the geology of north america as illustrated by native american stories

The Geology of North America as Illustrated by Native American Stories by Robert G. McWilliams 1

The Geology of North America as Illustrated by Native American Stories

Robert G. McWilliams

Professor Emeritus Department of Geology

Miami University Oxford, Ohio 45056

[email protected]


Introduction: Why Stories? Stories are widely used for teaching science at all levels (Eisen and Laderman, 2005; Isabelle, 2007; Konicek-Moran, 2010). Stories are particularly well adapted for teaching outdoors where other types of teaching aids are unusable. Stories can quiet restive audiences and command their attention. Stories can be memory devices for organizing major ideas. Stories provide rich context science teaching methodology that is easily adapted to a wide range of learners with the use of the Internet as illustrated in this book. Specifically, the stories and demonstrations in this book are intended to help teachers and their students achieve the first category of the National Science Education Standards (NSES) namely, Unifying concepts and processes in science by providing teachers and their students with a simple but powerful idea to help them understand the natural world. In addition, this book addresses one of the particular objectives of Earth and Space Science in grades 5 – 8, namely the development of an understanding of the geosphere (crust, mantle and core) as it relates to the other components of the Earth system. Furthermore, the stories and demonstrations in this book are specifically intended to help high school teachers and their students understand the dynamic equilibrium of crustal movements, geochemical cycles in Earth systems during geologic time. The NSES (p.188), states that approximately half of high school students will need a great deal of assistance and concrete examples to understand these concepts. Lastly, the stories in this book give teachers and their students an opportunity to view science through the culture of another people in another time, which in turn provides teachers and their students the opportunity for classroom interaction and critical thinking about the differences between scientific and non-scientific explanations of natural phenomena. What follows is a combination teacher’s manual and classroom activity book. I’ve formatted it for easy reproduction and adaptation by teachers of all levels. It is written in pretty much the way I told it to over 1,700 elementary and secondary school teachers to whom I taught geology in the field between 1986 and 2010. Those teachers encouraged me to adapt the Native American stories and to develop the demonstrations described in this narrative and it is to them that it is dedicated. The story of Turtle Island The this story comes from the Woodland Indians who originally lived in the area south of the Great Lakes between the Appalachians and the Mississippi River. The Miami Indians for whom the Miami River and Miami University of Ohio were named were Woodland Indians. I taught geology at Miami University and lived only a few miles (km) from the Miami River for over 35 years. I’ve always had great interest in and admiration for Native Americans and I therefore particularly enjoy telling this story (adapted from Burland, 1985). A very long time ago, the people lived in the sky because the earth was covered with water. In the sky, there lived a beautiful woman who was the daughter of a powerful chief. The chief thought his daughter was sick and asked the tribal healer to cure her. The healer told the woman to sit next to a tree in the sky, where the people lived.


Then the healer told his assistants to dig a large circular trench around the roots of the tree. They dug so far that the woman, the tree, and the earth clinging to its roots fell from the sky. For this reason the woman is called Woman-Who-Fell-From-the-Sky. The swans saw the woman falling from the sky and so they gathered her up on their wings just before she fell into the World Ocean. The swans carried her to Great Turtle, the oldest and wisest of all the animals, set her on his back and told Great Turtle: She has no place to live. The great turtle summoned all of the animals and said: The tree that fell from the sky and that is now on the bottom of the world ocean, has attached to its roots sacred earth. We need someone to dive to the bottom and bring some sacred earth to the surface. Without hesitation, Duck dove into the sea. Even though Duck was a powerful swimmer he couldn’t dive deep enough to even see the bottom of the ocean. Then Beaver tried. Beaver was gone a long time but even though Beaver could see it, he couldn’t touch the bottom. Otter plunged and managed to touch bottom but had to return immediately for air. The animals thought that the project was so hopeless that hardly anyone noticed when Old Lady Toad, the homeliest and most ridiculed of all the animals dove into the ocean. Old lady toad was gone for so long that everyone thought she drowned. When she finally emerged, she climbed up on the back of the great turtle and spit out the sacred earth that she had gathered from around the roots of the tree which fell from the sky—and died. Great Turtle remained silent and when he was certain that all of the animals understood the necessity of Old Lady Toad’s sacrifice, he said: This is sacred earth and it has the power to grow. And it did. It grew into the place where Native Americans lived and called Turtle Island. Turtle Island is the continent that we now call North America. Turtles are among the most primitive and oldest vertebrates. Turtles first appear during the time of the dinosaurs, during the Mesozoic, but unlike the dinosaurs they are still thriving. Some turtles are very hardy and can live for a hundred years. When you first see a turtle, you might mistake it for a rock. But then you quickly realize that a turtle is a moving, living organism. I don’t claim North America is an organism but I am saying that like a turtle, North America is slowly moving across the globe. Furthermore, at first glance one might think a turtle is a simple, uncomplicated animal. But if you look closely you immediately discover that the animal that lives between two rock-like shells is as complicated and beautiful as any other creature. To someone who is not a geologist, North America might seem like a huge slab of rock covered flat-lying layers of sand and gravel. But if you travel around North America you quickly discover that the rocks below the flat-lying rocks of the plains are wonderfully deformed and exceedingly complicated rocks of all types. You will also discover if you travel, observe, and think long enough, that the deformed and complicated rocks that underlie the plains are the foundations of ancient mountains that have been eroded flat. The story of Turtle Island says that in the beginning there were no continents and that somehow the “sacred earth” of the ocean was drug up and the continents began to grow. What is this “sacred earth”? As a geologist and storyteller, I say that what the story calls “earth” are the mountains from which continents are assembled. And furthermore, I


suggest that the sum of time it took to create both mountains and continents deems them worthy of great reverence. Geologic Chronology In everyday speech, geologists divide the time span of the earth’s history into four intervals. The most recent, the current interval is the Cenozoic Era that began about 65 million years ago at approximately the time dinosaurs became extinct. The preceding interval, the Mesozoic Era, the “ age of dinosaurs” began about 250 million years ago. The Paleozoic Era, the “age of invertebrates” begins about 540 million years ago, at the same time that invertebrate fossils first become common. The earliest interval, the Precambrian Eon includes all the Earth’s history from the very beginning of the Earth about 4.6 billion years ago, to the beginning of the Paleozoic (Figure 1).

