i Iowa Geology 1995 Iowa Geology 1995

Iowa Department of Natural Resources Contents Larry J. Wilson, Director

Agriculture and Groundwater: The View from Big Spring 2

Geological Survey Bureau 109 Trowbridge Hall Jumbo - A Runaway Artesian Well 7 Iowa City, Iowa 52242-1319 (319) 335-1575 The Cambrian - Ordovician Aquifer http://www.igsb.uiowa.edu and the Northeast Iowa Landscape JO Donald L. Koch State Geologist and Bureau Chief Iowa's Sesquicentennial 12

Landscape Features of Iowa 14 COVER: Some of Iowa's most fascinating scenery is found in the Loess Hills. The alternating peaks and saddles along diverging ridge crests were sculpted Geology of Backbone State Park 23 from thick deposits of loess, carried by wind from the adjoining broad valley of the Missouri River. The loess originated as silt, left in the valley Satellite Images of Iowa Landscapes 26 following glacial meltwater floods between 12,000 and 50,000 years ago.

Living w ith the Land 28 Cover photo by Don Poggensee

Jean Cutler Prior Editor Patricia J. Lohmann Publication Designer

Printed on Recy cled Paper Left: Tbe Big Agriculture and Groundwater: Spring water­ shed in Clayton The View from Big Spring County is dominated by Robert D. Libra agriculture.

Right: Sinkholes funnel surface nmoff directly into the underground aquifer.

rains generate surface runoff, they capture and direct it into the aquifer. Shallow aquifers are vulnerable to contamination from activities on the land surface. In the Big Spring basin, and across Iowa, the major surface activity is agriculture , and the major contaminants are nitrate (from nitrogen "My u1tcle Earl's dream was to find a Big Spring is Iowa's largest, and it fertilizer) and herbicides used on corn spn·ng large enough to rear more trout. . .. has been used as a water source for and soybeans. In late fall of 193 7, my husband Otto we1tt trout-rearing ever since Mary and Otto The Geological Survey Bureau to look at Big Spring. He was awed by its Bankes put it to work in 1940. Iowa's began investigating the relationships size and called Earl; he too was amazed. DNR has owned the spring since 1961. betiveen agriculture and groundwater ... Tbe spring is located at the base ofa big Typically, 15,000 gallons of groundwa­ quality in the late 1970s. Anecdotal bluff, about 550 feet from the Turkey ter flow from the spring each minute, evidence, often from dairy farmers and River. It bubbles up through the ground fed by fractured rocks of the Galena water-well drillers, suggested that on top of a shelf oflayered rock four to aquifer. These rocks have been slowly widespread increases in nitrate con­ five feet higher than the river level. In dissolved by circulating groundwaters, centrations were occurring in the 1940 ... Big Spring deposited 33,000 to1ts forming features such as caverns and extensive, vulnerable bedrock aquifers of silt in the big fishing pond. We thought sinkholes. Across most of the 100- of northeast Iowa. The Big Spring that by closing sinkholes, sediment to the square-mile groundwater basin drained basin, which is almost entirely agricul­ ~ ~ spring could be controlled. We saw dead by the spring, the Galena aquifer lies tural, allowed for a direct study of '------"----' ~ animals, trash and old DDT containers i1l near the land surface and readily agriculture's environmental effects. those sinkholes that really scared us." receives downward-percolating water Equally important, the presence of Big Fractured dolomite ofthe Galena aquifer from large rainstorms or snow melt. Spring and its definable groundwater underlies most ofthe Big Spring basin Mary Bankes, Sinkholes are present in about one basin provided a unique opportunity landscape. The His tory of Big Spring tenth of the basin, and when intense to measure the volume of groundwater

