By Matthew Blackett - Coventry University
1. Forgotten super volcano in Indonesia
The threat posed to the world by Yellowstone super volcano, in the United States, it is well documented. Less well known (or recognized), however, it is for being one of many that poses a catastrophic threat to the planet.
The Lake Toba super volcano, on the Indonesian island of Sumatra, is currently home to the largest volcanic lake on Earth, formed 74,000 years ago, when the largest eruption in 25,000 years occurred in the past. It is estimated that around 2,800 cubic kilometers volcanic ash and lava were released into the atmosphere, 12% more than was expelled in the last Yellowstone eruption 2.2 million years ago.
A waiting game: Lake Tabo super volcano. (SK Ding, CC 2.0)
And it may be about to explode. Like any super eruption, the enormous amounts of ash and sulfur dioxide produced can have a devastating effect on the global climate. But a number of factors and the possibility of a Super Toba eruption are far more daunting than Yellowstone.
Toba is located on the densely populated island of Sumatra, is home to more than 50 million vulnerable people, and is only 40 km from the Indian Ocean where catastrophic tsunamis (of which we have recent experience) would undoubtedly generate. Furthermore, in recent months, reports Volcanic gases and warming of the Earth's surface have led to the suggestion that the sleeping giant may wake up again.
2. The Collapse Hilina
Forget the widely publicized mega-tsunami threat that has been attributed to the possible collapse of the Cumbre Vieja volcano in The Palm of the Canary Islands. A much greater danger is posed by the possible collapse of the southern part of the Kilauea volcano on the Big Island of Hawaii. Called the Slump Hilina, this could launch 12,000 cubic kilometers of rock into the Pacific Ocean, generating a mega-tsunami that would spread around the Pacific Ocean and in a matter of hours would reach the western coast of North America, flooding coastal communities.
There is evidence that a similar collapse near Mauna Loa around 120,000 years ago generated a tsunami with a height over 400 meters. Even as recently as 1975, Slump Hilina's movement generated a smaller, but destructive tsunami that reached California. Considering that the crisis is continuously active and in motion, it could only take one shake of an earthquake in the tectonically active state to set this chain of catastrophic events in motion.
3. Tsunami in the North Sea
The North Sea may seem like an unlikely location for a devastating tsunami, but climate change led to concerns that a underwater landslide in the region, it could just lead to this.
There is a precedent. Scientists have suggested that more than 6,000 years ago, a sharp rise in sea level is attributed to a changing climate and rapid thawing of ice, adding weight to underwater glacial deposits on the edge of Norway's continental shelf, destabilizing causing a long landslide of 300 km. That generated a tsunami that reached heights of up to 20 meters in the Shetland Islands, ten meters off the north coast of Norway and six meters outside western Scotland.
The land is again experiencing rapid climate warming and the associated thawing of the ice sheets in Greenland and West Antarctica, a similar event could be possible today, affecting coastal populations of Scotland and Norway (around 3m) - and maybe even London.
4. The huge ‘Cascadian ’
At the bottom of the Pacific Ocean, off the west coast of North America and running from Northern California to Vancouver Island, is in a subduction zone - a place where the soil of the Pacific Ocean is compromised below the North American landmass.
The rate of movement of the ocean floor here is currently only 40mm a year, but the top of the system is currently stuck, which means that the North American plate is being compressed. At some point, the pressure that is pushed up has to be released, it is in the form of an earthquake, perhaps up to magnitude 9. This could cause the coastal region to sink by up to 2m and a horizontal displacement of 30m.
Shortly after the intensely diminishing shocks, the offending coastal community will be struck by a tsunami that could outshine that of the japanese sling 2011. About 7 million people live in this region, Vancouver, including Seattle, Tacoma, and Portland.
How feasible is that? Well, scientists calculated that in the last 10,000 years, the region suffered41 major earthquakes, which occur with an average interval of 244 years - the last was magnitude 9 and occurred 315 years ago.
5. An extra-terrestrial threat
Perhaps the greatest threat to the modern world is posed by our own star. Periodically, the Sun emits a solar flare, an intense cloud of energetic photons and particles with the energy of millions of hydrogen bombs exploding at the same time. Once released, these clouds reach Earth's upper atmosphere within a day or two, and in many cases the most common people on Earth would be the hardest hit.
If it intensifies enough, anyway, a solar storm could devastate electrical systems both in orbit, such as satellites, as well as on the ground, since energetic electrons cause an accumulation of charge.
One of the largest known events was that of 1921, which knocked out the United States telegraph service; But scientists have calculated that a similar event would occur in society depending on today's technology, it could knock out many satellite systems, disabling global communication, the internet and the global positioning system. Chaos could ensue.
The intensity of solar flares varies in a cycle of approximately 11 years, and fortunately, in 2014 saw the most recent peak to come and go without significant impact. We can only hope that the same can be said for the future.EcoPortal.net
Matthew Blackett, is a full professor of physical geography and natural disasters at the Coventry University
This article was originally published in The Conversation.