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Archive for March, 2010

Why, you might ask, would anyone discuss ballooning in a serious history of science? It’s just a hobby.

Well, first of all, ballooning was and still is a really interesting conquest of one aspect of the physical world; second, balloons remain an important tool in the study of weather, though they now go unmanned.

Ballooning Defined

Ballooning means using a vehicle that is inflated and floats. Airplanes, which are heavier than air, came after the balloons.

Principles and limitations

A balloon can be floated with hot air, which is cheap but inevitably cools; otherwise, balloons use some gas that is lighter than air. Hydrogen and several other gases are fairly cheap candidates, but they’re also flammable, so they’re dangerous. Helium is safe but expensive.

When hot air is used, the balloon loses altitude gradually and naturally as the air cools. If you take a heater up with you (and don’t set fire to the balloon) you can easily change altitude by letting the air cool or by re-heating it. This is nice because you can sometimes find a different wind direction by changing altitudes; on the other hand, sometimes you can’t — all these first experiments were done before much was understood about high-altitude world-wide winds such as the jet stream. It was incredibly risky, but on the other hand, that’s how we learned what was up there, and some people have more curiosity than prudence, perhaps due to an oversupply of serotonin.

When a light gas is used, the balloon only comes down when the gas leaks out. You gain altitude by dropping ballast – a few bags of sand work well and can be emptied little by little; and you lose altitude by letting the gas out. Eventually, someone struck on the idea of building a valve into the balloon. Keep in mind that there’s always a danger in riding a balloon which goes where the wind takes it, rather than in a direction you can plan, so you want maximum control over altitude at least.

Tethered balloons were a fashionable amusement for a while; they give their passengers a good, unobstructed view of the world, and, compared to building the Eiffel Tower or the Empire State Building, they were (and still are) a relatively a cheap way to get up pretty high and view an awesome landscape.

In time, horizontal, torpedo-shaped balloons, called dirigibles, were developed. These could be steered, and were soon adapted for commercial use, even for international travel, including circumnavigating the world. Inevitably, however, one burned, bringing the commercial dirigible flight to an ignominious end.

Rozier balloons use both hot air and gas (in separate compartments) to get the advantages of cheap hot air for altitude control, and helium for lift. Rosier himself crashed while trying to cross the English Channel, but modern long flights in balloons use his idea – hot air is cheap and allows easy ups and downs; the light gases are more expensive, but they provide lift as long as you can keep them from leaking.

History of ballooning

The Kongming Lantern was developed in China, a few centuries B.C. It is basically a candle attached to a small air pocket – the candle keeps the air hot for as long as it burns. The invention is attributed to Zhuge Liang, who lived in the 3rd century AD, but it seems clear that the little device was around long before that. In any case, the lanterns were made of bamboo and oiled rice paper and were used for signaling; then, being pretty, they were used for festivals. Not a good plan for a dry climate, of course — it’s dangerous if the balloon comes down before the fire dies — but obviously a very pretty sight if all goes well.

Ahem: the history

In 1710, Father Bartolomeu de Guzmao of Sao Paulo Brazil, visiting in Lisbon for his education, made a large paper balloon which had a clay fireplace inside and which lifted off in the presence of the king of Portugal. Since he was inside a building, the servants quickly attacked the balloon, lest it set fire to the curtains. Within a year, the good father himself took a short flight which ended in a minor crash. He survived the crash, but his reputation was never the same. Still, he was the first man to go so high. Those Portuguese!

In 1766, Henry Cavendish produced hydrogen, which is lighter than air, and Joseph Black immediately suggested the possibility of a manned balloon. The race was on to get into the sky. Because it was difficult and expensive to make hydrogen Cavendish’s way, the use of hydrogen waited until people learned to obtain it by electrolysis of water; then it was relatively easy and cheap.

