Tag Archive: Geography

This collection, containing 13 programs on 4 discs, looks at the geological history of specific places on the Earth. The series is grounded in plate tectonics and geological activity, with plate tectonics and glaciology being foremost.

In some ways it is a good introduction to how geological forces act, but as a geophysicist I do have some caveats.

First, while the geological dangers are very real, the program has a tendency to emphasize the “this could happen tomorrow” aspect. There is very little emphasis on what we can do to minimize the effects of possible geological disasters. (All right, there’s not much we can do if Yellowstone blows again, but things like evacuation routes and plans for tsunamis and engineering for earthquakes are hardly touched on.)

Second, the programs do not distinguish among kinds of faults and plate boundaries. While mid-ocean ridges are recognized as divergent boundaries, the difference between transform boundaries such as the San Andreas Fault and convergent boundaries is never clearly described. Nor is the difference between ocean-continent convergence (which produces ocean trenches, volcanoes and massive earthquakes) and continent-continent collisions (responsible for the mountain belt extending from the Himalayas to the Alps.) The latter are capable of producing far greater earthquakes, as the potential area of breakage is far larger, and are also responsible for the “ring of fire” around the Pacific.

Third, the story of each region is told as if the scientists just had to find the missing pieces, and as if they knew what they were looking for. In many cases, the findings were a total surprise and the interpretation we accept today is quite different from what the researchers who found the information at first tried to make of it. I know — I was watching as plate tectonics gradually became the accepted framework of geology.

Overall the series is worth watching if you have any interest at all in how the world came to be as it is today. But take it with a grain of salt – the writers of the narration didn’t always know what they were talking about.

Individual programs are:
The San Adreas Fault
The Deepest Place on Earth (Challenger Deep)
Loch Ness
New York
Driest Place on Earth (Atacama Desert)
Great Lakes
The Alps


Plate Tectonics: Part I

The important thing about science is that it has a built-in mechanism for corrections. It doesn’t always work as well as it should, because scientists are people and resist changing their beliefs. The fact remains that assumptions are always open to challenge.

I was reminded of this in watching a DVD on How the Earth was Made, which I’ll review soon. The point I want to make here is that the DVD presents examples as if the scientists involved were searching for pieces of a puzzle that they knew had missing pieces. More often the major breakthroughs – such as plate tectonics – are made when a gradually increasing number of people realize that the accepted theory just doesn’t explain something. Or many somethings. Essentially, that the puzzle pieces available have been put together wrongly, and the picture is in fact quite different.

This happened with plate tectonics.

I wasn’t involved directly, but I was at the Geophysical Institute when it happened, and had a chance to read many of the papers as they came out. And I was interested enough to do just that.

Even as early as grade school, I was unsatisfied with the encyclopedia’s explanation of mountain-building and geosynclines. What the encyclopedia said was that mountains were formed by the cooling and shrinking of the Earth, much as wrinkles are formed on the skin of a drying apple. Erosion wore the mountains down, depositing the sediments offshore, and the weight of those sediments pushed the ocean crust down so the mountains grew higher. It did not make sense to me, even then. These processes would have resulted in filling the oceans and leveling the mountains, not building them!

When I was a little older – high school age – I was given a book that gave some of the results of the International Geophysical Year – the IGY. The one that stuck in my mind as an unsolved mystery was the discovery of major east-west trending faults in the Pacific Ocean. Based on the offset of newly discovered magnetic stripes, these faults had large displacements – tens to hundreds of miles. But the displacements totally disappeared when the faults reached land! Not only could the east-west displacements not be found, in places such as the California coast there were well-known faults such as the San Andreas tending more nearly north-south.

At Harvard I took a basic geophysics class, hoping it would help me make sense of what seemed to be an increasingly frustrating puzzle. What I learned there – and it was the cutting-edge science of the early 60’s – left me as puzzled as ever.

Gravity measurements had proved that continents stood higher than oceans because continental rock was less dense than ocean rock. This was known as isostacy – the height of terrain essentially depended on how high it floated on the mantle.

Continental drift was nonsense – there was no way continents could plow through oceanic crust, and there were no traces of any such plowing through on the sea floor. The matching of rock formations on the opposite sides of the Atlantic was sheer coincidence.

Exchanges of plants and animals over  geological time were via land bridges.

The elephant in the room, from my point of view, was that isostacy did not allow sea floor to rise and form land bridges.

