GG 101 Program 2 Down to Earth

Honolulu Community College

Program 2

DOWN TO EARTH


Hello. Welcome to Program 2, Geology and Geophysics 101. Today'slesson is Lesson 1 in the Study Guide. It's called "Down to Earth.

Before we actually begin the assignment, I want to remind you that you can't just watch television to complete this course. It's very important also to use the study guide and the textbook; hence, as a supplement to the material that we see here on the television screen.

For these early assignments I'll help you by talking you through the steps that you should take to study.

Generally, these are outlined in the study guide, and we'll be doing these pretty much the same way,but by the third or fourth lesson I'll leave this to you to do on your own.

But, for the early lessons I will remind you. Okay.

So the first thing you should do before viewing the video is to read the text assignment.

Be sure to include the introduction, summary, terms to remember, questions for review, and questions for thought in your reading. Try to answer the questions, especially the review questions, and do this again before viewing the video.Pay special attention to the diagrams and photographs and study them until yourecognize what it is that they are trying to show you

LESSON ASSIGNMENT

The assignment for this lesson is in the textbook, Chapter 1, pages 3 to 23. Particularly, you should note the photograph of Mt. Robson facing page 3 in the textbook as you look at the photographs in the Table of Contents of the text.

On pages 8 and 9 you will find a physiographic map of the United States, which you should study. And get in the habit of using this map to locate the various regions that we'll be talking about as we go through the course.

For this lesson also you should review Box 1.2, pages 19 and 20 on plate techtonics and the scientific method.

And, also, finally, study Table 1.1 on page 22 to learn the eras of geologic time.

After reading the text assignment, you should study the key terms and concepts.

Only then should you watch the video, using the viewing guide and the study guide to help you focus on what you should be learning from the video

After that, read the "Putting It All Together" section in the study guide and complete any activities noted in the study guide.


It's important that you follow this sequence in order to make sure that you get the important points.After all this, review the material, go back and look at the text, look at the pictures, and especially look at the questions and complete the self-test that you'll find in the study guide. Finally, go back to Learning Objectives at the beginning of the lesson and make sure that you've completed each one.


OBJECTIVES

There are several objectives for this lesson.

I'll review these with you briefly.


One of the difficulties we have in visualizing geology is visualizing Earth's features. The best place to study geology is out there, outside in the real world.

The classroom doesn't allow us to do this although you will be taking some field trips as we go through the course. The videos provide pictures of things that you probably won't be able to visit and catalogs them in such a way that you can relate to the course material.

What we are going to see in this lesson is basically an overview of Earth processes, resources and hazards.

 

In other words, why do we need geologists at all?

Are geologists important?


You see, everything that we use, all of us, depend upon the Earth. All the materials that we use:plastic, glass, metals, petroleum. Everything comes from the Earth. We don't get things from outside the earth.We need to understand where these things come from so that we can learn how to manage them.

It's also important to note here that we use mostly non-renewable resources.

What are non-renewable resources? What do we mean, "non-renewable"? We mean, of course, that once we use them we can't make more.

Trees and timber, for example, are renewable resources.

Renewable resources such as "trees." When we use a tree, we can plant a new one, but petroleum and minerals have been created through geologic processes over hundreds of millions of years.

In fact, the oil that we're using now was created by Earth processes hundreds of millions of years ago.

There are some things to note specifically about this video One of the goals of this course, and specifically of this lesson, is to appreciate the uniqueness and the wonders of Earth.

One of these things is the immensity of geologic time, the vast span of time in which these processes have been operating on Earth.

We also note that Earth is unique because it has the water and temperature requirements that are necessary to sustain life.

Life is one key element on Earth.

Other planets in our solar system, although they may be similar to Earth in other ways, lack water and, therefore, are lifeless.

As you view the videos, look at the pictures of the landscape and try to imagine.

Use your imagination.

Ask yourself, "How did that feature get there"?

Everything is there as a result of some geologic process.

I'll also note that during the videos that the narrator of the videos will not always call attention to the features that are being observed. You can help yourself be successful in this course if you learn to look at the features and try to relate the things that you're learning to the pictures that you see on the screen at a given time.

Before we actually view the video, I want to take you through some of these topics and see if we can't get a sense of what we're dealing with here.

The first thing I want to talk about is geologic time.

