Lake Toba in Sumatra, Indonesia, is today a lush tropical paradise. But 73,000 years ago a supervolcano erupted here, causing the ground to collapse and creating a large basin that is today filled with water. The eruption brought humans to the brink of extinction.
Credit: iStockphoto
In just 50 years, there's been a profound change in our relationship with the planet. In 1950, there were still remote locations on Earth - frontiers with new mysteries, new adventures, new cultures and new resources.
But by the end of the 20th century, our expanding population and the rise of science, technology and global communications had merged it all into an almost seamless tapestry.
Today, it's as if all of humanity lives on a single island - 'Island Earth'. It's an island with finite resources, coupled with a steady stream of warmth, light and energy from the Sun.
The Earth is ancient and geological time-scales are long. As a species, we are young and our time-scales are short. Scientists call these 'deep time' versus 'shallow time'.
Resources may be renewable on the deep time-scales of millions of years. But the time-scales relevant to human survival are shallow: decades to centuries. Many of the resources that we consume today in great quantities were formed over aeons; we cannot rely on natural processes to create more of these resources.
Even living in 'shallow time', we are affected by many 'deep time' geological processes: plate tectonics - the gradual motion of continental plates and the subduction of the seafloor into the Earth - have given us the minerals and ores we mine.
But they have also triggered a variety of rare, yet highly dangerous, natural disasters. Both long and short geological time-scales are important to our needs, and to our survival.
Disasters range from 'natural disasters' to 'stealth disasters'. In one, natural processes build and store energy over short or long periods that is eventually unleashed; in these, human beings have no involvement.
At the other extreme, human actions trigger changes that eventually cause calamities. People are fascinated by natural disasters, the so-called force majeure (or 'acts of God') that you find in insurance policies: earthquakes, volcanic eruptions and tsunamis. They grip people's imaginations and generate frenetic media coverage.
Many natural disasters result from geological processes. They often have a sudden onset and immediate consequences, such as earthquakes, hurricanes or volcanic eruptions.
Within a few generations, depending on where you live, you can see examples of natural disasters; but many of the largest have occurred on biblical time-scales or longer.
Stealth disasters are not so spectacular, and get far less attention - except from the insurance industry. They are caused by humans, but involve the natural systems that support us. They develop gradually, but their consequences are not evident over short time spans.
