Geology of the National Parks

Textbook: Science, Geology, and National Parks


Faces of presidents Washington, Jefferson, T. Roosevelt, and Lincoln carved into a mountainside.
Mount Rushmore
Credit: R.B. Alley

Your Geosc10 instructional team is made of people who love Science, Geology, and National Parks. We hope you, do, too, and if not, we'll try to show you why we do. These “big-picture” questions are probably more important than anything else covered in this class.

We humans have always had a love-hate relationship with our “tools.” Cars are great, but getting run over by one isn’t. Televisions are great, until you really want to have a heart-to-heart discussion with someone who is deeply engrossed in a playoff game. Science collects the wisdom of the world’s peoples, their experiences and insights, and then tests that wisdom repeatedly, revising and improving, to help us learn to do things we want. This may be humanity's greatest tool... but that also means that occasionally someone may not like it.

Sometimes, a person becomes unhappy when their idea loses to a better one. In the early 1600s, when Galileo advocated the idea that the Earth orbits the sun, Pope Urban VIII saw conflict with certain verses in the Bible (e.g., Psalm 93, “The world will surely stand in place, never to be moved”, or Psalm 104, “You fixed the earth on its foundation, never to be moved”; both quoted here from the New American Bible, although Urban VIII would have read them in Latin.) Some religious authorities of the time did not see any necessary conflict between these verses and Galileo’s ideas, and the Pope initially had been at least somewhat open to Galileo’s ideas. But, the Pope eventually turned Galileo over to the Inquisition over this supposed heresy, and the Inquisition forced Galileo to recant, sentenced him to house arrest, and banned his book and future publications. (It is an interesting question whether the problem was really Galileo’s sun-centered view, or whether the Pope got mad because Galileo's book featured a dialogue with the Pope's favored views spoken by the "loser.")

The papacy subsequently decided that the reality of the Earth orbiting the sun did not undermine scripture, and astronomers could do their job while the religious leaders did theirs. Indeed, rather interesting scientific discussions have been hosted by subsequent popes.

It remains that sometimes conflict arises between some members of some religious or other groups and some aspects of science. In 2005, for example, the state school board in Kansas changed their definition of science, apparently to enable teaching in science classes of ideas that repeatedly have been rejected as being nonscientific by courts and scientific organizations. After another election that changed membership, in 2007, the board restored to their definition that science is a search for natural explanations for what we observe in the world around us. We will have a chance to discuss these ideas later in the course, because Kansas and other states have continued to fight over the issues.

So, let’s look a little more carefully at what science is, and isn’t.

Why Science?

The reason for science is clear—tightly coupled to engineering and technology, science really works. The products of scientists and engineers are tested in the real world every day. Oil companies hire new geologists, geophysicists, and petroleum engineers when the old ones retire because those scientists and engineers really do find oil and make money for the oil companies. Congress funds biomedical research because it keeps lengthening our lives and curing diseases. You read this on a computer, designed using the principles of quantum mechanics, and using the remarkable discoveries of materials scientists and engineers.

High school teachers like to expound on the scientific method. Scientists do have a method of sorts, and it helps them achieve their results. But lots of people—astrologers, palm readers, telephone “psychics”—have methods that don’t get funded by industry and Congress. The typical industrial officer could not possibly care less how a scientist achieves a result, but only that the result is achieved.

Across campus, scientists are sometimes viewed as just another group for the sociologists to study. Scientists have their own tribes, mating rituals (!), and other social interactions. Scientists seek fame and fortune, lie, steal, and violate their mating rituals in much the same way that other humans do. The extremists in sociology have gone so far as to argue that science is only a social construct, one of many possible ones. This, however, is the kind of intellectual exercise that gets academics in trouble with the real world. Anyone with a little common sense knows that it is possible to have a cruise missile deliver a small exploding device to a selected building in another continent using some clever applications of Newtonian physics, and that no other human social construct can make a similar claim. Mere social constructs do not design new antibiotics that save millions of lives, either.