The earth, as far as we know, is about 4.6 billion years old, 4.6 billion years. How long is 4.6 billion years? It's a number that we can write. We can write 4.6 followed by 9 zeros, but exactly how long is this?

It's hard to imagine how long it really is and most people, even trained geologists, have trouble really comprehending how long a time 4.6 billion years is.

But to give you several examples that might help to give you a sense of this vast span of geologic time that we're concerned with.

For example, the tallest mountain on earth, Mt. Everest, about 30 thousand feet tall; that is 30 thousand feet above sea level. The rate of erosion, that is the rate at which Mt.Everest is being lowered by water, is about 2 tenths of a millimeter per year

Two tenths of a millimeter is very small. It's about this much.

For every year Mt. Everest is about 2 tenths of a millimeter lower than it was before. How long would it take at the rate of 2 tenths of a millimeter per year to lower Mt. Everest completely to sea level?

It would take about 40 million years.

Well, 40 millions years is almost as hard to imagine as 4.6 billion years.

The numbers by themselves don't mean anything.


Let me put it this way. In Earth's history there have been over more that one hundred forty million year periods.

That is to say that in Earth's history Mount Everest could have been lowered to sea level more than a hundred times.

This brings up a side question that we'll also consider as we go through the course. If a mountain on Earth can be leveled more than 100 times in Earth's history, why do we still have mountains in the first place?

You would think that all of the mountains would have been removed.

Well, that brings up the point, of course, that there must be some process, which causes new mountains to form; otherwise, the entire Earth's surface would simply be flattened over to sea level. So the fact that we have mountains at all points to this process.

There's another example of a way to visualize the time.

Let's look at our Island of Oahu here on Hawaii.

The Hawaiian Islands are relatively recent figures on the Earth. In fact, the Island of Oahu is only about 3 million years old In fact, 3 million years ago the Island of Oahu was about the size of Haleakala on the Island of Maui, a mountain about 10 thousand feet tall.

This 3 million years is only an insignificant fraction of Earth's history.

In fact, there have been fifteen hundred three-million-year periods in Earth's history.

In other words, there's been enough time to make the Island of Oahu 1,500 times in Earth's history.

If the age of the Earth was one year, then on that scale this 3 million years would be about one day's work, about eight hours.

Again, it's very difficult to imagine how long geologic time really is, but once we start to comprehend how much time there has been for processes to take place, then we can start examining how these slow processes can produce large changes over long time periods

For example, your fingernails, my fingernails, grow somewhere between 5 and 10 centimeters per year. This, as we'll see, is about the same rate at which new ocean crust is added at seafloor ridges.

If fingernails have been growing at a rate of 5 to 10 centimeters per year, throughout the entire history of the Earth, they would stretch a little more than 30,000 miles past the moon.

In other words, the fingernails would be 286 thousand miles long if they'd been growing since the age of the Earth.

As you progress through the course, when we're talking about these processes, although the processes themselves are very slow, that Earth's history encompasses such large amounts of time that there's plenty of time for even these very small processes to create very large features and very large changes.

There have been many attempts throughout the history of the study of the Earth to try to explain how these processes come about.

Before the concept of geologic time was understood, it was thought that changes occurred rather rapidly, followed by rather long periods of quiet.

All creation myths, for example, have stories about flooding or volcanic eruptions or earthquakes or major events, which radically change the face of the earth.

The key to understanding geology lies in a concept called "the principle of uniformitarianism," or sometimes just called "the principle of uniformity." If we examine the word, we can see what this means.

"Uniformity" means the same In fact, another way to state to the principle of uniformitarianism is to note that the present is the key to the past. That means that similar geologic forms are created by similar processes, but if we see a volcano now and a volcano that's older, we can recognize certain similarities between the processes that created it.

It also means that we accept that rates and processes are not so much different now than they were in the past. Large amounts of time are needed to create physical changes, so if we understand how a process works today, then we can look at results of those processes that happened in the past and then go back and interpret the history of the Earth.

Understanding the history of the Earth, you see, is a way of understanding where to find resources and understanding how to predict geologic hazards. The other thing we learn from uniformitarianism is that although catastrophic events like volcanic eruptions and earthquakes may occur, that they're limited in magnitude, and that if we have a sense of what size of hazards we can expect, then we have a way of looking back into the past to see how these geologic hazards have shaped the earth and what role they've played in shaping the Earth through the time.

