The Captain polished off his whiskey and stood up, knees creaking. “I’ll go on ahead and see if I can rustle up a PhD or two.” He pecked his wife on the cheek and ducked out the door, suddenly full of energy. He loved the old geology building, with its entrances lined with pebble mosaics, its gaudy brass doors, its display cases filled with fascinating rock samples and fossils, and its dank basement where undergrads would camp for weeks memorizing mineral samples or peering in frustration at thin-samples in polarizing microscopes. It was one of the older buildings on Campus, built in the early twentieth century with an eclectic mixture of architectural styles and decorated by scientists with an enthusiastic lack of taste. The charming old heap of limestone contrasted sharply with the stark, ominous, utilitarian boxes that surrounded it on three sides. The 1970s and 80s had been an awkward time for Campus architecture. The monstrosities produced in those dark days looked as if their architects borrowed heavily from the design of Soviet-bloc tenement housing. There were some portions of campus where, if a man had just regained consciousness after a night of heavy drinking, he would find it difficult to convince himself he was on the campus of one of the largest universities in the country and not a state funded housing project in the slums of Bratislava.
The Captain had spent most of his four years of college in the building, and its nostalgia was overpowering. He had spent much of his time between patrols tucked away in some old geologist's office with a few professors, passing a bottle and philosophizing on rocks. Deb found these sessions repugnantly boring, and would recoil in horror when he would inevitably invite her to join him. He had long since given up hope that she would enjoy the rock-talk, but it amused him to watch her fabricate excuses, so he never failed to ask her to come.
The Captain was friendly with the entire faculty and knew most of the graduate students by name. He knew there was only one man who would take pleasure in holding an impromptu, late night lecture. Dr. Rudolph Burns was in his late seventies, one of the oldest men on Campus. Despite his advanced age and perpetually failing health, the craggy old geophysicist still taught five classes a week, and an evening seminar on Fridays. He held both undergraduate and graduate classes in several subjects, clinging to his lectern for support, squinting through horn rimmed glasses with lenses thick enough to stop a bullet. He was renowned for his deadly aim with blackboard erasers. If a student was unlucky enough to nod off during a lecture, he would be assured a chalky revival by one of the well placed missiles.
Noting the late hour, the Captain bypassed the original section of the building which housing the classrooms and teaching laboratories, heading instead for the annex. The annex, one of those unlucky structures which looked as if it had been designed by Slovakian communists, was a three story rhombic prism behind the original building. A two story bridge over a breezeway was the newer lump of concrete's only connection to the limestone of the old structure. Built to house faculty offices and research labs, it was now the department dormitory. Each full professor was designated a block of offices and a lab in which to live and work. Graduate students were packed in on the third floor, sometimes as many as four to an office. All over campus, the various academic disciplines had similar arrangements.
The Captain could hear a frantic muttering behind the door to Burns' quarters. Smiling and shaking his head, he hammered savagely on the door. It was violently yanked open before he could land the third knock. The gaping maw of a ten gauge shotgun yawned before him. At the other end of the huge weapon, a thin, grey haired man squinted down the sights through fishbowl lenses. He had once been tall, but years spent hunched in front of computer screens or peering through microscopes had slumped his posture. An unruly bush of white hair sprouted from his upper lip and mingled inextricably with the twin grey and black forests growing from each nostril. Similar tufts jutted from each ear.
The Captain, still smiling, raised his hands above his head in surrender. "You got me old man, don't shoot! I promise I'll give up this life of sin and spend my time helping the poor if you just give me this one chance!"
"McLelland, you meddling young bastard, what are you doing beating on my door in the middle of the night like the goddam gestapo?" The professor lowered his cannon and leveled a stern squint at him.
"I have a gift for you, Doc: In my travels I've found a ragged troop of young deviants uninitiated in the mysteries of the world of rocks. I wanted to give you the opportunity to fill their empty minds with wonder. Unless, of course, you feel like you’re getting too old to teach?”
The ancient professor scoffed at the suggestion, “You’d better watch that impudent mouth, young man, I’ve still got a few more years of putting students to sleep left in me. Let me get a few erasers good and chalky, I’ll meet you down in 106 in twenty minutes.” He started to close the door but stopped suddenly, poking his head out, “Err…What is it they need to learn?”
Captain McLelland smiled again, “I caught them arguing about volcanoes. I think they need to hear how the world was made.”
“Ah, the question of the epoch: ‘where did all the ash come from?’ Splendid, I’ll be down shortly.”
****
Precisely twenty minutes later, the wizened old geophysicist hobbled into the small classroom, a jumble of papers and ragged books clutched to his thin chest. He looked them over with a skeptical and well-practiced eye. The young rangers were scattered throughout the risered bank of well-worn seats. The Captain and his wife had claimed two of the chairs in the front row.
Burns shuffled to the dented steel desk in the corner and gently deposited his mess of papers, pretending to sort them for a moment. Apparently satisfied with their arrangement, he moved to the center of the room and propped himself against the lectern. He glanced myopically around the back of the room for a moment, then gave the Captain an impatient look, one bushy white eyebrow raised slightly. The gentle chatter of excited young men and women had reached a crescendo.
