“This mixture builds up slowly, deep within the rocks at the margins of the continent until the pressure is great enough that it erupts violently. Every subduction zone produces this type of volcanism. It is characterized by explosive, spectacular eruptions driven by the presence of volatile components, highly viscous magma, and immense quantities of ash and projectiles of molten rock commonly known as bombs. It is important to remember that the material which erupts is produced entirely within the continental rock itself and therefore its composition is directly related to the composition of the source rock. It is not molten mantle material erupting at the surface, but rather the 'granite' of the continent which is made to melt by the introduction of a catalyst. Once again, I must assure you that this is an extreme oversimplification. The actual processes are much more complicated.
"Besides the two mechanisms for volcanism we have discussed, one gentle yet constant, the other profoundly violent yet sporadic, there is another. As we discussed, these first two types are essentially the product of convection within the mantle and the interactions of the crustal plates which are driven by this convection.
"Convection drives the third type as well, but on a smaller scale. This last type we will call 'hot-spot' volcanism. Now, it is tempting to think of mantle convection in terms of these pretty circles I've drawn on the board here, but in reality the pattern of rising heat and sinking cool is complicated and chaotic. The physics which govern this are beyond the scope of this lecture, so let's turn instead back to our culinary metaphor. If you watch the surface of a pot of boiling water, you will notice a number of dimples on its surface. These dimples are the tops of columns of hot water rising to the surface. The water in the center of the dimple is hotter than the water which is rolling to the edges. You will also notice that these dimples vary in size and position. Variations in the heat source cause this lack of uniformity. Convection cycles within the mantle are similarly chaotic. Besides the huge rolling plumes on which the crustal plates ride, there are also smaller, localized plumes, driven by variations in the heat produced at the mantle/core boundary. Some of these small, hot plumes are geologically fleeting, but others are persistent. The causes of these heat variations are not well understood, but they can be readily identified by the presence of so called hot spots.
“The most famous example of a hotspot is that which is responsible for the creation of the Hawaiian archipelago. I assume most have you have at least seen this on a map before, but just in case, will illustrate what I mean." He moved back to the blackboard and drew several blobs in a curving line, increasing in size from left to right. "This is a rough approximation of the islands of Hawaii. The largest island, Hawaii itself, is the peak of an active volcano. Each smaller island is also the peak of a volcano, but they are all extinct, meaning they are no longer geologically active. Each of these volcanoes was actually created by the same stationary source of heat. As the crustal plate moved to the left, the stationary heat source was constantly forming melt and that melt was erupting and cooling at the surface. Each of the peaks represents a period when the speed of the plate slowed and the erupting lava had more time to accumulate. The larger the island, the slower the plate was moving. It's worth noting that the volcanism in action here is not the violent, explosive variety driven by volatile gases on the margins of subduction zones. The composition of the source material for the melt, oceanic 'basalt', is such that the magma which is produced is low in viscosity and low in volatile gases, allowing it to erupt in a constant but calm and docile manner, patiently piling up into mountains. Once again, I must stress that the composition of the material which erupts determines the style of eruption, and that the composition is entirely dependent on the source rock…Hah!”
The old man moved surprisingly quickly; the eraser bounced off Stone’s forehead in a milky cloud of chalk dust. The startled scout, caught dozing off, looked around the room, blinking.
"Now, we grow closer to an answer to our original question: where did all the ash come from? Hawaii is, of course, not the only hot-spot in the world. There are a number of other examples, but most of them are currently located under oceanic crust, forming chains of volcanic islands. Yellowstone, however, is one of the few known examples of a continental hot-spot.
"The Northwest United States is a region with a long history of volcanism. The majority of this can be attributed to the subduction of a small section of oceanic crust known as the Jaun de Fuca plate. There is evidence in the region of a number of extremely violent and large scale eruptions from the past hundred million years. Early geological studies of the area attributed these to subduction volcanism, but some of these eruptions occurred hundreds of miles inland. When the geologists discovered the large magma chamber under Yellowstone, they took a second look at the evidence of ancient eruptions. Rather than the squat cones of coastal subduction volcanoes, these ancient calderas resembled the result of huge explosions. Careful study revealed that, just like Hawaii, the ancient eruptions were arranged in a curving line, the product of a stationary heat source burning through a moving crustal plate. If a relatively constant plate speed was assumed, the eruptions were clearly fairly regular, occurring every seven hundred thousand years or so. The scary thing was, it was overdue. The magma they had discovered was clearly ready to erupt. For this reason, the government set up sensors to monitor the situation, hoping for some warning. They watched it for fifty years.
"We don't know if they had much warning, despite the years they spent watching it. I knew a few people who worked on the project, but had no contact with them in the weeks before the eruption. When it blew, it was much bigger than they had expected. Bigger than any before. The last eruption from that caldera produced around a thousand cubic kilometers of material. We estimate this one threw out nearly ten times that on the first day. There was so much force behind the initial explosion that the majority of the ejecta ended up in a low orbit. It’s been falling ever since. The caldera itself has continued to erupt violently for the last thirty years, although we have little hard evidence of that other than the fact that we have three meters of ash on the ground and it’s still falling. The question is, why is there so much?