So this Lesson, "Down to Earth," looks at the Science of Geology and the geologists who practice it in its various forms. It not only gives us a sense of what geologists study, but we also get to meet a lot of geologists and understand that geology is, overall, a human endeavor.

Okay. Mainly, this video examines three aspects of what geologists do and why they do it.

So, let's watch the video.

Major funding for Earth Revealed was provided by the Annenburg CPB Project.

Throughout the vast reaches of our solar system, from the tiniest bits of dust and ice to the huge gaseous planets, conditions that might support life as we know it are conspicuously absent.

On Venus, for example, a dense noxious atmosphere combines with a thick cloud cover to trap solar energy with extraordinary efficiency. The result is a surface temperature of about 475 degrees centigrade.

On Mars, conditions are not quite so brutal, but hardly conducive to life. The main surface temperature on the Red Planet is minus 23 degrees centigrade, and the Martian atmosphere is very thin, composed primarily of carbon dioxide with some nitrogen and argon.

But there is one planet in the solar system whose physical properties foster the growth of living things, a planet whose distance from the sun permits moderate temperatures, whose size enables it to hold an atmosphere at which organisms can respire, shielded from cosmic radiation.

This is Planet Earth, home to an incredible diverse flora and fauna.

With it's abundant water, moderate temperature and oxygen rich atmosphere, Earth is the ideal habitat for life,the only such place in our solar system. To understand why the Earth is so extraordinary, it's necessary to trace the historical development of our planet and to understand the processes of nature which operate today.

This is what the science of Geology is all about.

Geologists do more than collect rocks and catalog fossils. Geology is a study of the whole Earth, and the goal of geologic research is to understand as best we can how the entire Earth works.

This planet's geologic activity is driven by what geologists refer to as Earth's two heat engines: one internal, the other external.

These are dynamic processes that convert heat energy into mechanical energy, which, in turn, causes geologic change.

The Earth's internal heat engine is powered by heat from radioactive decay deep within our planet. It drives a process known as "convection,"which causes hot material to flow from the interior of the earth slowly toward the cooler surface.

Earthquakes and volcanoes are results of convection.

The earth's external heat engine is essentially solar powered. It sets in motion a cycle known as the hydrologic or water cycle that has important ramifications for the landscape of this project.

When rain or snow falls on the land's surface, more than half the water returns to the atmosphere by evaporation or by transpiration from plants. The remainder percolates down into the Earth to become ground water or flows over the land's surface as runoff in streams and rivers.

Over long periods of time, this moisture of the Earth's surface helps rocks decompose, forming soil. Water washing down hillsides and flowing in streams loosens and carries away the rock and soil particles.

The Earth's two heat engines do not work in isolation; Instead, they perform a kind of ongoing balancing act. Mountains originally raised by the Earth's internal forces are worn away by weathering and erosion, driven by the external heat engine.

These heat engines working together provide the fuel for this enormously complex machine we call "Earth," and it is the detailed workings of this dynamic planet that geologists are continually trying to better understand.

There's never been a more exciting time to study geology than right now. Since the 1960s Earth Science has undergone something as a Renaissance as new evidence about the way the Earth works has replaced old simplistic perceptions.

This new knowledge has been blended into a single inclusive theory of Earth's history and function, the Theory of Plate Techtonics. We now know that the outer skin of the Earth is composed of individual pieces or plates that slide around on a partially molten layer below.

Geologists are struggling to understand the processes which move the plates and the interactions between the plates themselves. But today there is an even more compelling reason for unraveling the mysteries of the Earth's interior: the need to locate the natural resources upon which civilization depends.

Minerals, petroleum, fresh water, fertile soil.

These natural resources are not in unlimited supply, and we are consuming them faster than they're formed. Geologists play a crucial role in this challenge. Using their knowledge of the way the Earth works, they uncover new sources of minerals and fuels and plan ways to extract them, economically and with minimal harm to the environment.

Geologic resources are essential for modern civilization. With the exception of solar energy, nearly everything humans depend on comes from the Earth. Everything that we build our civilization with, our homes, the car that you drove in with today, what was it made of, how it was fueled. The material you're sitting on or your desk, the pencil you write with.

All the materials that we live with on an everyday basis come from the Earth.

Somehow they've got to be extracted from the Earth, and the geologist has that principal role.

While there is a wide range of resources which play key roles in modern civilizationit is petroleum that garners most of the world's attention. For Geophysicist Stephen Scott, the search for oil and gas is an ongoing challenge.

