DOCUMENT RESUME SE 061 223 ED 417 088 Weisgarber, Sherry L.; Van Doren, Lisa; Hackathorn, AUTHOR Merrianne; Hannibal, Joseph T.; Hansgen, Richard Hands On Earth Science. TITLE Ohio State Dept. of Natural Resources, Columbus. INSTITUTION 1997-00-00 PUB DATE NOTE 21p. Ohio Dept. of Natural Resources, Div. of Geological Survey, AVAILABLE FROM 4383 Fountain Square Court, Bldg. B-2, Columbus, OH 43224-1362. Classroom Teacher (052) PUB TYPE Guides MF01/PC01 Plus Postage. EDRS PRICE Classification; *Concept Formation; *Earth Science; DESCRIPTORS Elementary Secondary Education; Geology; *Hands on Science; Learning Strategies; *Minerals; Models; Plate Tectonics; Science Activities IDENTIFIERS Ohio ABSTRACT This publication is a collection of 13 hands-on activities that focus on earth science-related activities and involve students in learning about growing crystals, tectonics, fossils, rock and minerals, modeling Ohio geology, geologic time, determining true north, and constructing scale-models of the Earth-moon system. Each activity contains detailed instructions and a list of necessary equipment. (DDR) ******************************************************************************** Reproductions supplied by EDRS are the best that can be made from the original document. ******************************************************************************** HANDS ON Division Of Geological Survey Eat TH SCIENCE \AO CRYSTAL GARDEN by Sherry L. Weisgarber 00 00 0 This often used project provides wonder and excitement as the crystals grow. Materials: 6-7 barbecue charcoals or stones (1 to 2 inches across) shallow bowl (aluminum pie pan works fine) 4-6 tablespoons table salt 4-6 tablespoons liquid laundry bluing (see NOTE below) 4-6 tablespoons water 1 tablespoon ammonia (be careful using ammonia around children) food coloring Collect several small pieces of limestone, brick, coal, or barbecue charcoal. You may want to try a bowl of each to determine which material grows the best crystals. Place the charcoal or stones clus- tered together in the bowl. Mix all of the ingredients together, except the food coloring, in the order listed using the same amount of salt, bluing, and water for each batch made. Pour the mixture very slowly over the stones with a spoon. The mixture may not be dissolved depending on the number of tablespoons of ingredients used. You may want to make different batches using different amounts of ingredients to see which works best. Drop food coloring over the coated stones. Using different colors produces a variegated crystal garden. Crystals should begin to form in about 20 minutes and continue growing for a day or two. Adding any excess mixture to the bottom of the bowl over the next few days may keep the garden growing longer. This creation will crumble very easily, so don't move it around too much. NOTE: Laundry bluing comes in a small blue bottle and generally can be found in the laundry sec- tion of a grocery store next to the starch and bleach products. SOURCE: Kids create!, Laurie Carlson; and Nevada Mining Association, Lois K. Ports. U.S. DEPARTMENT OF EDUCATION Office of Educational Research and Improvement PERMISSION TO REPRODUCE AND EDUCATIONAL RESOURCES INFORMATION DISSEMINATE THIS MATERIAL HAS KrbiCENTER (ERIC) BEEN GRANTED BY T 's document has been reproduced as eceived from the person or organization originating it. Minor changes have been made to improve reproduction quality. Points of view or opinions stated in this TO THE EDUCATIONAL RESOURCES document do not necessarily represent INFORMATION CENTER (ERIC) official OERI position or policy. BEST COPY AVAILABLE 01-110 DEF:6.1.1-1\AENT OF NATURAL R_ESOUR.CES Division Of Geological Survey HANDS ON Ed,N11-7-11--1 SCIENCE EGG TECTONICS by Sherry L. Weisgarber Plate tectonics, or the continental drift theory, was first suggested in 1912 by the German scientist Alfred Wegener. The theory, which states that the Earth's surface, or crust, is divided into six to nine major plates that slowly move and change in size, was not widely accepted until the late 1960's. The theory supposes that all the continents were once part of a supercontinent called Pangea. This theory explains why continents that are now widely separated from each other possess rocks and fossils of the same extinct plants and animals. Geologic events and features such as earthquakes, volcanoes, moun- tain ranges, hot springs, and geysers also can be explained using plate tectonics. The slow (1-4 cm per year) movement of tectonic plates causes one of three types of boundaries: divergent boundaries, where plates separate; convergent boundaries, where plates collide; and transform boundaries, where plates slide past each other. The following activity simulates these plate boundaries using a cracked eggshell. Materials: 3 (or