mantle was hotter in the island basalt source region higher temperature to permit melting at higher pressure Presumably hotter mantle means lighter mantle and there we are with a plume Recent investigations show that lava from many many little seamounts both in chains and out have the same chemical peculiarities as the island lavas This implies that there is a ubiquitous source of these lavas not just a few special hot spots Besides these geochemical approaches to the problem we can try using seismic data to try to directly image the plumes The results so far are quite ambiguous Some plumes seem to be detectable all the way down to the core but many others show low seismic velocities hot rock only in the uppermost mantle Clearly the true cause of ageprogressive island chains and the actual pattern of mantle convection are both related and unknown It s up to your generation to gure out what s really happening and to rewrite the text books f a HOT S39P0T 80 130 e 153200 180 90 D 90 180 m I m L ma M F EU quot1 1 4 a a 1 5 457 Longitude degrees W HzMa 10 H x mm ow 53 M43 Esm Mo 14 75 LS H 1 actquot C LV 3 E deva on r39o ush mass V6693 beaches soils C OhS k C J pht39wL I t i R z S Cve39ams E FSB2001 mm u 4 gunn m u My w mm r n 2000 Edllnwwun upu moo 39 Mornsoul mintSuny Ma I Lkm Plaque Ixmnspnauquo Pna qu rag Coup sst a men l39zrchige d I Soci z d39apris Scar a Ruralmo was modi Pm szw m 11 Sociczy archinth from 5cm x RomNDo ms 35quot g 2 cm bnrhym u39iqu d l mhigel a la me 39 39 apr s la can du 55054 icuilla yulyn39 ic SudEn 1m Hammad mu m39 the society 1rcHglagoSHO39L Palyne si SudEu mo Sans d2 a live an CHEETDI39H E Momma m u Bailingshausan Tupi Maupiti Scily Maupuhaa Muoera Tahiti 39 Talatapu Mlll Fig 7 L39ige du es d l Sod z d39apr u Bloussz R 1985ng of Sodas Islands from onussz R 1953 eheua Morhmw 3 1 296 L 30 39V 25 Li M Fig 3 Can hyysom viqu 1 Ram moanm l musivzr a 2 typ am Topogr ic map of u u Scum ongM Ada d w lyn si Fungal madi lion 5 c 11 TM hi mapafTahn ourcezoks39l39 Mm In a P0 mm Pancake mo 39 ppm um Putto quot 3 l M0 Fig 5 hypsou riqu du pruqu39aza d BanEon Topogra hi map of BariBan Scum 10m Am a Polyakin Fmsaisg ndi 5 1 Mt Fig 6 Can dz Moy 39ia mll localis an Nordeuux d l39archipcl d In Socie n To gognuhic may of Map lia Scum Add 195 Morten IWZ 2 6 5 6 397 L E 435K 1 I lt26 28 k a A my a ngactp H13 CLASS 26 EOLIAN DEPOSITS INTRODUCTION In the previous class we studied average global wind patterns and processes of eolian wind erosion and transportation Today we ll present an idealized eolian system and focus on eolian sedimentary deposits AN IDEALIZED EOLIAN SYSTEM Our system starts high in mountains bordering a desert basin Snow melt and occasional rain storms lead to ephemeral streams and debris flows These bring sediment from the mountains and spread it out in alluvial fans at the foot of the mountains On the bare desert oor there is little or no vegetation to bind the sediments and little moisture to hold the grains together Strong winds carry away the sand silt and clay As time goes on and the finer grains are removed only the coarse sand gravel and pebbles remain forming a lag deposit or desert armor At this point erosion would cease but in our example new sediment is sometimes brought down to the desert The sand rolling and saltating travels downwind and may pile up to form a train of discrete sand dunes The sand travels up the windward sides of the dunes in the form of little ripples Then it pills up at the crest and eventually cascades downward forming a steep lee face In this manner grain by grain dunes can migrate downwind Typical speeds are tens of meters per year At the downwind edge of the basin the dunes may stall and pile up so that little sand continues down wind The silt and clay particles from the desert may be swept up by strong winds and carried upward and onward in suspension The dust storm clouds may reach altitudes of many kilometers and travel hundreds of kilometers before the particles reach the ground On land the silt and clay may form a blanket of sediment draped over the landscape like a snow fall We ll examine these loess deposits later today The finest clay akes may be carried way out into the sea The resulting red clay deposits are the default mode sediment in the deep sea It s found almost everywhere but often is obscured by much more voluminous sediment of other kinds SAND DUNES As you can read about in the text there are many kinds of eolian sand deposits most of which are classified as dunes If the sandmoving winds are dominantly from one direction a variety of transverse dunes are formed In transverse dunes the crests are aligned at right angles to the wind as are water waves The dunes may be up to hundreds of meters high and the wavelengths may be as large as several kilometers These dunes have a single leeside slip face Where sand is scarce only little crescent shaped barchans are found Longitudinal dunes linear dunes seif dunes with two slipfaces form when the wind alternates between two subparallel directions These dunes can be huge with a maximum length of over 700 km Star dunes have three or more slip faces and are built where the effective winds are highly variable in direction Unlike the other dunes we ve looked at star dunes do not migrate They may be km s in diameter and 100 s of meters high At least two kinds of dunes are found in vegetated coastal settings Retention ridges are dunes located along a beach The ocean side may be marked by blow outs which are more or less circular depressions On the landward leeward side is a crude indistinct slip face In some circumstances These dunes may progressively widen and bury everything in their path Alternatively they may migrate inland and move away from the beach In parts of northern England and Scotland there are good historical records of towns churches and other works of man being buried in sand only to emerge decades or centuries later You can imagine the legal hassles this would lead to Outer Cape Cod is famous for its parabolic dunes These were built of glacial outwash sands by powerful northwest winds In map view these dunes are shaped like a U or parabola open on the upwind side northwest end The slip face is crescentic in shape These dunes may be km s long by 100 s m high LOESS DEPOSITS As we have seen de ation of fine sediments is encouraged by drought overgrazing animal tracks offroad vehicles The resulting dust storms can transport silt and clay for hundreds of kilometers A famous example is transport of Sahara dust all the way across the Atlantic to Florida the Caribbean and even the Amazon basin Darwin figured this out when thick red dust settled on the decks of the Beagle when it was hundreds of kilometers off the coast of Africa The term loess pronounced cclurse comes from the name