Oil companies typically use seismic studies of Earth's crust to assist in locating reserves. One technique, known as reflection seismology,is especially useful.

In reflection seismology, what we try to do is generate that source or that shock wave ourself and try to reflect that off of subsurface rocks and record it at the surface with geophones. We do that by sending out a truck into the field, which we have a truck called a "viborcise truck," that actually shakes the ground.

A vobercise truck would shake the ground in an up and down fashion, much like a jack hammer on a construction site shakes the ground, and so what we're trying to do is use the technology so we can see the secrets of the earth below.

Because the shock waves interact differently with different kinds of rock, reflection seismology help geophysicists find geologic structures that commonly contain oil and gas. Such structures can be detected, not only by seismic techniques, but by observation from aircraft or satellite as well.

This method of long distances viewing is called "remote sensing." It's a way of looking at very large areas very quickly and getting an overview. Particularly since the advent of satellite remote sensing, we have had the luxury of being able to look at very large areas of the Earth's surface at one time and get an integraded idea of what's going on.

What remote sensing has done or satellite remote sensing, particularly, is given us a chance to look at the inter-relationship between widely separated features and see those in a way that we've not been able to see before.

In one recent investigation of the potential oil and gas reserves of Pakistan, 28 separate images were combined to form a mosaic, which showed numerous spectacular geometric structures. Because of their remoteness, many had not been seen by ground-based geologists. This opened up new areas for oil and gas exploration.

But remote sensing is by no means limited to the search for new sources of energy. It has also been used to study changing vegetation patterns, locate mineral deposits, track pollutants, and search for another critical resource, "ground water." The amount of water lying underground is vast, more than 30 times the total supply of water stored in all the world's lakes and rivers. Civilization depends heavily on ground water, and as population rises, this resource becomes increasingly valuable.

The thing that ground water is almost always there, but it may be too deep to be economical to drill. It also may not be of good purity.

Today we have severe problems with pollution, contamination,and ground water, as we go deeper, gets older, gets hotter, and gets saltier,so you don't want to go real deep.

In the Southern California area, there are a number of factors that create a favorable environment for ground water, including very permeable soils, a large storage capacity and a steady supply of surface water. At the Orange Country Water District, Jim Goodrich is responsible for managing the ground water supply. He is concerned both with the quantity and the quality of available water. So what we've done at Orange County is developed a very sophisticated ground water monitoring program, which uses service water sampling, production well sampling, and dedicated monitoring well sampling.

Our monitoring wells are drilled to a depth of about 1,500 feet and isolate and tap up to 18 zones that we can monitor individually, so that if a contaminant is coming towards us, towards a production well, we can find it before it becomes a problem and institute a mitigation.

Like water, soil is a geological resource essential to sustaining civilization. For farmers like Wayne Silkland, who lives in California's Mojave Desert, maintaining a fertile plentiful supply of soil is an ongoing struggle. The chief threat is erosion, which can be caused by either rain or wind.

Rain is a fairly minor situation here in the desert. We only have four inches of annual rainfall. Sometimes it all comes at one time, and we do have some runoff from sloping parcels or some stream bank erosion in streams that are normally dry, but that's relatively minimal.

Our major problem with soil erosion results from the wind, and that can happen at any time of the year: winter, summer, fall. It doesn't matter, and we have fairly heavy winds for long periods of time, and we have to take a number of precautions related to that.

To dissipate the strong winds that can remove a half inch or more of soil in a single day, Silkland has planted dense rows of trees known as windbreaks around his fields. He's also turned to the United States Department of Agriculture for additional ideas.

After visiting Silkland's farm and learning about his primary concerns, soil conservationist, Rick Argyle drew up a soil management plan. This plan included suggestions about how frequently to plow the fields, as well as recommendations concerning water management and crop rotation.

Along with the use of windbreaks, these soil conservation technique are making a significant difference on Wayne Silkland's farm. These improvements are not just quick fixes but substantial changes that will keep Silkland's soil productive for years to come.

Whether the specific issues are soil, minerals, oil and gas, or water, there is a growing awareness that modern civilization is rapidly depleting Earth's supply of previous natural resources. And it is geologists, who are devising new ways to more intelligently extract and conserve these resources.

But their role extends well beyond the hunt for resources. Earth scientists are also deeply involved in helping of the world's population safely coexist with this planet's geologic hazards.

