Within the early hours of April 7, 1934, a tsunami tore by means of the slender Norwegian fjord of Tafjorden. What triggered it, and what does it imply for the way forward for Norway’s fjords?
Norway is known for its lovely fjords. Their steep mountain partitions, deep blue waters, and trickling waterfalls make for an awe-inspiring sight. Tafjorden isn’t any exception.
But, with the wonder comes the chance. These mountains received’t stand perpetually. They’re present process erosional processes on a regular basis, and in the future, they may fall.
In Norway, rockfalls generally happen above a fjord. Because the rock displaces a major quantity of water, it might set off a sequence of huge waves referred to as a tsunami. The small cities of Tafjord and Fjørå have been sufferer to such an occasion in Tafjorden in 1934.
Rockfall tsunamis threaten among the most lovely areas and tight-knit communities in Norway. With the intention to perceive the hazard and presumably predict future occasions, we have now to look again in historical past.
Let’s take a deep dive into the 1934 catastrophe that surged by means of the small cities of Tafjorden.
A catastrophe ready to occur
Tafjorden is positioned within the Sunnmøre district of Møre and Romsdal county, east of Ålesund. It’s the northern internal department of Storfjorden. Its sistering southern department is the well-known Geirangerfjorden.
In 2015, the movie “The Wave” or “Bølgen” was launched, depicting a rockfall tsunami that’s predicted to happen within the neighboring Geirangerfjorden.
Tafjorden has a complete size of 12 km, and at its widest, it’s 1.Eight km throughout. It’s lined by steep cliffs and mountains that attain simply over a kilometer above the ocean.
A mountain referred to as Langhammaran is positioned on the northern facet of Tafjorden. It’s lower than 10 km away from each Fjørå and Tafjord. It towers 730 meters above the floor of the water.
Since 1870, a crevice was seen in Langhammaren. Residents of the close by city Fjørå witnessed the crevice’s growth and saved their distance from the underside of the cliff.
However they have been unaware of the devastating consequence a rockfall might have within the slender fjord.
Bringing down a mountain
Rocks are usually seen as strong, dependable, and never-changing. However from the point of view of a geologist, this couldn’t be farther from the reality.
One such instance of how rocks change on the timescale of our lives is thru catastrophic occasions reminiscent of rockfalls.
These catastrophes outcome from small, gradual processes which may be invisible to us however are regularly going down.
In actuality, mountains are crammed with fractures of variable sizes, often known as crevices. Rain and groundwater seep into the fractures and may freeze if the local weather permits.
Because the quantity of ice is bigger than liquid water, this causes the fracture to widen. When the ice melts, extra water is ready to percolate into the widened fracture, growing the quantity of ice when temperatures freeze once more.
This course of is named freeze-thaw and is a typical trigger for rockfalls in mountainous areas. Rockfalls may also be triggered by earthquakes.
The seen crevice in Langhammaran was greater than 1.5 meters extensive by 1930. A few of the residents of Fjørå started warning of a catastrophe.
They’d observed that the crevice, which they as soon as used to leap over, was now so extensive they must construct a bridge to get throughout it.
On the innermost a part of the fjord, the residents of Tafjord have been uninformed of the rising fracture.
The unexpected monstrous wave
The consequence of a rockfall in Tafjorden was unknown to its residents. Little did they know that the big quantity of rock that may fall into the fjord would displace an equal quantity of water. That creates what is called a megatsunami.
Most of us are accustomed to tsunamis that kind on account of subsea earthquakes.
Because the water column is displaced, waves are created with wavelengths of a whole bunch of kilometers lengthy and amplitudes lower than one meter excessive within the open ocean.
As they method land, their amplitude can attain a couple of meters in a course of referred to as wave shoaling.
Tsunamis can journey at speeds of a whole bunch of kilometers per hour, destroying every part of their path earlier than drawing again the wreckage out to sea.
However, a tsunami created by a rockfall in a slender fjord will initially have a wave amplitude of tens to a whole bunch of meters.
The displaced water travels up the other cliff face in what is named a surge wave.
Because the waves journey away from the supply, their vitality and amplitude lower. Steady interplay with the fjord partitions creates incident waves and wave exercise that may final for hours.