Period Began Eon Era Period Millions Evolutionary Events Of Years Ago __________________________________________________________________________________________________

Quaternary 2.5 First Humans

Cenozoic First Grasses Tertiary 65 First Large Mammals

_______________________________________________________________________________ Cretaceous 145 Mesozoic Jurassic 200 First Birds and Mammals Triassic 250 Beginning of Age of Dinosaurs Phanerozoic _______________________________________________________________________________ Permian 299 Pennsylvanian 318 First Reptiles Mississippian 360 First Winged Insects Paleozoic Devonian 416 First Trees and Amphibians Silurian 443 First Land Plants and Insects Ordovician 488 First Corals Cambrian 542 First Fish and Shellfish ____________________________________________________________________________________________________ Precambrian Oldest Rocks 4600 Beginning of the Solar System Figure 1

Geologic Time Scale and Major Events


This informal division of geologic time is comparable to the fourfold division of human history. The Precambrian is analogous to prehistoric time, the part of human history before writing and about which comparatively little is known. The Paleozoic is analogous to ancient history, the time of the earliest civilizations in Mesopotamia and Egypt. The Mesozoic corresponds to the medieval interval following the fall of the Roman Empire. The Cenozoic is roughly comparable to the modern era that began with the Italian Renaissance. (For more detailed information about geologic chronology, go online to http://en.wikipedia.org/wiki/Geologic_time_scale.) Geologic Time Although the simplified division of geologic time is intuitive, geologic time is not. A million years strains our understanding and a billion years is incomprehensible. Imagine counting at the rate of one digit per second without stop. How long would it take to count to a million? The answer is more than ten days. How long would it take to count to a billion? The answer almost 32 years! At the same rate it would take over 140 years to count to 4.6 billion–the age of the Earth. Here’s another visualization. Consider the time span of the Earth’s history as equal to the distance from the tip of your nose to the tip of your extended arm, approximately one yard (meter). One swipe of a fingernail file on the tip of the fingernail of your middle finger would erase the distance represented by the time span of humans on Earth. Mountains arise from slow almost imperceptible crustal movements but the Earth is very, very old and there is lots of time for small movements to create mountains and for small mountains to grow to large mountains and for large mountains into rows of mountains that are squeezed together into continents. What are Mountains? In ordinary speech we call a high point of land a mountain. That definition works for ordinary conversation but doesn’t work for geologists. The Earth is 4.6 billion years old and only the “recent” mountains, mountains created less than 600 million years ago, are still recognizable as high points of land; all the really old mountains have been worn flat or have been swept into the sea. Moreover, there are high points of land that aren’t mountains. For example, the highest point near Oxford, Ohio, where Miami University is located, is the Rumpke landfill (garbage dump) that is approximately1000 feet above sea level. On the other hand, Elk Ridge, across the highway from Miami University Geology Field Station, near Dubois, Wyoming is about 8,000 feet above sea level and about four times higher than any place in Ohio, and yet, neither Elk Ridge nor in any place in Butler County, Ohio are mountains. Therefore, geologists have to look for and use indirect evidence to locate and interpret the truly ancient mountains. Archeologists try to figure out the history of ancient people, but the people are gone and most of their works are destroyed. Most often archeologists have to excavate to find even the trace of the foundation of what used to be a dwelling. Therefore, archeologists use indirect evidence such as trash heaps and the types of materials used in construction to infer how ancient, now-gone people lived. Likewise, geologists use indirect evidence to figure out the origin and history of the ancient, now-vanished mountains.


There are three types of indirect evidence that are indicative of both ancient and modern mountains. The first of these indicators is deformed sedimentary rock. Sedimentary rock is composed of the residues of rocks eroded from the mountains and is deposited most commonly by water but also can be deposited by wind (air) and ice. When a sedimentary rock layer is deposited, it is laid down horizontally. A sedimentary rock layer is not like a rug that mimics the uneven surface on which it rests. Instead, like snow, a sedimentary rock layer is deposited horizontally even if the surface on which it is deposited is bumpy and potholed. Probably the most familiar example of deformed rock is tilted sedimentary rock layers. Tilted sedimentary rock layers are actually parts of the giant wrinkles spanning tens of miles (km) called anticlines and synclines. The part of a wrinkle forming an arch is called the anticline. The part of a wrinkle forming the trough is called the syncline. The low end of a tilted rock layer points in the direction of the center of the syncline and the high end points to the direction of the center of the anticline. (For useful illustrations and additional information about anticlines, go online to http://en.wikipedia.org/wiki/Anticline. For information about folds go to http://en.wikipedia.org/wiki/Fold_(geology)). For information about faults go to http://en.wikipedia.org/wiki/Fault_(geology). The second familiar indicator of rock deformation is a place where sedimentary rocks have been broken by compression or stretching. The fissure between broken rock layers is called a fault. In short, tilted, wrinkled, sedimentary rock layers and (or) broken, faulted sedimentary rock layers indicate the rocks have been deformed by compression or stretching. Igneous and metamorphic rocks are the third type of indirect evidence for mountains. Of course, like folded and faulted sedimentary rock, igneous and metamorphic rocks also indicate deformation when bands of minerals in the rock are contorted and twisted, but the point I am making is that even undeformed igneous and metamorphic rocks indicate the crust has moved and built a mountain. Igneous rocks are rocks that were melted by the Earth’s interior heat. Lava is molten rock (magma) that hardened on the Earth’s surface and is the best-known igneous rock. The molten rock that intrudes other rocks on its ascent to the surface and then solidifies below the surface is called intrusive igneous (plutonic) rock. Metamorphic rocks are rocks whose minerals have been re-crystallized by the Earth’s pressure without melting. This may seem contradictory or even impossible because pressure causes ice to melt. But ice and water are important exceptions to the otherwise almost universal rule that pressure prevents melting. Rock at the surface would melt at this temperature but the pressure of the surrounding rock beneath the surface is so great that the atoms in the minerals cannot expand, and therefore cannot melt. The pressure is so great that instead of melting, the atoms in the minerals re-crystallize without melting into denser, metamorphic minerals. (For a concise and well-illustrated elementary discussion of sedimentary, igneous, and/or metamorphic rocks go on line to http://en.wikipedia.org/wiki/Rock_(geology). In summary, geologists define both modern and ancient mountains as places where there has been deformation caused by crustal movement. Crustal movement and deformation