In 1783, the Montgolfier Brothers, who owned a paper company and could produce paper in massive quantities, took off from near Paris in a hot air balloon. The (their pilots, that is) went almost 6 miles (ten kilometers), keeping the air hot with a cast iron stove (Eek!) up there below the paper balloon, and feeding the fire with straw. (Are you kidding?!) They could not see each other from the opposite sides of the stove, and they couldn’t hear very well, either, so they had to shout. People on the ground heard their excited shouts, and assumed they were exclaiming about the view. In fact, one was saying, “Let’s get down; this is long enough,” and the other was shouting, “Don’t just stand there; put more straw in the fire.” Eventually they came down safely.

In December, another team, using hydrogen, took off, also from near Paris, and stayed in the sky for several hours. When they got down, one stepped out and so lightened the basket that the balloon immediately rose again to 10,000 feet. It was intensely cold, intensely solitary, and memorably scary, but the design included a valve that would let out the gas in case there was need of descent. He made his observations of barometric pressure, temperature, and wind, opened the valve, and came safely and gracefully down. He never went up again.

Two years later, the first sky disaster took place when a balloon crashed in Tullamore, Ireland, and set the town on fire. They lived and rebuilt with a phoenix as their seal. I don’t know who flew this, and I assume he died.

The first American flight was in 1793, with George Washington in attendance, and the first balloon that could be steered (what a concept!) was Henri Giffard’s balloon in 1852. It was launched in France, and here’s a link to a picture. It doesn’t look like something anyone could steer, but what do I know?

Reconnaissance.

Obviously balloons had a potential reconnaissance value, and the military of every nation eyed them thoughtfully as soon as they began to look like something that might turn up in the other guy’s arsenal.

In America, at the first Battle of Bull Run (also called the first battle of Manasses) on July 21, 1861, the Union had a balloonist who, using flag signals, helped them direct their artillery fire to the precise location of the enemy headquarters. The Union lost that battle anyway, but they would have lost much worse without the balloon. Reconnaissance balloons were then towed along the Potomac for other battles, including Vicksburg and Sharpsburg. The Confederates also tried ballooning, but they couldn’t match the Union supplies.

There was some discussion of using balloons for dropping firebombs, but evidently that seemed ungentlemanly in those gracious days, so it didn’t happen until we got into a war where the values didn’t include gentlemanliness.

In the winter of 1944-45, the Japanese sent balloon firebombs riding the jet stream to the US. Automatic altitude sensors triggered gas escape if they got too high and sand leakage if they got too low. Only a tenth of the released balloons arrived – but out of 9,000, a tenth was plenty dangerous. It took a while to figure out where they were from, but geologists examined the sand that was used to control their altitude and recognized the mineral configuration of the Japanese coast. Little harm was done though some children were killed at a picnic, but the Americans realized that if bio-weapons were loaded on such craft, the damage would be incalculable and this was an active concern. American B-29s ruined the hydrogen generation plants, and the war came to an end before the next winter.

(The jet streams were not at the right latitude to bring us balloons in the summer.)

Meantime… aircraft

Balloons and dirigibles had the effect of whetting the appetite for true airplanes, whose concept, however, is actually somewhat different, being heavier than air, not lighter, and the first prize for this achievement goes to the Wright brothers. It is true that in France, in 1898, a Brazilian inventor named Alberto Santos-Dumont flew an untethered balloon craft around the Eiffel Tower and back to Parc Saint Cloud in thirty minutes. He won the first prize for manned and steered flight, so Brazilians credit him with accomplishing the first manned flight. Note that this was a dirigible, not a heavier-than-air craft.

After the Wright Brothers, ballooning diverged from the development of heavier-than-air craft. Dirigibles had a generation of commercial life, but the usual problems proved insurmountable: hot air does not last, helium is too expensive, other gases are too dangerous. A fellow named Zeppelin made several large dirigibles that worked commercially, crossing the Atlantic and even going round the world, but eventually, inevitably, disaster struck. The famous Hindenberg caught fire while landing; 35 of the 97 on board died, and that was the end of ballooning.

Sport Ballooning

Well, not quite the end.

In the 1950’s, Ed Yost 50’s started modern ballooning as a sport, using rip-stop nylon and following the Rosier design of some hot air for altitude control and some gas for a reliable long life. New records for all aspects of ballooning were set year by year until, in 1999, the Breitling Orbiter 3 circumnavigated the world in 3 weeks.