more) hard-boiled eggs 3 (or more) water-based markers Gently tap the eggs repeatedly on a table while rotating them to produce cracks all around the eggs. Trace along the major cracks with a water-based marker. Gently squeeze the eggs until slight movement of the shell pieces occurs. Look for places where pieces of the eggshell separate. This area represents a divergent boundary. Most divergent boundaries on the Earth are hidden beneath the oceans and are characterized by volcanism, earthquakes, and massive heat flow due to molten rock (magma) rising up from the mantle, which is the thick layer of rock separating the crust from the core at the center of the Earth. The Mid-Atlantic Ridge on the bottom of the Atlantic Ocean is an example of a divergent bound- ary; here the North American Plate and the Eurasian Plate are separating, causing sea-floor spreading and new oceanic crust to form. Next, look for places where two pieces of eggshell are colliding. This area represents a convergent boundary. Two events can occur when plates converge. If denser oceanic crust collides with lighter continental crust, the oceanic crust will buckle under the continental crust down into the mantle. This process is called subduction and is characterized by earthquakes, rock deformation, and volcanism. The volcanic Cascade Range of the Pacific Northwest was formed by sub- duction of the Juan de Fuca Plate under the North American Plate. If two equally dense continental crusts collide, both plates will resist being subducted. In this process, the continental crust folds and deforms into a mountain range. The Himalayas are an example of a mountain-building episode which began 25 million years ago and is still occurring today as India travels northward, colliding with Asia. Finally, look for places where one piece of eggshell slides past another. This area represents a transform boundary. The crust is not destroyed here as it is at a convergent boundary, nor is crust created as it is at a divergent boundary. As the two plates slide past each other, earthquakes occur. The San Andreas fault in California is an example of this type of boundary. NOTE: After this experiment, use the eggs to illustrate the layers of the Earth. Cut the egg in half. The shell represents the crust. The thick egg white represents the mantle. The egg yolk represents the core. SOURCE: Terrific Science & Math (Miami University), Fall 1993; and Earth and Its Resources, Creative Teaching Press. 3 OHIO EDEF'ARTMENT OF NATURAL RESOURCES HANDS ON Division Of Geological Survey EARTH SCIENCE W) EVERYONE LOVES FOSSILS by Sherry L. Weisgarber What exactly are fossils? Fossils are the remains of past life. This definition includes anything that is a clue to past life, such as the bones of dinosaurs and mammoths, the tiny shells of one-celled animals, trails and footprints, worm burrows, leaves, tree trunks, seeds, and microscopic spores of fungi. Fossils occur in sedimentary rocks such as limestone, shale, and sandstone. Because Ohio is cov- ered with sedimentary rocks, fossil collecting is a popular hobby for many Ohioans. How do fossils form? Some of the plants and animals that died in the geologic past were buried by sediments before they could decompose. After burial, the soft tissue of the organism slowly decom- posed, but the harder parts of the plant or animal remained intact. The sediments eventually were hardened into rocks, preserving the harder parts of the organisms, such as bones, shells, teeth, leaves, and stems, that we find as fossils today. Fossils are preserved in a variety of ways. The hard parts of some organisms are permeated by minerals in a process called permineralization. Petrified wood is an example of permineralization. Many plants are preserved as compressions. In this process, the remains of the organism are squeezed by the rocks that surround it until all of its liquids and gases are removed, leaving only a thin film on the surface of the rock. The hard parts of many Ohio fossils were dissolved by ground water moving through the sediment or rock and replaced with minerals in the water. This process is called replacement. In Ohio, common replacement minerals are pyrite and silica. Ground water also may dissolve the original material without replacing it with other minerals. If the sediment hardened into rock before the fossil was dissolved, the rock retains the imprint of the fossil, which is called a mold. A mold may later be filled with other sediment or minerals precipitated from ground water, making a cast of the fossil. A cast is a replica of the original fossil in a different material. The following classic activity illustrates the concepts of molds and casts. Each student will need the following materials: plastic fork sea shell, twig, or other small object petroleum jelly paper cup 