If you look west from most places in Seattle, you can see majestic Mt. Rainier looming tall and snow covered 80 miles to the west. Mt. Rainier is not just one of America’s most magnificent mountains. The U.S. Geological Survey says it is one of American’s most dangerous volcanoes, and that 80,000 people live in one of the zones that could be obliterated by a lahar—the wall of mud and rocks and water that speeds down the flanks of erupting volcanoes at 40-50 miles an hour—if Mt. Rainier erupts again.

Or rather, when it erupts again.

Just down the road, roughly 27 million Californians live within 30 miles of a major earthquake fault zone where seriously damaging ground shaking could occur in the next 50 years. It might take longer than that, or it might be sooner, but like Mt. Rainier erupting, the question of a major earthquake hitting some part of California is not a matter of whether it will happen. It’s just a matter of when.

It’s the same with hurricanes on the eastern and southern coasts, where more than 12 million people live right on the sure-to-be-hit shores of the Atlantic or Gulf of Mexico, and with serious floods that sooner or later will imperil some of the tens of millions of people who choose to live along rivers throughout the country. Everywhere you look, in fact, people live—many of them voluntarily—in harm’s way. Why?

Natural disasters provide one of the clearest examples of the subjective, emotional, affective nature of the psychology of risk perception. Why would anyone in their right mind choose to live in the shadow of a volcano, or directly above a huge earthquake fault zone, or on coasts and rivers that flood? Because when it comes to risk perception, being in one’s "right mind" has less to do with rational probabilistic risk assessment than you might think.

Most of us don’t live where we do by full and complete choice. We are where we are because of a job, or family, or some other circumstance beyond our total control. After all, no matter how hard we paddle our canoe to direct it where we want to go, the river of life makes a lot of the decisions for us. But millions have chosen to come ashore right where they are, right smack dab in the way of natural disasters. In fact, many people choose to return to dangerous locations after their homes and belongings have been destroyed by natural disasters, sometimes even after they’ve lost loved ones. What is up with all that?

At least five aspects of our subjective system of risk perception come into play.

• First, there is the powerful influence on our choices of Risk versus Benefit. The greater the benefit of some choice or behavior, the more we play down any associated risk. A lot of the places that lie in the shadow of serious danger are nice, picturesque, valuable places to live.

• Then there’s Optimism Bias. As in, “It won’t happen to me.” We tell ourselves that all the time, another one of the cognitive games we play in order to engage in risky behavior.

• Then there is the matter of Choice. People who choose to live in risky places are there voluntarily, and a risk you choose to take feels less scary than the very same risk if it’s imposed on you.

• Then there’s the problem that the beautiful natural environment you want to live in is, well, natural. Risks that are natural feel less worrisome than risks that are human-made. Never mind that human-made climate change is probably already contributing to all sorts of extreme weather, and that rivers now flood more frequently because humans have drastically reduced the ability of natural wetlands to absorb heavy rains. Floods and storms and volcanoes and forest fires are still called "natural" disasters, and that’s part of why living on a shoreline or in the lahar zone of an active volcano is less scary than living next to a nuclear power plant, which is way less of a risk.

• Finally, there is our Problem with Probability. We make all sorts of screwy—wrong—assumptions about "the odds." Lots of people who experience a “once-in-a-lifetime” storm or flood—like those who just weathered Superstorm Sandy—figure that makes it less likely that they’ll have to face anything like it. Sorry. Next year’s weather hasn’t gotten that memo. At best you can only estimate the likelihood of big storms or floods or earthquakes by looking at the pattern over a long time, and long means way longer than your puny lifetime or mine.

So those who are able to choose where they live, blithely risk living in harm’s way. And for the same reasons they aren’t worried about being there in the first place, they are often uninsured and unprepared, which only leaves them at greater risk. Most of the time the view is spectacular and the weather is fine and their lives are happy and safe. But then the ground shakes or the winds rage or the waters rise, and another huge round of suffering and loss, injury and death, reminds us all that subjective emotional way we read risk and try to protect ourselves, whether they are natural disasters or any other kind of potential peril—sometimes put us squarely in harm’s way.

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