One of the more serious hazards in terms of potential destruction is volcanic eruptions. And while there is no way to eliminate eruptions, scientists are continually refining their techniques for forecasting such events.

Probably all volcanic eruptions are preceded by and accompanied by measurable changes in the physical or chemical state of the volcano, and one of the principal means of monitoring or measuring the changes, at least the physical configuration of the volcano is by means of what we call "ground deformation studies."And this simply is just a term for measuring the changes in the shape of the volcano.

In a research project underway in Alaska, geologists are studying one of the most powerful events of the Twentieth Century, the 1912 eruption of Mt. Katmai. Scientists there believe this is an excellent setting in which to learn more about how explosive eruptions occur.

It all happened in about 60 hours.

We know exactly when, the date, the time, and, also, which is as very unusual is that it came up through an area where nothing much had happened volcanically before. It came up through a very simple part of the Earth's crust, and, finally, the system is perfectly preserved.

Usually, in events of this type, there's an enormous amount of collapse at the vent, the area is flooded by water, or it occurs in a very complex area, and it gets eroded away. In this case, the whole system is perfectly preserved, so the size, the simplicity geologically, and the preservation make it an exceptionally good place to try to understand the basic processes of explosive eruption. Although much data have already been collected, the Katmai Project is still in its preliminary stages. Research may continue here for years, bringing with it new discoveries that will improve our understanding of volcanoes.

Volcanic activity potentially threatens millions of people worldwide, but equally threatening is another common geologic phenomenon, "earthquakes."

Geologists have a general understanding of how earthquakes occur and the areas most prone to earthquakes have also been identified, but much remains to be learned about these events. While scientists have successfully identified some signs of impending earthquakes, these precursors give little clue as to exactly when an earthquake will strike or how large it will be.

Along one pastoral stretch of the San Andreas Fault near Parkfield, California, scientists hope to learn more about earthquake precursors and what actually happens during an earthquake itself. Geophysicists are using a sophisticated array of devices to closely monitor movement along the fault. The objective is to spot any changes that may signal an impending quake.

The Parkfield Experiment has three goals.

While earthquake prediction is a significant goal for geologists, most stress that earthquake preparation is even more important. First of all, we must try to shore up existing structures and make them more earthquake resistant. There is no such thing as an earthquake-proof structure, not at least an economically built one, but we can make things earthquake resistant, so that loss of life is minimal, maybe zero loss of life.

That can be done now and should be.

It's very expensive, but we must restrengthen old buildings, old structures.

Furthermore, we have laws on the books that prevent building new structures in earthquake-prone areas where the dangers are excessive. Those laws should be maintained and perhaps even strengthened.

We have also building codes that require modern buildings to be built sufficient to withstand intense ground shaking. Continued research into building structures of all sorts and their resistivity to earthquakes must go forward.

That's something we can do now.

We don't need to know when the next earthquake is going to occur to know it's important to build buildings that stay up and don't lose windows and facing material in the event of an earthquake.

Even more destructive than volcanoes and earthquakes are mud flows, landslides, and other related earth movements. Every year they exact staggering toll on populated areas. In some places, people have attempted to live with land movements although not always very successfully.

When new construction is planned for areas with slopes, geologists are often called uponto evaluate potential landslide risk.

Let's take alook and see where we are.

Ultimately, this can help minimize the risk of death and destruction due to landslide activity.

The human population of this planet is now close to 6 billion, and it's increasing exponentially. Many of the world's population centers are located in areas threatened by natural geologic hazards, such as earthquakes, volcanic eruptions, and landslides.

Geologists are working to understand the exact nature of hazardous geologic processes like these and then applying this knowledge to reduce the toll on human life.

The teeming industrialized societies that have resulted from this population explosion have also spawned environmental problems which are only now being recognized. Geologists are actively involved in the battle to overcome a broad range of these problems. And as the world's population continues to grow, the environmental challenge looms ever large and the stakes grow even higher.

Today's earth scientist is expected to play a dual role:

Geologists and earth scientists in general are the scientists who are capable of dealing with the problems of resource extraction and the environmental protection. We, therefore, have a dual obligation to society to maintain our material base by providing the resources to the populace and by maintaining some control over environmental degradation.

We can't have it both ways.

Every time we modify the environment , to some extent it is degraded. We can't make it better, no matter what some of the ads may say. So we've got to be certain that we use our resources as wisely as possible. Earth scientists know the nature of the resources, where they're located, what their occurrence is, how can we extract them efficiently.