I went to the Geophysical Institute as a graduate student partly because of these mysteries, but I was sidetracked into atmospheric science and ice fog. Nevertheless, I stayed interested, and since many of the seminal papers in plate tectonics were published in the Journal of Geophysical Research (JGR) I watched the plate tectonics revolution happen. Next week I’ll talk about some of the breakthroughs that eventually led to the new paradigm of plate tectonics.

I wrote this for the Alaska Science Forum in 1987, but it’s as true as ever. Besides, the Quaternary creatures of Alaska were a large part of the inspiration for my soon-to-be-released novel, Tourist Trap.

Imagine yourself in a spaceship approaching the earth, eighteen thousand years ago. The ice-covered Arctic Ocean is blindingly white in the early June sunlight, but not just the ocean — all of Scandinavia and parts of Europe and the British Isles lie under a glittering sheet of ice as well. Drift ice fills the northern Atlantic, and the warm blue waters of the Gulf Stream, which you expect to see swinging north of Norway, flow directly across to Spain. As you continue westward, Long Island and Cape Cod are mere piles of rubble at the edge of an ice sheet that rivals the one in Antarctica today. A massive lobe of ice pushes south of what will someday be the site of the Great Lakes, and Canada is an unbroken wasteland of ice, bounded on the south by rushing summer meltwaters that will someday become the Missouri and Ohio rivers.

The North Pacific and Alaska come into view — more ice? Yes, but not only ice. While the Coast and Alaska ranges are massive bastions of white, there are great lakes thawing under the summer sun in the Copper Basin and the inner part of Cook Inlet. And between the Alaska and Brooks Ranges there are wide sweeps of grassland, green with meltwater and the warmth of the sun, extending westward across what has been and will be the Bering Sea to Siberia, then sweeping onward thousands of miles to the back of the European ice sheets. Only an occasional mountain range carries an ice cap there, but areas of tan and gray are visible even from space — dust storms, sand dunes, and plains of silt and gravel dropped by the meltwaters from the glaciers. North of the ice-capped Brooks Range, the cracks that opened in the chill of last winter filled with drifting sand, rather than snow.

As you move into the Fairbanks area for a landing, you startle a small herd of shaggy ponies into headlong flight, and a few moments later a group of bison stampedes as well. Their small hooves, designed for speed on hard ground, are only slightly impeded by the moisture still oozing from the few remaining patches of snow. This is mineral soil, blooming with grasses, sedges, sagebrush and wildflowers in the spring flush of moisture, not muskeg.

The trumpet of a startled mammoth splits the air from the line of willows and taller grasses along the river, and a family of the huge, long-haired animals moves into view. They are edgy, and with good reason — a saber-toothed tiger has had its eye on the new calves for several days now.

Eighteen thousand years ago is an extreme case, near the height of the last ice age. But if you picked a random time in the last half million years, it would likely be closer to the icy picture I’ve just described than to the world we are familiar with today. Less than ten percent of this period has been as warm as the last few thousand years, or with as little ice on the land. Exact dating prior to about thirty-five thousand years ago (the limit of accurate radiocarbon dating) is still a problem, but many lines of evidence suggest a long series of ice ages, separated by relatively warm interglacials around ten thousand years long and close to a hundred thousand years apart. Our current interglacial has lasted a bit more than ten thousand years. Are we due for another ice age?

Since the glaciers of Antarctica, Greenland, the Canadian Arctic, and the mountain glaciers of modern Alaska together account for a third of the total area of the great ice sheets of the glacial maximum, we could argue that we are still in an ice age — that even what we think of as interglacials are in fact mere pauses in an ice age that has lasted for well over a million years.

Whether we label our era a minimal ice age or a true interglacial, our present civilizations are in balance with the climate. Consider: sea level rose over three hundred feet in the last twenty thousand years, drowning what was once dry land. Vast areas of the Bering and Chukchi seas, for instance, were steppes and cold deserts when the water that now covers them was locked up in glacial ice. Much of our concern about the onset of a “greenhouse” warming comes from the possibility that parts of the remaining land ice could melt, causing a further rise in sea level. If that should happen, shoreside cities — Homer and Honolulu, Nome and New York — might go the way of the Bering land bridge. Ice ages are by no means a problem only of the past.

This is an excellent DVD for getting across the idea that the inner workings of the earth, while at times disastrous, are essential for life.

The DVD actually has two programs, both originally shown on the Discovery channel: Inside Planet Earth and Amazing Earth. The graphics are intriguing, though some are repeated a bit too often. The actual camera work is excellent.