of a town in Alsace the region between France and Germany In geology it refers to deposits of windblown silt In particular it refers to finegrained sediment de ated from glacial outwash plains and carried eastward across Europe and Asia by the prevailing westerly winds In France and Belgium the loess sheet is patchy and only meters thick Farther east in Ukraine and Russia the sheet is continuous and much thicker Even farther east in China the loess sheet is hundreds of meters thick In the United States a significant loess deposit is found east of the Missouri and Mississippi rivers During glacial times the channels and ood plains of these rivers were covered with outwash from which the fines were de ated As in Europe and Asia the prevailing winds were from the west so the loess is located downwind from the source Loess has several distinctive and diagnostic properties and there has always been controversy over its origin The fact that it is draped over the underlying surface rather than horizontally stratified indicates that the particles settled out of suspension either from air or from water Detailed examination revealed shells of land snails and casts of plant roots These observations plus the difficulty in outlining plausible huge lakes lead to the conclusion that deposition was on land Loess being largely fresh glacial rock our is extremely fertile It has high porosity and with the aid of vertical joints drains very well There are no boulders to interfere with plowing Thus it s no surprise to learn that much of the worlds most productive agricultural areas are loess regions In the loess regions of Mongolia and China many people live in caves excavated in the loess These are very comfortable being cool in summer and warm in winter The downside as for example in 1556 are mass deaths over one million from collapse during a big earthquake LOESS AND THE BATTLE OF WATERLOO In 1815 Napoleon was on his last legs The armies of England and Prussia were moving westward through Belgium into France Combined the allied armies greatly outnumbered the French The emperor s only hope was to defeat the British before the Prussian army arrived on the scene The scene of course was part of the loess plateau south of the Village of Waterloo Wellington and the British army were stationed high and dry on the welldrained loess Napoleon and the French were on a loess highland to the south In between was a stream valley all muddy from recent rains Impatient to dispose of Wellington Napoleon ordered an attack The first problem was that the artillery got bogged down in the mud thus delaying and weakening the assault Then as you can read in Les Miserables disaster struck The French cavalry charged uphill and then disappeared into the infamous sunken road Loess is very low density and easy to compact so any roadway lies meters below the surrounding area De ation and compaction turns any road into a ditch39 in this case a big one which the Napoleon did not know was there and could not see from a distance The French cavalry charge was halted until dead men and horses filled the sunken road to form a bridge of corpses The attack continued but with less than eXpected energy The battle was lost and the empire as well 80mm WHQD SYSTEM sanA39tramypmi sanAdunes 055 0 0quot O M X QQQQ 9003590002 W FsB ZCOI un u 2 3 F 304 nupzrd39we 39 39l 1 I 5 f 17 u 1quot s 3 w x39 f t 3382001 WM ce San s Tuavos39a V21 03 Sam A11 Ave S 7 S lcv anw gn39bo LLLCero ware Post39Y39iH M s 39Pem an a39n Yeso Fm re Carmth an E P 11832003 CLASS 41 FOSSIL FUELS INTRODUCTION Fossil fuels such as coal petroleum oil and natural gas are the basis of modern civilization The fuel needs of hunter and gatherer societies can be met by biomass mainly as wood but larger societies rely primarily on fossil fuel As civilization has moved I won t say progressed from small farming hamlets to giant cities and as more and more machines were invented the demand for energy grew greater and greater There is a strong correlation between per capita energy use and standard of living Our apparently insatiable appetite for material possessions motorized travel large houses imported food and so on may be setting the stage for serious trouble in the form of climate change Given that burning of fossil fuel produces C02 a potent greenhouse gas there is the possibility that ever increasing fuel consumption will alter the climate with many negative consequences coastal ooding loss of farm land droughts and water shortages and so on Paradoxically there may be resource wars to control the very energy sources that may make the world unfit for human habitation How can we avoid these con icts That s a great challenge for your generation ORIGIN OF OIL AND GAS These fuels are the result of a long series of steps accumulation of carbon in living tissue burial of organic carbon and conversion of this into oil and gas maturation On land the greatest production of organic matter takes place in equatorial rain forests Rivers such as the Amazon and Orinoco carry it to the sea Marine plankton diatoms algae prosper where nutrient rich deep waters well up to the photic zone where the plankton live What s important here is not the present geography but that of the past when the carbon was being taken up by plants and animals Overall little carbon is preserved on the continental shelves The waters there are rich in oxygen and sedimentation rates are generally low so the organic matter is oxidized to produce C02 In the deep ocean also there is abundant oxygen and very slow sedimentation As a result the sediments are reddish as on the shelf and little organic carbon is preserved On the continental slope especially in cones and fans at the mouths of large rivers the sedimentation rates are high and the dissolved oxygen is low The gray and green sediments are rich in carbon Again note that the important thing is the paleogeography not the present It takes a combination of time and temperature to convert buried organic matter to oil and gas Within broad limits the important control is the product of temperature times heating time Oil is produced most effectively at temperatures of around 100 degrees C whereas gas production centers around 150 degrees At significantly lower temperatures the chemical reactions don t occur and at higher temperatures the oil and gas are destroyed What this means is that the oil and gas we burn today dates largely from the Cretaceous and Early Tertiary times Formerly existing Paleozoic and Mesozoic oil and gas has been overcooked and destroyed and organic matter in younger rocks has yet to be converted matured On a human time scale oil and gas are not renewable resources Although oil and gas were formed through long heating of old rocks the oil and gas elds of today exploit accumulations