Science differs from other human endeavors in that its disputes are appealed to nature. In art, you cannot judge whether Picasso or Rembrandt was a “better” painter. You can study the brush work, perspective, social context, or whatever, and learn a tremendous amount about art from the discussion, but you cannot reach an objective decision on who is better. But if asked whether Aristotle’s or Newton’s physics work better, we can answer the question.

This is where the scientific method comes in. We study Aristotle’s ideas and Newton’s ideas until we figure out some way that they differ. This allows us to propose an experiment: if we do A, Aristotle expects B to happen, and Newton expects C. Then, we do A, and see what happens. If it comes out C, Aristotle is wrong. In reality, one test is never definitive—the fans of Aristotle might claim that the experiments were rigged, or the experimenters didn't really understand Aristotle's ideas and so did the wrong test. But after many tests, the answer becomes obvious. Science has then progressed—we’ve gotten rid of something that was wrong.

Science remains an exercise in uncertainty. If Newton “beats” Aristotle, that means Aristotle is wrong, but it doesn’t mean that Newton is right—maybe he’s just lucky, or pretty close, but not quite right. As it turns out, Newton’s ideas fail for things that are really small, really large, or moving really fast, and we have to turn to quantum mechanics and relativity. (But all that fancy physics reduces almost exactly to Newton’s description for things of size and speed that we usually deal with—bigger than atoms, smaller than galaxies, and much slower than the speed of light—so, Newton was and is useful.) Science thus cannot give the ultimate answers to anything, because we’re never sure whether we’re right, close, or lucky. We can only say that, if we act as if the scientific results are true, we succeed (in curing diseases, finding oil, etc.).

Science is an expensive way of learning about the world. Suppose you’re a farmer and you’re trying to feed yourself. You try an idea (say, burying fish heads with your corn seeds, or planting during the dark of the moon), and the corn grows well. So you do that every year. If it works, great. If it doesn’t work but doesn’t hurt, no big problem. If it actually makes things worse, well, you might starve, but not many other people are bothered.

Now, suppose you’re a modern farmer trying to feed 100 people. If you try something that actually makes things worse, many people may starve, and some of them may get really mad at you before they do. So, you start asking whether the fish-head works, and whether two fish-heads would work better, or whether other parts of the fish would be better, and so on. One test doesn’t do it—crops grow well most of the time, so most things you test (such as planting in the dark of the moon) will seem to work even if they really don’t help.

The modern solution is to have a scientist helping the farmer, trying things carefully, and trying them many, many times, figuring out which ones really work better, and communicating those results to others who are interested. All that testing takes a lot of effort, but it is cheaper in the long run for important things. Rather than 100 people each trying to feed themselves, and some failing and starving, we have a scientist, a farmer, a tractor manufacturer, a trucker and a grocer feed all hundred, freeing 95 to do something else. (Enjoy! You probably don’t have to spend the summer hoeing corn to keep from starving over the winter.) So, although science is expensive, for important things it is cheaper than ignorance. For unimportant things, living with a little more uncertainty may be easier.

Science has been wildly successful on simple questions: If I drop a rock, how fast will it fall? If I put a lot of a certain isotope of uranium in a small area, what will happen? If I use steel beams this big, in this pattern, how heavy a truck can drive over the bridge without breaking it? Most of physics, much of chemistry, and some of medicine fall in this “simple question” part of the world.

Science is gaining ground on some harder questions. Predicting weather or earthquakes, understanding and curing cancer, understanding and managing ecosystems and biodiversity—these are more complex, involve more interactions, and may have limits on predictability (chaos), but real, useful progress is being made. The research frontiers lie in these complex systems. Much of geology lies in complex systems, and we are in the midst of some great advances in geology.

Science has a ways to go on really hard questions, such as predicting how various actions will impact the working of society and the health and happiness of people. And science cannot address many questions—“How should society work?” is a value judgment, not a question of reality, and is not part of science.

Science is restricted to the search for natural explanations of the world around us. This does not mean that science opposes religion or claims that there is no God. (Some scientists may do such things, but many other scientists don’t.) Quite simply, no experimenter knows how to guarantee the cooperation of an omnipotent deity. A miracle, by definition, cannot be repeated reliably by anyone in any lab anywhere in the world, and so must fall outside of science.