That must be an important goal for the future, to make certain that we use our resources as efficiently and as effectively as possible with as little waste as possible for future generations. Whether the resource in question is fossil fuel, soil or ground water, geologists are charged with a unique responsibility:

Providing the public with a fundamental awareness of how Planet Earth functions.

Perhaps more than any other science, geology has influenced the evolution of civilization and the history of nations. Natural geologic hazards have devastated cities and contributed to the fall of governments.

The geographic distribution of fossil fuels, precious metals, and gems, and industrial minerals, have created empires and caused wars. It has allowed the citizens of some nations to enjoy boundless prosperity while those living in less fortunate regions, struggle to eke out a marginal existence.

But geology has given us more than oil, and metals, and predictions of natural disasters. The Science of Geology was founded, not more on economic benefit, but from human curiosity about the Earth, and it's provided us with a way to understand this planet we call "home."

Geologists rarely conduct experiments. It's not possible to carefully control the geologic conditions in this global laboratory.

Instead, working from the shreds of evidence that have escaped erosion and destruction by geologic processes, geologists have pieced together the details of Earth function and history.

The image of earth from space is a kind of visual metaphor for the Science of Geology. From space we could perceive only the dimmest of clues about the planet lying beneath the swirling clouds and deep blue oceans. To unlock the mysteries of our complex and beautiful planet and to understand it's significance to our own lives, we must carefully examine the processes and products for geologic activity, and during the course of Earth revealed, that's exactly what we propose to do.

Major funding for Earth Revealed was provided by the Annenberg CPD Project.

Earth is an amazing and complex planet.

Before we go on with the summary, I want to note that you will be seeing much repetition in these videos as the detail emerges. Much of the stuff that was on this video; in fact, I think it's safe to say everything that was on this video will be covered in more detail as we progress through the course, and this is an introductory sort of video, so if you happen to miss a few things and didn't catch all the details, all of it will come back as we go through this.

To summarize, I'd like to ask a few questions and sort of go back and look at some of the things that the video dealt with.

The first thing I would like for you to answer on your own. You can look at the textbook and also go back to the video.

What kinds of things do geologists study?

Let's also--I want to ask the question,

"Do you think geologists are good at predicting natural disasters?"

Part of the answer to that question comes in understanding what we mean by the word "predict."

You see, in order to make a forecast, we have to understand how Earth works. If we're going to try to say when a particular volcano is going to erupt or when an earthquake is going to take place, we need to understand, not only how all volcanoes operate or how all faults work, but how this specific volcano or this specific fault is operated.

The distinction here-- I use two different words.

On one hand, I use the word "prediction," and, on the other hand, I use the word "forecast." And it's important, I think, to understand the difference between these two words.

A prediction, you see, is a way of saying that a particular event will occur at a particular time and a particular place, so if I was to issue a volcanic prediction, I might say that Kilauea on The Big Island will erupt tomorrow at 10 o'clock.

Well, we understand so little about the Earth, that it's impossible at this point; in fact, it may always be impossible to make these kinds of predictions. So rather than make predictions, what most earth scientists do is, instead, to make a forecast.

The distinction between the"prediction" and the "forecast" is a fairly simple one.

A "forecast" is a way of saying that a particular type of event, a geologic event, like an earthquake or a volcanic eruption-- This event has a high probability of happening within the given region within a particular amount of time, so as opposed to the idea of "prediction," I might say that Kilauea is likely to erupt over the next five years, or I might say that a particular size earthquake is likely to occur in Northern California in the next 20-year period.

I also want to note something, I think, the video didn't particularly cover, which has to do with why don't geologists make more forecasts or predictions?

There are several reasons for this.

As I noted before, the distinction between "prediction" and "forecast" is not always clear in the minds of people who are hearing the reports.

The other danger, I'd like to fall the "chicken little problem" or the "cry wolf problem."

Everybody knows the story of Chicken Little. Chicken Little ran around saying, "The sky is falling! The sky is falling!" And, of course, nobody paid much attention.

The story about the boy who cries "wolf" is even more relevant. Everybody knows the story, right? The boy goes around crying he's seen a wolf. The first time he tells the story, everybody panics and everybody listens. The next time, fewer people listen. By the third time, nobody pays any attention to him at all.