2 3 Measurements are made ofa newly .formed rates were possible. Indeed, signifi­ dramatically during this period. This sinkhole, caused by collapse ofsoil and cant reductions have slowly occurred response resulted from both the shallow rock into a subten-anean cavern. as farmers became more confident that increased water volume passing lower rates of fertilization would work through the soil and groundwater for them. Nitrogen fertilizer input system - four times more in 1993 than increased by a similar amount. By the declined by a third from 1981 to 1993, in 1989 - as well as from leaching of early 1980s concentrations commonly from 174 to 115 pounds/ acre, with no unused nitrogen left over from the approached the limit set by the U.S. affect on yields. This represents a two drought. Any improvement in water EPA for drinking water (45 mg/L). million pound reduction in nitrogen quality resulting from decreased Higher concentrations occurred during use, saving basin farmers about nitrogen applications was again lost in wetter recharge periods, a pattern also $360,000 annually. the effects caused by the extreme seen in basin wells, streams, and tile While nitrogen inputs have climatic variations. drainage. When the amount of nitrate decreased significantly, relating these The studies at Big Spring have emerging from the basin in surface and declines to changes in Big Spring provided the nation's longest running groundwater was totaled for typical groundwater remains a problem. The and most detailed record of the years, it was equivalent to one-third of effects of nitrogen reductions, occur­ relationships between agriculture and the chemical nitrogen fertilizer which ring gradually over a decade, are at water quality. Perhaps the most basin farmers had applied. Additional present largely lost in the year-to-year important thing we have learned is that losses of nitrate, such as uptake by climatic variables - particu- aquatic plants, also occur and sug­ larly rainfall. On an annual gested the actual loss from fields was basis, nitrate concentrations equivalent to half of the chemical rise and fall with the volume fertilizer applied. Herbicides were also of water discharging from detected in the groundwater, with Big Spring, which is a atrazine present in low but detectable Ari Bc111s reflection of the volume of concentrations year-round. precipitation recharging the The initial findings at Big Spring aquifer. Nitrate concentra­ leaving a known area. When dis­ resulted in the creation of the Big tions showed a general charge volumes are combined with Spring Basin Demonstration Project, a decline from 1982 to 1989, contaminant concentrations, the total cooperative effort involving basin but so did the discharge amount of a given contaminant carried farmers and numerous state, federal, from Big Spring, which George llallbcrg by the water can be calculated. Since and local agencies. The project, which reached its lowest point dur­ 1981, water quality and discharge and began in earnest in 1987, increased the ing 1989, the second year of Water samples .from Big Spring, .following a heavy rain.fall across the basin, show the increase in suspended sediment agricultural practices have been tracked scope of water-quality and land-use extreme drought. While cam·ed by the emerging groundwater. in this natural laboratory. monitoring, and greatly expanded some of the decline may Initial investigations in the basin, education and demonstration programs reflect the decrease in nitro- along with existing data, yielded aimed at improving the economic and gen applications, the effect cannot be water quality responds slowly to valuable information on the agriculture environmental performance of agricul­ separated from the decrease in re­ changes in agricultural chemical inputs, - water quality connection. During the tural practices. Improved nitroge n charge and nitrate delivery to the particularly when those changes occur 1960s and 1970s the use of chemical management was an important part of aquifer. Wetter-than-average concli­ slowly themselves. We need to take nitrogen fertilizer in the basin in­ these efforts, as the magnitude of tions occurred after the drought, the long view when trying to document creased almost three-fold, and nitrate nitrate losses from fields in the basin culminating in the "great flood of water quality improvements, and Iowa's concentrations at Big Spring had indicated that reductions in application 1993." Nitrate concentrations increased Big Spring helps provide the focus. •:•

4 5 In 1886, a well for a creamery was JUMBO drilled at Belle Plaine in the Iowa River valley; this well also tapped the ARUNAWAY sand and gravel aquifer. The elevation of this well was about 100 feet lower ARTESIAN than the previously drilled livestock wells, resulting in a strong flow of WELL water from the well. At the well head, the artesian pressure level of the Robert D. Libra aquifer was sufficient to lift the water 67 feet above the surface. Several other wells were drilled into the aquifer at Belle Plaine, and while the Since the settlement of Iowa began strong flows complicated construction in earnest over 150 years ago, tens of of the wells, they were completed thousands of water wells have been without incident. drilled, bored, or dug. Drilling and In August 1886, the city of Belle construction of wells is at times a Plaine contracted to have a well drilled difficult and frustrating endeavor, as for fire protection. This well soon unseen conditions lying hundreds of became widely known by the name feet below the land surface must be "Jumbo." In the words of geologist anticipated and dealt with. While the W.H. Norton (1896): "The notoriety of drilling of some water wells might be Jumbo was strictly that of a member of described as a "routine" operation, the the criminal class, and began with his drilling of others is decidedly not. resistance to control, and lasted only In the 1880s, a number of wells until his final imprisonment. The drilled north of Belle Plaine in Benton beginning of the trouble lay in the fact County encountered a sand and gravel that the driller attempted to use the aquifer at a depth of about 300 feet. force of the flow in reaming out the The aquifer has since been shown to two-inch bore, which he had put fill extensive parts of an ancient river down for want of a larger drill, to valley, and to be overlain by relatively three inches, the dimension specified impervious glacial tills. These tills act in the contract. This task the water hydrologically to seal the aquifer and speedily accomplished in the create strong artesian pressures. The unindurated clays and sands, but not water levels in the wells north of Belle stopping there went on and soon Plaine, which were located in the enlarged the bore to over three feet in uplands above the Iowa River valley, diameter." H.R. Mosnat 0898) notes, rose to within 25 to 50 feet of the "When the driller saw the result of his surface, depending on the surface inexcusable carelessness, which result elevation. These wells yielded large he ought to have foreseen, he hastily volumes of water that although some­ decamped and was not heard of until what salty, were acceptable to livestock. the popular excitement had subsided."

