Earthquakes, volcanoes demonstrate how our beautiful planet was made
Positive side to destructive forces of nature explained
New Year is the most important holiday in Japan. From January 1-3, all businesses close, bonenkai (yearforgetting: forget last year; look to the future) parties are held, temples are visited, and on January 2, the Imperial Palace in Tokyo opens to the public with the Emperor and imperial family appearing each hour to greet the hundreds of thousands of visitors who steadily promenade across the bridges into the Palace grounds.
In 1992, I was in this giant crowd with Japanese friends.
Their six-year-old son sat on my shoulders, giving him a clear view of the royal family across the masses, as I am taller than most Japanese.
It was a remarkable experience for me to share in this most important Japanese national holiday.
At the beginning of 2024, the New Year celebrations were muted.
The imperial family cancelled their appearances. Rescue was the major concern.
Japan sits on the “Ring of Fire” and the tectonic plate it rides on moved on January 1 in a magnitude 7.6 earthquake, shifting the land upwards by 1.3m and sideways by another metre.
Tens of thousands of houses were destroyed, hundreds of people were killed, and roads cracked and collapsed. Aftershocks continued the shaking, for a while coming at 15minute intervals. It is a major disaster.
In November 2023, all 4,000 residents of the Icelandic town of Grindavik were evacuated in anticipation of an impending volcanic eruption.
For the first time in 800 years the volcanoes of the Reykjanes peninsula began erupting on December 18, pumping lava fountains 50m high.
Iceland straddles the mid-Atlantic ridge where the Eurasian and North American tectonic plates are separating at a rate of 4cm per year, cracking open the crust so that hot lava flows out to create new land. By this process, all of Iceland has been created in only the last 30-million years.
What powers the volcanoes? Why does the Earth’s surface move and shake with devastating earthquakes?
The core of the Earth is as hot as the surface of the Sun — 6,000°C!
The Earth formed 4.5-billion years ago in a disk of gas and rock spun off as the Sun was born.
Rocks and asteroids crashed into each other, growing into planets.
The energy released melted the entire Earth, allowing heavy iron and nickel to settle to the core, and lighter elements to float to the top.
The Earth now has a solid iron inner core, a molten iron outer core, then a mantle of rock that slowly flows in hot rising columns and cooler falling sheets over billions of years.
On top of all that floats the thin, lighter rocky crust where we live.
The inside of the Earth is cooling as the heat flows towards the surface.
Half that heat is left over from the original melting, the other half comes from radioactive decay of the elements uranium, thorium and potassium.
The heat is transported by the churning hot rock of the mantle, and that in turn pushes the light crustal plates around.
Where those plates crash into each other, as for the Ring of Fire and Japan, and where they tear apart, as for Iceland, earthquakes and volcanoes occur.
While we focus on the human tragedies wreaked by earthquakes and volcanoes, it is the collisions of the crustal plates that create mountains and rearrange the continents with great impact on evolution and natural systems.
The Himalayan mountains of Asia are only 50-million years old; the Andes of South America only 20 to 30million years.
The mantle in the Earth will eventually cool. Continental drift will stop. There will be no new mountains and old ones will be washed to the sea.
The cycle of life will change dramatically from what we now enjoy.
This may happen in only a billion years, or it may not occur before the death of the Sun in about 5-billion years – nothing for us to worry about.
But it is worth realising that for all the news of death and destruction, there is a good side to earthquakes and volcanoes. They are part of the dynamic building of our beautiful planet.
Donald Kurtz is extraordinary professor at North-West University in Mahikeng. He has an A-1 rating from the South African National Research Foundation, its highest rating. He also holds appointments in the UK of emeritus professor at the University of Central Lancashire and visiting professor of astrophysics at the University of Lincoln. He was previously professor of astronomy at the University of Cape Town, where he worked for 24 years. Don has more than 500 professional publications and was awarded the 2022 Service Award of the Royal Astronomical Society for a lifetime of public outreach and for his service on many international committees. He and his wife, originally from Grahamstown, now live in Port Alfred.
The mantle in the Earth will eventually cool. Continental drift will stop. There will be no new mountains and old ones will be washed to the sea. The cycle of life will change dramatically from what we now enjoy