The scientist does not want to find himself or herself in the position of the boy who cries "wolf."

There's several examples of this that have occurred. For example, in fall of 1990, a geologist made a prediction that there would be an earthquake on the New Madrid Fault. The New Madrid Fault is in the interior of the United States and would affect the region around St. Louis, Missouri and the continental interior. I use the word "prediction" here because in this case this geologist made a prediction that this earthquake would occur in a fairly limited period of time in December of 1990.

It turns out that this particular geologist was an untrained amateur geologist, who did not have access to all of the information that really is needed to make a successful forecast.

The result of this is almost predictable: mass panic. When this prediction was made, people not only in the region where the prediction was made, but people in the surrounding areas. In fact, people as far away as Cincinnati, 500 miles away, jammed to stores to horde supplies. They jammed the phone lines trying to talk to their relatives and make plans. They jammed the highways. People evacuated the cities, and, of course, the earthquake didn't happen.

Now, even in the case where the earthquake or hazard does happen as predicted or as forecasted, it's still dangerous for this reason to make forecasts.

There are several other things I want to note about the video.

One of these has to do with the dual role of the geologists. It's interesting that geologists, on one hand, have the role of locating resources, and, of course, to locate earth resources, such as minerals, petroleum, water, and soils, we have to understand the processes that create them.

On the other hand, geologists are also charged with preserving these natural resources.

It's kind of a tricky role for the geologist to find himself in.

Finally, what is it that makes Earth different from the other planets? When we look at other planets, we see that many of them are in no way like the Earth. The one thing that you recognize about Earth, I should say, as you look at it from space, is the presence of ocean.

Earth is sometimes called the "blue planet."

The presence of large amounts of water on earth affect it geologically in ways that make it significantly different from the other planets. In order for their to be liquid water on the earth, the temperature of the surface has to be just right.

That means that if the Earth was a little closer to the sun, the temperature would be too hot; there would be no liquid water. If, on the other hand, the Earth was a little further from the sun, the temperature would be colder, and there would still be no liquid water; in this case, the water would be ice, so the planet happens to be just the right distance from the sun, so that water can exist, not only in liquid form, but also in the gaseous form in the atmosphere and as ice.

As we'll see, the role of ice and the role of water in the atmosphere plays a significant role.

It's also true that the presence of large amounts of water in this particular temperature range just happen to be right for the presence of life. It's, although geologists don't usually consider "life," that's usually left to the realm of the biologist, we have to understand that "life" plays a very important role on the Earth.

Most significantly, our present atmosphere, which contains a lot of oxygen, is there because of life processes. We note that volcanoes are responsible for a large amount of the gases in the atmosphere, but the presence of life has modified this original atmosphere until it's as it is today, the presence of oxygen and large amounts of water vapor in the atmosphere.

The other thing to note here is that if we compare other planets in the solar system; for example, Venus, which is the next planet closer to the sun, and, also, Mars, which is the next planet out from the sun, we note several similarities, but also several important differences.

Venus, for example, has very high surface temperature, virtually, no oxygen in its atmosphere, and no surface water.

Mars, on the other hand, has a very thin atmosphere, which also doesn't have a large amount of water and very little oxygen in the atmosphere.

Another significant difference has to do with the surface itself. Pictures taken by spacecraft of the other planets, including Mars and Venus, show a very heavily cratered surface. As was pointed out in the video, it's thought that this cratered surface comes from impacts of meteorites early in the history of the planet. The question remains, then, why is it that here on earth we have no craters?

You see, we believe that the Earth was formed along with the rest of the planets at about the same time, so Earth should have been heavily cratered like the other planets.

Well, the answer to the question is very simple. Water is a very active geologic agent, and water on the Earth's surface plays a very large role in smoothing out surface features, so that even if the Earth was heavily cratered, which we assume that it was, the evidence of that cratering has been removed by the active erosive power of water on the Earth's surface.

Okay, I noted at the beginning of the program that the question of why we still have mountains if there has been more than enough time to erode the highest mountains down to sea level a hundred times.

Why do we still have mountains?

The answer, of course, is that Earth is geologically active.

There are tectonic processes, which originate deep in the Earth, which have the effect of raising new land above the surface, so we see that on the surface of the Earth, the geology of Earth is actually a complex interaction between constructive forces of building and destructive forces of erosion.

That ends the lesson for today. Be sure to tune in next time for Program 3 and Lesson 2.