of these uids in younger rocks Because oil and gas are lighter than salty ground waters they oat upward migrate into younger overlying strata Most oil and gas elds are located in sandstone beds and limestone strata However this isn t the whole story as we need traps to prevent the rising uids from venting at the surface There are many places where fossil fuels leak out at the surface One classical site is on the shores of the Caspian Sea where natural gases burn continuously These perpetual fires are thought to have inspired the Zoroastrian religion In 1898 Columbus noted tar seeps on the island of Trinidad You ve all seen pictures of sabretooth tigers trapped in the La Brea tar pits of California brea ar As I said there must be special structures or traps to stop or retard the escape ofthe fossil fuels You can study about traps in your book METHANE HYDRATES Methane hydrates are a strange material that was almost unknown in nature until a couple of decades ago This material is a solid that consists of fivesided H20 rings forming cages around methane CH4 molecules In nature the methane hydrates occur in the upper few hundred meters of marine sediment in water depths of around 500 to 1000 meters Drilling and seismic evidence indicate that there is often gaseous methane in the sediment pores below the hydrate layer Taken together these methane accumulations are the biggest reservoir of organic carbon and potential fuel in the world There are also large amounts of methane hydrates under permafrost in the Arctic Whether the methane is stored as a gas or as a solid hydrate depends on both pressure and temperature The gas is favored by high temperature and low pressure whereas the hydrate exists only at high pressures but low temperatures A striking result of this is that when samples of hydrate are brought rapidly from the deep sea to a ship s deck they explode The rapid pressure drop leads to rapid explosive conversion of hydrate to gas These phase relationships are the basis for two catastrophe scenarios One of these is a deduction based on the greenhouse effect We burn more fossil fuel thus producing more C02 Because of the greenhouse effect the world gets warmer The ocean warms up too as do the deepsea sediments As the sediments warm the methane hydrates in them become unstable turn to gas and vent to the surface This newly released methane CH4 is a to positive feedback and runaway heating of the atmosphere At present there are at least two serious efforts to obtain methane from hydrates in Japan from the sea and in Canada from permafrost Stay tuned for new developments 5 ch SUngNABI LlTI Siama no of 7 V7hj 7 c expectancy 2 1 E Cc 7 65 3009 per capiz a 3930 oa v on 7 FsBaom E gR GY SOURCES 53ng Western Europe 13 Africa 93 Central outh America Bf bj Eastern Eurune Former USSR 51 Far East and Oceania 42 9 200 temperature 639 W MM 0 Km 5 temperaturc X time Fss zocn F SBZOO1 r r r r r r LLLLLL 0500 9900 1 h4 deJH rm METHANE HYDRATE temperature C 399 O 29 3 1158200l METH A N E HYIDRR EEL ale675A km KKK femperature gt 4 1 sea Jete FSB 2001 V quot I quot39 quotIlu 139l39u1h39i39IE II LJfIJJLt luxur CLASS 30 SEISMIC WAVES AND INTERIOR OF THE EARTH INTRODUCTION Most of what we know about the interior of the earth comes from seismic evidence Just as a doctor can study your insides using ultrasound elastic waves and Xrays electromagnetic waves a geophysicist can learn about the earth using seismic waves elastic and groundpenetrating radar electromagnetic The radar however is limited to depths less than a few tens of meters so we won t discuss it in this course sign up for ES796 to learn about this exciting new technology In describing the passage of waves through the earth we can either use wave fronts like crests of ocean waves or rays lines in the direction of wave travel The two systems are equivalent because the rays are always perpendicular to the wave fronts Earthquakes radiate two basic classes of waves bodywaves that travel throughout the earth and surface waves that travel near the surface and die out at depth BODY WAVES Pwaves compressional primary pushpull can travel through all materials solids liquids and gases They are the fastest of all seismic waves The particle motion particle orbits are parallel to the direction of travel ray and perpendicular to the wave fronts Wave speeds are about 03 kms in air atmosphere 15 in water ocean 6 in granite upper continental crust and 8 in peridotite upper mantle Swaves shear secondary shake travel only through solids Their speed is about twothirds that of Pwaves in the same material The particle orbits are parallel to the wave fronts and perpendicular to the rays Shear waves can be polarized in a manner similar to light waves SURFACE WAVES These waves travel round and round the exterior of the earth They are tied to the surface as ocean waves are tied to the ocean surface Like ocean waves they die out at depth and their speed depends on their period or wave length dispersion Surface waves travel slightly more slowly than shear waves Rayleigh waves have particle motion in a vertical plane and Love waves oscillate in a horizontal plane Much earthquake damage is caused by big surface waves TRAVELTHVIE DATA For over a century the international seismological community has been recording and interpreting seismic data These data are used to infer the velocity of seismic waves in the earth The velocities in turn are used to infer what the materials inside the earth are Traveltime curves are graphs of the time it takes waves to travel from the epicenter to the seismograph For example it takes a Pwave about 12 minutes to travel an angular distance of ninety degrees An Swave takes roughly 50 longer to travel the same distance The fact that the travel times depend mainly on distance implies that the velocities in the earth depend primarily on depth or radius from center of earth not on specific location In other words the wave velocities show spherical symmetry The traveltime curve for surface waves is very simple The times plot as a straight line proportional to distance39 the waves just go round and round the surface of the earth For Pwaves and Swaves the times also increase with distance but the curves become less steep lower slope as distance increases This indicates that the velocities of these body waves increase with depth Beyond a distance of about 103 degrees something very odd happens Swaves are not recorded beyond this distance39 there is a shadow zone This observation in our primary evidence for a liquid outer core Recall that shear waves can not pass through liquids Beyond the same distance Pwaves are recorded but at much greater times than we would anticipate from the first part of the graph The interpretation of this Pwave shadow zone is that the Pwaves