A friend of mine recently announced that he's moving out of Oregon's Willamette Valley because he doesn't want to be there when the big earthquake hits. The Pacific Northwest is due for a big temblor sometime within the next century or two, and the longer the fault remains locked, the worse the earthquake will be when it finally lets go.

So where does this friend of mine move? Into the shadow of not just one, but three major volcanoes. In a forest that has seen devastating wildfires nearly every year for the last decade.

"If you want to move somewhere safe," I told him, "you should move to...." Big pause. Where?

There's no place on Earth that's immune to natural disasters. For that matter, there's no place off Earth that's immune to them, either. Nature is pretty much one big disaster after another, from earthquake to fire to flood to tornado to hurricane to landslide to volcano to asteroid impact to solar flare to gamma ray burst to the Big Rip that will (maybe) eventually tear the entire universe apart down to its component subatomic particles.

Why is the Earth, and the universe beyond, so dangerous?

The Earth is a big place. Really big. It's roughly 16,000,000,000,000, 000,000,000 times bigger than you. So anything the Earth does is unlikely to slow down even a smidgen if you're in the way. The amount of energy in a typical hurricane is about 10,000 times as much energy as in a typical nuclear bomb. A major earthquake (8.0 on the Richter scale) puts out about 2,000 bombs' worth of energy. Even a tornado, a very localized phenomenon when compared to the size of the Earth, puts out at least one nuclear bomb's worth. These events are simply too strong for us to do anything about.

In space it's just as bad, or worse. An object in low orbit moves at about 17,000 miles per hour. At that speed, a stray washer hits like an artillery shell. Luckily most everything in the same orbit moves in more or less the same direction at the same speed, but it's easy enough to launch something at a different angle. It can even go retrograde, which means its 17,000 mph would add to the other object's 17,000 mph. If a loose wrench got into a retrograde orbit, it would hit the International Space Station at 34,000 miles per hour. It would turn to plasma in an instant, but it would already be halfway through the space station by then and the plasma would still be moving fast, so it would leave a wrench-sized hole in one side and a car-sized hole in the other on its way out. An astronaut in-between wouldn't even slow it down.

And that's nothing compared to the scale of most cosmological disasters. The Moon was formed when a planet the size of Mars smashed into the proto-Earth. Supernovae sterilize everything for maybe fifty light-years around them. Gamma ray bursts (energetic jets given off by supernovae) can sterilize a solar system like ours from halfway across the galaxy. Entire galaxies can (and do) collide, spewing their stellar guts out into the cosmos on a truly phenomenal scale.

And yet, life thrives on the Earth. Only rarely do we get a catastrophe great enough to threaten much of it, and so far none of those catastrophes has been great enough to totally extinguish it. That seems kind of unlikely when you think about all that could go wrong. If we're so insignificantly small compared to the Earth and the universe beyond, why haven't we been squashed like a bug on a highway?

There are several ways to answer that question. One is with the Anthropic Principle, which basically states that if conditions weren't right for us to survive, we wouldn't be here to ask the question.

Another way of looking at it is to realize that statistically there has to be at least one place in the universe where life not only exists, but thrives. Random chance in an infinite universe will create that place somewhere. That place is here, and we're the life that evolved there.

Those answers are more philosophical than scientific, though, and they're a bit unsatisfying. Fortunately there are more satisfying—and more scientific—answers.

The Sun radiates about a kilowatt of energy onto every square meter of the Earth's surface. That sounds like a lot of energy, and it is, but it's not enough to power a hurricane or even a tornado continuously. Storms like these have to build up over time, gathering energy from updrafts and downdrafts until their combined momentum starts the big swirl that eventually turns into a natural disaster. They rage for a few minutes in the case of tornadoes to a few days in the case of hurricanes, but eventually they blow themselves out. There just isn't enough energy input to maintain their fury.

Earthquakes and volcanoes are similar. They're powered by the Earth's internal heat rather than by the Sun, but they have the same energy budget. Once a fault has slipped and triggered an earthquake, it takes a long time before that fault can build up enough pressure to slip again. Likewise, a volcano can blow off a lot of accumulated magma but it eventually runs out and has to go dormant while it replenishes its reservoir. That's why Hawaii is a chain of islands rather than a continuous wall from Midway to its present position. The hot spot that creates the volcanoes that build the islands goes dormant for a while after it erupts, and continental drift moves the sea floor onward in the interim.