7 most sensational, their extravagance increasing according to the square of the distance from Belle Plaine. Euro­ pean papers published accounts of the water spouting hundreds of feet into the air, with a roar that could be heard for miles and even pictured people being rescued by boats from the third and fourth stories of houses!" Other reports connected Jumbo's unleashing with the great Charleston earthquake, which occurred four days later, and to renewed geyser activity in Yellowstone Park. This prompted Professor Cham­ berlain to comment "The only simili­ tude of seismic disturbance, as the cause of this well, was in the moral faculties of said reporter." Many other wells were drilled into the buried sand and gravel within the Iowa River valley between Belle Plaine and Marengo, and were often allowed to flow relatively unchecked. The great artesian pressures have therefore been decreased over parts - but not all ' - of the area. As the Belle Plaine weekly newspaper noted in 1986, "Beneath this city lurks a monster dis­ covered 100 years ago." The Geologi­ Photos of "Jumbo" cour1csy 'I11c Universily of Jowa Cal vin Collcc1ion. cal Suivey's research driller, Daiwin Evans, found the aquifer was still a force to be reckoned with when he The flow from Jumbo roiled out of carloads of sand. "The quantity was local historian recounts, 163 feet of 18- drilled a test hole into it in 1984. the three-foot bore in a fountain that certainly so great that only with the inch pipe, 77 feet of 16-inch pipe, 60 While his efforts to control and plug stood five feet high. Estimates of the greatest effort could the ditches be kept feet of 5-inch pipe, an iron cone 3 feet the hole took a few hours, as opposed initial, maximum flows varied from open to carry off the water" (Mosnat, in diameter and 24 feet long, 40 car­ to 13 months, the situation prompted 30,000 to 50,000 gallons per minute. 1898). Chunks of fossil wood and loads of stone, 130 barrels of cement, him to comment: "We were about five The flow diminished rapidly, and two stones weighing over two pounds and an inestimable amount of sand minutes away from making "Good weeks later was calculated to be about were also hurled from the well. and clay." Morning America." Meanwhile, in 2,000 gallons per minute, by Professor Norton (1896) describes the effort While Jumbo was obviously an Belle Plaine, a bronze plaque attached T.C. Chamberlain from the University to stem the flow, which ultimately took unusual occurrence, Mosnat (1898) to a granite boulder still marks the spot of Chicago. Along with the water over 13 months: "During this time the notes, "The accounts of the well given where the runaway artesian Jumbo came sand - an estimated 500 to 1,000 well, 193 feet deep, devoured, as the in newspapers were in many instances entered the history books. •:•