travel more slowly in the core than in the overlying mantle Detailed study of the core Pwaves implies the eXistence of a solid inner core CRUST From a seismic point of view the crusUmantle boundary the moho is marked by a change in Pwave velocity from about 67 kms to over 8 kms In terms of common rock types these velocities correspond to gabbro above and peridotite below Detailed study indicates that the continental crust is about 38 km thick on average Pwave velocities increase downward from about 62 kms grainite to 67 kms gabbro It is incorrect to say that the continental crust is granite The average composition is closer to diorite The oceanic crust averages about 7 km thick The crust has a three part structure with gabbro plutons at the base diabase basalt dikes in the middle and basalt lava ows on the top The deepest drill hole in ocean crust is near the aXis of the Costa Rica Rift part of the midocean ridge system This hole penetrated the lavas and bottomed in the sheeted dike compleX about 1300 m below the ocean floor On the continents the deepest hole is located in Arctic Russia This hole is over 12 km deep and given that it started in highly metamorphosed mid crustal rocks means that a substantial fraction of typical crustal thickness has been drilled Xenoliths brought to the surface in volcanic eruptions give us additional evidence for crustal composition MANTLE Most mantle xenoliths are peridotite a fact that supports the seismic arguments for a peridotite upper mantle Sampling of big fault scarps of the midocean ridges has shown that peridotite lies below the crustal gabbros Ophiolites sections of ocean crust and upper mantle thrust up above the sea include peridotite at the base The worldwide distribution of basalt volcanoes implies a worldwide source as we discussed before peridotite is a suitable source Finally most meteorites fragments of planetesmal bodies are similar to peridotite CORE All our arguments for the composition of the core are indirect We don t have any samples of the core and little prospect of ever getting any Perhaps the closest analogs we have are iron meteorites These are interpreted as being fragments of the cores of earthlike planetesmals Diamond cell experiments can determine seismic velocities and densities of materials at temperatures and pressures thought to eXist in the core The results indicate that iron is the only suitable candidate At the higher pressures of the inner core the iron is solid whereas it s liquid at the relatively lower pressures of the outer core The seismic case for a liquid outer core was developed by Inge Lehmann a Danish seismologist Fluid motions of the liquid iron outer core are thought to drive the magnetic field of the earth We ll discuss earth magnetism in a few days LNTERQampOF THE EARmi hot spv mgs hot quot hes ehot Volcanoes hot wuza i 623 gtv Sol 391 A Shape 1 uf gmxri vg 61 5539 ma me tic ne cehl SHOWN Seismi C wEUES a SakiARWuIASoiici CsB 2002 SE rm c fWAVEs P WAVE s SWAVE 3 P883001 313 2001 39 TKAVE LTme Cvkves 25 39 Q 2 s 2 3 207 9 5quot 39 5 g 01 9 Lt 5 0 r T I qo t o dist ance deg rees FSBJOO I 325m c Vemcmas 395 2 4 i1 Veoc39t j kMs 03 CRUSTALEEFRBCTIOQ 00 Monoaow x H09 o 39 1 j ar 0 dzktanca KM 00 M A 1 1 so km amp 6 kinS crust 8 kmS mantle 882001 fl gtgtO O n gtgt0r0 OltMMIM lrhvo aXosrscJ x3 apnea MANILE AND Cora Parquot dot39x tg 139 V0 3 dre g e d R armoqu C9311 oph39ioM ces dbmu39mo xenoll ns m etem ri c es basakt comic abun Aances VP 3 VS V3 mekeov c es spem c vaw cj 83002 moodmmu HQV 0 0M gt S 9amp5 u vs 367 mJwZW mmdn Bad 5 7ANgt 7 lt 94004 I 0 20 a mv J Llt T 33 w mcjnohm iv 2 x m m iufnfmcG Fm L 1 klt Llt mu w mcluqrnm ma a096 al l m aw V Neom CLASS 21 GLACIAL DEPOSITS INTRODUCTION We can look at a glacial deposit from several points of view One is the character of the sediments including such properties as grain size sorting and composition Another is the morphology form and location of the deposit Thirdly we are interested in the origin of the deposit Broadly speaking there are two basic kinds of deposits Glacial till is poorly sorted material including all size grades from clay to boulders in England till is called boulderclay An ideal lodgement till is plastered down onto the rock beneath a moving glacier These tills tend to be dense because of the combination of poor sorting that is there are lots of small particles to fill spaces between the large ones and pressure from thick glacial ice Thus till tends to have low porosity can store little water and low permeability water does not flow through till easily Till is found as ground moraine as drumlins and as end moraines The former is an irregular sheet perhaps a few meters thick The surface of ground moraine tends to be very irregular with many ponds and bogs Drumlins are streamlined hills shaped like inverted spoons elongated in the direction of ice flow They tend to occur in groups and may be up to hundreds of meters long and tens of meters high The precise origin of drumlins is subject to debate End moraines are ridges that mark times when the glacier terminus stalled at one place for a long time End moraines can be hundreds of meters high many kilometers wide and tens of kilometers long The other main category of deposits are waterlain39 that is they were deposited from running meltwater These sediments are characterized by stratification In any given layer the sediments tend to be well sorted i e have same grain size Porosity tends to be high for all grain sizes Permeability is high in sand and gravel but low in silt and clay Some of the prominent kinds of stratified sand and gravel deposits are eskers subglacial stream deposits and outwash plains from meltwater streams out in front of the terminus of a glacier We ll look at the seacoast region of New Hampshire in more detail after discussing how sealevel changed at the end of the Wisconsinan most recent ice age SEALEVEL CHANGES The recent Wisconsinan glaciers reached their maximum extent about 21000 years ago and were in retreat by about 18000 years ago During glaciation sealevel was lower in most parts of the world because so much water was stored in the ice sheets rather than the sea The average draw down was about 120 meters In detail the picture is more complex Far from the ice in Panama for example relative sealevel has been rising ever since the melting began The 120 meter rise is similar to that at other coasts far away from the ice sheets and presumably represents just the effect of melting In contrast regions near or even under the former icesheets have experienced a sealevel drop of hundreds of meters Places like Scandinavia Greenland and the islands of Arctic Canada are famous for postglacial beaches now hundreds of meters above the present sea In these places the relief of ice pressure