1/4 to 1/2 cup plaster of paris 1/4 to 1/2 cup water small plastic margarine dish Cover the small object, representing a dead organism, with a thin layer of petroleum jelly to keep it from sticking in the plaster of paris when it hardens. Put the plaster of paris into the margarine dish. Add water gradually to the plaster of paris, stirring gently with the fork until the plaster is thick and creamy. Gently tap the bottom of the dish onto the table to force out any air bubbles in the plaster. This layer represents the soft sediment that the organism fell into when it died. Let the plaster harden for about 1 minute so the object won't sink to the bottom of the container. Press the small, petroleum-covered object into the plaster and allow it to dry thoroughly, preferably overnight. Remove the object from the plaster. You now have a mold of your object. Leave the mold in the container and coat the entire surface of the dry plaster with a thin layer of petroleum jelly. Mix another batch of plaster of paris in the paper cup. Pour this mixture over the mold and allow it to dry. This layer represents the overlying sediments or the minerals precipitated from ground water that fill in the mold, making a cast of the original object. When the plaster is dry, separate the cast from the mold. It should separate easily along the layer of petroleum jelly. You now have a fossil cast and a fossil mold of your original object. SOURCE: Ohio fossils, ODNR, Division of Geological Survey; Water, stones, & fossil bones, National Science Teachers Association; and The earth science book, Dinah Zike. OHIO DEPARTMENT OF NATURAL RESOURCES 4 HANDS ON Division 0-F Geological Survey SCIENCE E.d15.1:7-11-1 OHIO GEOLOGY WORD SEARCH A B C D E FICEJ LLSNAGQ R S T IVWOYRAYCDEFEH MSALTNTPQPSTNVG Y E A B C D E F H H I I M N L S S PQSNTUFWLYQABCRUFGA J CTMOOEORUTUVWBYEMEC I D E L O T I T K I SNSYAETTUAVT I I R S E M A K P O R M T U I Z A B A N A N G S E XYYEBL I EDGE I JKLENPMDRSBR I D E S K O G N O P O S V W X Y Z L A N D S L TUFWAYZSACDETGRAVELM N O S E V A C H V H X R T S S C E I FGH I JKLSNOASQSTRV I OZOELAP F T H C I JKLMNH PNOR I U V C Look for these words, all related to Ohio geology, within the arrowhead diagram. The words may read forward or backward, and across, down, or diagonally. Further information on these words and their relation to Ohio geology is included in the Ohio Geology Crossword Puzzle (Hands On Earth Sci- ence No. 5). ISOTELUS BRINE KAMES CAVES LANDSLIDES CLAY COAL LIMESTONE EARTHQUAKES MAMMOTHS PALEOZOIC ERIE FLINT RIVERS FOSSILS SALT SAND GAS SANDSTONE GLACIERS SHALE GRAVEL GYPSUM TEAYS TOPOGRAPHIC ICE IRON TRILOBITE Created by Sherry L. Weisgarber and Lisa Van Doren OHIO DEPARTMENT OF NATURAL RESOURCES 5 HANDS ON Division Of Geological Survey SCIENCE \AO OHIO GEOLOGY CROSSWORD PUZZLE ACROSS The period of the Paleozoic Era that includes the oldest (about 450 millon years old) rocks exposed in Ohio. They are 4 exposed in southwestern Ohio and contain the state fossil. These glacial features are channels gouged into bedrock surfaces by abrasion by rock fragments contained in the 6 glacier and high-pressure, sand-charged meltwater along the bottom of the glacier. The largest and best known are on Kelleys Island in Lake Erie. This mineral resource is commonly associated with 33 DOWN. In the late 1880's, Findlay, Ohio, was famous for its 8 plentiful and cheap supplies of this mineral resource. This sedimentary rock formed by lithification of clay-size fragments. It is mined in Ohio for use in the brick industry. 10 This mineral resource forms in the same manner as 34 ACROSS. In Ohio, it is mined and used exclusively for the 11 manufacture of wallboard (sheetrock), although other uses include plaster of paris and as an additive in cement. A glacial feature composed of sand and gravel, generally in the shape of a conical hill. These features commonly are 13 mined for their sand and gravel or are used as sites for cemeteries. The era of geologic time in which all the surface bedrock of Ohio was formed. During much of this time, from about 600 14 million years ago to about 225 million years ago, Ohio was in tropical latitudes and covered by a warm shallow sea. Natural features in which water flows from a higher to a lower elevation. Many of these features in Ohio formed when 17 glacial meltwater eroded channels in bedrock or thick sediments. This geologic hazard happens where slopes are steep and rock layers weather easily. This phenomenon is common in 20 shales and clays of southwestern Ohio, southeastern Ohio, and along the Lake Erie shore. This type of map depicts the elevation of the land surface using contour lines and also shows lakes, streams, roads, 22 houses, and more. This rock is made up mostly of calcium carbonate and forms as a precipitate from sea water or by accumulation of shell 25 fragments on the bottom of tropical seas. This rock is mined for a variety of uses, especially as a construction material. 