Amazing.

Pass the serotonin.

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Of course thousands of things happened in geology in the 20th century, but two stand out as changing the whole approach to geology not just one particular detail. These two are plate tectonics and space geodesy. The first is a new and more comprehensive view of the Earth and its changes, based on the idea that whole continents move about on an underlying sea of convecting rock. The second is the vision and then the use of a new set of tools, specifically satellites that would look at the earth from above and, using camera and radio, send whole new images of everything we have ever seen or known or tried to map.

Plate tectonics

What makes mountains? The effort to answer this question had gone through a lot of changes by the twentieth century. Obviously some mountains are volcanic – but equally obviously to the thoughtful observer, others are not. Mount Monadnock – and all other monadnocks – are just fragments of high land, leftover after the erosion of everything else. They are not and never were volcanic.

Why didn’t they erode with everything else? Maybe there was an especially resistant stone formation at the top of a monadnock, such as the vast slab of pure quartz on top of South Pack Monadnock. But that’s not a common form. Other questions persist.

Why do mountains march in lines?

So many of our mountains are in lines and chains. Why is that? A line of mountains demands that the geologist look for the reason for the line, not just the reason for the mountain. That’s much more demanding. Even if it’s volcanic, why would a bunch of volcanoes be lined up? On the Moon and on Mars, they’re just random pock-marks. Why is Earth so different?

Kudos if you know the answer, but then ask yourself at what point in history might you have guessed it?

Could continents drift?

The concept that whole continents might be on the move, the concept of continental drift, is generally thought of as a 20th century idea, but it was first proposed in 1596 by Abraham Ortelius. Isn’t that a surprise! He was a Flemish cartographer, just 100 years after Columbus, and so he was basically one of the first men to compare the coastlines of the Americas with the matching coastlines of Europe and Africa. The match leaps to the eye, and he suggested that volcanism and floods had separated these vast lands. At a certain simple level, this is not far from the truth: continental rifting involves volcanism and can open interior lands to the nearby ocean; but notice that now we are talking about an extraordinarily extended line of volcanism – the mid-Atlantic rift. Look at it! Thousands of miles long! How does that happen?

MId-Atlantic Ridge/Rift

Here is the center of the Atlantic Ocean, assumed to be a plain until discovered to be quite otherwise!

The failure to find an explanation for such massive rifting prevented the acceptance and development of Vesalius’ idea for the next 300 years. Not for lack of effort! It was proposed that the interior of the earth was more dense than the outer crust (which is true) and that periodically the interior simply burst through original super-continent, breaking it up into the continents as we now know them.

Wrong.

Alternatively, it was proposed that the Earth gradually enlarged by consuming the ether, and this enlargement stretched the original continent and then pushed its pieces apart.

Wrong; almost funny. Note that such growth would change the gravity of the Earth and its relationship with the Moon.

The idea of a broken super-continent would have been dropped completely except that new evidences for a past closeness between the continents kept surfacing in things like similar fossils or similar stone and soil chemistry in precisely the locations that would once have been close if the matching coastlines were attached in ancient times.

From continental drift to plate tectonics

In 1912, Alfred Wegener marshaled all the evidence for continental drift and argued forcefully for it. The idea never went away again, but there was still no credible mechanism to drive the motion of entire continents. He even pointed to the Mid-Atlantic Ridge zone as a spreading zone, but there seemed to be no way for the continents to ride over the wide oceans, so he dropped it. He wasn’t seeing the continual generation of new ocean floor as part of the picture.

In 1928, Arthur Holmes suggested that convective motions in the mantle might drive the motions of the continents.

If you go to make oatmeal, jelly, or soup from soup bones – any cooking that involves an episode in which scum rises to the surface, — you have a chance to see how convection cells from the bottom of the pan drive little mats of surface material from side to side, occasionally joining them, occasionally breaking up a large mat. In the case of cooking, the scum is soon driven to the sides of the pan, but on the Earth, the bottom of the pan is the inside of the planet, and there are no sides. The mats of scum, the islands and continents, go from side to side and are occasionally driven all together, and later driven all apart.