allowed the land to rise isostatic rebound much faster than the sealevel rose from melting The relative sealevel history in coastal New Hampshire and Maine is more complex because both effects are roughly equal As the local glaciers were leaving the area relative sealevel was tens of meters higher than at present The land was still depressed from the weight of the ice rebound is not instantaneous and sealevel was high As time went on and the glaciers retreated far from the shore the land rose rebounded and sea level dropped to about 30 meters lower than present This minimum sea level was reached about 10000 years ago Since then the effect of world wide ice melt has dominated and sealevel has risen to its present elevation Because of this complex sealevel history the glacial deposits here are somewhat different from those where deglaciation occurred only on land GLACIAL DEPOSITS IN SOUTHEASTERN NEW HAIVIPSHIRE The oldest glacial deposits in southeastern New Hampshire are drumlin tills Based on internal weathering profiles and other data it is thought that some of these tills are Illinoian in age That is they have survived from before the recent Wisconsinan glaciation Beech Hill and Hicks Hill are local examples These and other examples have up to 50 m of till although some have only thin till on top of bedrock knobs Till also forms a discontinuous blanket a few meters thick over the region There are no obvious end moraines in the area As discussed earlier relative sealevel was tens of meters higher during deglaciation than it is now In other words the glaciers didn t leave by melting as much as by calving They oated away in the sea as big ice bergs As a result two distinct kinds of sedimentary deposits were laid down Right at the ice edge meltwater streams poured into the sea They quickly slowed down and sand and gravel were deposited in big stratified heaps These icecontact deltas were built up to sealevel and their at tops mark the elevation of the sea at that time These deposits are important aquifers Examples include Pudding Hill between Dover and Durham and the hill on which downtown Lee is located At the same time that the sand and gravel deltas were being built the finergrained outwash was carried into the sea where it settled out in the quiet ocean waters These marine clays are found not only on the present sea oor but also are located on land up to almost the elevations of the delta tops Thus they are a second line of evidence for a previously higher sea level Although analogous deposits in Maine include abundant fossils including mammoths none have been found in New Hampshire Maybe you ll be the first person to find some As sealevel rose over the past 10000 years a distinct suite of sediments were laid down These include sandy beach deposits salt marsh peats and uvial deposits in the river valleys The beach and peat deposits have moved inland following the shore line The peats record the sealevel rise in detail as the plants and shells in them can be dated by C14 As far as I know no one has studied the river deposits in any detail WHY ARE THERE MAMIVIOTH FOSSILS IN MARINE CLAYS You can work on this one BELATWE 35A LEVEL 1504 RSL 00quot m 50 i iIn gt v 4mmxx Wage 0 NEW W 5ooo IQ T mpoo pres en 7 mud mrsh 55 san vgravd UV339R A beach 3332001 50 wo Moczue sm s Dhmm ma cggb CDSMmM Th menu D 39hLLL 358 2004 Down wasfin8 Calvin8 l878 UPknm H7 Kits au bk hk 1975 Go kwmt H38 Go 3939waif I Vlo Louaee H57 TutJ1 HG Bra cv H78 Moore Remit KB quot73 CLASS 27 GEOLOGY OF THE OCEAN FLOOR INTRODUCTION The oceans cover about 70 of the globe They contain important resources such as fish fossil fuels oil gas methane hydrates heavy minerals gold diamonds cassiterite as well as sand and gravel The oceans also provide major transportation routes and offer many opportunities for recreation Marine sediments and sedimentary rocks are a detailed archive of earth history Most of what we know of evolution comes from fossils incorporated in oceanic deposits Most longterm climate change evidence is also found in marine sedimentary rocks The oceans are the main water source for precipitation on land and last but not least phytoplankton produce much of the oxygen that we breathe Today we ll look at some of the technical advances on which our knowledge of the sea oor is based Then we ll look at marine sediments STUDYING THE OCEAN FLOOR Before the nineteenth century almost nothing was known of the sea floor Widely spaced soundings yielded depth information around some harbors and other shallow places Meager sampling gave information on surficial sediments of continental and island shelves During the 1800 s substantial progress was made The main technical advance is that soundings were done with steel wire instead of hemp rope and the winches were driven by steam not muscle power This new equipment was used primarily to survey routes for transoceanic telegraph cables These surveys gave us our first hints of the midocean ridge system Geologists such as Darwin and Dana demonstrated that most ocean islands are basalt volcanoes with or without limestone caps The Titanic disaster and submarine warfare in the Great War of 19141918 led to rapid development of SONAR technology Sound waves were used to measure water depth Initially a survey ship would stop to be quiet emit an acoustic pulse and listen for return echo Timing was done using a stop watch In the late 1920 s it became possible to measure depths from a moving ship and record the echoes as a profile on a roll of paper The German research vessel Meteor mapped the MidAtlantic Ridge between Africa and South America in great detail In the 1950 s echosounding became routine and many deepsea cruises contributed to a much more complete mapping of ocean depth Seismic re ection sounding first developed in the Oklahoma oil patch in the 1920 s was employed to map sediment thickness and stratification Sediment cores up to ten meters long were taken systematically throughout the oceans and deep oil wells were drilled on the shallow continental shelf Basalt and peridotite were dredged from the midocean ridges The 1960 s saw the introduction of deep drilling throughout the deep seas These wells 100 s to 1000 s m deep gave detailed information including samples right down to into the basalt crust During this decade plate tectonic theory was proposed and soon accepted by most earth scientists we ll study the evidence soon From the 1970 s to the present there has been continuous development and use of multibeam echosounders and sidescan sonars that permit mapping of wide swaths on both sides of a ship not just a narrow profile under the ship At the same times detailed analysis of satellite orbits has given us an essentially complete view of Q the major bathymeteric features of the ocean basins