26 These elephantlike animals became extinct about 10,000 years ago. They lived in Ice Age spruce forests typical of Ohio at that time, so many fossil remains of these creatures have been found here. This mineral resource formed by the accumulation, compression, and alteration of plant remains deposited in wide- 27 spread swamps in Ohio about 300 million years ago. Ohio ranks second nationally in the consumption of this mineral resource for electrical generation. 29 This group of fossils is characterized by two grooves that divide the animal into three distinct lobes, giving these animals their name. These fossils are common in the Ordovician- and Devonian-age rocks of western Ohio. This huge river flowed northward across Ohio more than 2 million years ago and was destroyed by the glaciers. Its 30 valley and tributary valleys were filled with several hundred feet of glacial sediment and are now important sources of water (aquifers). more or OHIO DEPARTMENT OF NATURAL RESOURCES 6 cictur nnpv AVAILABLE 31 By Civil War time, Ohio was a leading producer of this mineral resource. Native ore was heated in a furnace using limestone for a flux and charcoal from trees for fuel. 32 Several specimens of this precious gemstone have been found in Ohio. It is the hardest mineral known and is used as an industrial cutting tool. It is speculated that the glaciers scraped up them up from Canada or the Upper Peninsula of Michigan and deposited them in Ohio. 34 Thick deposits of this mineral resource, also known as halite, precipitated from sea water during the Sil- urian Period, 400 million years ago. Two underground mines in Ohio produce this mineral resource from about 2,000 feet beneath Lake Erie. Ohio ranks fourth nationally in the production of this mineral resource. 35 A mineral resource formed by the decomposition of plant matter in glacially associated bogs. It commonly is used in soil mix. 36 At least 120 of these geologic phenomena have been experienced throughout Ohio since 1776, especially in western Ohio. DOWN Geologic features formed beneath the ground surface by dissolution of limestones and dolomites by weak 1 acids in ground water. These features can be found in the Silurian- and Devonian-age rocks of western Ohio. The remains or traces of past animal or plant life. 2 3 Tiny flakes of this precious metal can be found in nearly any stream in the glaciated portion of the state. It comes from rocks that were scraped up by the glaciers from Canada and deposited in Ohio. 5 This mineral resource is found in two types of deposits in Ohiobeneath coal seams in eastern Ohio and in association with glacial lakes. Two uses for this mineral are in pottery and bricks. 6 Masses of ice that flow in a specific direction and originate from the compacting of snow by pressure. Over two-thirds of Ohio was covered by at least three of these ice sheets during the Pleistocene Epoch (about 2 million to 10,000 years ago). 7 The raw material, especially of a metal, that is mined to be processed into a final product. 8 A pebble- to boulder-size sediment of variable composition. It commonly occurs with 12 DOWN. Many homes have this material in their driveways. 9 Genus name of the trilobite that is Ohio's state invertebrate fossil. A type of map that shows the distribution of rock units at the surface as if all overlying unconsolidated 11 materials have been removed. A fine- to coarse-grained sediment of variable mineral composition that was formed by erosion and carried 12 by glacial meltwater in Ohio to be deposited as outwash. This deposit and 8 DOWN are mined and used extensively as construction materials. This lake was formed when the glaciers deepened the basin north of Ohio, allowing a large meltwater lake 15 to form. 16 This era of geologic time began about 70 million years ago and continues to the present. Erosion rather than deposition was the dominant force during this time because Ohio was high above sea level. The most abundant mineral in Ohio 19,000 years ago. It has a low melting point, hardness of 1 to 2, and 18 specific gravity of less than 1.0. In many areas of the state this mineral was more than 1 mile thick. 19 This rock is composed of sand-size rock fragments cemented by calcite, silica, or iron. These rocks com- monly formed as beach, river-channel, or delta deposits. Ohio ranks first nationally in the production of building stone from this type of rock. These animals were related to the modern Indian elephant and became extinct about 10,000 years ago. 21 They lived in Ice Age grasslands, so their fossil remains are not common in Ohio. . 