Fires eventually run out of forest, floods recede, and landslides skid to a stop. There isn't enough energy for them to continue forever.

Farther afield it's the same story. There are thousands of asteroids out there in the solar system, but only a few are on Earth-crossing paths. Most of the ones that might have hit us already have, back when the Earth was being formed in the first place. Gamma ray bursts are so rare and so directional that we've only been hit a couple of times, if at all, and those were probably hundreds of millions of years in the past. Same for nearby supernovae. We might have been uncomfortably close to one only 2.6 million years ago, and its effects on marine life defined the boundary between the Pleistocene and the Pliocene epochs. But none of those events was powerful enough to wipe out life entirely, and we've had plenty of time between events to regenerate.

That's really the core of the matter: The same vastness that makes life so insignificant by comparison also works in life's favor. The Earth is so big, something somewhere will survive pretty much anything nature throws at it. And life has plenty of time between events to recover. It can spread back into areas that were devastated, and it can evolve to meet new conditions. The dinosaurs weren't so lucky when the big asteroid hit 65 million years ago, but mammals came out of that smelling like roses. And the dinosaurs didn't do all that poorly, actually: We call them birds nowadays.

So what about our current ongoing disaster, global warming?

It's a blip on the graph.

That's not to say it's insignificant. It could lead to mass starvation, wars, and quite possibly the extinction of humanity along with many thousands of other species. But in the grand scheme of life on Earth? It's a trifle. It could even be a good thing if it gets rid of us, since long before global warming began to bite us we were wiping out species at a rate that rivals the worst extinction events in the history of life on Earth.

For us, though, it will prove vexing. One of the biggest reasons is the energy budget that I mentioned above. Global warming puts more energy into the atmosphere and into the oceans, which means hurricanes can last longer. Even regular rainstorms and snowstorms can last longer. With more energy to work with, they can hold more moisture in suspension and drop more of it on Sheboygan.

John Barnes wrote a novel¹ about a particularly alarming threshold event that we really shouldn't ignore: Hurricanes typically die when they encounter land, but if they have enough energy they can cross that land and resume their buildup once they hit warm water again. When global warming puts enough heat into the atmosphere and into the oceans, we could see hurricanes that persist for months, swirling all the way around the planet again and again, wreaking more or less continual havoc.

We could see tornadoes wide enough to take out entire cities.

Hailstones the size of baseballs could become common. (Prediction: Parking garage rates will go up.)

We're already seeing wildfires greater than ever before. And of course there will be flooding. Florida was once a reef. It will become one again.

So what's a person to do? Move out of the areas most likely to suffer from natural disasters? The Pacific Northwest is predicted to be one of the areas least impacted by climate change. But there's that pesky Cascadia earthquake to contend with, and a whole row of volcanoes from Mt. Rainier in Washington all the way to Mt. Shasta in northern California. And the Pacific Northwest is mostly forest, which has been burning at a truly alarming rate every summer for the last decade or so.

Wyoming is pretty uneventful ...except for the Yellowstone supervolcano.

Kansas is nice and flat and...oh, yeah, The Wizard of Oz.

Missouri? Arkansas? Tennessee? Kentucky? Google "New Madrid fault."

And so on. There's no place on Earth where you can be guaranteed safety from a natural disaster. You can pick your likelihood, but even then you're never sure. A house on my hillside, 500 feet above the valley floor, flooded when rainfall overfilled a natural spring.

The best you can do, and in my opinion the best you should do, is to prepare for a disaster. Keep drinking water and dried food and medical supplies on hand. Know where high ground is, or a tornado shelter, or a quake-proof public building.

And rather than run away, run to help those in need. That's why I stay in the Willamette valley despite the threat of the big earthquake that will certainly, eventually, come. When it hits, I want to be here to help my neighbors.

Because if there's anything that can be done about natural disasters, it's helping one another after one hits.

¹  Mother of Storms
 

Jerry Oltion has been a science nut since he was old enough to spell "curious." He has written science fiction almost as long, and has done astronomy somewhat less. He writes a regular column on amateur telescope making for Sky & Telescope magazine, and spends many, many nights a year out under the stars.