Extremely detailed studies of the sea oor have been made possible by deep research submersibles such as Alvin Now let s look at some results GLOBAL TOPOGRAPHY AND BATHYlVlETRY Ocean water covers about 71 of the globe but only about 60 of the globe is covered with ocean crust The difference is explained by the fact that the shallow continental shelves have continental crust Mean continental elevation is about 800 m with a maximum of over 8000 m at Mount Everest Very little land has elevations over 2000 m Note that the high elevations of Greenland and Antarctica are caused by lots of ice not by rock The high areas are in narrow mountain chains located along active collisonal plate margins The average depth of the ocean is 3800 m with the deepest water exceeds 11000 m in the Marianas Trench Except for the very edges the shallowest sea oor is found along the midocean ridges These are anked by deeper basins on either side THICKNESS OF SEDIIVIENTS AND SEDIIVIENTARY STRATA Deep wells and seismic soundings give us very good estimates of the thickness of sediments and sedimentary rock almost everywhere on earth These deposits are rich in many useful resources such as fossil fuels metal ores fertilizers and construction materials They also preserve a record of earth history and organic evolution Except in mountain belts the strata on the continents seldom exceed 2000 m in thickness The old Precambrian shields of Canada Scandinavia and Siberia are almost without sedimentary strata repeated glaciation has apparently stripped it all away The Precambrian shields of South America Africa India and Australia have little sedimentary material also The explanation is that these areas have been stable for so long that erosion has dominated their history Most of the ocean has only a few hundred meters of sedimentary material One reason is that the ocean floors are very young The other is that sedimentation rates are very low in most places far from shore The thickest deposits are found in the deltas and submarine fans cones of big rivers such as the Mississippi Amazon Orinoco Ganges and so on These rivers all drain high mountains Big deposits are also found offshore of glacial troughs Saint Lawrence Antarctica and under passive continental margins There are also very thick deposits in the Caspian Sea and Persian Gulf SEDIIVIENTS ON THE ATLANTIC PASSIVE MARGIN OF NORTH ANIERICA Let s take a cruise from Cape Cod southeastward to the MidAtlantic Ridge What sediments would we find on and under the sea floor On the shelf water depths rarely exceed 100200 m The surficial sediments are mostly left over from the Ice Ages when glaciers advanced far out on the shelf and locally the sealevel was lower These sediments have been reworked eroded and moved around during the subsequent rise of sealevel Sand and gravel are the most common sediment Because of abundant oxygen at these shallow depths the grains are reddish with iron oxide coatings At present little active sedimentation is occurring The continental slope extends from the edge of the shelf down to about 2500 m depth The slope is the steepest part of the Atlantic passive margin The most common sediments are silt and clay Colors are gray from organic carbon and green from reduced iron compounds These dark colors are a result of low oxygen dissolved in the water see ES501 Oceanography for a more detailed explanation The steep slope is the site of intense mass wasting leading to numerous gullies and submarine canyons Sediment accumulates on the slope for a while but most eventually moves to deeper water The continental rise is located between about 2500 m and more than 5000 m The slope of the rise is much less than that of the continental slope The rise is largely built of huge overlapping fans or cones Big levied channels route coarse sediments across the rise and onto the deeper abyssal plains Sand and gravel are found in the channels whereas the overbank deposits are silt and clay At greater depths we find the abyssal plains These are the attest large areas on earth with gradients of less than 1 m per km They are built up of turbidity current deposits and debris flow deposits interbedded with red clays Even farther from shore but at somewhat shallower depths are the abyssal hills The sediments here are primarily red eolian clays draped over rugged basalt terrain produced at the axis of the midocean ridge The ridge itself is covered with calcium carbonate ooze a limey deposit produced by planktonic organisms such as foraminifera and pteropods The youngest parts of the ridge have not yet accumulated significant amounts of sediment HOW SEDHVIENT GETS TO THE DEEP SEA Turbidity currents and debris flows both move sediment from temporary resting places on the continental slope down to the rise and abyssal plains Turbidity currents are ows driven downslope by gravity The concentration of sediments in a typical flow is similar to that in a muddy river on land As the currents reach the rise andor abyssal plains they slow down and begin depositing sediment At any given place the first sediment laid down is coarser than the last In other words the deposits are graded A typical large flow might last for a few days and lay down a meter of sediment Then centuries might go by as red clay accumulates and the site awaits the next ow Like turbidity currents debris flows are driven downhill by gravity The difference is that debris flows are much denser they are similar to wet cement owing out of a mixer Nevertheless they can travel hundreds of kilometers over gentle slopes The sediments tend to be poorly sorted and inversely graded As with turbidites the debrites are laid down rapidly between long periods of slow red clay accumulation In contrast to turbidity currents and debris ows which go downhill contour currents run parallel to the bathymetric contours On the east coast of the USA the currents flow southward over the continental rise They act somewhat as wind does on land The silts and clays are carried away and eventually are deposited where the currents wane The sand is concentrated into ripple marks and dunes Much of the rise is covered by wellsorted crossbedded sandy contourites Ocean currents and winds carry fine sediment out to the deep sea where it eventually settles to the ocean floor Plankton such as foraminifera and diatoms often are the major sediment producers far from land MEHODS OE S wbx Iaoo39s 180039s qqo s jnmumkp 1 50 s Hut 9663 a I 395 N705 3 4 a LnUH 0 ll w J x 39quot t J I FSB39200 Saturday January 9 1999 GIF image 504x324 pixels Page 1 3339 6339 9TH Latitude 0 W S en s 3Y3 quot iquot 39 1 I II 1 39u n Ii in i II II 39n39 w39I 0 30 s 90 E 90 E Im E narE 15 15W 120W m am am Longitude fszxzd vu 21 i 30 soon 4030 301 0 2030 4030 63m topography m tilezlllEsciLab1Communications