23 The period of the Paleozoic Era that includes the youngest (about 280 million years old) rocks exposed in Ohio. They are exposed in southeastern Ohio. Type of chemical used for radiometric dating. 24 28 This mineral resource is Ohio's official gemstone and has been used longer than any other mineral com- modity in the state. Items made from this resource by American Indians have been found from the Atlantic Coast to Louisiana. 33 This complex hydrocarbon formed when the plants and animals that lived in Ohio's shallow Paleozoic Era seas died and were chemically altered. In the late 1800's, Ohio was the leading national producer of this important energy resource. skeai apqs aludelBodol auolspurs treuund wad Dpzoared pups . lres aio uulolnopio s2an!.! auolsaum apspue! atm! suopoisew ao! umsda . sanooa stnounuetu mil snialosi . adoios! Ho !alma pia o!BoloaS sa apg sialogiS lulu silsso! swrenbillrea re03 ARP apzouaD spuourelp STLIaArD isn CRIOM The idea for this puzzle came from the New Mexico Bureau of Mines and Mineral Resources Lite Geology (Fall 1993) and Robert F. Kunst. Created by Sherry L. Weisgarber & Merrianne Hackathorn 411_0LE iEST. COPY HANDS ON Geological Survey Division 0-F SCIENCE ROCKS AND MINERALS ARE EVERYWHERE Ohio's rocks and minerals can be used for a variety of items. Match the rock or mineral to the item for which it is used. There may be multiple matches. sandstone dinner glass plastic toy oil clay gel toothpaste paper limestone peanut butter hand lotion gypsum paste toothpaste Kitty litter salt 14111411Ltt 1111111M1~1111, I 1 1411C 1 bakery cake icing bricks shale .AIAP cold tablets asphalt road coal sand/gravel dandruff shampoo electricity ANSWERS auolsatull la/tea/plies = pew lreqdse Aep `alegs = sppq = iaunqlntread MOD = oodunqs Hrupugp umscia = Bum aNeD fuaNeq . aucnsatuit = alseckpool alsed /Cep = lam Anpi auolsatuu 'ARID = Jaded Cep 'no = uonoi puey auolsatull 'auolspues = ssei2Jauulp Dgseid auolspues = alsecknool Ito = Created by Sherry L. Weisgarber and Lisa Van Doren 01-110 IDEF'A.1.7N/1E111- OF NATURAL R.ESOU R_CES HANDS ON Of Geological Survey Division SCIENCE Mdehd-T1-1 No. MODELING OHIO'S GEOLOGY by Joseph T. Hannibal, The Cleveland Museum of Natural History Geologic maps are representations of the geology of an area. For example, the geologic map of Ohio shows the distribution of bedrock belonging to six geologic systems, that is, rock laid down during corresponding geologic time periods. Geologic maps generally are colorful, and commonly are accom- panied by cross sections that help in their interpretation. Still, it's not always easy for the student to understand what these maps rep- resent. One hands-on way to help understand such maps is to make your own three-dimensional model. It is quite easy to make such a model of Ohioall you need is plaster, a mold shaped like Ohio, paints, and a geologic map of Ohio. Many craft stores sell plaster and molds for making plaster objects. If your craft store does not have an Ohio mold, the store can order molds of Ohio and other states from the Deep Flex Plastic Mold Co., Murfreesboro, Tennessee. Their Ohio mold produces casts that are 5.5 x 5.5 x 1.0 cm in size. Multiple molds can be purchased for classroom use. Inexpensive acrylic paints can be used for painting your model. Six colors will be needed for the top view and two additional colors for the cross-sectional view. A simple, page-size geologic map illustrating the geologic systems can be ordered from the Ohio Division of Geological Survey. To make your three-dimensional model, mix plaster according to the recipe on the container and pour it into the plastic mold. Let it dry for at least two hours. Then, using the geologic map of Ohio as a guide, paint the area representing rock belonging to each geologic system a different color. The top view will be easy it's the same as the map. The sides of the model will be more difficult, requiring an understanding of the tilting (dip) of the rock layers beneath the surface and a basic understanding of geologic principles. The accompanying illustration will help. When painting your model, be sure to remember that younger rock layers in Ohio overlie older layers; this is the Law of Superposition. In a classroom, students can either work in small groups or make individual models. The final model can be protected by spraying it with an acrylic fixative. Teachers may want to make a large-scale plaster map; directions for such a map are given in the reference cited below. Geologic maps also can be made using different colors of play clay or similar materials to represent rocks belonging to different systems. However, because of shrinkage during drying, these models will not be as attractive as well-painted plaster models. The geological gourmet might prefer to make edible geologic-map cookies. This project requires a state cookie cutter (available, for