So at least Holmes had a mechanism, but it seemed too far-fetched. The pressures on the mantle are very powerful and it is very rigid. And if ever the continents were driven together, why not stay that way?

Well, for one thing, there would be a build-up of heat below such a large continent, and that might soften it and start volcanism… Maybe.

But even aside from heat buildup, the convection cells which are carrying the continents change in size and orientation – convection cells are more or less random things – and when two cells are pressed together such that their upwelling centers draw near, the stress on the overlying land is such as to pull it apart. This is happening right now in Nevada, and is the cause of its extensive hot springs.

Still, continental drift was not accepted until the 1960’s. It was hard to imagine the convection of solid rock, no matter how hot. It was only when all the ocean floors were surveyed in detail in the 1950’s that deep-ocean ridges were found in every ocean and a new piece of evidence needed a home. Now the question changed from: could the Mid-Atlantic ridge be a spreading zone? to the question: why does every ocean have these ridges?

It was in answer to that question that Arthur Holmes’ suggestion finally took its proper place in geology and the slow, slow convection of the mantle, solid as it seems, was accepted.

We know, then, why mountains often form in lines and ranges. Mountain ranges are formed by the subduction of one tectonic plate below another and the resulting turmoil (long story for another day) along the line of contact.

Mars and the Moon don’t convect, and thereby hangs a tale.

Space geodesy

The second great shift in 20th century geological understanding was a matter of new tools, and was as fundamental as the invention of the telescope.

The basic difficulty about mapping the whole Earth so that you can really see these mountain ranges and their rivers, lakes, and other geology, is that it is so hard to measure great distances. You can walk across your garden with a tape measure; fine. You can, with a good watch and a good companion and good weather, time the difference between the moment that stars disappear behind the Moon in different locations. That can be translated into miles. And, once you have the instruments, you can even send mirror blinks from mountaintop to mountaintop and time them for distances, presuming that the mountaintops are not too full of vegetation to see or too glacial to climb or too full of wild animals or volcanic smokes to prevent access. No mountain will help you measure the Pacific, of course. Airplanes help, but you have to know your speed and direction, and so many things confuse that, jet streams for one.

So it’s difficult, you see.

But if you could go to the Moon and just calmly look down…?

No, the Moon is too far away to be much use.

But… If you had an artificial moon, a satellite that was just high enough to stay in orbit but just low enough to stay in good communication and take good pictures, that would really help. When John O’Keefe proposed this to the Army Map service after World War II, they thought it was ridiculous. But then they changed their minds and it happened. Satellites are totally a part of our world now, and what they have told us about everything from inaccessible mountain ranges, to magnetic anomalies is a crucial part of our comprehensive geological knowledge. Life without satellites seems like life in the stone age.

Ah, if  Mungo Park could have had just one such picture of the river he was surveying!

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Let me just give you four famous names to anchor the idea of what sorts of things went on in geology in the 19th century. Actually, all of these four belong to the first half of the nineteenth century, a time when fossil hunting became an international pastime. Although the actual dates of the animals behind each fossil were not clear for another century, the work of sequencing them went forward through the work of many men and women. Let’s start with the most famous woman, because she really was justly famous. Probably would have been more so if she’d been wealthy.

Mary Anning

Mary Anning was famous for finding many fossils, including the first nearly full set of Plesiosaurus bones, the first squaloraja, an ancient form that lies between sharks and rays, and several other firsts. She was the child of a cabinet-maker and fossil hunter, not a member of the upper classes who could afford to comb the beaches for bones day by day, and it took a long time to build her reputation. Not only did she find fossils, however, but she read up on all her finds and became a real expert in the anatomy implied in all the bones she discovered, and she corresponded with several men who were quite professional. Her dates are 1799 – 1847, so basically the first half of the nineteenth century, and if you want some local color on the topic of 19th century fossil hunting, read about the “bone wars” in South Dakota.