Netscape VoZONavigatorAA20 Folde ludnesday Febluary 17 1999 GIF Image 799x422 pixels Page RUST51 s dim39emthic flleEscith M 39 U Au v 4 nquot QQEAM SE DMEN139 FP 2001 MIDOCEAN RHDGEi tr OPHGOLCEQ F88 2001 Histogram of formation ages of ophiolites in the world Number of ophiolite 1000 V 500 0 Formation age of ophiolite Ma 3 pr 1J0 a 20120 I m I 32 mwbo CEAN S DUW NTS a UHou39M39hc debVH39e m w WWW 7 k comm 42v A I Fse2oo4 quotVG T ck ivc sprea has p Fore I am Svrea ing 2382ggg CLASS 7 VOLCANIC ERUPTIONS INTRODUCTION Today we ll focus on how and why volcanoes erupt Why are some eruptions very violent and others less so Why are there many different kinds of volcanoes How does magma ascend to the surface Just where does magma come from We ll address these questions after reviewing the four main types of lava Komatiites were very hot very uid lavas that erupted from fissures and formed thin extensive lava ows They did not produce significant amounts of ash or build big conical mountains With few minor exceptions komatiites have not erupted since the Archaean In contrast basalt lavas are very common in all geologic ages and on the ocean oor and the continents Basalt lavas are hot and uid They erupt from central vents to build large shield volcanoes but also from fissures to produce basalt plateaus ood basalts The eruptions are mainly lava with only minor amounts of pyroclastic material Andesite lavas are cooler and much more viscous than basalt lavas Andesite ows are short and thick Averaged over time the eruptions produce roughly half lava and half pyroclastic material ash tephra and mainly build composite cones stratovolcanoes Most andesite volcanism is associated with plate subduction These volcanoes are found on island arcs and in continental arcs Rhyolites are erupted very violently from central craters The lava is cool highly viscous and charged with large amounts of volatiles The bulk of the erupted material is pyroclastic in the form of huge tuff sheets Rhyolite volcanism is found in volcanic arcs in continental rifts and over continental hot spots VIOLENT AND QUIET ERUPTIONS Violent eruptions andesite rhyolite correspond to lavas that are relatively cool highly viscous and heavily charged with dissolved volatiles H20 C02 Quiet eruptions komatiite basalt are associated with very hot lava very low viscosity and low amounts of dissolved volatiles The viscosity is controlled by several factors One is temperature at high temperatures silicate melts are less viscous more uid The presence of large amounts of volatiles also lessens viscosity Silica content also has a strong in uence on viscosity In low silica melts there are few linkages between the silica tetrahedra In high silica melts the tetrahedra are much more connected polymerized and the viscosity correspondingly high Let s now compare and contrast basalt and andesite eruptions ERUPTION OF A BASALT VOLCANO At a midocean ridge or a hot spot basalt magma forms by pressure release melting of mantle peridotite The new melt is lighter than the surrounding rock and of course is uid The result is that the lava ows upward until at a maximum the pressure of the lava column is balanced by the pressure of the surrounding rock Basically there s a race between upward ow of the magma and freezing along the way Basalt magma is hot highly uid and poor in volatiles Thus to a good approximation the lava simply wells up out of the ground and ows away downhill Often the initial eruption is from a ssure producing a spectacular fire fountain and broad sheets of lava As time goes on the more vigorous upwelling erodes the fissure walls leading to faster more localized ow Thus eventually the ow may be confined to a single vent and a conical shield volcano may start to grow There are few volatiles to blast the lava into ash Because of the low viscosity many of the volatiles quietly bubble up to the surface of the ows One of volcanology s big secrets is how magma from partial melt over vast volumes of source rock maybe 100x100x100 km gets focused into a single vent Maybe you ll figure out how this can happen AN ANDESITE ERUPTION Andesite magma is relatively cool highly viscous and highly loaded with volatiles such as H20 Ascending magma tends to pool and accumulate in a magma chamber a few km below the surface As time goes on the chamber grows bigger and bigger As crystals start to grow in the chamber they provide nuclei on which steam bubbles grow With the passage of time more magma is added to the chamber more crystals grow and more steam exsolves Eventually the roof of the chamber fractures and the pressure drops As material is vented to the surface more and more volatiles exsolve and gasrich lava ows to the surface Because of the high viscosity the bubbles can t easily escape This leads to a chain reaction in which more gas leads to faster ow leads to more gas to more violent ow and so on until the chamber is emptied As the eruption progresses the chamber is filled first with lava then lava with gas bubbles and finally a lava foam Eruption has to happen to accommodate the increase in volume as the gases expand As the eruption proceeds ash is carried high into the sky Some of the height is caused by the speed of the erupting material but most is a result of heating the air The glassy foamy magma bubbles rapidly heat the surrounding air which then rises high into the air dragging the hot ash with it The ash eventually falls to earth either as a blanket over the surrounding countryside or as a more localized groundhugging nuee ardente After the eruption the empty magma chamber can no longer support its roof and the roof collapses forming a caldera As magma continues to rise the chamber starts to refill setting the stage for a new eruption An andesite volcano may erupt hundreds or even thousands of times over the course of a lifetime of a few million years RHYOLITE ERUPTIONS These resemble andesite eruptions but are much larger and much more Violent The main products are huge sheets of ash big enough to cover whole states Some of the ash lithi es to become tuft Other ash is so hot when it lands that it sticks together to make welded tuft or ignimbrite 100 s KM 10 s 391 s 10039s Komataate Basaxt Andes tte th olite HOO C IZOO mooquot soo b A 2 A 5 7 A A 9 5 fva 332662 3 Esquema geomnumko dd bhno Cennoome cuno N PLACA PAUFKA PLACA NORTEAMERKANA MEXICO A PLACA 17 cows BLODUE umms PLACA CARIBE 6 1 0 we PLACA39 WNAZCA z 33 HOT SPOT BASALT ISLAND 4 N IOO km likkosphev 49 2 3 2 I ask enospherg Ascent o Magma V O waterquot V 23 basnLt39 3 395 39Pe n39 a ttl39e e 1238 200 ComPos ITE che ERU PT 0N3 I nuee av evxte 39calAe ra A Tgx F 7 mass FSB ZOM CLASS 40 ORE DEPOSITS GEOLOGY OF GOLD INTRODUCTION People have used and treasured metals for thousands of years Classically history