instance, from the Ohio Historical Society, 1982 Velma Ave., Columbus OH 43211). A simple sugar cookie recipe from any general cookbook can be used. A glaze frosting can be made using powdered sugar, a tad of warm water, and a few drops of food coloring; again, a recipe can be found in any general cookbook. At least six colors of frosting will be needed for a geologic map of Ohio. You can try making three-dimensional cookies by cutting out a thicker than usual cookie. However, if you are not an expert cookie maker you will find it difficult to frost the sides of the cookies, so it may be best to simply do the top view of the map. Add a chocolate chip to identify your city. One warningmaking edible geologic maps takes time! If this project is done for the classroom the cookies can be baked at home by the teacher or by parent volunteers the day before frosting in class. SOURCE: "A simple, inexpensive method for making a three-dimensional geologic model of your state," by Suellen Hopfer and J. T Hannibal, in On the rocks: earth science activities for grades 1-8, S. G. Stover and R. H. MacDonald, eds., SEPM (Society for Sedimentary Geology), 1993. OHIO 1:7EFAR.-T-MENT OF NATURAL RESOURCES 9 HANDS ON Division Of Geological Survey Ed4N1e.:TAI-1 SCIENCE UNDERSTANDING GEOLOGIC TIME by Sherry L. Weisgarber Time. A simple concept we take for granted every day. "I have a karate class in two hours." "One more day until the weekend." "My birthday is in eight months." "I have worked here for 12 years." "The Ohio Geological Survey originated nearly 160 years ago." "The Age of the Dinosaurs began 245 million years ago." "The Earth is 4.6 billion years old." Well, wait a minute. Maybe the concept of time, espe- cially geologic time, is not so simple. It's easy to comprehend the time span of "one more day until the weekend." However, it is not so easy to comprehend the time span of "the Earth formed 4.6 billion years ago. How much is a billion? One billion seconds from the beginning of 1996 would be the year 2029. How much is a million? If a person lived for 1 million days, they would be 2,740 years old. These analogies may help put into perspective the immensity of geologic time. We hope the following activity of making a human time line will help even more. This activity is easier to do outside. You will need an area approximately 260 yards in length, 260 yards of twine, and some masking tape. Mark off the twine in yards using the masking tape and a yard stick. The last yard measured should be marked off in feet. The last foot measured should be marked off in inches. Assign each student an event from the list below. The outdoor scale used here is 2 inches = 1 million years. The student representing the formation of the Earth should pace off 254 yards from the present. The rest of the students should then pace off their respective distances from the present for their assigned events. For example, the student representing the beginning of life on Earth would pace off 194 yards from the present, and the student representing the first reptiles would pace off 18 yards from the present. When the human time line is complete, start with the formation of the Earth and have the students shout out what event they represent and how long ago they happened. For example, "I am the first reptile. I appeared 330 million years ago." Remember, the student representing the beginning of the Earth will have to shout very loudly, as they will be more than two football fields away from "the present"! The students representing "recent" events, those events closer to the present, will be crammed together at the end of the time line. If the students cannot fit closely enough together, use longer pieces of tape to mark the event on the twine and have the students stand to the side. This activity can be done inside using a smaller scale, such as 1/10 inch = 1 million years. The time line can be made on adding machine paper and then taped to the wall. The students could also draw pictures of their events and tape them under the time line on the wall. For "recent" events, a larger scale could be used. This larger scale time line could be taped under the longer time line, indicating that much has happened in a relatively short period of time. SOURCE: Ranger Rick's nature scope: digging into dinosaurs, National Wildlife Federation; Historical geology of North America, by Morris Peterson, J. Keith Rigby, and Lehi Hintze, Wm. C. Brown Company Publishers; Understanding and collecting rocks & fossils, by Martyn Bramwell, Usborne Publishing; Fos- sils, rocks, and time, by Lucy Edwards and John Pojeta, Jr., U.S. Geological Survey. NOTE: Maps showing the geology and glacial deposits of Ohio are available from the Division of Geological Survey. Timeline starts on reverse OHIO DEPARTMENT OF NATURAL RESOURCES