8 9 Along the eastern margins of Alla­ and sandstone units in the overlying makee and Clayton counties, towering Oneota, Shakopee, and St. Peter rock bluffs form a picturesque back­ formations. Across the eastern two­ drop for the Mississippi River. The thirds of Iowa, the "Jordan aquifer" river's flow of water and commerce provides water for food processing, toward the Gulf of Mexico is obvious, manufacturing, irrigation, and cooling, yet life-sustaining water also moves in addition to drinking water for both through the rocky cliffs above. The municipal and non-municipal users. cliffs, which form some of the most Properly developed wells generally spectacular scenery along the upper yield several hundred to over 1000 gal­ Mississippi Valley, are outcroppings of lons per minute (gpm) and occasionally one of Iowa's most widely used may produce in excess of 2000 gpm. sources of groundwater - the Cambrian­ From its outcrop belt in the north­ Ordovician aquifer. east corner of Iowa, the Cambrian­ Near Waukon Junction in Alla­ Ordovician aquifer dips southwestward makee County (photo left), rugged beneath the landscape at about 18 feet cliffs expose almost the entire se­ per mile. This gradual tilt buries the quence of strata that comprises this aquifer to depths greater than 2500 aquifer. The rocks at road level feet in south-central Iowa, where the consist of the porous, loosely ce­ town of Murray, in Clarke County, is mented Jordan Sandstone. Higher in the last community along the aquifer's the bluff, the better cemented, more slope to withdraw water for drinking resistant dolostones of the overlying use. Along the slope of the aquifer, or Oneota and Shakopee formations downdip, the dissolved mineral stand out as cliff-formers. These same content of the water gradually in­ rock units outcrop from McGregor creases to undesirable levels. In the northward into Minnesota, and they western third of Iowa, elevated dominate the landscape of many well­ concentrations of sulfate, sodium, known points of interest, such as magnesium, chloride, and bicarbonate Yellow River State Forest, Effigy Mounds prevent the aquifer's use as a water National Monument, and Mt. Hosmer supply. Downdip, water yields are City Park at Lansing. also reduced significantly because of The aquifer's name is derived from an increase in the mineral cement the geologic age of its constituent holding the rock grains together. rocks - Cambrian and Ordovician ( 480 Additional uses for the rocks of the to 510 million years old). This wide­ Cambrian-Ordovician aquifer include spread source of groundwater, also high-quality concrete aggregate in referred to as the ''.Jordan aquifer," is northeast Iowa, reservoir rock for the one of the most dependable sources storage of natural gas in Dallas, Louisa, for large capacity wells in Iowa. The and Washington counties, and the name "Jordan" comes from the sand­ potential for purified freshwater storage stone in its lower portion, but the for the City of Des Moines. •!• aquifer actually includes the dolostone

11 IOWA'S SESQUICENTENNIAL

roads intersecting on one-mile squares able minerals, stone, sand and gravel helps us navigate the countryside. that were geologically stored for Hay is mowed and bailed, seasonally thousands or m.illions of years have scoring Iowa's hillslopes with intricate been mined and quarried from the webbed patterns (photo above). Dams earth. Urban lands are excavated and and levees regulate the flow of water rearranged to suit builders and con­ In 1996 Iowa will celebrate 150 landscape. People, however, are also through the state's lowlands, while form to legal regulations. The left­ years of statehood. Sesquicentennials part of the landscape, and their artificial ponds and reservoirs hold overs of our daily lives are buried in are historical milestones, and compari­ mechanized earth-moving ability also water in place among the rolling hills. landfills. And the quality of one of our sons between then and now are makes them a major force altering the Terraces are bulldozed into place most basic needs - the drinking water inevitable. Geological perspectives on land surface. across the steeper hillsides to slow the supplied by underground geologic 150 years of human histo1y may seem In just 150 years, people have loss of soil and moisture from the land. strata - can be compromised by this like a mismatch of time scales. People imprinted a variety of cultural patterns Meandering river channels have been human activity, sometimes in unex­ tend to think of the landscape as a across the state's terrain. Glacial straightened and confined between pected ways and over long periods of permanent, unchanging feature of our boulders stranded in Iowa thousands narrow embankments, forcing rivers to time. lives, with modifications during such a of years ago have been moved by erode deeper courses, in turn lowering In few other states having rural, geologically brief span of time as generations of farmers from fields to local water tables and draining adja­ dispersed populations does the impact being almost insignificant - but that is fence rows (photo above). Plows and cent wetlands. Miles of clay tiles and of 150 years of human activity domi­ not true. Geologists recognize that planters annually turn over the upper plastic tubing have been laid beneath nate the landscape as completely as it Iowa's floodplains, hillslopes, gullies, few inches of most of rural Iowa, acres of landscape to redirect infiltrat­ does here in Iowa. •!• and karst regions are dynamic, natu­ loosening the soil in furrows to the ing rainwater and hasten drying of the rally changing portions of today's forces of wind and rain. A grid of land surface. Deposits of non-renew-