are recognized by the presence of one or all of the following: deformed and faulted rocks of any kind and by the presence of igneous rocks and metamorphic rocks. Rock Forming Minerals The story of Turtle Island tells us North America grew from the tiny bit of mud that Old Lady Toad dredged from the bottom of the world ocean and spit out on Great Turtle’s back. One of the essential themes of the Turtle Island story is that tiny, seemingly insignificant changes over the incomprehensively long spans of geologic time bring about almost miraculous growth. The atoms of elements are the smallest building blocks of the rocks that compose the mountains and that, in turn, comprise the continent. The atoms of the 92 natural elements chemically combine with themselves and other elements to form compounds also called molecules. Geologists call the compounds that constitute rocks minerals. There are more than 4,000 geologically created compounds called minerals. But the group of minerals called silicates, like Old Lady Toad’s tiny mouthful of mud, is by far the most important building block of rocks. (For useful additional information about minerals go online to http://en.wikipedia.org/wiki/Mineral. For information about felsic minerals go online to http://en.wikipedia.org/wiki/Felsic. For information about mafic minerals go online to http://en.wikipedia.org/wiki/Mafic. Silicate minerals are composed of the elements silicon and oxygen with or without other elements. Rocks composed principally of iron rich and magnesium rich silicate minerals are called mafic rocks. Those composed mostly of aluminum rich and potassium rich silicate minerals are called felsic rocks. The continents and the mountains that comprise the continents are mostly felsic rocks, of which granite is the best-known example. The crust beneath the sea floor and that supports the continents is mafic rock of which basalt is the best-known example. The most important distinction between the continents and the surrounding Earth crust is that continents are composed of predominately granite-like felsic rocks, and the surrounding and underlying crust is composed of basalt-like mafic rocks. North American Mountains The most obvious North American mountains are the multiple rows of mountains west of the Great Plains and scattered over the western third of the continent called the Cordillera. The Cordillera begins in the Aleutian Islands, and extends inward from the Pacific Coast and southward through Canada and the United States, onward through Mexico, Central America, and South America. The swath of mountains called the Cordillera includes the Rocky Mountains, the Sierra Nevada, the Cascades, the Coast Range, the Brooks Range, the Basin and Range and other mountains too numerous to mention. (To see more maps of North American mountains and the distribution of rocks in North America go online to http://en.wikipedia.org/wiki/North_america and scroll down to physical geography.) To understand the confusion of mountain names, it helps to know that the names and boundaries of these mountain chains, ranges, groups, and individual mountains are purely arbitrary. For example, US Highway 27 travels north from Hamilton through Oxford, Ohio where Miami University is located into Indiana. Between Hamilton and Oxford the highway is called US 27. Once it enters the city limits of Oxford it is first called Patterson Avenue, then takes a left turn and is called High Street and then it turns right


where it is called College Street, then a left turn where it is called Church Street until it crosses the railroad when it is once again called US 27 until it encounters the next town in Indiana. The point is that names and dimensions of mountains are as arbitrary as street and road names that vary depending on location and who is naming them. More importantly, individual mountains and clusters of mountains are simply local manifestations of titanic deformations affecting the entire continent. The crustal movement and deformation that built the Cordillera began in the Precambrian, continued through the Paleozoic, the Mesozoic, and the Cenozoic and are still being deformed and uplifted today (Figure 2, on next page).


Figure 2.

Distribution of North American mountains. Shaded areas include both the sub aerial continental plains and the submerged continental shelf. The Appalachian Mountains include the Marathon Mountains of west Texas, the Ouachita Mountains of Oklahoma and Arkansas, the exposed igneous and metamorphic rocks in the New England states of the U.S., in New Brunswick, Nova Scotia, and Newfoundland in Canada.


The Cordillera meets everyone’s expectation of what a range of mountains should be. They are high, and rugged with steep slopes and deep valleys, igneous and metamorphic rocks are common throughout, and the sedimentary rocks are deformed and faulted. The second most obvious mountain group is the Appalachian Mountains east of the Central Plains along the east coast of the continent (Figure 2). The central portions of the Appalachians extending from Pennsylvania to Georgia are clearly mountains. But the mostly buried Appalachian Mountains extend south and westward into the Ouachita Mountains of Oklahoma and the Marathon Mountains of Texas. Likewise, the deeply eroded Appalachians extend northward from Pennsylvania into the Catskills of New York, the White Mountains of New Hampshire, and continue northeast through Maine and into Nova Scotia where they abruptly end in the Atlantic Ocean. Like the Cordillera, the Appalachian Mountains began to form in the Precambrian and underwent dramatic deformation, metamorphism and intrusion by igneous rocks throughout the Paleozoic. Unlike the Cordillera, however, deformation in the Appalachians ended in the early Mesozoic. Erosion and deposition beginning in the middle Mesozoic has partially worn down and partially buried the original mountains. Geologists can recognize the remains of the Appalachians, even where they worn down to sea level as for example, in Maine or where they are mostly buried as for example, between Georgia and Oklahoma, by presence of deformed rocks, igneous and metamorphic rocks. The least obvious but most extensive North American mountain group are the mountains that comprise the vast plain north of the Great Lakes called the Canadian Shield (Figure 2). The Canadian Shield is composed of at least four, perhaps as many as seven groups of Precambrian mountains, all of which were squashed together, eroded flat and buried when the Paleozoic began. Once again geologists are able to recognize and distinguish the surviving foundations of these mountains by the presence of deformed rocks, igneous and metamorphic rocks. Although what is called the Canadian Shield is only well exposed in Canada, the same cluster of Precambrian mountains underlies the entire continent of North America and is well exposed in the bottom of Grand Canyon. The Canadian Shield is what makes North America a continent. In the geologic sense of the term, a continent is a raft or a platform felsic silicate rock created by squeezing together Precambrian mountains. The Growth of North America Here’s how you can re-enact the story of North America’s growth. While sitting at a table (or while imagining you are), put your left elbow and palm on the edge of the table closest to where you are sitting. Now pretend that the edge of the table represents the Earth’s equator and your palm represents North America. The tips of your fingers represent what is now northern Canada; your wrist represents what is now southern Mexico. Your thumb is on the side that represents the east coast and your little finger is on the side of your hand that represents the west coast. At the beginning of the Paleozoic, 540 million years ago, what we now call North America was located so that what we now call Canada was on the east coast, what we call Mexico was on the west coast. During the Precambrian, more than a half billion years ago, North America was slightly south or astride the equator. Since that time North America has been moving counter clockwise, north and west–like a single swipe of a windshield wiper. Now rotate your arm at the elbow so that your palm rotates in a smooth arc across the table. During the Paleozoic,