Georges Cuvier

Georges Cuvier was actually a little earlier than Mary Anning, 1769-1832. You may remember Joseph Banks and his trip to Tahiti in 1769, just by way of orienting yourself: Cuvier was born while Venus was transiting the Sun. At the end of his life, in 1832, America was trying to hold off the crisis of slavery, and it was still thought that this could be done peacefully.

Anyway, Cuvier’s greatest achievements had to do with taxonomy. He recognized the depth of the difference between African and Asian elephants, which meant they had been separated for a long period of time; then also recognized that the bones of megatherium were an entirely different animal, a mammal of similar size, but not a particularly close relative. In that context, he came to believe that there had been extinctions and therefore catastrophic change in the distant past. This was a whole different line of evidence for drastic changes in ancient times, and also an argument for noticing the substantial family differences among animals which must also suggest long periods of past time.

William Smith

The third name is William Smith, also born in 1769, but Smith lived a little longer, in spite of incredible hardships, including an effort to steal his work and accuse him of the thievery. This is the man who made that incredible map of England, showing how the sedimentary layers – coal, limestone, sandstone, etc, — crossed the entire breadth of England, rather than being random pockets here and there.

We first met Smith when we began to talk about coal mining, because it was in the coal mines – in the mineshafts to be specific – that he first saw the repeated sequence of sedimentary layers which he later mapped so fully. Here’s the map (click to see the whole map):

William Smith's geologic map of England

Look for the intersection of all these complex layers -- and find the city of Bath, England

Alexander Brogniart

Our fourth name is Alexander Brogniart, a Frenchman who lived from 1770-1847. While others were finding fossils and cataloguing them, this man did the important footwork of developing a system of index fossils, so that the little stone creatures came to mean specific geologic eras. He worked with trilobites, all of which are 250 million years into the past, with dinosaurs which belong to the time period between the trilobites and the age of mammals, and with the most recent times as well. What this indexing meant was that after Brogniart, the discovery of a fossil became a quick way to assign a geologic era to the rock that enclosed it, thus helping others close in on the geologic dating system that is now familiar. And all this work was primarily by way of a hobby related to his mining interests. His salaried job was in ceramics, and he did pioneering work there as well.

From sequences to dates: 20th century

It was with the 20th century discovery of radioactivity by Marie Curie, and then the discovery of the half-lives of various isotopes, that genuine dating of rocks became possible. Whole new vistas opened as the sequences so painstakingly put together were gradually transformed into dates. Geology gradually became a story, not just a geography of mining or quarrying, and the geologic column became the means of learning the stories of local landforms, their changes and the history of the animals who once roamed them.

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18th Century

By the 18th century, a certain amount of wrangling about sedimentation had led to two famously conflicting theories:

There were the original young-earthers, called Neptunists who stuck with the Biblical chronology and tried to make geology fit. One of their famous representatives, Abraham Werner, 1749-1817, believed that almost all stone was sedimentary, having originally accumulated by precipitating from the mineral-rich oceans and falling to the bottom of the sea: thus this school of thought is named for Neptune, the Greek god of the sea. Whatever events didn’t fit into this gradual schedule were assumed to belong to some catastrophe – the principal catastrophe being, of course, the Great Flood of Noah. Obvious volcanism was thought to be rare.

On the other side were the eternal-earthers, then called the Plutonists, who thought primarily in terms of volcanic origin and were therefore named for the Greek god of the underworld from which such stone must come. They loved seeing large swaths of time and swept to the conclusion that the world was eternal.

Because there was a constant stream of new evidence for an earth older than anyone had yet imagined, the Plutonists were always pushing on the Neptunists, and making fun of them. The Neptunists, in turn, accused the Plutonists of being irreligious; it was sometimes fully true, but not always.

Old vs eternal

In any case, the gulf between “old” and “eternal” is vast, indeed infinite, and after a hundred years of Plutonist push, it was discovered that, while the earth is very old, about 4 ½ billion years, it is not eternal, not even a trillion or a hundred billion years old, not even ten billion. Even the entire universe is finite in time, being only 12-14 billion years old. The lines of argument have changed only slightly, however, and it remains exceedingly difficult to get the eternal-universe camp to talk sense about the implications of a finite universe or to get the young-earthers to talk sense about the great age implied in geologic processes.