was organized in terms of metals none stone age copper age bronze age and iron age These successive stages are based on increasing ability to separate metals from their ores exploitable mineral deposits The earliest metals used were the native metals These include most gold some silver and copper and a little bit of iron from meteorites The oldest artifacts of native metals date from over 20000 years ago The next step about 5000 years ago was learning how to separate metals such as copper tin lead and zinc from sul de and oxide minerals In addition mixing of metals produced alloys such as bronze copper plus tin or zinc that had more useful properties than the individual components themselves Iron was more difficult to separate from common iron minerals hematite magnetite pyrite Aluminum although the most common metallic element in the crust was not even discovered until 1825 and was considered a rare and precious metal until little over 100 years ago Napoleon III supplied his dinner guests with sets of aluminum cutlery costlier than gold DISTINGUISHING GOLD FROM PYRITE AND MICA Pyrite fool s gold is readily distinguished from gold Gold is much much denser has no cleavage has a gold streak is malleable and will not burn Pyrite has cubic cleavage a black streak and burns in air with a blue ame and sulfurous odor Weathered mica akes may have a gold or golden brown color Their density however is very low so the akes are easily separated from gold dust using a prospector s pan GEOLOGY OF GOLD Gold occurs in many geologic settings of which three are the most important Epithermal gold deposits are basically hydrothermal veins associated with subduction zone volcanoes The magmatic heat sets up a convective system in which hot water rises in the central part of the system and cool water descends around the edges It is not altogether clear if most of the gold comes from the magma or is leached out of the surrounding country rock As the goldbearing uid rises and cools quartz sulfide minerals and gold crystallize in veins Gold is commonly found associated with rhyolite and andesite volcanoes The epi in epithermal means that the goldbearing veins were emplaced at shallow depths less than a few km underground and have been exposed by eros1on As the name implies mesotherma gold deposits were emplaced at greater depths and thus deeper erosion is needed to expose them Thus it is no surprise that most of these deposits are found in very old rocks of the continental shields Archaeanolder than 25 billion years The deposits are associated with granitegreenstone belts These consist of sea oor volcanics basalts and komatiites and marine sediments largely volcanoclastic turbidites that have been modestly metamorphosed to greenstone facies These rocks were then folded and faulted and intruded by younger granites The gold occurs in veins intruded into both lithologies but usually near the granitegreenstone contacts Unlike these two kinds of quartz vein deposits the third common kind of gold deposit is sedimentary Placer deposits consist of particulate gold laid down in stream and beach sands The gold comes initially from vein deposits that then follow the rock cycle weathering erosion transportation deposition The gold being very dense tends to settle to the bed of the stream wherever the velocity decreases One puzzling fact is the apparent concentration of gold at the very base of the placers In some fashion the gold must be able to work its way down to the lowest levels of the deposits SEPARATION OF GOLD FROM ORE Gold forms only a tiny fraction of most deposits To get the gold we must separate it from the quartzrich ore There are three common processes for doing this The oldest the patio process is to crush the ore and then soak it in mercury Hg The liquid mercury dissolves the gold The goldbearing liquid is then distilled to drive off mercury vapor and to concentrate the gold The potential for mercury pollution is vast A newer process uses cyanide KCN a deadly poison to leach gold from huge piles of ore heap leaching The liquid leachate is then mixed with aluminum whereupon the gold is precipitated The newest processes use goldloving bacteria to extract the gold from big vats or even directly from streams You can read more about this on the intemet FAMOUS GEOLOGISTS Many college majors in geology and related fields have achieved great success in other areas Although their accomplishments probably are primarily due to their intrinsic abilities it is possible that geological training helped prepare them Geologic education stresses many different skills such as reading writing measuring drawing and calculating Computer skills are important Much student work is done in teams so interpersonal skills are essential Geology students also deal with land owners government officials civic groups and even people in other countries Geologists have to work with incomplete and imprecise data This breadth of theory and practice provides a strong background for success in many other fields as the list below will demonstrate Colin Powell geology Chief of Staff of the Army Secretary of State Bruce Babbitt geophysics Secretary of the Interior Harrison Schmidt geology First scientist on the moon US Senator Harry Wu geology Revealed secrets of Chinese gulag Emil Constanescu geology President of Rumania Morgan Fairchild geology TV actress Herbert Hoover mining engineer President of USA Bob Farrelly geology movie producer Dumb and Dumber Something About Mary Wen Jiabao geology Primier of China ngek j gd QHQ Pmszv Cdow gol Sold lbsXc r metal mum Wav mss 272 395 6671 spect c lt3er 3 15 5 when 3o amp Hack clenuaj nowz 39hone WUQEUc zvi k hub t c nugsds Cubs 0 mumm mj ml usluceu39t opaipe Que Sveeh 333001 12km FSB2001 gI KLIMANTAN JAVA l Significant Mineral Deposits 1 MI Main Mlnemlized Magmalic Arcs W39W39 utter Ca iIe and Mitchell 1994 INDONESIA LOCATION OF SIGNIFICANT 5 quot WNERAL DEPOSITS Killnme len Gavan Lake Huon Lain swam BMR PSO B will ag 1 Granitoids Mafirmexavolcanics I Mdac rnttusxons I LEGEND Int media elo 19mg mel olcanks an relate meme me 5 Ulllamafb Inhusions COICMeII Alkalm Comalex 1 Melasedimenls Roads D Headlmme Hemlo deposu Figure I Regional geology o he Heron Bay quotcm Muir 068 report 289 1997 Hemlo greenslone bequot showing the gemog cal setting o he Hemlo gold dems modi ed SE 3 ATlorU F quotOLD H9 G M Wm M v cn NuCN gym U 882001 PLQCER g OL39D F33 2001 basall gabbro NpV graanLe metamorphic 0 KM 0 a e alluvium 1 0 6d 00 a 00 GI 00 0 ago r lt quot A V v VI v o O 9 D 0 M o o 6 e O 0 B o 5 G C v V vv v N A A I r n Y L x f ltquot xx X 9 6 2 l tons eld 400 t SOUTH AFRICA U N m 1 STATE 5 AUSTRALAR INDGNES tR Cl HMR Russm CAmABA PERU UZBEszmw GH ANA 41w toeax 200 1 F53 2002


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