Despite being the only hospitable planet in the solar system, Earth can be a pretty dangerous place to inhabit. In its 4.5 billion-year history, the planet has gone through at least five major extinction events, the last of which struck about 66 million years ago. The so-called Cretaceous-tertiary extinction occurred when a 6.2 miles (10km) asteroid struck near the modern-day Yucatan Peninsula in Mexico.
The event is believed to have wiped out three-quarters of all animal and plant life.
And the threats to life do not have to be external – supervolcanic eruptions and megatsunamis can all strike without outside influence.
When Mount Tambora erupted in 1815 – the most powerful volcanic eruptions in recorded human history – the ash and gases spewed by the volcano chilled the planet by as much 3C, leading to the infamous “year without summer”.
Some scientists fear an even bigger supervolcanic blast could be much worse for the planet’s climate, triggering a nuclear winter and food shortages – and that is only one of the many catastrophes that could strike.
In a 2015 article titled Five global catastrophes that could happen tomorrow, geologist Matthew Blackett has listed some of the most worrying cataclysms that could affect the whole world.
1. Lake Toba eruption
Although Yellowstone volcano in the western US receives a lot of attention, Lake Toba is a much less talked about volcano.
The supervolcano is found on the Indonesian island of Sumatra and is the world’s largest volcanic lake.
Lake Toba formed some 74,000 years ago when it last erupted.
According to Oregon State University, it was the largest volcanic eruption on Earth in the last two million years.
Dr Blackett, a reader in Physical Geography at Coventry University, said: “Toba is located on the densely populated island of Sumatra, home to over 50m vulnerable people, and is only 40km from the Indian Ocean in which catastrophic tsunamis (of which we have recent experience) would certainly be generated.”
2. The Hilina Slump of Mount Kilauea
Mount Kilauea is Hawaii’s most active volcano and yet it took the world by surprise in 2018 when it covered nearly 14 square miles of land with lava between May and August.
But according to Dr Blackett, an even greater threat than the volcano erupting is the volcano’s collapse into the Pacific.
The collapse is known as the Hilina Slump and it is estimated it could dump some 12,000 cubic kilometres of rock into the ocean.
The slump would likely trigger a devastating megatsunami.
Dr Blackett said: “Even as recently as 1975, movement of the Hilina Slump generated a smaller, yet destructive tsunami that reached California.
“Given that the slump is continually active and moving, it might only take a jolt from an earthquake in the tectonically active state to set in motion this catastrophic chain of events.”
3. The North Sea Tsunami
According to Dr Blackett, the North Sea could also see a megatsunami strike in the future.
The North Sea Tsunami could be triggered by a submarine landslide.
And the risk of this happening rises in a warming climate.
Dr Blackett said: “There is a precedent. Scientists have suggested that over 6,000 years ago, a sharp sea-level rise, attributed to a changing climate and a rapid melting of ice, added weight to the submarine glacial deposits at the edge of the Norwegian continental shelf, destabilising them and causing a 300km long landslide.”
This tsunami likely reached a height of 20m in the Shetland Islands, 10m on the Norwegian coast and six metres on the western and northern coasts of Scotland.
4. The Big One
A major earthquake known as the Big One could one day strike the west coast of the US near California.
This earthquake could strike along a subduction zone running from Northern California to Vancouver Island in Canada.
The subduction zone marks the spot where the Pacific Ocean floor is slowly being pushed under North America.
Dr Blackett said: “The rate of movement of the ocean floor here is currently just 40mm a year but the upper part of the system is currently stuck, meaning that the North American plate is being compressed.
“At some point, the pressure being built up has to be released and this will be in the form of a massive earthquake, perhaps up to a magnitude 9.”
To put into perspective, a magnitude 8 earthquake devastated Mexico City in 1985, bringing down hundreds of buildings and killing at least 5,000 people.
5. Major solar flare from the Sun
Solar flares are the one threat on this list that could come from outer space.
Solar flares are large expulsions of plasma from the Sun that can and have hit our planet in the past.
If they are powerful enough, they can fry electronics and cause blackouts.
Dr Blackett said: “One of the largest known events was in 1921, which knocked out the US telegraph service; but scientists have calculated that should a similar event happen in today’s technology-reliant society, it could knock out many satellite systems, disabling global communications, the internet and the global positioning system. Chaos could ensue.”
Luckily for us all, there is no evidence any of these events will strike anytime soon, if at all.