James Hutton

The most famous early representative of the Plutonists was James Hutton, (1726-1797) who believed that when volcanic rock was worn down to sediments, it went into the sea and was then recycled as new volcanism. He believed that all this took place in eternal cycles. His doctrine of uniformitarianism held that all sedimentary rock was formed by incredibly slow processes, just the same sort we see now.

Several of the most fascinating and famous geologic formations on earth were first brought to the attention of the scientific world by Hutton and now bear his name. They are each called Hutton’s unconformity, as if there were only one, but, having found one, he soon found others. Siccar point is the most striking and famous. Here is one image made available by Wikipedia:

Hutton Unconformity, Siccar Point

Notice the horizontal and vertical layers of rock.

An unconformity is a geologic formation in which the lower layers are separated from the upper not merely by a change in chemistry, as if climate had changed, but by a change in orientation, enforcing the interpretation that one formation was deposited, lithified (turned into stone), tilted at some rakish angle, then eroded, and then used as the bedrock for a new round of sedimentation. Such sequences inevitably pushed Hutton’s thoughts beyond the time frames of his contemporaries.

How far beyond?

I do not know whether or how he spelled that out, but he was certainly thinking of tens of thousands of years, and that does not include the volcanic recycling which he assumed must also take place in endless cycles.

Georges Buffon

His French contemporary, Georges Buffon (1707 – 1788) thought that the earth must be 75,000 years old, based on the cooling rate of iron, which he figured must have started out molten, worldwide, and then gradually cooled over the history of the earth. 75,000 years doesn’t seem like much now; it’s not even close to a million. But it took him out of Bishop Ussher’s realm.

Land and volcanism

Just to be clear, and in regard to the Plutonists: the earth was originally molten and in that sense all rock has indeed, a fiery origin. As magma comes in contact with the upper crust, it cools and it eventually encounters weather and then, as they saw, it must slowly erode into the sea. But (hello Neptunists!) there is no easy step from here to new volcanism. When tectonic plates collide, a certain amount of crust goes under, but it is almost always the basaltic ocean floor which dives, being heavier than continental rock. Only in the case where two continental plates collide, as in India’s encounter with Asia, does one continental plate ride up, and this does not necessarily breed volcanoes. Basically, continental rock remains continental rock through most changes, and the amount of continental rock is therefore always growing over time. It does not regularly recycle as volcanic rock.

Both slow (uniformitarian) and fast (catastrophic) processes are at work in geology, some of them having a few cycles, but most eventually submitting to a definite arrow of time.

For a cyclic example, we might notice that all the continents have been assembled into one supercontinent at least three times, then broken up and re-assembled. Cyclic.

For examples of a time arrow, there is (despite all news stories!) less volcanism now than a billion years ago, and the radioactive elements, which provide a significant percentage of the earth’s heat, are not renewed, so the earth is actually cooling from within, long term. Although this particular kind of cooling has nothing to do with global climate change, which has a cyclic character, it is a one-way process.

Furthermore, as implied above, the amount of continental rock is slowly growing, for even sediments that fall into the sea cannot be confused with the true seafloor which takes its origin in the mantle and is volcanic.

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Beyond mining, first millenium

After the miners, came the quarries, — stone and eventually limestone and then marble. And then there were the men who noticed the things that implied a history.

In the first century, Pliny the Elder noticed that amber was fossilized resin; he also wrote about gold mining with an eye on geology. He died in connection with the eruption of Mt. Vesuvius, apparently in an attempt to rescue a friend.

Tertullian, & Eusebius, a few centuries later, both recognized that the presence of marine fossils on land meant that the land and sea must have had different distributions in ancient times. Because Italy is located at the meeting place of not two but three tectonic plates, the network of marble is stunning, but there are plenty of marine shells even in marble but also in various other soils, so that anyone in Italy is apt to be confronted with them.