the heyday of the invertebrates, roughly between a half billion and a quarter of a billion years ago, North America was in the tropics. During the Mesozoic, the time of the dinosaurs, roughly between a quarter and a tenth of a billion years ago North America was in the subtropics. During the Cenozoic, the time of the modern mammals, North America moved into the temperate and polar regions. At the beginning of the Paleozoic North America was about three fifths of its present size. So now, curl your pinky and ring finger into a fist behind your palm and repeat the windshield-wiper arc up from the table edge. While rotating your arm and hand counterclockwise slowly bring your ring and pinky back parallel to your other three fingers. The purpose of this demonstration is to show that during North America’s trip across the Pacific Ocean it grew by colliding with and adding bits and pieces of the ocean floor and other continents—like rain and snow on the leading edge of a windshield wiper. The wrinkled western two fifths of North America that accumulated during North America’s counter clockwise sweep across the globe is now called the Cordillera. What about the Appalachians? The answer is that during the Paleozoic North America rotated roughly thirty degrees counterclockwise into the tropics north of the equator. What we now call Europe, Africa, and South America were parts of a single continent called Gondwanaland during the last half of the Paleozoic. At the end of the Paleozoic, Gondwanaland collided with the east coast of North America, welding all of the world’s continents into a single continent called Pangaea. (You can see a color animation of the breakup of Pangaea by going online to http://en.wikipedia.org/wiki/Supercontinentf.) You can re-enact the collision that created the Appalachian Mountains by holding your fingertips ninety degrees from each other (in the same way basketball players sign time out). Then by rotating your right palm toward your left, like a closing a door you can see that the collision of your fingertips is analogous to the formation of the northern Appalachians when the part of Gondwanaland that we now call Europe collided with North America. The collision of the rest of your fingers and palms are analogous to the creation of the central Appalachians when the part of Gondwanaland that we now call Africa collided with North America. By closing the heels of your hands and forearms together you re-enact the creation of the Appalachians usually called the Ouachita Mountains in Oklahoma and Marathon Mountains in Texas when the part of Gondwanaland we now call South America collided with North America. Beginning in the early Mesozoic, the giant continent called Pangaea broke up into the present seven continents. During this time of breakup North America continued its counterclockwise rotation to its present position. What about the Canadian Shield? There are at least four groups of ancient mountains that comprise the Canadian Shield and comprise the core of North America. Although we don’t know the all the details, the same types of collision, accretion, and rifting that created the Appalachians and the Cordillera created each. Therefore, ocean floor sediments– Old Lady Toad’s mouthful of mud– are transformed into mountains, and mountains are transformed into continents. Where do the ocean floor sediments come from? The answer is that they come from the erosion of the mountains. When the mountains are eroded the sediments become the plains that cover the area between the mountains. Rivers and glaciers erode the plains and dump them in the ocean. Atoms and molecules are the building blocks of the minerals comprising


sediments and sediments are the building blocks of rocks. Rocks are the building blocks of mountains–mountains are the building blocks of continents. Story of Mount Mazama and Crater Lake One of the reasons I became a geologist is because I grew up in western Oregon, surrounded by volcanic rock and only 90 miles from Crater Lake. The ancestors of the Klamath people were living in Oregon when Mount Mazama erupted, creating Crater Lake, 6006 years ago. I adapted the following story from the one that Chief Lalek, an eighty-year old Klamath Indian, told William M. Colvig, his nineteen-year old visitor in 1865 (Clark, 1953). One time when Chief of the Below World was on top of Mount Mazama, he saw and fell in love with Loha, a Klamath woman who was cherished by all who knew her. Chief of the Below World told Loha of his love and asked her to return with him to his lodge inside Mazama. There, he said, she would live forever. But the tribal wise men warned Loha that even though they also loved her, she could never, nor should she ever, want to live forever. Following their instruction, she refused Chief of the Below World by hiding from him. When Chief of the Below World learned that the people had unanimously refused his proposal, he became furious and in a voice like thunder swore that he would destroy all the Klamath with the Curse of Fire. Through the stars surrounding his home. The mighty form of Chief of the Above World descended from the sky and the two spirit chiefs began a furious battle on the mountaintop. The mountain shook and crumbled. Red-hot rocks as large as the hills hurtled through the skies. Burning ash fell like rain. Chief of the Below World spewed fire from the mouth of the mountain. Fleeing in terror, the people found refuge in the waters of Klamath Lake. Then the oldest of the tribal wise men raised his voice so all could hear. Only a living sacrifice will turn away Chief of the Below World’s revenge. But who among us will offer himself as a sacrifice? No young person will want to make the sacrifice answered the second oldest wise man. You and I have but a few more years to live. We should be the ones to throw our torches and ourselves into Chief of the Below World’s fire pit. After a period of silence, the two old men lighted their pine torches and started toward Mount Mazama. From the waters of Klamath Lake the people watched in astonishment as their torches, brilliant against the night sky moved to the crest of the volcano. There the old men paused, and then, with their torches high above their heads, jumped into the fiery pit. The generosity of the old men energized Chief of the Above World. Once more the mountains shook and the earth seemed to tremble on its foundation. When Chief of the Below World was finally driven back into his home, Mount Mazama collapsed upon him and after many years rain filled the great crater. Distribution of Volcanoes and Origin of Crustal Movement Volcanoes are not randomly distributed over the Earth but instead are arranged along belts or chains (Figure 3).