12 13 Shifting sand dunes occupy pan ofan abandoned channel of Landscape Features of Iowa the Upper Iowa River in Allamakee County. •.. -.. -- -. -: _,, 1be sand accumulated - Jean Cutler Prior ..---- :.-- ... when waterflowed -- through this meander l ... -.· much earlier in the The topographic features seen on the following pages illustrate valley's histo,y. Wind the range of picturesque diversity that is present across our state. In .... also deposited sand ...... --~. ~ here during later dry addition to their beauty, each of these landscape views reflects pen·ods. some aspect of Iowa's geologic history. Understanding the geologic setting of various types of terrain is essential for citizens concerned ..- .. ·- -.. '"'\;_ with farming, urban expansion, recreation, excavation of mineral - 1r resources, pumping of groundwater supplies, landfilling of waste Jean Prior materials, and other environmental and natural resource issues. Also, it is useful to think about these landscapes in terms of their Gary I liglushoc, (owa St.11e Universit y influence on the distribution of native plant and animal habitats, on various soil types, on the potential for archaeological remains, and on patterns of historic settlement. Learning more about the features Left: 1be island-braided of Iowa's landscape increases our understanding and appreciation channel ofthe Mississippi of the views around us and the ground beneath our feet. River occupies the floor of a gorge eroded through steep rock-lined bluffs in Clayton County. 1be deeply entrenched river valley was shaped by glacial meltwater floods between 18,000and 9,500 years ago.

Right: 1be Iowa River forms sweeping meander loops as it flows across its floodplain in Tama County. Scars ofearlier migration channels of the n·ver are visible in the fields and woodlands. Floodplains are underlain by porous alluvial deposits that yield valuable groundwater supplies. 1bese shallow resources are vulnerable to contamination from the land surface. Hump-backed ridges rise from the gently rolling landscape in southeastern Linn County. These ridges, known as paha, are always oriented NW to SE. They are all that remain ofa once higher glacial plain and are Above: Ocheyedan Mound is an often capped with isolated, conical hill composed wind-bloum loess of sand and gravel. It is an and sand. excellent example of a glacial kame, formed as meltwater Tim Kcnuni~ carried sediments offthe gla­ cier surface and deposited them into a cavity in the slow­ ly melting ice.

Right: Gullies are deep, narrow erosional cuts through the landscape. Their development and growth is an active geologic process within S1a n M itchem the silt-dominated Loess Hills topography of western Iowa. Gullies widen and lengthen headward ( upslope), eroding quickly, especially after heavy rains.

I ~ '€ ~ ::,c :I ~ ii vS ~ A glacial moraine in Dickinson County appears as a series of irregular broken ridges .2 I crossing the landscape. These are the hummocky accumulations ofpebbly debris that t settled out ofstagnant, slowly melting glacial ice about 13,000 years ago. ~ i' :i: I I ~ I v i

Crooked ridges with steep sideslopes characterize the Loess Hills of western Iowa. They are composed of thick deposits of silt carried by the wind from the adjoining Missouri River valley during seasons when glacial meltwater flood sediments were exposed. There is a sharp contrast between prairie and encroaching 16 woodlands in this topographic setting. 17 Glacial erratics are boulders of igneous and metamorphic rock, native to geographic regions well north of Iowa. 7be erratics in this Black Hawk County pasture were carried into Iowa by glacial advances over 500,000yearsago. They were concentrated at the land surface by later erosion, which removed the fine-grained deposits once surrounding them.

7bese shallow wetlands are a series of g lacial kettles on Doolittle Prairie State Preserve in Story County. A subtle drainage system connects them, as noted by the soil moisture and vegetation patterns. These linked "prairie potholes" mark a route taken by glacial meltwater through a maze ofs lowly disintegrating glacial ice about 13, 000 Circular depres­ years ago. sions, some filled with water or clumps of trees, mark the location ofsinkholes in this Clayton County aerial view. Gary I lightshoc, Iowa State Univcrsily Sinkholes form by :I collapse of thin soil and unstable rock Dendritic drainage into underground patterns crease these crevice or cave cropped fields with openings. Shallow branching routes along aquifers are vul­ which precipitation I nerable to contam­ runoff is channeled into ination problems in n"/ls, creeks, and rivers. this geologic set­ 7bis effective drainage I ting. Though most network has reshaped I common in north- the glacial plains left af­ eastern Iowa, sinkholes are also seen in Floyd and Mitchell counties and in the ter southern Iowa's last I Burlington area ofsou theastern Iowa. contact with glaciers, over 500,000 years ago. 18 The discharge ofwater from Cold Water Spring crosses a sen·es ofrock riffles as it flows away from a bluffof dolomite bedrock. Springs develop where groundwater flow is intercepted by the land surface, usually along the steep sides of valleys.