In short, science is a human social activity but differs from other human social activities in that the ideas of science must be tested against reality. Science enjoys a special place in society because science is so successful. Science shows which ideas are wrong, and also identifies ideas that scientists cannot disprove. If we act as if these not-yet-disproven ideas are true, we are successful in doing things. These not-yet-disproven ideas remain conditional because we might find better ideas in the future. Science keeps track of what works and what doesn’t, to save future workers trouble. Science is a meritocracy—good ideas tend to rise to the top, no matter who originated those ideas. (This may take a while because scientists are human with human failings, but the triumph of merit is more likely and faster in science than in most human activities.) Science tests the structure of knowledge continually—a good scientist does not tiptoe around the tower of knowledge put up by earlier scientists, but tries to tear that tower down. Only those ideas sturdy enough to survive such attacks are saved, so the scientific edifice is exceptionally sturdy.

Why National Parks?

Societies have tried many different ways to deal with private versus group ownership. Private ownership often raises ethical questions—did you really come by that piece of land fairly? Can you claim for your king some land that was already occupied by other peoples? Do other species have land rights? Public ownership often raises the “tragedy of the commons”—if I can sneak a few more of my sheep onto the public green, I’ll gain in the short term, even if, in the long term, we all lose because the extra sheep kill the grass.

A big waterfall spills into a canyon.
Lower Falls, Grand Canyon of the Yellowstone River, Yellowstone National Park
Credit: R.B. Alley

The US tradition has focused on private ownership, but we’ve also recognized the benefits of public ownership. The idea of a National Park—taking the really choice pieces of the country and placing them under public control—is a US idea, developed by the Washburn expedition to Yellowstone in 1870 and eventually enacted by Congress in 1872.

Since then, the idea of national parks has spread across the nation and worldwide. This is surely one of the great ideas of the modern world, to save key scenic environments in the public domain.

However, the national parks of the United States, and the world, face a grave dilemma. The act establishing Yellowstone and the concept of national parks specified “conservation... unimpaired for...future generations” and “to provide for the enjoyment” of the parks. Saving a wild region for the future while having it enjoyed by millions of visitors each year is perhaps the largest of many difficulties facing the parks today.

Elk eating grass.
Elk, Banff National Park (Canada)
Credit: R.B. Alley

Most of the national parks were founded to preserve geologic features—the geysers of Yellowstone, Crater Lake, the Grand Canyon, the Badlands, etc. Many national parks were founded when they were, biologically, small pieces of a vast, unbroken range of similar habitats. Today, the parks are often becoming islands of natural environment in a sea of human-controlled and human-altered land. Thus, much focus on the parks today involves biodiversity. We will revisit the questions of biodiversity and island biogeography later. (Yes, this is a geology course, but some things are too important to pass up just because they belong in a different department.)

What is Geology?

Geology, broadly, is the study of the Earth. Geologists and friends—geophysicists, geochemists, geobiologists—study the rocks that make up the Earth, the history of the Earth as recorded in those rocks, and the processes that change those rocks. This includes oil and ores, landslides and volcanoes, dinosaurs and meteorites, and much more. Most geologists are involved in one of four areas: i) finding valuable things in the Earth (gold and silver, diamonds, oil, building stone, sand, and gravel, clean water, etc.); ii) warning of geological hazards (volcanic explosions, earthquakes, landslides, groundwater pollution, etc.); iii) building an operators' manual for the Earth (Earth System Science); and iv) informing/entertaining (What killed the dinosaurs? How has the Earth changed over time?).

Historically, most geologists have worked at finding valuable things. These geologists have been truly successful, too successful for their own good, in fact. Some of the things we extract from the ground are very cheap today (after you subtract off inflation and taxes), so there have been fewer jobs for geologists with mining companies than in years gone by. Oil prices have gone up recently, and oil companies have started a hiring boom (talk with any of us in case you're interested in a career move). The US used to spend a lot more money on cleaning up groundwater pollution than we have recently, but it turns out that an immense amount of that money was spent on lawyers arguing about paying for cleanup rather than on scientists and engineers cleaning up. A lot of geologists are not happy with this situation and hope that finding and restoring clean water will be more vigorously pursued in the future.