Figure 3 Distribution of the major boundaries between the tectonic plates and associated chains of volcanic mountains. Parallel lines and arrows show separating plates along rift zones. Converging plates along subduction zones are shown by saw teeth.

There are three major volcanic belts. First is the chain of volcanoes that divide the world’s oceans along the Mid-Atlantic Ridge, the East Pacific Rise, and the Mid-Indian Ridge. The second is the Pacific Ring of Fire (also known as the circum-Pacific Belt) that encircles the Pacific Ocean. The third is the chain of volcanoes extending from across the Mediterranean from Gibraltar, across the Himalayas into Indonesia (Figure 3). Not coincidentally, earthquakes are common below each of these three volcanic belts. Not only are both the volcanic and earthquake zones found together, both belts encircle the Earth in the same way as the seams encircle a baseball. Just as with the seams of a baseball, if you follow a chain of volcanoes around the globe you will discover eventually it returns to the starting place. (To see a detailed map of earthquake epicenters along plate boundaries that mostly coincide with volcanoes along plate boundaries and for additional information, go online to http://en.wikipedia.org/wiki/Earthquake.) The fact that chains of volcanoes and earthquakes encircle the planet suggests what earth scientists have now demonstrated, namely that the Earth’s crust is cracked and that the crust is moving.


Size of Volcanoes Nearly solid, relatively cool magma produces the smallest volcanoes, pyramid-shaped mountains with a base typically tens of miles (km) or less broad and a total height less than a mile (1.2 km) called cinder cones. Wizard Island in the center of Crater Lake is a cinder cone. Very fluid, extremely hot magma produce the largest volcanoes, pancake-shaped mountains with bases typically more than tens of miles (km) wide at the base and a mile (km) or higher are called shield volcanoes. The cones in Hawaiian Volcanoes, and those in Haleakala National Parks and the Hawaiian Islands themselves, are shield volcanoes. The differences in size and profile of cinder cones and shield volcanoes are the result of the differences in the distances which very hot fluid lava and relatively cool viscous lavas can spread from the vent before solidifying. Sometimes volcanic magmas alternate between relatively cool and very hot. Volcanoes due to these types of magmas are called composite volcanoes (but also called stratovolcanoes) because their size and profile are about half way between those of a shield volcano and a cinder cone. Mount Mazama, which holds Crater Lake, is a composite volcano. Sizes of Volcanoes and Types of Plate Movement Earth scientists now say the Earth’s “ hard crust” is like the shell of a cracked egg. The “hard crust”, or lithosphere is broken into about a dozen large, irregularly shaped, 60 mile-thick (100 km) fragments of lithosphere called plates (Figure 3). (To see 17 pages of color diagrams showing the relationships between the lithosphere, the asthenosphere, the mantle and different types of plate movements, search Google for Lithosphere and Asthenosphere and then click on Google Images. The Hypertext Transfer Protocol, HTTP, is much to long to print here). First, a rift zone is a deep fissure created where the plates separate by moving in opposite directions (Figure 4, on next page).


Figure 4

Sketch of different types of plate movement on a simplified globe showing how rifting, subduction and transform movements are related.


The fracture in the rift zone reduces the pressure on the very hot rock at the bottom of the crack. The release of pressure allows the rock to expand and melt. The molten rock becomes lava that floods to the surface forming shield volcanoes along the line of separation. Second, a subduction zone is where crustal movement pulls one lithospheric plate under another, as when one playing card slides under another when the deck is shuffled (Figure 4). The pressure generated as one plate is pulled under and collides with the overlying plate, deforming and metamorphosing the rocks along the subduction zone. This is why deformed rocks and metamorphic rocks are two of the primary indicators of ancient mountains—the very forces that generate igneous and metamorphic rocks also produce mountains. Pressure within and below the lithosphere is so great that rock cannot melt. But when subduction pulls wet rock 60 miles (100 km) and more below the surface the wet rock melts and produces giant plumes of magma. Now I need to digress and explain why subduction of wet rock creates magma. It turns out that mixtures sometimes have lower melting temperatures than do pure substances. For example, pure tin melts at about 200 º C and pure lead melts at about 300º C but a mixture 60% tin and 40% lead melts at about 180º–20º lower than either pure lead or pure tin! (This is why solder melts before the pure metals it is used to join.) The same is true with the wet silicate rocks pulled 60 miles (100 km) or more beneath the surface by subduction. A mixture of water and silicate rock melts at a lower temperature than the surrounding dry silicate rock. The rate of subduction and the amount of water mixed with the subducting silicate rock varies and hence the conversion of high-pressure rock into magma is erratic compared to the rate of magma formation in a rift zone. Therefore, instead of producing shield volcanoes, a subduction zone produces composite volcanoes, which result from the episodic eruption of cold and hot magma. The volcanoes that encircle the Pacific Ocean, called the Ring of Fire and the volcanoes of the Mediterranean, Himalayan-Indonesian Belt are all subduction volcanoes. In addition to the kinds of movement in rift and subduction zones, there is a third type of plate movement called a transform. A transform is where crustal movement pulls one plate parallel to another, as when two cars pass each other in opposite lanes of a two-lane road. Transforms result because the Earth is a sphere and transform faults connect the movement of separating plates (rifting) to converging plates (subduction). Transform faults typically do not create volcanoes. You can approximate the relationship between rifting, subduction, and transform movement on the Earth by interlacing your fingers and touching opposite thumbs (like when you are getting ready to twiddle your thumbs). In so doing you create a sphere that represents the Earth. Now, pull your hands apart and let your right thumb slide under your left thumb. Where your right thumb slides under your left represents subduction. Where your fingertips separate from the base of your fingers represents rifting. Where your fingers slide past each other in opposite directions represents transform faulting. Also notice, as you do this demonstration, your hand-made sphere remains the same circumference because the expansion created by the rifting fingers is equalized by the contraction caused by the subducting thumb.