My only objection was that at times the narration could be misleading. True, we have been in an ice age for the last 40 million years. But most of the evolution of mammals – and certainly of humans – has taken place during that period. We are adapted to an ice age in the broad sense. My concern is that many people will take “ice age” to mean the periods like 20 thousand years ago, when ice sheets covered much of North America and Europe.

Over all, I found this a good program if a bit sensationalist – and this is my field, so I am aware of shortcomings.

There are times when I slap myself on the head and wonder how I could have been so stupid. Not often twice in the same day, as was the case today.

I have been worried about the local predators, with no warnoff. All the while, I have of course been recording this on the computer in the emergency capsule. Today it occurred to me to check out what else was in the computer programming.

There is a library. With detailed information on how a warnoff is made. My first reaction was “wonderful — if I could get the parts.” Then it occurred to me to check whether the library had an inventory of what was in the emergency capsule.

It does. Ant the supplies include a limited number of all-purpose chips that can be programmed in a variety of ways. Including those necessary to produce a warnoff.

It may take some tuning, but it seems I shall soon have some defense against being eaten.

You – whoever you are that may be reading this – have no idea what a relief it was to know that I would soon have the basic protection I have been accustomed to since infancy. More than just accustomed to – it had honestly never occurred to me that anything would want to eat me.

All afternoon I labored, thinking that now I could start exploring a little farther from the capsule. Not too far; the capsule still provides protection while I sleep. Then, shortly before I finished the first warnoff, I had another “duh” moment. I can teleport. Not to somewhere I have never been, of course, but as long as I am eating regularly, I can teleport back to the capsule. So I can travel a full day’s distance from the capsule and still have its safety at night. Furthermore, there is nothing to stop me from memorizing the last place I reach in the evening and teleporting to that place the following morning, to continue my exploration. Why, I could cover the whole continent!

It is growing dark, and while the surviving solar cells of the capsule keep the computer going, I do not wish to use them more than necessary. Tonight I shall try to remember all I can of what I saw of this landmass as I crashed. I think the ocean was to the west, and I should try first to find it. Then work along its shores, find a river, and follow it inland. Perhaps I can find the reason the local herbivores seem to regard me as a predator.

(Earlier Parts of Jarn’s story can be found by searching “Writing — Confederation History.”)

This is the third in the Walking With Dinosaurs series in terms of geologic time and the second in terms of release date. Like others in the series it is unclear what is imagination and what is fact, but the rendering of extinct animals is excellent. One comment on all the “Walking With” videos — animals make sounds for a reason. It may be to freeze or to scatter prey, to communicate with others, or to intimidate a rival — but an animal waiting for an opportunity to attack is silent.

The video is ten years old and some of the paleontology is out of date. So are some of the locations – the evidence for land-dwelling forerunners of the whales, for instance, comes mainly from Pakistan and it is somewhat questionable to put an Ambulocetis in Germany.

The first DVD has six episodes. The first “New Dawn,” is set in the early Eocene, when the earth had settled down from the K-T boundary event and the extinction of virtually all large animals. Mammals are still small, and the descendants of dinosaurs — the birds — are the dominant predators.

Later in the Eocene the mammals are beginning to take over, and the second segment, “Whale Killer,” focuses on marine and estuarine life. It also considers the climatic results of changing ocean currents due to plate tectonics.

The third episode, “Land of Giants,” is set in the Oligocene and focuses on a single type of animal, the indricothere, although others are shown as well. Imagine a rhinocerous the size of a giraffe! I’m not sure they gave their indricotheres the right environment, though.

The early evolution of our own species is covered in the fourth episode, “Next of Kin,” which centers on an australopithecine clan. Grass has now evolved, making backgrounds much easier for the filmmakers to find. This episode is relatively recent, only a little more than 3 million years ago.

The fifth episode. “Sabre Tooth,” is set in South America a million years after the Panamanian land bridge has opened, ending 30 million years of isolation. The old top predators were terror birds, much like those of the first episode. This episode focuses on the North American predator that has replaced them, the sabertooth cat.

The sixth episode, “Mammoth Journey,” takes place in Europe at the height of the last ice age, when two sub-species of humans shared the territory with a number of cold-adapted animals. Living in Alaska and knowing that mammoths did quite well here during the ice age, I am not so sure that the cold would have forced them to migrate out of the lush pastures of the North Sea, though.

Don’t forget the second DVD in the set. This has a good deal of information on how the episodes were made, interviews with the producers, model-makers and animators, and some behind the scenes information on the animals themselves and the evidence for their existence.