"Now, to answer the young lady's very astute point about the quantity of ash, we must turn to theory. Let us consider the concept we have revisited several times: that the material which is erupted is directly related to the material from which it is created. For this reason, as we have discussed, continental eruptions are necessarily more violent and produce large amounts of ejecta, including ash. We think Yellowstone was a special case, unique in modern geology. The magma which accumulated beneath the park was not the product of partial melting brought on by a chemical change like that of a subduction zone, but rather formed through the direct application of heat from the mantle. Because of the degree of heat which was applied, a much more comprehensive melt could occur.
“We will call this 'majority-melt' to differentiate it from the partial-melt which occurs at subduction zones. When a portion of rock undergoes majority-melt, a significant percentage of its volume is lost to magma. When this magma rises to the surface to collect in magma chambers, something must fill the volume which it vacated. As the rocks exposed to the hot-spot majority-melt and lose volume, the surrounding rock presses in from all sides. This fills the volume left by the rising magma, and it provides fresh rock to be cooked by the mantle heat. This turns into a vicious cycle of magma production and constant volatile eruption.
“Only two things can disrupt this cycle: One, the heat source is taken away, or two, the lithostatic pressure of the surrounding rock decreases enough to slow down the introduction of fresh source material for magma production. Since hot-spots are geologically long-lived, as evidenced by a certain long string of islands in the Pacific, the first is unlikely to happen. The second is more likely, but will take a significant amount out time, especially if the cycle is occurring in the middle of a huge continent with tremendous lithostatic pressures at work. The
amount of material that must be removed from the area in question before the stress in the rock relaxes enough to kill this melt cycle is immense. Something on the order of tens of millions of cubic kilometers...
“That, ladies and gentlemen, is essentially where all the ash came from. It wasn’t just a volcano, it was the volcano; the largest eruption ever recorded. It was, and continues to be, an explosive caldera derived from an extraordinarily active hot-spot and stuck in a majority-melt cycle. You can just call it a supervolcano for the sake of brevity.
“I must stress once again that this is all just an oversimplified theory. We have not visited the caldera since it blew. We do, however, occasionally receive anecdotal reports from travelers. If they are to be believed, then Yellowstone is still active. The occasional ashfalls which still occur are ample evidence to support that. We’re also told that thirty years’ worth of eruptions have created a supervolcano which rivals the size of Olympus Mons. Perhaps one day we will have the resources to mount an expedition to investigate, but I fear I will not live to see the day. The pursuit of science has always been hampered by the petty squabbles of men and government.
“Questions?”
****
His agent told him the Republic was finally mobilizing. It was time. His army had grown steadily, in size and in confidence, for over a month. The region’s citizens had shuddered in terror at the tumor in their midst. Dozens of villages and homesteads lay smoking and lifeless from his men’s savagery. He had let the planes fly over unmolested, welcoming the exposure. He hoped the soft men of the Republic were trembling behind their walls of ash.
The ranger companies watched him too. They crouched in the brush in the hills around the camp. The irony amused him. They had relentlessly pursued these ragged outlaws until they were desperate. He had used that desperation to build an army. Now those rangers hid from those same ragged outlaws, desperate for their own army to come.
Before he left he made sure it came too late for some. He regretted the old ranger wasn’t with them, his first and greatest enemy. His hatred for the old man festered like an open sore. He relished the thought of their next meeting.
The pathetic screams of the once hard men, bleeding in the bushes, were but a pale appetizer for his coming triumph.
He let the fathers and brothers of hanged men do the work. When they had finished, the Chief marched his army to war.
Chapter 7
September, 0 PC (2015 AD)
*
“There existed a sharp dichotomy within the survivors; it was apparent even in the first few weeks. There were those who worked to rebuild, and those who worked to destroy.”
-Kristen Harrisburg, ‘The Grey Panic’; RNT University Press, 36 PC (2051 AD);
*
They didn’t bother following us. We lay trembling and exhausted in the bed of the truck for the first two miles, risking a glance over the tailgate every few minutes to check for the headlights which would betray a pursuit.
We stopped when we reached the first crossroad. An ashfall had begun at some point during the short fight. It was coming down thick now, a dusty blizzard. Deb and I walked up the line of vehicles, checking that everyone had some form of breathing protection and performing a quick head count. Close to thirty people were missing, I assumed either dead or dying at the hands of the Fellowship. When we returned, discouraged, to the truck at the back of the line, we found Mike and Clint leaning under the raised hood. The light from their flashlight reflected wildly off the fluttering ash. I approached as they pulled the cover off of the engine air intake. Mike pried the filter out, raising a cloud of fine ash. He shook it out and replaced it, shooting me a worried glance.
"We'd better check them all," I said in response, "Deb and I will keep watch back here. And tell Scott to stop every couple of miles. We need these trucks to last."