Consequently, the different kinds of plate movement produce the different sizes of volcanoes. First, rifting along the oceanic ridges releases pressure and thereby creates very hot magma that becomes giant shield volcanoes. (Hot spots also produce shield volcanoes, most famously in the Hawaiian Islands. The cause and nature of hot spot volcanoes is currently a subject of debate among geoscientists. (For a concise description of the alternate hypothesis for the cause and significance of hot spots go online to http://en.wikipedia.org/wiki/Hot_spot_(geology).) Second, subduction around the Pacific Ocean and along the Mediterranean Sea eastward into Indonesia produce not only deformed and metamorphic rock but also create the alternately very hot and relatively cool magma that feeds intermediate-sized composite volcanoes. Third, the smallest volcanoes, cinder cones, are found on and near both shield and composite volcanoes and are not the result of any specific type of plate movement. Lastly, transform movement deforms and metamorphoses rock but normally doesn’t produce magma or volcanoes. Cause of Plate Movement The story of Crater Lake and Mount Mazama asserts the mountain is the aftermath of the struggle between Chief of the Above World and Chief of the Below World. Present day earth scientists agree except that they say volcanoes and mountains result from the struggle between heat and gravity. If it seems hard to understand how gravity can cause the crust to move and create mountains, here’s a demonstration that makes it more comprehensible. Stand facing a table with your left middle finger resting lightly on the edge. Next, extend your right arm as if you are pointing to something off your right shoulder. Now raise your right foot off the floor and support yourself with your left foot. In less than a minute you will find yourself being pulled, at first very slowly, and then rapidly to your right and thus demonstrates how gravity pulls things out of balance and causes them to move. In the above demonstration, your shoulders and extended arm represents a crustal plate. Your left shoulder represents the hot part of the plate next to the rift zone and your extended right hand represents the cold part of a plate sliding into a subduction zone. The point of the demonstration is to illustrate that crustal movement is triggered by the cold end of the crustal plate sliding into a subduction zone and as it does so it pulls the other end of the plate away from the rift zone. The cold end of the plate slides into the subduction zone because it is denser. The rising of the hot end of the plate is analogous to a hot air balloon that rises when the air inside is heated. Likewise, the sinking of the cold end is also analogous to a hot air balloon that goes down when the air inside cools. To recapitulate: gravity pulls a cold dense section of the lithosphere into the asthenosphere. As it does so, gravity stretches and fissures the brittle lithosphere elsewhere, thus creating a rift that allows magma to escape and create a hot, less dense section of lithosphere. Why the Lithosphere Is So Easily Broken We think of the plates that comprise the lithosphere as thick and strong only because we are small in comparison to the size of the Earth. The Earth is about 8,000 miles (9,600 km) in diameter and consequently the 60 mile-thick (100 kilometer-thick) lithosphere comprises less than one percent of the Earth’s diameter and therefore the plates are not only very thin, but are also very weak in comparison to the size of the Earth.


The Earth’s Physical and Chemical Properties If you imagine that the four fingers of your left hand represent Earth’s radius, the distance from the surface to the Earth’s center, each finger represents about 1000 miles (1,200 km). Starting from the center, your pinky represents the thickness of the Earth’s solid iron-nickel core and your ring finger represents the Earth’s liquid iron and nickel core. Together, the solid and liquid portions of the Earth’s core comprise about half the Earth’s radius. Notice the upper and lower core have the same chemical compositions but opposite physical properties. The core doesn’t have any known effect on movement of the plates. Your middle and index fingers together represent the thickness of the mantle. The 2,000 mile-thick (2,400 km) mantle is composed of mafic silicate rock, that is, rock composed of silicate minerals rich in iron and magnesium. The entire mantle is solid, not liquid. The aesthenosphere and the lithosphere together comprise the uppermost 120 miles (144 km) of the mantle. The aesthenosphere has approximately the same composition as the rest of the mantle and is different only in being especially soft and pliable – like peanut butter. The overlying lithosphere of which the plates are composed is likewise roughly the same composition as the asthenosphere and the rest of the mantle but instead of being pliable is easily broken—like peanut brittle. The important thing to understand is that the difference between the lithosphere and the asthenosphere, like the difference between the inner and outer core (and for that matter, ice and water) is physical, not chemical. I like to use the differences between peanut butter and peanut brittle to emphasize the differences between the asthenosphere and the lithosphere. Both peanut butter and peanut brittle have similar compositions because both are mostly peanuts. Likewise, both the asthenosphere and the lithosphere are predominately composed of mafic silicate rock. Furthermore, just as peanut butter is soft, putty-like, and pliable and peanut brittle is rigid, hard, and brittle so is the asthenosphere soft in comparison to the brittle lithosphere. Why are the continents and the mountains made up of granite-like felsic silicate rocks and the lithosphere and the rest of the mantle made up of basalt-like mafic silicate rocks? The reason is because during rifting and subduction parts of the lithosphere melt. Although the lithosphere is composed predominately of mafic silicate minerals, it also contains felsic minerals. The felsic minerals melt before the mafic minerals and therefore, every time the lithosphere begins to melt, felsic minerals are extracted from the lithosphere and concentrated in the mountains which in turn, are squeezed together to form the continents. The partial melting of the lithosphere during rifting and subduction accomplishes a separation of similar compounds just as when distillation separates pure water from seawater, a solution of salt and other compounds. In summary, the innermost half of the Earth, the core, is composed of iron and nickel. The inner half of the core is solid and the outer half is liquid. The core has no known effect on crustal movement that creates the mountains and the continents. The upper half of the Earth is composed of solid mafic silicate rock. The 60-mile (100 kilometer) thick asthenosphere is an exceptionally soft and pliable peanut butter-like layer of the mantle beneath the brittle, rock-like 60-mile-thick lithospheric layer. The lithosphere differs from the rest of the mantle because it is brittle and contains gigantic “islands” of felsic silicate rock called continents.