A fiveday has passed, and I am still alive. Life here almost certainly uses left-handed proteins, which is good news for me as I have only a few months’ worth of provisions with me. This means I must learn to live off the land.

I have been watching what the local herbivores eat and sampling it, but the leaves and the fibrous ground cover have too much cellulose for me to digest. Fruiting bodies and seeds are much more digestible, and in some cases even palatable, but they have to be sampled with caution – some are toxic. There are a number of local herbivores probably a good deal better to eat than the vegetation they thrive on, but I cannot bring myself to call them to me to kill them. If I see one injured or in pain I would have no such scruples, but the local predators generally kill the weaklings.

Oh yes, the predators. I’ve seen several more. They are all afraid of fire, and I get the distinct impression some have seen it in a context other than wildfires. There are several of the ambush predators: a yellow-coated variety that weighs a good deal more than I do and hunts in groups; the spotted one I mentioned before, and a smaller, incredibly fast spotted one that seems unable to climb trees. There is a group that makes a weird noise and has a rather hunch-backed silhouette. Others resemble the pack hunters but appear solitary. Like most predators, they are perfectly willing to scavenge each others’ kills.

I hope that the modifications I made to the emergency capsule are sufficient to keep them away while I sleep!

The herbivores are even more varied. Many have horns on their heads, ranging from simple knobs to daunting scimitars. These all feed on the fibrous stuff. There are some huge ones that I thought at first sight had tails at both ends. At least two varieties occur in large herds. One is horned and I think migratory. The other is one of the few animals I have seen without horns, but they have a very distinctive coat – black and white striped.

What really has my attention is that almost all of these animals are frightened of my presence. Not that I seem strange to them, but as if I am a known predator. Could there be a species here superficially similar to my own? If so, they are rare in this area.

In many ways this is a retrospective. Walking With Dinosaurs came out almost 12 years ago, in 1999. Last century stuff. But it set the stage for all the dino-documentaries that have come out since.

When it came out, realistic computer-generated dinosaurs were certainly a possibility in movies – Jurassic Park preceded and partly inspired Walking With Dinosaurs. But managing this quality of CGI on a television budget, treating the whole thing as a documentary and bringing in paleontologists not only as advisors but at times as collaborators, was new.

I do have some quibbles with the six episodes. First, there are a few places where the narration is just plain wrong. I’m not talking about things that were learned after the film was made or guesses that are presented as fact; I’m talking about things like the statement that carbon monoxide is heavier than air. In fact, it is almost exactly the same density as air. The suffocating, low-lying gas that is produced by volcanic action, and is heavier than air, is carbon dioxide.

Second, there are many things in the DVD that are pure guesswork. Some of these are pretty obvious, like the colors of extinct animals. No real problem there — they had to be some color, after all, and why not pattern them after existing reptiles? In some cases, such as pterosaurs getting around on the ground, even the paleontologists learned something from the animators’ efforts to get the animals to move. But flat statements such as the one that cynodonts paired for life, for instance, seem sheer guesswork.

Finally, this DVD has to be watched with recognition that a great deal has been learned about dinosaurs in the last 12 years. We now know, for instance, that a great many of the predatory dinosaurs had feathers, probably both for insulation and for display. Our ideas about the social life of dinosaurs are also undergoing a transition. The DVD shows Tyrannosaurs as solitary animals, guarding their territories jealously. There is increasing evidence that they may have hunted in packs, with a social life more like wolves.

Do look at the second DVD, the one that has “The making of” sequence. This points out things that are all too often ignored in later dino-documentaries, such as the fact that grass evolved quite recently, and was never present when the non-avian dinosaurs were alive.

This was the first made of the “trilogy of life” series, though it is the middle one in terms of geologic time. This trilogy is still probably the best of the dino-documentaries.

We broke 12 hours of daylight Friday, 2 days before the equinox. Why? And is this just due to my being close to 65 degrees North, or is it a more general anomaly?

There are two parts to this peculiarity. One is latitude combined with the finite diameter of the sun, which can be calculated. The other is the refraction of the atmosphere, which varies from day to day and can only be estimated.

Let’s take latitude first. Sunrise and sunset are defined as the time that the upper edge of the sun is just visible above a flat horizon. “Equal days and nights” (which is what equinox means) assumes the dividing line between day and night is the time when the center of the sun is on the horizon, assuming light moves in straight lines. If the sun rose vertically, as it does at the equator, it would rise at a rate of about 1 solar diameter a minute, and the calculated sunrise time based on the center of the sun would be only half a minute after the time the upper edge first showed.