Long continuous rock bluffs, called palisades, line the Upper Iowa River valley. These picturesque clijfs result from the river eroding against dolomite, a resistant rock unitformed 450 million years ago. Such scenic landscapes in northeastern Iowa reflect the presence ofsedimenta,y bedrock fonnations close to the land surface.

This inside view ofa cave entrance at Maquoketa Caves State Ar1 Bettis Park illustrates an example of karst topography. Such features also include springs and sinkholes, landforms which result from groundwater movement slowly dissolving shallow limestone or dolomite bedrock.

The oldest bedrock formation visible anywhere in Iowa outcrops at Gitchie Manitou State Preserve in Lyon County. The distinctive reddish cast ofthe Sioux Quartzite is seen here along An outcrop ofsedimen­ the edges of 'Jasper tary rock displays Pool," an 1800's­ horizontal layering, era quany on the which reflects the rock's preserve. These origins in a marine durable, quartz­ environment. Vertical rich rocks are 2.6 fractures, caused by later billion years old. earth stresses on the Glacial erratics of bn"!tle dolomite, contri­ this formation are bute a blocky appearance easily recognizable to the outcrop. These and may be found various planes of for many miles to weakness are flowpaths the southeast. for groundwater movement.

Jean Prior 20 The preservation of unique or GEOLOGY Of dramatic geologic features has been a significant goal in the establishment of many of Iowa's state parks, and an IACIIOIE understanding of the geology of these park lands can enhance our apprecia­ tion of Iowa's natural heritage. It is to SlAlErAII this end that the Geological Survey Bureau is undertaking a program to BRIAH J. WITZKE summarize the geologic features of our state parks, beginning appropriately at Backbone. The rocks so wonderfully dis­ A narrow and precipitous ridge of played in Backbone State Park were rock, once termed the "Devil's Back­ originally deposited as lime sediments bone," towers prominently above an in a shallow tropical sea that covered entrenched meander loop of the the Iowa area about 430 million years Maquoketa River north of Dundee in ago, a time geologists term the Silurian Delaware County. This ridge provided Period. These sediments were chemi­ both the inspiration and namesake for cally altered to form rock composed of Iowa's first state park, which now dolomite, a magnesium and calcium encompasses a region of river bottoms, carbonate mineral, with scattered wooded slopes, and dramatic rocky nodules of chert. The Silurian rocks at cliffs. Backbone State Park was Backbone belong to the Hopkinton dedicated in 1920 to preserve the Formation, an interval of dolomite natural beauty of this special area for strata that forms a productive part of the enjoyment of future generations. the Silurian aquifer across much of As we move beyond the 75th anniver­ eastern Iowa. Solutional openings, sary of Iowa's state park system, we fractures, caves, and active springs are mindful of the important role our provide evidence of water movement public parks play in providing recre­ through these strata at Backbone. ation, education, and inspiration for Fossils are preserved in the rocks both young and old alike. We owe a at Backbone as natural molds or as debt of gratitude to the foresight and silica (quartz) replacements. The wisdom shown by the Iowa leaders lower strata display an abundance of who established our state parks as corals and sponge-like lasting treasures for all the people. stromatoporoids, all fossils of long­ extinct forms. The upper strata are crowded with molds of clam-like ledges and crevices in weathered Silun·an­ brachiopod shells, many oriented as age dolomite form the backdrop for this they would have appeared in life. family outing in the late 1890's at Geologists have termed these shell-rich Backbone State Park. layers the "Pentamerus Beds," named

