Well, I was going to write a blog specifically about Tambora today, but the volcano world is abuzz with news about El Hierro in the Canary Islands (Spain). Both Tambora and Hierro have not erupted in recent times. Tambora last erupted in 1815 and killed nearly 80,000 people (although this number varies greatly depending on the source). Hierro last erupted in the 1700's, so there are no witnesses left alive that would have seen either of these erupt.
Hierro is an interesting monster. Its neighboring island of La Palma (also an active volcano), along with Hierro, have been responsible for some of the largest and deadliest tsunamis in human history. In fact, Hierro unleashed a 100 meter tsunami that slammed into the East Coast (New York area) about 10,000 years ago. La Palma is thought to be the biggest tsunami threat to the East Coast of the US, as the island has already begun to 'fall apart'. A huge fissure runs down the middle of the island, and GPS records about 10cm a year of motion into the ocean with the sliding land precariously waiting to catastrophically release. There is nothing that will stop this, and an eruption on La Palma will likely speed this process.
Hierro is a tourist destination, and as of this writing, approximately 53 tourists have been evacuated, and thousands of residents are preparing for what seems to be an inevitable volcanic eruption on the paradise island. Over 8,000 tremors have been recorded in the past couple months, and some articles are saying that elevated CO2 emissions are present in certain areas. The largest quake so far has been a 3.4 quake. Some residents are saying they can hear the volcano at night, with low rumblings underneath that get louder and louder. Quite freaky!
If Hierro blows, nobody quite knows what characteristics this eruption might have. The activity center appears to be within the collapse area of the 10,000 year old tsunami generating landslide. It looks like a half-moon shaped crater on the North West side of the island. This could also be a caldera. If it is a caldera explosion, or even submarine, the explosions generated could be quite large. However, Hierro has a long history of simply eruption cinder cones, and small lava flows... so time will tell. In any case, it is unprecedented in our history.
And in Indonesia, residents have voluntarily evacuated near Mt. Tambora, the volcano with the largest historical death toll in semi-recent history. Tambora is a large stratovolcano truncated by a 4.5 mile wide caldera. The shape is symmetrical and reminiscent of Oregon's Crater Lake volcano. But residents should not fear this volcano as much as they might, because the most damage it could ever produce has already been done. Likely, Tambora will see either phreatic (water hitting magma) eruptions and minor explosions, or an effusive, dome building event within the crater. The risk of a gigantic mega explosion (its last one had a VEI of 7 out of 8) is almost nonexistent, unless it chooses somehow to become a supervolcano, which will not happen. Or, Tambora might not even erupt at all. In any case, it is a spectacular volcano, and one worth checking out on Google Earth. News out of the region is spotty, so I am relying on reports from John Seach, the Smithsonian Global Volcanism Report, and other news sites I can find.
Hierro however, is probably the more exciting and scientifically fascinating volcano to keep an eye on, as it appears this volcano could erupt any day now. The quakes are getting more and more shallow, and residents are getting more and more nervous. They don't know where or when this volcano might have magma break the surface, the type of eruption that's in store for them, nor how long the eruption may last for. But it should be a spectacular display of nature's power, and people should take heed- just because a volcano has not erupted in a long time, does not mean it can't happen at any second. Fortunately for the residents of Hierro, it seems the volcano is warning them far ahead of time!