McLelland took the hint. He half turned in his seat, catching the nearest group of rangers with an icy stare and cleared his throat loudly. The room fell into obedient silence. The Captain turned back and gave the professor a small nod.
"Well then," Burns began, "I trust everyone was able to finish their pressing conversations?" His eyes traversed the room, as if expecting a response. "Splendid, we can begin then. Now, your Captain has informed me that he has foolishly spent all his time training you to kill and has completely ignored his responsibility to ensure you a sound academic education. I know most of you were wards of the state, so you must have had some rudimentary schooling. And, since you each volunteered for the rangers rather than enroll in the only institute of higher learning in the country that is both free to all and still in operation, I must assume that you are satisfied with the paltry level of knowledge that was beaten into you in your primary schools?" There were a few nods from his audience, "Of course you are. I will maintain, however, that you are all idiots. Uneducated ignoramuses." This elicited sour looks. A few of the rangers muttered to each other angrily. Captain McLelland smiled to himself, his expression hidden to those behind him. He had heard this lecture a dozen times.
"Oh I don't blame you for your anger, I know that's not something one would normally say in polite conversation, especially to a bunch of highly trained killers, but it is, sadly, the truth. I am confident that I can prove it if you will allow me.
"For example, if you were to take a shovel outside the Campus walls, find a level spot, and start digging, your hole would be, on average, ten feet deep by the time you reached what thirty years ago would have been ground level. That's a little over three meters. The surface area of the US in pre-pillar days was close to ten million square kilometers. Now, let's assume, for arithmatic simplicity, that the whole thing is covered to the same average depth." He moved slowly over to the blackboard as he spoke.
"I'll write this out for you so you can follow it. Ten million kilometers square times three meters high is thirty million cubic ki
lometers. Thirty million cubic kilometers of material. Over thirty years that works out to eighty thousand cubic kilometers a day. I will pause to let that soak in.” He paused.
“Now, obviously that figure has an awfully large margin of error – there is such a thing as topographic relief, after all, so we can’t assume all ten million square kilometers are covered to the same depth. Further complicating the matter is the fact that we honestly don’t know the status of the rest of the world. There might very well be ash on the ground in Russia or India as well, but there has been no communication. For the purpose of this argument, we will ignore such far off lands and focus instead on what we can lay our hands on. We could, I suppose, endeavor to generate a more precise volume, but we geophysicists don’t usually have much need for exact figures. What matters is the order of magnitude. Regardless of what the precise volume is, we can all agree that there is a lot of ash on the ground.
“Now, tell me someone, during the comprehensive schooling provided by the state school, did any of the sad lumps that called themselves teachers happen to tell you where all of that came from?" He paused again, peering out at the room. "Don't be timid. You there, in the pirate costume."
Unphased by the jab at his appearance, Pirate lowered his hand. With a triumphant glance at Lee, he responded proudly, a hint of bile in his voice, "Everyone knows, a volcano erupted up north. One the scientists had been watching for a while. Yellow-something. It was bigger than they expected."
"Who agrees with young Mr. Sparrow here?" A scattering of hands were raised. "I rest my case. You see, the thin layer of education that was spread on you by the state has shown itself to be woefully insufficient. You are wrong. No, I suppose that's unfair. Yellowstone did blow. You are, to a small degree, correct, but there is a portion of your statement which is, at best, a naïve approximation of the truth. Can anyone think why that might be?" He peered around the room again. The rangers looked unsure now.
Lee spoke in a soft voice from the row of seats near the front that she shared with her sister, "Because there's too much ash to have come from a volcano?"
The old professor raised his eyebrows in mild surprise. "Ah, I see a lack of education does not preclude intelligence at least. Too much ash, very good young lady.
"Three billion cubic meters of volcanic ash over thirty years is a lot. That's many times more than any volcano in recorded history, or any we know of in the rock record. We don't have time to go into too much detail, but suffice it to say that one run-of-the-mill volcano could not have produced all of this material in just thirty years. So then, the question remains unanswered: where did it all come from? Would anyone like to know the answer?" A few rangers nodded. "So would I. The fact is we don't know much. What I can tell you is that Yellowstone is not some run-of-the-mill volcano.” He squinted at Pirate again. “No, my young swashbuckler, it was not a volcano which erupted. A more accurate statement would be that a caldera exploded, or perhaps we could even call it a supervolcano, although I’ve never liked either term. Allow me to explain:
"Yellowstone, as your Captain and his lovely wife will remember, was at one point one of our more spectacular national parks. One of the more popular tourist attractions in this park was a huge geyser nicknamed 'Old Faithful'. This was basically a column of superheated water that would periodically erupt from the ground. Around the middle of the last century, a few geologists decided to define exactly what the heat source was for this phenomenon. A seismic investigation revealed a large body of magma beneath the park. This was strange. There are plenty of places where magma accumulates within the crust, but they are almost all associated with subduction zones." The professor broke off to peer out at the rangers again. Confusion was evident on their faces. With a sigh, he continued, "Ok, maybe I had better take a step back. We'll touch a bit on plate tectonics first." He paused to gather his thoughts, then moved surprisingly quickly back to the board and drew three concentric circles.