23 by a complex record of erosion and sedimentation on the Iowa landscape. Eastern Iowa was not covered by glacial ice during the last glaciation, the Wisconsinan, but significant modification of the park's landscape occurred as ice sheets spread into the north-central part of the state. A large amount of sediment was delivered to the eastern Iowa valleys during the period of maximum glacial cold about 16,000 to 21,000 years ago. Iowa was in a periglacial zone; frost action and erosion were intense, and the valleys of Backbone park filled to a level about 25 feet above the present floodplain. Remnants of this valley filling are preserved in the park as terraces of sand and gravel. Also, wind-blown sand and loess deposits associated with this glacial episode D:1ryl Smilh, Univcrsi1y of Northern Iowa accumulated along large southeast­ Forested rocky bluffs dominate the pictur­ trending ridges forming "paha." Such a esque views seen throughout the park. feature extends southeastward from the park's old fish hatchery. A complex cumulative history after the characteristic brachiopod resulted in the rocky landscape we see fossil. The fossils seen at Backbone today in the park, amplified by the provide a glimpse of ancient life that latest stages of erosion and sedimenta­ once inhabited the tropical sea bottom. tion operating during the last 20,000 The rocks now seen at Backbone years or so. The geologic processes lay buried beneath younger rocks and that continue to modify the delightful sediments for untold millions of years. landscape of Backbone Park are slow It was the inexorable onslaught of by human standards, ensuring count­ erosion that ultimately exposed these less future generations the opportunity rocks at the surface. The bedrock to enjoy this special area along the surface in Iowa evolved in response to Maquoketa River. •:• recurring episodes of erosion, inter­ rupted by periods of renewed deposi­ tion and burial. In particular, the Ray ,\ndcrson waxing and waning of continental ice Rainwater mouing slowly through shallow bedrock along vertical and horizontalfractures sheets across Iowa over the last 2 dissolves the dolomite, resulting in caves and springs. Such "karst terrain "features are million years or so was accompanied visible at Richmond Spring, a popular stop within the park.

24 25 7be Mississippi River flows through a narrow valley between Davenport and Rock SATELLITE IMAGES Island- Moline. Streaked deposits of Of IOWA LANDSCAPES wind-blown sand and silt cross the landscape between the Missis­ sippi and its tributa,y, James D. Giglierano the Wapsipinicon River.

Satellite images taken from over400 miles in space pro­ vide a unique perspective on Iowa's landscape. Broad geologic features can be seen underlying farm fields, forests, roads and towns. Geological forces have modi­ fied these landscapes for thousands ofyears, while human activity is a recent, but also significant agent ofchange. 7be wide Missouri River valley in Fremont County was excavated by glacial meltwaters. Since then, the river has meandered from side to side, leaving the scour marks evident here. Today the river is confined to a narrow portion These views were taken by the Landsat 5 spacecraft and of its floodplain by engineered levees, but the Flood of '93 again covered are shown in 1alse color. " Blue and green represent much ofthe area between the bluffs. bare soils with varying degrees of moisture. Pink and red indicate healthy pastures and forests. Open water is black, while roads and towns are white and magenta.

7bisjune 1991 image reveals the broad arc of the Algona glacial moraine across Kossuth County. Remnants of countless lakes and wetlan ds are seen as darker areas be­ neath the bare soils ofdrained and plowed crop land. 26 27 Living

with the Land . • •

In anticipation ofIowa's sesquicentennial, Iowa Geology highlights the state's natural beauty as reflected in its land­ scapes. La.ndscapes are one ofthe most obvious aspects of the state's geology. A change in appearance ofthe terrain is usually the first tip-offthat a change in geologic materials occurs beneath the ground. Satellite images show us the breadth and scope ofdifferences in terrain, and that these features coexist with the effects ofhuman activity. Differences in geologic materials need to be recognized at both local and regional scales. Within a bold northeastern Iowa rock bluff lies the essence ofan aquifer that below ground supplies thousands ofIowans with drinking water. Within the flow ofa spring lies the oppor­ tunity to measure how groundwater quality responds to chang­ ing agricultural practices. And in the uncontrolled rush of groundwater from a well in Belle Plaine is a reminder that we don't always know what to expect. Beneath the landscapes we live on today are older materials from land--and seascapes that existed here in the geologic past - sea floors, coral reefs, shore lines, coastal swamps, tropical river systems, and melting ice sheets. In a practical sense, we live with these buried landscapes as well, for we depend on their characteristics in many ways. We need to understand Iowa's past and present landscapes, their shapes, depths, and composi­ tions in order to bring reliable information to bear on the environmental and resource issues oftoday and tomorrow.

Jean Cutler Prior Editor

Turkey River Mounds State Preseroe Clay ton County 28