In the early hours of April 7, 1934, a tsunami tore through the narrow Norwegian fjord of Tafjorden. What triggered it, and what does it mean for the future of Norway’s fjords?
Norway is famous for its beautiful fjords. Their steep mountain walls, deep blue waters, and trickling waterfalls make for an awe-inspiring sight. Tafjorden is no exception.
Yet, with the beauty comes the risk. Those mountains won’t stand forever. They are undergoing erosional processes all the time, and one day, they will fall.
In Norway, rockfalls commonly take place above a fjord. Since the rock displaces a significant volume of water, it can trigger a series of large waves called a tsunami. The small towns of Tafjord and Fjørå were victim to such an event in Tafjorden in 1934.
Rockfall tsunamis threaten some of the most beautiful regions and tight-knit communities in Norway. In order to understand the danger and possibly predict future events, we have to look back in history.
Let’s take a deep dive into the 1934 disaster that surged through the small towns of Tafjorden.
A disaster waiting to happen
Tafjorden is located in the Sunnmøre district of Møre and Romsdal county, east of Ålesund. It is the northern inner branch of Storfjorden. Its sistering southern branch is the famous Geirangerfjorden.
In 2015, the film “The Wave” or “Bølgen” was released, depicting a rockfall tsunami that is predicted to take place in the neighboring Geirangerfjorden.
Tafjorden has a total length of 12 km, and at its widest, it is 1.8 km across. It is lined by steep cliffs and mountains that reach just over a kilometer above the sea.
A mountain called Langhammaran is located on the northern side of Tafjorden. It is less than 10 km away from both Fjørå and Tafjord. It towers 730 meters above the surface of the water.
Since 1870, a crevice was visible in Langhammaren. Residents of the nearby town Fjørå witnessed the crevice’s expansion and kept their distance from the bottom of the cliff.
But they were unaware of the devastating consequence a rockfall could have in the narrow fjord.
Bringing down a mountain
Rocks are typically viewed as solid, reliable, and never-changing. But from the viewpoint of a geologist, this couldn’t be farther from the truth.
One such example of how rocks change on the timescale of our lives is through catastrophic events such as rockfalls.
These catastrophes result from small, slow processes that may be invisible to us but are continually taking place.
In reality, mountains are filled with fractures of variable sizes, also known as crevices. Rain and groundwater seep into the fractures and can freeze if the climate permits.
Since the volume of ice is larger than liquid water, this causes the fracture to widen. When the ice melts, more water is able to percolate into the widened fracture, increasing the amount of ice when temperatures freeze again.
This process is called freeze-thaw and is a common cause for rockfalls in mountainous regions. Rockfalls can also be triggered by earthquakes.
The visible crevice in Langhammaran was more than 1.5 meters wide by 1930. Some of the residents of Fjørå began warning of a disaster.
They had noticed that the crevice, which they once used to jump over, was now so wide they would have to build a bridge to get across it.
At the innermost part of the fjord, the residents of Tafjord were uninformed of the growing fracture.
The unforeseen monstrous wave
The consequence of a rockfall in Tafjorden was unknown to its residents. Little did they know that the large amount of rock that would fall into the fjord would displace an equal amount of water. That creates what is known as a megatsunami.
Most of us are familiar with tsunamis that form as a result of subsea earthquakes.
As the water column is displaced, waves are created with wavelengths of hundreds of kilometers long and amplitudes less than one meter high in the open ocean.
As they approach land, their amplitude can reach a few meters in a process called wave shoaling.
Tsunamis can travel at speeds of hundreds of kilometers per hour, destroying everything in their path before drawing back the wreckage out to sea.
On the other hand, a tsunami created by a rockfall in a narrow fjord will initially have a wave amplitude of tens to hundreds of meters.
The displaced water travels up the opposite cliff face in what is called a surge wave.
As the waves travel away from the source, their energy and amplitude decrease. Continuous interaction with the fjord walls creates incident waves and wave activity that can last for hours.