The Story of Turtle Island Continued The most insightful and pedagogically useful part of the Turtle Island Story is the second half (adapted from Burland, 1965). It turns out that Woman-Who-Fell-From-the-Sky was pregnant. When her time came she gave birth to two boys. The first was Tsenta. The second, Taweskare, was so impatient he couldn’t wait to be born in the normal way. In a rambunctious fury he hacked and forced his way out of his mother from below her armpit and in so doing caused his mother’s death. Tsenta was slow and gentle. Tsenta created the broad plains and the wide meandering rivers. He created the useful plants like the oak and the pine that we use for shelter and he created the gentle animals, deer and rabbit that we use for food. Taweskare was impetuous and destructive. Taweskare destroyed the plains and made mountains, he transformed the wide meandering rivers into the roaring torrents that cut canyons. He created poisonous plants and the cactus and he made fierce and dangerous animals: the bear and the wolf. But Tsenta is more powerful than his brother and was able to drive him away from the east. Tsenta uses all the processes that wear down the surface, weathering, land sliding, wind, water and glacial erosion to wear the Precambrian mountains into the nearly flat surface that we now call the Canadian Shield and covered the parts of the Precambrian mountains that underlie the Gulf Coast and the Central Plains with sediment. Tsenta has partly, but not completely leveled the Paleozoic mountains we call the Appalachians. From the debris of the Appalachians he is making the coastal plains and continental shelf along the eastern and gulf coasts of North America. Taweskare still controls the west where there are earthquakes, volcanoes, hot springs and geysers that are the consequences of the new mountains he is still making. Even though Taweskare still runs amok in the west, Tsenta is undoing Taweskare’s work to create the Great Plains. (Pat Betteley, a former student and now a sixth grade science and social studies teacher in Madison, Ohio collaborated with illustrator Robert Rath to create a comic script of this story published in the May/June 2011 (volume 27, no 8 issue of Faces magazine.) The concept that unites all of these stories is the idea that death begets birth and that birth causes death. The great turtle made certain that the animals understood the significance of Old Lady Toad’s death before he told them that the sacred earth has the power to grow. What Chief of the Below World creates, Chief of the Above World destroys. What Taweskare creates, Tsentsa destroys–endlessly. One of the central ideas of Native America mythology is that in order to create, something must be destroyed. (For an discussion of the universal mythic themes depicted in the Turtle Island story and the story of Crater Lake, see Sullivan, 1989.) North America West of the 100th Meridian Geologists, geographers and almost everyone else know that western North America is different from eastern North America (Figure 5, on next page).


Figure 5

Map showing the location of the 100ø Longitude (100th Meridian) and the geographic differences between western and eastern North America.


The west is “high and dry”. The really high mountains of the west begin above two miles (2.4 km) above sea level. In contrast, the highest mountains of the east are scarcely more than a mile (1.2 km) above sea level. The rain comes from the Pacific and the Atlantic Oceans. The two mile-high (2.4 km) mountains of the Cordillera prevent the eastward migration of rain from the Pacific. The result is that west of the 100th meridian (longitude) a year’s worth of rain is usually less than a 20 inches (50 cm) per year (except along the Pacific Coast) and often less than 10 inches (25 cm). In contrast, the rain clouds of the Atlantic Ocean and the Gulf of Mexico move almost unobstructed throughout the east where a year’s worth of rain is commonly more than 20 inches (50 cm) and in many places more than three feet (1 m). The West is high because the Pacific plates are being pulled under western North America. Subduction produces magma that rises up, heats and thereby causes the western edge of the continent to expand. The ocean is flooding the eastern edge of North America because of the combined effects of glacial melting and the expansion of seawater as it warms. (The ocean is rising on the Pacific Coast, too, but the Pacific Coast is rising faster than the ocean.) On the west coast, the mountains emerge from the sea. On the east coast, the oceans flood the plains. Barren rock characterizes the mountainous west because in most of the west there isn’t enough rain for plants to flourish. On the other hand, abundant rain allows forests and meadows to cover the plains of the east. Valleys and mountains are characteristically steep and narrow in the west because the rate of uplift is more rapid than the rate of erosion. Broad valleys and gently rolling hills characterize the east because abundant rain collapses and erodes steep slopes more rapidly than uplift can create them. The East is different from the West in another way. North America east of Glacier National Park (near the intersecting borders of Idaho, Montana, and Canada) and north of the Missouri and Ohio Rivers was covered by continental ice beginning about two and a half million years ago until between 15 and 10 thousand years ago. In eastern North America mile-thick continental ice shaved off the hilltops and filled the valleys with glacial sand and gravel. But west of Rocky Mountain National Park (west of Denver) and Glacier National Park, Taweskare uses mountain glaciers to cut deep, vertical-walled U-shaped valleys and instead of cutting off mountain peaks, he sharpens them into spires called horns. (For a map of the extent of North American mountain glaciation the Cordilleran Ice Sheet and of North American continental glaciation, the Laurentide Ice Sheet, go online to http://jan.ucc.nau.edu/~rcb7/namQ.jpg). Tsenta uses continental ice to make eastern North America flatter. Contrary as ever, Taweskare uses mountain glaciers to make western North America more jagged. Sacred Wheel of the Arapaho The Wind River Indian Reservation, the home of 2500 Eastern Shoshone and 5000 Northern Arapaho, is located less than 20 miles from the Miami University Geology Field Station. The Sacred Wheel of the Arapaho, also sometimes called the Hoop is a supple branch that has been bent into a circle to look like a snake swallowing its tail (Figure 6, on the second following page).


The only genuine illustration of the Sacred Wheel is a photograph in a very scarce anthropological monograph written by G. A. Dorsey in 1903. Fortunately, you can download the entire book by going online to Google Books and searching for Sacred Wheel of the Arapaho. (The Hypertext Transfer Protocol, HTTP, is much to long to print here). There you can see a photo of the actual Sacred Wheel in Plate 1, between pages 12 and 13. Dorsey’s description of the complex symbolism of the Sacred Wheel is found on pages 12-21.)