Warning of geological hazards is also a growing field. As more and more humans build houses on floodplains, debris-flow deposits, and other indicators of past disaster, these people become more dependent on someone to tell them if and when the trouble will return. Many geologists favor a different approach—find out where the dangers are, and then don’t build in those places—but real estate developers often don’t listen. (In the spring of 2012, a bill was introduced to the North Carolina legislature—although not passed in its original form—to make it illegal to use the best science to tell coastal people the regions that might be attacked by the sea. This echoed efforts a century before by developers in San Francisco to discredit scientists who correctly argued that the earthquake that had just devastated the city meant that additional earthquakes were possible.)

The disaster of Hurricane Katrina in New Orleans and surroundings in 2005 really showed the dangers of building in harm's way. With over 1800 dead, and over $100 billion in damages (that is $300 for every person in the US!), Hurricane Katrina definitely caught the attention of many people. Interestingly, geologists had known of the impending disaster, and warned of it, for decades, as the city slowly sank beneath river-level and sea-level. Thousands of Geosciences 10 students had studied this issue in the years before the storm struck (and you’ll get to look into the issue soon).

The operators’ manual for Earth is a new idea. It may be the most important thing geologists can do for the future of humans. We humans are everywhere today—living on every continent, tilling more and more of the land, claiming as our own more and more of the productivity of the planet. We have changed the forests, changed the soils, changed the atmosphere, changed the waters—nowhere on Earth remains free of our imprint. Credible estimates indicate that we and our close friends—cows and corn and chickens and house-cats and Chihuahuas—are using roughly half of everything made available by the planet. We are managing to support roughly 5 billion people pretty well (out of the 7-plus billion of us here), with population projected to reach 9 or 10 billion in a few decades, so we are planning on doubling the number of people we support well.

Given that we are doing this, and we will continue to do so, many thinkers believe that it would be wise to have a better idea of how all of this works and what we are doing. You would not try to repair a fine watch without knowing how it works—take a few pieces out and you may never get it running well again. We are doing precisely that to the planet, changing a lot of things we don’t understand. Earth System Science is the attempt to understand the planet, its water, air, ice, rock, and life, well enough to learn the consequences of our actions so that we can make wise decisions. Earth System Science is in its infancy, and we do not even know whether we will ultimately succeed, but many of us believe that it is an incredibly important effort.

And, there is always education and entertainment. Some people really like to know things, and geologists have some of the most interesting stories to tell. Perhaps you will find some of the stories here to be interesting.

A Brief Overview of Geology

This text will try to show you not only what geologists learn, but how we learn it. For the first few chapters, however, we ask you to take our word for some things. You will see statements such as “The Earth is 4.6 billion years old.” Before we’re done, you will also see where that number comes from, how good it is and much more about it. But we can’t do everything at once.

Anyway, we believe that the universe started in a “Big Bang” about 14 billion years ago. The Earth is “only” about 4.6 billion years old. We live in a second-generation solar system because the planets and the sun contain abundant chemicals such as iron that was first formed during the death of older stars. So, there were some stars, and they exploded and generated gases and dust, and something (another nearby star exploding?) caused that gas and dust cloud to be compressed a little. Once the dust and gas started falling together, gravity took over. Eventually, most of the mass went to form the sun, which was squeezed enough under gravity that the sun’s hydrogen began fusing to form helium, in the process releasing energy—sunlight! Some of the gas and dust collected into planets.

Assembly of the Earth involved falling together of lots of big and little chunks. The largest chunk was probably about the size of Mars. It hit the Earth after most of the assembly was finished and blasted enough material off the Earth to make the moon. (Note that there is still a little rumbling in the scientific literature about this Mars-sized moon-forming collision, so stay tuned...)