We turned right on the next highway and stopped at the first underpass we came to. The wide expanse of road decking had kept the ash from accumulating too thickly beneath it, but wind driven drifts had piled the stuff high on either side. The resulting cavern was barely wide enough for our convoy to squeeze in, but it provided much needed shelter from the intensifying ash storm. After emptying the trucks' air filters again, we gathered for a meeting at the side of the road. My surviving neighbors arranged themselves on the sloping concrete embankment there, the thin light of a small fluorescent lantern illuminating their weary, ashen faces. They looked like I felt. Adrenaline had left them now. They were drained; physically and mentally exhausted. Their eyes were downcast, struggling to balance the shame of losing their homes and friends with the relief that comes from narrowly escaping death.
I gave everyone a moment to reflect on the night's events, then began to speak, my voice reflecting back to me from the thick concrete pillars.
"I wish I could stand here and deliver a rousing speech. I wish I had words which could heal your pain and inspire you to keep going. The fact is, I don't know what to say. They beat us. They burned our homes and killed our friends. They're probably following us right now to finish the job.
"It's my fault. I let you all down; I got those people killed; I lost our home. There are no words to convey the sorrow and regret I'm feeling right now. We should hold an election right here. You deserve a new leader, someone who can protect you. Please, I won't blame any of you, choose someone else."
There was a loaded silence. One by one, my neighbors looked up at me, eyes hooded in shadow from the cold lantern light. I could feel the anger buzzing in the air. I deserved it. I had proposed the majority of the defenses which had just collapsed. I had negotiated with the Fellowship. I had failed to shoot the enemy leaders when they stood in front of me issuing threats. The young psychopath at the helm of the madness had slept in my home and eaten my food.
I had killed their friends and family. I had burned their homes.
They began to mutter to each other, glancing with scorn in my direction. Their words, inaudible to me, seemed to seethe with rage. I stood silent, hanging my head in shame, waiting for them to denounce my poor leadership. When they finally spoke, however, their anger was directed at my apology rather than my failings.
"Are you done?" Janet Borger, the veterinarian, began in a cold voice, "because if you're done feeling sorry for yourself we can make some plans. How dare you try to take all the responsibility for this mess? What, you think you can fall on your sword and the rest of us will just move on, consciences clear? The last thing we need right now is you feeling sorry for yourself. We need you making decisions. Tell us what to do! Where are we going to go?"
Shocked, I turned to the rest of the group. Many were nodding in agreement. "I just thought..."
"You just thought what? That we'd tar and feather you because a twelve year old psychopath and a group of religious fanatics decided to attack us? How could that be your fault? If anything, we should be praising you: you're the reason we're still alive right now. Remember: it was your idea to plan for an escape. You saved all of our lives and most of our supplies." More nods from the small crowd. "If it hadn't been for you, we wouldn't have had a neighborhood to defend in the first place.
"We're all in agreement: you're the one we want in charge, you've proven yourself full of good ideas. But it pisses us off to see you standing here trying to take the blame for something that's not your fault rather than figuring out what our next move is going to be."
"Do you all feel the same way?" I asked, suddenly sheepish. There were more nods. Deb shrugged. "Ok then. We'll stay here until dawn. We'll need sentries. Deb and I will take first watch. Everyone else try to get a few hours rest.”
****
In the chilly morning light, we gathered for another meeting. My neighbors, wrapped in dusty blankets, huddled over steaming mugs of coffee brewed clumsily over a camp stove. I paced in front of them, my eyes bloodshot from lack of sleep. I had kept watch all night, trying to decide on a course of action. The answer had finally come to me as the gre
y to the east began to lighten.
“Something occurred to me this morning. Back there when the reverend was making his threats and going on about abominations and corruption of man, I didn’t take him seriously. I thought maybe it was his way of justifying looting and murder. I thought he was just after our supplies, but I was wrong. I think he really believes he’s been chosen by god to destroy civilization. Think about the way they attacked. Once they broke in, they just started setting houses on fire. They weren’t looting, they were destroying.
“I’ve been trying not to think about it, but I think it’s time to come to terms with the fact that civilization is collapsing. For the last month, we’ve been sitting around, waiting for this all to be over. We’ve been treating this like it’s the aftermath of some hurricane or earthquake, as if we just need to hunker down and survive until the government sends in disaster relief. The fact is, we haven’t seen any evidence that there is a government left at all. Everything’s been torn down around us and we’ve been waiting for the adults to come and help us. Well, that’s not going to happen! We can’t waste any more time waiting for help. We’ve got to help ourselves. If we want to see civilization again then we’re going to have to build it. The first step on that road is to preserve what’s left.
“Those lunatics back there aren’t just a band of looters and murderers. If they aren’t stopped soon they’re going to wipe out everything we have left. I’m not just talking about people’s houses. Think about how hard it will be to start over if they tear down the hospitals, the airports, the bridges, the schools. Just look what they did to the power plant. It might be years before we can build another one. They have to be stopped.
“You all know full well that ten miles from here is one of the largest universities in the country. Everything we need to rebuild is right there: a power plant, medical facilities, greenhouses, living quarters for thousands of people, and, most importantly, a huge library. If the reverend and his ‘Fellowship’ get their hands on it, we’ll be set back a hundred years. It’s the only thing standing between us and the dark ages. We have to get there first, we have to protect it!”
Ash: Rise of the Republic Page 12