At higher latitudes, however, the sun appears to rise at an angle and sunrise and sunset appear slower. At 65 degrees latitude the sun’s path at the equinox is 65 degrees from the vertical, and a little trigonometry stretches that half minute to about 1 minute 10 seconds, or twice that in day length. Latitude alone is still not enough to allow our days to be 12 hours 15 minutes long at the equinox. For that, the refraction of the atmosphere becomes important.

The apparent break in the spoon handle is due to refraction.

Everyone is familiar with refraction, though you may not know it by that name. The optical illusion of a broken spoon in water is caused by the fact that the speed of light in water is less than that in air. Yes, the speed of light in vacuum is constant, but in any other transparent medium it moves a little slower. When it crosses a boundary between two transparent media with different speeds of light, any light rays not moving at a right angle to the boundary are bent. Air is one of those transparent media, and while the speed of light in air is not a great deal slower than that in vacuum, there is enough of a difference that the bending affects what we can see.

The actual difference in speed depends on the density and moisture content of the air, which in turn depend on pressure, temperature and relative humidity. Air near the ground is almost always denser than that above it, and this is particularly true at sunrise. The change with height is gradual, and thus the light rays are not bent sharply, as in the water-air interface, but curved along the earth’s surface. Objects far away appear higher than they are, and this certainly applies to the sun at sunrise. The amount by which the sun appears higher in the sky than it really is will depend the atmospheric density and how it changes with height.

For practical purposes the time of sunrise is calculated assuming that the upper edge of the sun is visible when the center of the sun is 50 minutes of angle—almost a degree—below the horizon. This also means that the sun at the equinox will rise not quite due east, as it “rises” while it is still physically below the horizon and slightly north (in the northern hemisphere) of east. The difference, however, is slight.

Refraction is also responsible for the fact that the sun appears to flatten as it approaches the horizon when setting or just after rising. The part of the sun closest to the horizon is more strongly affected by atmospheric refraction than is the upper part of the sun, so the two appear pushed together and the sun appears flattened, rather than round. I’ve probably overused this in Tourist Trap.

Sunset Dec 21 at Fairbanks, latitude 64 degrees 50 minutes. Photo taken about 2:40 pm, looking a little west of south.

Happy Southday! (Or, if you don’t follow time as measured on the planet Central, Happy Winter Solstice.) The days in the northern hemisphere are getting longer again!

Solstice has nothing to do with distance from the sun. In fact, we are rapidly approaching our closest approach to the sun, around January 3. But because the earth’s axis is tilted relative to its orbit around the sun, there are times (the solstices) when one pole or the other comes as close as it ever gets to pointing directly at the sun, while the other is as close as it can get to pointing away. That happened on Dec 21 this year with the north pole pointing as far as it could get away from the sun.

On the winter solstice, the sun never rises north of the Arctic circle, while it never sets south of the Antarctic circle. Closer to the equator it rises and sets, but the northern hemisphere days are at their shortest for the year, and the sun at noon is at its lowest in the sky. The low sun and short days combine to minimize the solar heating of the ground and water. The opposite is true in the southern hemisphere, where it is the first day of summer, and both day length and solar elevation are at their greatest for the year.

Our Earth’s axis of rotation is 23.5 degrees from axis of rotation of its orbit around the sun. What would happen if that angle were 0?

I actually invented such a planet, called Eversummer, for my second science fiction novel, Tourist Trap. It wasn’t exactly paradise!

The planet’s name, Marna thought, must have been picked out by a publicity agent.  Everspring would have been more accurate, or Everfall, or perhaps Constancy.  Maybe even Boredom.

The planet, with its rotational axis almost perpendicular to its orbital plane, had no seasons.  The poles were bitterly cold, glaciated wastelands where the sun forever rolled around the horizon.  The equatorial belt was an unchanging steam bath, the permanent home of daily tropical thunderstorms, varied by hurricanes along its poleward borders.  The desert belts, inevitable result of the conflict between the planet’s rotation and its unequal heating by its sun, were broad and sharply defined, with no transition zones where the rains came seasonally.  The temperate zones, between desert and polar ice, were swept year round by equinoctial storms, varied only by occasional droughts.  No monsoons, no seasonal blanket of snow to protect the dormant land, no regular alternation of wet and dry seasons.

Would you like to live on such a planet?