Why risk living on a volcano like Kilauea?

If a threat is constant, you're going to get used to it. That stands to reason, doesn't it? That's how it is for people who live in bush fire zones in the United States and Australia, perhaps even for those in Portugal and Spain. And it's got to be the case for residents on Hawaii's Big Island. Otherwise, why would you live surrounded by five or six of the world's most "famous" volcanoes - one of which has been a near constant threat for 35 years?

That's Kīlauea.

It's been erupting since January 3, 1983 when a cinder and spatter cone on its eastern rift zone opened up. And that cone is Pu'u 'Ō'ō. The US Geological Survey says Pu'u 'Ō'ō "ranks as the longest and most voluminous known outpouring of lava from Kīlauea's East Rift Zone in more than 500 years."

Read more: If you live near one of these volcanos, move!

Fountains of lava and ensuing lava flows have "repeatedly challenged residents." And that's putting it lightly. Up to the end of 2016, lava from Pu'u 'Ō'ō  had covered more than 144 square kilometers (55.5 square miles), it had spewed about 4.4 cubic kilometers (1.1 cubic miles) of lava, added 179 hectares (443 acres) of new land to Kīlauea's southeastern shore … and destroyed 215 "structures."

For "structures" read "homes"

When a series of earthquakes started to shake the Big Island in late April to early May, residents of Leilani Estates knew time was running short. By May 3, three separate fissures had opened up in the area, showing the first outbreaks of lava.

Seismic activity had been on the up for a few days when a 6.9 magnitude quake struck on May 4 at about 12:32 p.m. Hawaii Standard Time (22:32 UTC) - the strongest on Hawaii since 1975 - located only 16 kilometers from Leilani Estates. Soon after, there was another strong quake and a series of about 152 smaller aftershocks.

By the evening of May 5, a new fissure had erupted, producing lava fountains as high as 70 meters (230 feet) in the air. A fissure is a fracture or crack. Lava can spurt from a fissure for a matter of hours or days, and it sometimes flows back into the crack. That's known as "drainback."

At least seven fissures have been reported so far, with rockfalls and ashy plumes expected to continue for a while.

What is already certain, however, is that people have lost their homes, and most likely everything in them.

What did you expect?

It's a callous thing to say at this moment, "big surprise!" But in some of the earliest coverage, a local resident told reporters from an American network that she had heard people say just that. "What did you expect? You're living on a volcano."

And that is true. Hawaii is basically one big volcano - or, to be a little more precise, a string of land and seamount volcanoes. There are at least 17 land volcanoes, depending on your interpretation of the science (some don't include Pu'u 'Ō'ō, presumably because it is just a cone), and then there's the entire Emperor Seamount chain.

Alone on the Big Island, there's Kilauea, Mauna Loa and Mauna Kea, Hualālai, and Kohala. On Maui, Hawaii's second largest island, there's the West Maui Mountains, and Haleakalā, which accounts for about 75 percent of the entire island.

As with Pu'u 'Ō'ō today, Kilauea was not always considered a volcano in its own right. To begin with, scientists thought Kilauea was a mere bump on the southeastern flank of Mauna Loa. But more recent studies have shown that Kilauea has its own magma system, starting about 60 kilometers below the surface.  

Despite these facts, Hawaii remains relatively well populated. It is, after all, what another American network reporter described these passed days as "paradise."

According to statistics from Onboard Informatics, a company that says it has "data on every property in the country [USA]," reproduced by a real estate website called Point2Homes, the population around Kilauea has increased by 2.5 percent since 2010 - despite said constant threat.

Population within 5 km

• Kilauea           ~ 3,100
• Hualālai          ~ 36,000
• Mauna Loa     ~ 45
• Mauna Kea    ~ 126
• Haleakalā       ~ 26,000

[Source: Global Volcanism Program]

But perhaps that is what makes such danger zones around volcanoes, or indeed Australian and Californian bush lands that burn like clockwork, so attractive. They are cheaper than elsewhere because they are more dangerous than elsewhere, except on one price point: insurance. Many Hawaii residents are asking themselves today whether their home insurance will cover them for their losses. The answer is probably an emphatic, "No! What did you expect?"  

Read more: Moving hot spots: Scientists explain mystery bend in Hawaii-Emperor volcano chain

Life and other dangers

One local resident told Reuters reporters that he knew it was risky living in Leilani, but "if you want to live in Hawaii, it's really your only option." That's thanks - or perhaps not so much thanks - to the USGS's Hazard Ratings map for the Big Island. Leilani is in Zone 1, where lava flows are "most likely to occur." And that's keeping house prices down.

Conversely, it would be tough to get any insurance firm to cover you.

But even if you managed to get insurance, and you could afford it, why would you live on a volcano if you could live somewhere less dangerous? Because it's not just the lava you have to worry about, coming to burn your house, possessions, or you. It's also the potential for clouds of toxic gasses that volcanoes often emit - gasses such as carbon dioxide, sulfur dioxide, hydrogen sulfide and hydrogen halides. All these gases can be hazardous to people, animals, agriculture, and property, when their concentrations become high enough in the atmosphere.

Carbon dioxide can be lethal. Sulfur dioxide irritates eyes, skin and the respiratory system. In extreme cases, hydrogen sulfide, a nasty smelling "sewer gas" that you can't always smell, causes unconsciousness … and death. And if you survive all that, hydrogen halides can fall as a kind of acid rain in ash-producing eruptions, such as the current one at Kilauea, poisoning water supplies, agricultural crops and grazing land.

In a word, that would have to be paradise lost.