The falling-together of pieces makes heat. That heat partially or completely melted the planet. The melting allowed the planet to differentiate, or become layered. The denser material sank to make a core, mostly of iron, with some nickel and a few other elements. The lowest-density material rose to the top to form a silicate scum, or crust, floating on a vast mantle of denser silicate (see the sidebar on chemistry). The Earth is hottest in the middle, coldest on the outside. Heat favors melting, but higher pressure tends to make most liquids turn solid. These two effects compete in the Earth, so you find both solid and liquid down there. Going down in the Earth, the crust and the upper part of the mantle are solid (together forming the lithosphere) except in special places where volcanoes occur; the deeper part of the mantle is solid but soft, and has a zone about 100 km (60 miles) down in which a little melting occurs. The soft zone in the mantle is the asthenosphere--we won't learn a huge number of new words in this class, but we do get a few great ones! The core has two layers, a solid inner core and a liquid outer core.

Some of the Earth’s heat is left over from when the planet formed, and a lot comes from the decay of naturally radioactive materials in the Earth. As the early heat has escaped and the radioactive materials have decayed, the Earth has slowly been cooling off, but plenty of heat remains to drive geologic processes. The Earth has developed an atmosphere, oceans, and life, and a rich sedimentary history of how those developed. The atmosphere and oceans spend their time wearing down mountains, but the heat of the Earth keeps driving processes that build mountains up, so there is a near-balance. And all of this should become clear as we tour the national parks.

Sidebar: A Very Brief Chemistry Lesson

Most students reaching the university have taken a chemistry course somewhere along the way, but a few of you haven’t. Here is a BRIEF summary of chemistry, as a refresher for those who have had a chemistry course and as a teaser for those who have not. We do not use a lot of chemistry in this course, but it comes up often enough that you may find a summary to be helpful.

If we pick up anything around us (water, chewing gum, rocks, whatever) and try to divide it into smaller and smaller pieces, we will find that it changes as it is divided. A tree becomes a log as soon as we cut it down. If we dry the log before burning it, we find that it contained lots of water, plus other things that are not water. If we then use fire to break the log into smaller pieces, we find that we can do so, while releasing energy. Using tools and energy levels that are easily available to us, we will find that we can continue dividing something until we get to elements, but that we cannot divide the elements.

The “unit” of an element is called an atom. There are 93 naturally occurring elements, plus others that humans have produced. If we use even higher energies, such as those achieved in nuclear accelerators, we find that we can take atoms apart.

Each atom proves to have a dense nucleus, surrounded by one or more levels where electrons are found. It may prove helpful to think of electrons circling a nucleus the way planets orbit the sun, although this simplified model doesn't capture all the features of an atom.

The nucleus contains smaller particles called protons and neutrons. Protons have a characteristic that we call positive charge, electrons have an equal-but-opposite negative charge, and neutrons are uncharged or neutral. A neutral atom of an element contains some number of protons and the same number of electrons, with their positive and negative charges just balancing each other.

The type of atom, or element, is determined by the number of protons; add one proton to a nitrogen atom, for example, and it becomes an oxygen atom. (Breathing nitrogen without oxygen would cause you to die quickly; they are different!) The positively charged protons packed tightly in a nucleus tend to repel each other, but the neutrons act to stabilize the nucleus.

Some elements come in different “flavors,” called isotopes, which have different numbers of neutrons and so different weights. Slight differences in the behavior of isotopes allow us to use them to learn much about certain processes on Earth, as we’ll see later. All atoms of an isotope are identical, and all atoms of an element are nearly identical.

Chemistry includes all of those processes by which plants grow, we grow, wood burns in a fireplace, etc. Chemistry involves changes in how electrons are associated with atoms. An atom may give one or more electrons to another, and then the two will stick together (be bonded) by static electricity, the attraction of the positive charge of the electron-loser for the negative charge of the electron-gainer. An atom that gains or loses one or more electrons is then called an ion. Atoms may also share electrons, forming even stronger bonds and making larger things called molecules.

Most Earth materials are made of arrays of ions, although some are made of arrays of molecules. The ions or molecules usually form regular, repeating patterns. For example, in table salt, a lot of sodium atoms have given one electron each to a lot of chlorine atoms, making sodium and chloride ions. Then these stick together. One finds a line of sodium, chloride, sodium, chloride, sodium, chloride, and so on, and a line next to it of chloride, sodium, chloride, sodium, ..., and above each sodium there is a chloride, and above each chloride a sodium, in a cubic array. A grain of salt from your salt shaker will be a few million sodiums and chlorides long, and a few million high, and a few million deep.