Nevertheless, there is not much famous or detailed work in geology for a while – Christians being much occupied with survival after Rome fell, and again being so occupied as the Moslems swept across many parts of the Christian world. The Moslems themselves did some good work in chemistry and crystallography, both contributors to geologic understanding, but they were not systematic in their observations of the earth as a whole. It is possible that their rules against images hampered them. You can do chemistry and math without drawings, but geology is more difficult.

Islamic geology

Their shining light was named Al Biruni (973-1048 AD), right at the turn of the millennium. Like Tertullian and Eusebius, he theorized that various parts of the land must once have been sea, and then that the sea was doubtless once land, the two exchanging places again and again over time. This is a typically cyclic conclusion; the evidence is not exactly cyclic, though there are some exchanges that repeat. His cycles, however, were not eternal; he did not believe in an eternal universe.

Wikipedia offers this interesting quotation from his work:

“But if you see the soil of India with your own eyes and meditate on its nature, if you consider the rounded stones found in earth however deeply you dig, stones that are huge near the mountains and where the rivers have a violent current: stones that are of smaller size at a greater distance from the mountains and where the streams flow more slowly: stones that appear pulverized in the shape of sand where the streams begin to stagnate near their mouths and near the sea – if you consider all this you can scarcely help thinking that India was once a sea, which by degrees has been filled up by the alluvium of the streams.”

It’s not exactly right; India has been land for a long time and its rivers are its erosion, not its making. But it is an effort to make sense of the landscape in terms of known processes of change, not just take it for granted, so that’s very interesting.

European geology 14th – 16th centuries

In 1335, the citizens of Klagenfurt found the skull of a wooly rhinoceros. Clearly this was the head of an animal they had never seen, but one that had lived in their lands. Must be a dragon, perhaps the very dragon of mythology. A sculptor eventually (1590) made a statue of the dragon, and thereby offered the first paleontological reconstruction – the first effort to portray an animal of ancient times based only on bones. Not enough bones, of course; a wooly rhinoceros is not much like a winged dragon. But he was trying, and the skull is still in the local museum so you know they were interested.

Meantime, Georges Agricola 1494-1555 wrote a very thoughtful piece on mining. He actually recognized that mineral veins must be deposits from solutions rising in the cracks of the rock. That is, he understood that the minerals were originally waterborne and that the rocks were in place before the minerals were added. This positioned him to begin to understand the great time frames involved.

17th Century

Nicholas Steno (1638 – 1686—just 48 years) is the first of the geologists that are actually remembered in standard geology texts. By 1669, he had formulated several laws about sedimentary rock which remain very important:

1)    The law of superposition: that the oldest layer is on the bottom, and the next is superimposed. Seems obvious, but it was not until after he said it.

2)    Principle of original horizontality: that the sedimentary layers were originally horizontal; they were laid down in water and spread out over the bottoms of lakes and seas. Whatever upheavals (time again) might have turned them at some rakish angle from the horizontal, they started out flat.

3)    The principle of lateral continuity – a stratum will reach across the earth until it meets an impediment. This means that if you find a particular sequence in one place and the same sequence several miles away, it’s probably the very same deposit, not just an accidental match.

4)    The principle of cross-cutting discontinuities. Like Georges Agricola, Steno understood that sedimentary rocks might have cuts or cracks, and these might have filled with mineral solutions or volcanic debris. Either way, the discontinuities that cut across sedimentary rock must have formed after the rock was formed. Time, time, time is implied by these observations.

5)    Principle of enclosure printing. If the form of a solid object (such as a shell) is imprinted upon the surrounding material, that material was hardened later than the object was formed and deposited. That is, the dirt which is printed with a shell form was deposited on the shell. If the dirt had been there first, the shell would have had a hard time forming, just as we see tree roots that are shaped to the rocks that were there first.

This seems only common sense, of course. But the question had been asked whether shells grew in the soil as they do in the sea. He was asserting that the rock was formed long after the shells were dropped.