Figure 6

Sketch showing the Sacred Wheel of the Arapaho, the distribution of North American plains and mountains, and a simplified rock cycle.


According to the Arapaho, the snake swallowing its tail represents the world ocean surrounding Turtle Island. The world ocean has no beginning and no end. You can travel from the Arctic Ocean into the Atlantic. From the Atlantic you can go to the Pacific and from the Pacific you can go to the Arctic and so doing realize that the Atlantic, and Pacific Oceans are arbitrary names for different parts of a continuous worldwide ocean. The Arapaho also say that the snake depicted is a small harmless garter snake. I surmise that this is to indicate that nature, like a snake, at first seems threatening or even terrifying. But if you understand nature, just as if you understand this little snake, you realize that there is nothing to fear. The Sacred Wheel is decorated with four equally spaced clusters of eagle feathers. Among other things, the four clusters represent the four directions: north, south, east and west. But for my purpose, the most important point is that the feather clusters symbolize two of the pairs of opposites that govern our lives. The first pair of opposites is the east and the west. The east represents day and the west represents night because the Sun appears in the east and disappears in the west. Day is the end of night and beginning of night is the end of day. This pair of opposites control each day of our lives. The second pair of opposites is the north and the south. The south corresponds to summer and the north corresponds to winter. These two opposites control each year of our lives. The Sacred Wheel implies but does not depict the third pair of opposites: above and below. Above and below are implied where the four directions intersect at the center of the Sacred Wheel. This third pair of opposites are more plainly illustrated in the story of Turtle Island when the four animals, Duck, Beaver, Otter, and Old Lady Toad dive into and return from the world ocean four times. In the story of Crater Lake Chief of the Above World and Chief of the Below World go up and down as they first create and then destroy Mount Mazama. Above and below correspond to the birth and death of each creation and creature. The Rock Cycle I claim that in the most general terms, the Sacred Wheel represents the same concept that scientists recognize as the conservation of matter (Figure 6). Geologists call this continuous recycling of the Earth’s minerals and rock the Rock Cycle. No new matter is being created. Old rocks containing the same atoms and molecules that existed when the universe began are simply being used over and over to create different combinations of new rocks. I divide the rock cycle into four episodes: uplift, erosion, subsidence, and deposition. The four directions represented by the four clusters of eagle feathers on the Sacred Wheel can remind us of these four episodes. New mountains are growing on the rising western edge North America because that is where subduction is pulling the plates that comprise the Pacific Ocean floor under the North American plate. As gravity pulls the Pacific plates under the North American Plate, the rocks of the Pacific plates not only compress fold and metamorphose the leading edge of the continent; they trigger the eruption of magma that heats the leading edge of the North America and cause it to arch upwards.


In the north, the flat surface called the Canadian Shield is the result of erosion cutting down to almost sea level the four groups of Precambrian mountain ranges, mountains that originally were as high as the present-day Cordillera. The east reminds us that the eastern edge of North America is sinking. The reason the east coast is sinking is because the eastern edge of the continent is cooling and thereby becoming denser. The rate of sinking of eastern North America, compared to the rate of uplift in western North America is very slow, but the present-day rate of flooding is rapid because glacial ice is melting and seawater is expanding as it warms. The south, particularly the Gulf Coast and the Florida peninsula and the adjacent continental shelf are composed of sediments that are in some places more than six miles (7.2 km) thick exemplify the effects of deposition. These sediments were eroded from the mountains to the west and the east and now partly bury the southern Appalachians. How does the power of the below world make North America move? The heat produced by the radioactive elements of the Earth’s interior are the power of the below world. When this heat escapes as magma along the rift and subduction zones it causes the crust to rise. Gravity causes the crust to sink when it cools and becomes denser. The sinking of the cold lithospheric layer and the rising of the hot lithospheric layer cause the crust and all the continents to move. What causes erosion and deposition? In this case, the power of the above world is the power of the Sun’s heat that creates clouds by evaporating oceans, lakes and rivers. When the clouds cool and condense, gravity pulls rain, snow and ice downhill and erodes the continent. When rivers reach the ocean they deposit gravel and sand that become the continental plains, the continental shelf and the mud that covers the ocean bottom.

What we call the beginning is often the end and to make an end is to make a beginning.

The end is where we start from. T.S. Eliot (Little Gidding, No. 4 of Four Quartets)


References Burland, C. A., 1985, North American Indian Mythology, New York, Peter Bedrick Books. Clark, E., 1953, Indian Legends of the Pacific Northwest, Berkeley, University of California Press. Dorsey, G. A., 1903, The Arapaho Sundance: The ceremony of the offerings lodge. In Field Columbian Museum Publication 75, Anthropological Series v. iv, 12-21. Chicago: Field Columbian Museum. Eisen, A. and G. Laderman, 2005, Bridging the two cultures: a comprehensive interdisciplinary approach to teaching and learning science in a societal context. Journal of Science Teaching. National Science Teachers Association. HighBeam Research. 22 Feb. 2011 <http://www.highbeam.com>. Gill, S.D., 1989, Mythic Themes. In Native American Religions: North America, ed. L.E. Sullivan, 157-166. New York: Macmillan Publishing. Isabelle, A. D., 2007, Teaching science using stories: the storyline approach. Science Scope. National Science Teachers Association. HighBeam Research. 22 Feb. 2011 <http://www.highbeam.com>.

Konicek-Moran, R., 2010, Even more everyday science mysteries for inquiry-based science teaching. Arlington Virginia: NSTA Press.

National Science Education Standards, 1996, Washington, DC: National Academy Press, 262 p. Acknowledgements I wish to extend special thanks to Ohio Board of Regents Improving Teacher Quality Program and to Miami University for generous financial support for the Environmental Sciences for Elementary School Teachers Program. Thanks also to the following for insightful reviews and suggestions for the improvement of this manuscript. P. Betteley, J. Constible, R. Flinn, S. Hall, N. Harr, R. Lee, J. Mason, M. Parkes, C. Pliske, E. Soldo.

the geology of north america as illustrated by native american stories

Documents