The properties of the grain of salt—how it tastes, and dissolves, and breaks, and looks, etc.—are determined by the chemicals in it and how they are arranged. We call such an ordered, repeating, “erector-set” construction a mineral. Almost all of the materials in the Earth are minerals. Liquid water is not a mineral because the water molecules are free to move relative to each other, but liquid water becomes a mineral when freezing makes ice.

When the Earth formed, we received a few elements in abundance and only traces of the other naturally occurring elements. More than half of the crust and mantle is composed of two elements–oxygen and silicon. Most minerals and rocks thus are based on oxygen and silicon, and we call these rocks silicates. In silicates, the silicon and oxygen stick together electrically, with each little silicon surrounded by four oxygens. Silicon, oxygen, and six others–aluminum, iron, calcium, sodium, potassium, and magnesium–total more than 98% of the crust and mantle. Geology students used to be required to memorize the common elements, and their abundance, in order; for our purposes here, know that only a few are common, and we’ll come back to them later.

The silicon-oxygen groups form minerals either by sticking to each other by sharing oxygens, or by sticking to iron, magnesium, or other ions. Minerals that contain a lot of iron and magnesium are said to be low in silica, even though they may still contain more silicon and oxygen than iron or magnesium. In general, minerals high in silica are light-colored, low-density, have a low melting point, often contain a little water, and occur mostly in continents; minerals that are lower in silica usually are dark-colored, high-density, melt at high temperature, and occur on the sea floor or in the mantle more often than in continents. You may hear “basaltic” used for low-silica, because basalt is the commonest low-silica rock at the Earth's surface; similarly, “granitic” means high-silica because granite is a common high-silica rock.

This Course

It would be fun to take a tour of all the national parks, learning a little about each. But Penn State would not award you General Education credit for such a course—you are supposed to be taking a tour of a field of knowledge, in this case, geology.

So, we will take a tour of geologic ideas. But, some of the best geological features of the world are enshrined in the US (and other!) national parks. We will use national parks as illustrations, delving into park history and culture when we can, but concentrating on those things that illustrate how the Earth works.

View down into a valley at sunset.
Yosemite Valley, California
Credit: R.B. Alley

Scientific Literature—An Intro to Exercise 1

Scientists communicate in a lot of ways, but the most important is through the refereed scientific literature. Any scientific paper is first submitted to a learned journal, and the editor sends the paper out for peer review. In this, several recognized world experts read the paper and make sure it is “good.” Are the methods described well? Are uncertainties given? Is proper credit assigned to other sources? Do the equations make sense? Are substantive conclusions reached? If there are obvious errors, then the paper is sent back to the author or authors for revision. If the paper is unclear, or can’t be read well, or information is omitted, or if unsubstantiated claims are made, or anything else is wrong, the paper is sent back for revision. Only when the paper clearly and logically presents new results will it be published.

Peer review takes a lot of time and effort. Peer review also slows down publication of important results. (The papers authored by Drs. Alley and Anandakrishnan that have been of greatest use to other people were also the ones that had the hardest time gaining approval from reviewers, who check especially carefully on the big stuff.) And, there is no guarantee that the reviewers will get everything right; errors do sneak by. But peer review really raises the quality of the scientific literature above the quality of other sources that are available to you.

You can find information in many places—books, magazines, newspapers, the Web, speeches by public officials, graffiti in restrooms, etc. Some of this information is more reliable than others. In general, the more permanent a publication is, and the more expensive it is to get you the information, the better the information. (So the Web, which is cheap and has a huge turnover in websites, includes an immense amount of nonsense as well as some good stuff.) But, there are surely exceptions to this “rule.”

If something really matters, the refereed scientific literature, with its long traditions, its focus on accuracy, and its appeal to nature to test ideas, is the most reliable source available. Textbooks, lectures by professors, and other ways we give you information aren’t bad, but the refereed scientific literature is still better. You’ll have the opportunity to explore this in Exercise 1.