"I'll have to oversimplify to an extreme here, we don't have time to go into detail." He pointed to his drawing. "This is a cross section of the earth. The small circle in the center we will call the core. It is very hot. The thick section in the middle we will call the mantle, it is also very hot, though not as hot as the core, at least on average. The thin outer circle here we'll call the crust. This is what we all live on, it's the continents as well as the ocean floor. Now, as I said, the core is very hot. It consists almost entirely of molten iron and nickel. The center is solid, but we won't go into that. The portion of the mantle that is adjacent to this very hot core grows very hot itself. The portion of the mantle which is furthest from the heat of the core is much cooler. The temperature difference between the two regions drives something called convection.
"Think of it in terms of a pot of boiling water." he drew a crude pot on the board. "The water at the bottom of the pot, closest to the heat source, gets very hot, the water at the top, exposed to the air, cools off. The hot water rises, and the cold water settles; they displace each other. Hot water cools off when it reaches the surface and the cold water heats up when it gets to the bottom of the pot, and the cycle repeats itself until the heat source is removed.
"Going back to our simplified cross section of the earth, the core is the heat source, the mantle the water, and the crust the air above the pot. What you end up with is very similar to the boiling water, though on a much larger and slower scale. The huge temperature differential spurs a convection cycle. What this means is that hot material from lower in the mantle is constantly rising toward the surface, and cooler material nearer the surface is constantly sinking to take its place." As he spoke he drew a number of circles and arrows representing the convection cycles. “It’s tempting to think of this convecting material as molten rock, but that is inaccurate. The rock is not molten, it is merely under enough pressure and heat to display fluid properties. I won’t go into more detail about that, just take it to mean that it moves very slowly.
"Now, drastically oversimplifying again in the interest of brevity, we will say that the crust is made of two different materials, we will call them granite and basalt. The continents are made of 'granite', and the ocean floor is made up of 'basalt'. This material sits on top of the mantle like a broken eggshell. The continents and ocean floor are separated into dozens of discrete pieces called 'plates' which move relative to each other. The mechanism which drives this movement is extremely complicated, so once again we will oversimplify its explanation." He stopped briefly to point at the convection circles he had drawn.
"The easiest way to look at it is to consider the plates as 'riding' the convection. The hot mantle material is welling up in some places and sinking in others. Friction drags the crustal plates along with the convecting mantle material. Now, remember, we said that the plates are made up of two different materials. These materials have different densities. The oceanic 'basalt' is significantly denser than continental 'granite'. When the convection of the mantle forces these two materials together, the denser 'basalt' plate follows the path of least resistance and sinks underneath the less dense 'granite' continent. This process is known as 'subduction'. When one plate is subducted under another, suddenly there is less crust to go around. That portion of the oceanic plate which is beneath the continental plate is no longer at the surface and so must be replaced by new material elsewhere, otherwise the surface area of the Earth would be constantly diminishing. This new material is mostly produced in regions known as mid-ocean ridges." He pointed at the upwelling side of the convection diagrams on the board.
"Remember there is hot mantle material welling up from the core, and that the crustal plates are riding that convection at the surface? Well those plates are necessarily moving away from the upwelling. The portion of a plate which is being subducted lies on the down-welling portion of these convection cycles. At the opposite edge of the plate, hot mantle material is constantly welling up, melting, erupting at the surface, and cooling into new crustal rock. This material replace
s the crust which is lost to subducton at the other margin of the plate. Immense mountain ranges can be formed at these rifts. The speed of the spreading plates dictates how high these mountains grow. The most extensive mountain ranges on Earth lie along these mid-ocean ridges, but you will never be able to climb them. This is because, as the name suggests, they lie deep beneath the ocean. As a caveat, there are a few of these zones in the middle of continents, known as rift valleys, but they are distinct enough in their mechanism that we will ignore them for this lecture.
"For the purposes of our discussion, we need to consider the various kinds of volcanism. We've touched on the slow, seeping eruptions at spreading rifts, but what about classic volcanoes? Big, smoky, conical mountains, spewing fiery lava and exploding with ash and toxic gas? Volcanism such as this is the product of subduction. When oceanic crust is subducted, it's very wet. It's wet not only in terms of water being stuck in pores between the rocks, but it is also included in the crystalline structure of the rock, at the molecular level. As it sinks below the continental crust, it heats up. At a certain depth, the pressure and heat are great enough that the molecular water is released and rises into the overlying continental rock.
“Now, this continental rock is essentially dry, but it is under a considerable amount of heat and pressure. Under normal, dry conditions, that rock is basically stable, but when the water is introduced, the physical properties of the rock are altered enough to spark a process known as partial melting. Essentially, the added water lowers the melting points of the various mineral compounds in the rock. The lighter minerals and chemicals within the rock suddenly find that, with the introduction of the water, they are now at or above their new melting points. A fraction of the rock thus melts away. It is this partial melt which forms magma and gas.
Ash: Rise of the Republic Page 11