With veins of silver or gold, it is different. Clearly they get their shape from the shape of the broken rocks into which they intrude.

Steno also noticed that in the Apennines, the mountains of Italy, the lower layers had no fossils while the upper ones had many. He figured this meant that the stone of the lower layers was deposited before the flood, and the upper section afterwards. So historical geology was on the way, and there were long time frames involved. Had people remembered this observation, they would no have started down the route of attributing all sedimentation to “the Flood.”

Westminster Confession 1647

It is necessary at this point to mention Bishop Ussher – Anglican Bishop Ussher. He made a great business of studying scripture and proclaiming the date of creation at 4,000 years before the birth of Jesus. In 1647 his researches were enshrined in the Westminster Confession to which the Anglicans, the Presbyterians, the Congregationalists (mostly) and many others were committed to that date for over two hundred years. Some still are. When people say “the Church” had this or that quarrel with science, much of the difficulty came from this document, so it’s a document you need to know about, and a date to remember. It did not claim to be infallible (not exactly) nor did it represent all thinkers of all Churches, but it was there, and it was a very powerful influence on the thought of the English-speaking world.

Note that this is just 22 years before Steno published the laws that would eventually make such a recent date seem so untenable.

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History of geology: early mining

What is geology?

The study of geology involves several related things: landforms of course, rocks and mineral discoveries and then their relation to land forms, crystal forms and their contribution to the classification of rocks and minerals, and fossils (paleontology) which both date and are dated by their enclosing rocks. All these together then allow the development of historical geology, in which the geologic record becomes a record of the earth’s past – ancient climates and ancient animals and plants.

Beginnings of geology

With whom did geology begin? With Adam and Eve, I suppose, if you consider who first saw mountains and rivers.

Flint work goes back tens of thousands of years – flint mines — were remembered and revisited on a regular basis because tools with sharp edges were so valuable.

Inconceivable as it may seem, the Timna Valley near Eilat at the north end of the Red Sea was mined for copper in the 5th millennium B.C.  That’s seven thousand years ago! Copper is found as malachite, a striking greenish stone which must be smelted. How it was discovered that this stone yields copper is anyone’s guess. Perhaps such a stone was used for a fire pit and the discovery followed. Copper mines would eventually lead to the mining of copper ores with arsenic or tin as impurities, and the bronze that could be cast with these alloys of copper. Bronze may have started simply as the consequence of using impure copper ores, but these alloys are sometimes easier to cast and less apt to corrode, so (like many of life’s impurities!) they turn out to have their own value.

Somewhere long ago, gold was discovered. It is beautiful, shining even in its nugget form since it does not tarnish. It is easy to work with both because it is ductile rather than brittle, and so can be drawn out or hammered into incredibly delicate shapes. Egyptian jewelry of 3,000 B.C. was made with gold and precious or semi-precious stones.

There are coal stores at the location of forts along Hadrian’s Wall, so we know the Romans were using coal for heat, and therefore mining it, though not necessarily at any great depth. There are always places where it lies right at the surface, as a visitor to Pennsylvania can easily see. Coal can be made to yield a hotter fire than wood; such a hot fire is important for smelting and working iron. Interestingly, mining for ochre as a red or yellow pigment is associated with iron mining because this pigment is an iron oxide, and its sources are near sources of iron. Read about Clearwell Caves.

All this to say that mining was the practical study of geology in ancient times.

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Earth shadow

I remember how odd I thought it when my mother first told me that I was looking at the shadow of the earth itself. How can one see the shadow of the very planet one stands upon?

But it happens.

About sunset, the eastern part of the earth — the earth to the east of the viewer — falls into the shadow of the earth itself, just as any ball held up in the sunlight sits halfway in its own shadow. At this time, while the western sky holds the sunset colors of red and gold, the eastern sky has a certain share of those colors, but below them lies a distinct area of blue, purple, or blue-gray. This is the shadow of the earth falling on its own atmosphere.

Here it is from the field south of my house, facing east into the shadow.

As the sun sets, the earth falls into its own shadow, and the eastern sky is shadowed blue below its sunset colors.

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