The largest megatsunami ever recorded created a surge wave that was a whopping 524 meters high. It took place in Lituya Bay, Alaska, in 1958.
Twenty-four years prior, the impending threat of a megatsunami was unknown in Tafjorden. The residents of Fjørå and Tafjord were awoken in the early hours one morning by a roar and a rush of cold seawater.
The sounds of hell
Just after 3:00 AM on April 7, 1934, the crevice in Langhammaren finally gave, releasing three million cubic meters of rock into the fjord.
The residents were awoken by a loud noise, followed by a rush of wind into their bedrooms. Their houses creaked.
As the rock fell, it displaced water and air. It created a tsunami that was funneled down the fjord in both directions – one direction, out towards Fjørå, and the other direction further inland towards Tafjord.
It was dark, and no one could see the advancing waves. The residents were uneasy as “the sounds of hell” continued. Soon, silence, followed by the sound of rushing water.
The town residents scrambled as water seeped into their houses. Some escaped through windows onto their roofs, while others simply tried to barricade their doors.
Dragged out into the fjord
The houses along the shoreline received the full impact of the tsunami. A 20-year-old boy from Tafjord recounts being dragged out into the fjord with the drawback.
He briefly regained consciousness clinging to a board in the middle of the fjord before being thrown back towards the shore with the last wave.
Three tsunami waves reached the shoreline of the fjord, each one higher than the last.
The last and largest wave that reached Fjørå was 13 meters high, and the last wave that reached Tafjord was 17 meters high.
However, the initial megatsunami wave is estimated to have towered at 63 meters at its highest point.
The last wave hit the shoreline at 160 km/hr, tossing back what it had claimed.
The 20-year-old boy was found outside the post office, severely wounded, but alive. He lost both his parents and eight siblings that night. Miraculously, he survived the power of the last wave and described it as “swimming amongst monstrous ghosts.”
Other residents were quick enough to escape to high topography in between the waves. From there, they watched as the waves tore apart their houses and swept them out into the fjord.
The Tafjord tsunami claimed the lives of 40 people: 17 in Fjørå and 23 in Tafjord. Only 11 bodies were retrieved from the wreckage. Many of the survivors refused to talk about that night in the years after.
A clear scar was left on Langhammaren. It is visible to this day as a reminder of the tragedy that swept over Tafjorden, but also of the still present risk many mountains pose in the Norwegian fjords.
Could it happen again?
The Tafjord tsunami was the first natural disaster in Norway to receive widespread media coverage. It is considered to be one of the worst natural disasters to have occurred in Norway in the 20th century.
Scientists and geologists believe that a rockfall could happen again – in Tafjorden and many other fjords. It is only a matter of time.
Hagguraksla, the mountain northwest of Langhammaren, contains two unstable blocks that scientists believe could cause a similar event in the future.
They are continuously monitoring the movements of these blocks by measuring the width of crevices, similar to the one that was seen on Langhammaren.
In Storfjorden, another mountain, Åknes, has a widening crevice. It was first discovered by a local farmer who noticed that a crack had dramatically widened since his childhood.
Since 1989, the crack is being regularly monitored, and it is expanding 8-10 centimeters every year.
If the rock were to fall, it would release 54 million cubic meters into the fjord, which is 18 times the volume of rock released in Tafjorden.
The estimated height of the initial megatsunami wave produced by a rockfall of Åknes would be 80 meters.
Other unstable mountains that are being monitored in Norway are Mannen in Møre and Romsdal, Joasetbergi in Sogn and Fjordane, Gamanjunni 3 in Troms, Jettan in Troms and Indre Nordnes in Troms. Some of these are also likely to trigger a megatsunami and the destruction of local communities.
The communication and awareness of rockfall risk in Norway are improving.
Additionally, systems have been put in place that would warn local residents of a rockfall and its imminent tsunami.
If such systems are trusted, numerous lives can be spared.
Source: Norway Today