A small 2009 eruption at Sakurajima in Japan. Kimon Berlin / Wikimedia Commons. Whenever volcanoes are in the news, I see a lot of wild rumors roaming the interwebs. The worst kind are those that try to sow panic and fear amongst the people living near an erupting or potentially erupting volcano by either spreading false news or sensationalizing the events. Sometimes it is more innocent, where the media just gets the science or terminology wrong, like referring to the stuff coming out of a volcano as "smoke" (it's not) and that the "Ring of Fire" relates to anything beyond a good literary image. However, there are a few things I see consistently whenever a volcanic crisis emerges and I wanted to tackle these myths of volcanoes. I'm sure there are more out there, but these are the ones that really bug me.
One volcanic eruption will trigger another: This is a common claim when a volcano erupts in a country with a lot of other volcanoes, such as Indonesia or Japan. Although the source of magma might ultimately be from the same process (the mantle melting), almost all volcanoes are independent of one another. That is to say: all the volcanoes in an area are not all connected to a big, underground vat of magma they all share. So, an eruption at Agung is not going to cause other volcanoes to erupt. The closest thing to other volcanoes getting into the act during an eruption was the 1912 eruption of Novarupta in Alaska (the largest of the 20th century), where Katmai collapsed to form a caldera even though the eruption was happening in a saddle between Katmai and other volcanoes.
Eruptions get bigger the longer they last: There is the temptation to think that once a volcano starts erupting, it is only going to get worse. This is why we see headlines about Agung saying that people "are waiting for an eruption" when the eruption is already going, albeit in a fairly low level. Anytime something beyond volcano gases leave a volcanic event, it is an eruption. It might be plume that shoots up to 30 kilometers (100,000 feet) or a piddling hiccup that throws material 10 meters (3 feet) from the vent. Both are eruptions. Many times, the volcano will start erupting at a low level and just stay that way, so without signs that an eruption is going to get worse, like earthquakes or deformation to the volcano, don't assume that eruptions are leading to something bigger.
A volcano is "due" for a massive eruption (along with 'the world is "due" for a massive eruption'):
Let's all take a deep breath and say to yourself "volcanoes are never due for an eruption." It's true! No matter what you read in the news or see in the movies. Some volcanoes erupt frequently, some erupt every few thousand years. Neither is "due" to erupt if they haven't in some amount of time (which is usually pretty arbitrary). They will next erupt when the conditions are met for an eruption, usually as new magma rises from whatever source feeds that volcano ... and then there is an eruption. Volcanologists have not identified patterns or cyclicality to magma feeding most volcanoes. Take Fuji in Japan for example. It had VEI 4 or 5 (relatively large) eruptions in 1350 BCE, 1030 BCE, 930 BCE, 800 CE and 1707 CE. That's intervals of ~320, 100, 1730 and 1107 years. It means it can have big eruptions, but they're not spaced in any particular pattern. We're not "due". Volcanoes care not for your schedule.
These last two (well, three) to are related to how volcanoes interact with the Earth's climate. Every time there is even the potential of a moderate eruption, lots of the media coverage refers to the times that a very large eruption had some impact on the global climate. The best recent example would be the "Year without a Summer" in 1816 after the 1815 eruption of Tambora. Those are the exceptions to the rule. Even some of the largest recent eruptions like the 1991 eruption of Pinatubo or the 1982 eruption of El Chichón really only perturbed the global climate by fractions of a degree. It takes a very large eruption that sends material into the stratosphere to really impact climate.
Volcanoes will stop climate change/cause climate change: Volcanic eruptions are pretty much a constant over time. They might see spikes and lulls due to their mostly random distribution, but we have not seen any increase in volcanic activity on Earth in the past few millennia. So, even though volcanoes can emit carbon dioxide, they aren't causing the dramatic increase in carbon dioxide in the atmosphere (maybe it is the burning of all that carbon that was buried in the ground ... just maybe). So, volcanoes aren't to blame. Also, making our own artificial volcanoes or triggering eruptions to throw aerosols that can cool climate (like sulfur dioxide) into the atmosphere is a pretty terrible idea considering we don't really understand how it might impact the other parts of the global climate system.
"Super-eruptions" cause extinctions*: One of the biggest myths is that a big explosive eruption will cause global extinctions. It hasn't happened, or at the very least, we're never identified one. The eruptions that have been linked to extinctions are flood basalts, that are lava flow eruptions that can last millions of years ... and even not all of those have caused wide-spread extinctions. So, even a massive explosive eruptions like the last one at Yellowstone will not mean the "end of life on Earth." Sure, it might do in modern civilization for decades or more, but the world will go on. You can stop being worried about "super-eruptions".
Bonus: Climate change is causing more eruptions: This is a recent one, based on research that says that as ice melts in areas with volcanoes, the lowering of pressure on the crust will cause more eruptions. Now, there is real evidence that this happened in Iceland or parts of the Cascades. However, it was after the last Ice Age and it took thousands of years to manifest itself. There is no evidence that our current changing climate are causing volcanoes to behave any differently and likely, it won't be for centuries or more that the melting of ice in Iceland or Antarctica could cause volcanoes to potentially be more active in those locations.
So, rest easier about volcanoes. They can be very hazardous, but a lot of the hype is just that: hype.