The biggest megatsunami ever recorded created a surge wave that was a whopping 524 meters excessive. It happened in Lituya Bay, Alaska, in 1958.
Twenty-four years prior, the upcoming menace of a megatsunami was unknown in Tafjorden. The residents of Fjørå and Tafjord have been awoken within the early hours one morning by a roar and a rush of chilly seawater.
The sounds of hell
Simply after three:00 AM on April 7, 1934, the crevice in Langhammaren lastly gave, releasing three million cubic meters of rock into the fjord.
The residents have been awoken by a loud noise, adopted by a rush of wind into their bedrooms. Their homes creaked.
Because the rock fell, it displaced water and air. It created a tsunami that was funneled down the fjord in each instructions – one path, out in the direction of Fjørå, and the opposite path additional inland in the direction of Tafjord.
It was darkish, and nobody might see the advancing waves. The residents have been uneasy as “the sounds of hell” continued. Quickly, silence, adopted by the sound of dashing water.
The city residents scrambled as water seeped into their homes. Some escaped by means of home windows onto their roofs, whereas others merely tried to barricade their doorways.
Dragged out into the fjord
The homes alongside the shoreline obtained the complete influence of the tsunami. A 20-year-old boy from Tafjord recounts being dragged out into the fjord with the disadvantage.
He briefly regained consciousness clinging to a board in the midst of the fjord earlier than being thrown again in the direction of the shore with the final wave.
Three tsunami waves reached the shoreline of the fjord, every one greater than the final.
The final and largest wave that reached Fjørå was 13 meters excessive, and the final wave that reached Tafjord was 17 meters excessive.
Nevertheless, the preliminary megatsunami wave is estimated to have towered at 63 meters at its highest level.
The final wave hit the shoreline at 160 km/hr, tossing again what it had claimed.
The 20-year-old boy was discovered outdoors the put up workplace, severely wounded, however alive. He misplaced each his mother and father and eight siblings that evening. Miraculously, he survived the facility of the final wave and described it as “swimming amongst monstrous ghosts.”
Different residents have been fast sufficient to flee to excessive topography in between the waves. From there, they watched because the waves tore aside their homes and swept them out into the fjord.
The Tafjord tsunami claimed the lives of 40 individuals: 17 in Fjørå and 23 in Tafjord. Solely 11 our bodies have been retrieved from the wreckage. Lots of the survivors refused to speak about that evening within the years after.
A transparent scar was left on Langhammaren. It’s seen to today as a reminder of the tragedy that swept over Tafjorden, but in addition of the nonetheless current danger many mountains pose within the Norwegian fjords.
May it occur once more?
The Tafjord tsunami was the primary pure catastrophe in Norway to obtain widespread media protection. It’s thought of to be one of many worst pure disasters to have occurred in Norway within the 20th century.
Scientists and geologists imagine rockfall might occur once more – in Tafjorden and lots of different fjords. It is just a matter of time.
Hagguraksla, the mountain northwest of Langhammaren, accommodates two unstable blocks that scientists imagine might trigger an analogous occasion sooner or later.
They’re repeatedly monitoring the actions of those blocks by measuring the width of crevices, much like the one which was seen on Langhammaren.
In Storfjorden, one other mountain, Åknes, has a widening crevice. It was first found by an area farmer who observed crack had dramatically widened since his childhood.
Since 1989, the crack is being frequently monitored, and it’s increasing Eight-10 centimeters yearly.
If the rock have been to fall, it will launch 54 million cubic meters into the fjord, which is 18 occasions the amount of rock launched in Tafjorden.
The estimated top of the preliminary megatsunami wave produced by a rockfall of Åknes could be 80 meters.
Different unstable mountains which are being monitored in Norway are Mannen in Møre and Romsdal, Joasetbergi in Sogn and Fjordane, Gamanjunni three in Troms, Jettan in Troms and Indre Nordnes in Troms. A few of these are additionally prone to set off a megatsunami and the destruction of native communities.
The communication and consciousness of rockfall danger in Norway are bettering.
Moreover, methods have been put in place that may warn native residents of a rockfall and its imminent tsunami.
If such methods are trusted, quite a few lives could be spared.
Supply: Norway As we speak