What causes tsunamis and why they can be so deadly
Here are key facts about tsunamis and the damage they can cause:
A tsunami is a shock of water that spreads through the sea, usually triggered by a strong earthquake beneath the ocean floor.
The sudden, violent movement of the Earth's crust can thrust up or drive down a section of the seabed – with the rift displacing vast quantities of water that move as waves.
Tsunamis radiate in all directions from their source and can cover enormous distances, sometimes at the speed of a jet plane.
They are a rare phenomenon but can create dangerously powerful currents and cause deadly flooding in coastal areas.
Large quakes are the main driver of tsunamis, but the phenomenon can also be sparked by other cataclysmic geographic events, such as volcanic eruptions and landslides.
In 1883, a volcano shattered the Pacific island of Krakatoa, causing a blast that could be heard 4,500 kilometres (2,800 miles) away, followed by a tsunami that killed around 30,000 people.
Large storms or a meteorite falling into the ocean can also be powerful enough to cause a tsunami, according to the US National Oceanic and Atmospheric Administration.
The word "tsunami" comes from the Japanese words for "harbour" and "wave."
Tsunamis are sometimes referred to as "tidal waves" but experts say this is inaccurate because they are not related to tides.
At their point of generation, tsunamis have a relatively small wave height, with peaks far apart.
As the waves approach the shore they are compressed by the shelving of the sea floor, reducing the distance between the peaks and vastly increasing the height.
When they hit the coast, tsunami waves can strike repeatedly over several hours, or even days.
To those on the shore, the first sign of something amiss can be the retreat of the sea, which is followed by the arrival of large waves.
"The sea was driven back, and its waters flowed away to such an extent that the deep seabed was laid bare and many kinds of sea creatures could be seen," wrote Roman author Ammianus Marcellinus of a tsunami that struck Alexandria in 365 AD.
"Huge masses of water flowed back when least expected, and now overwhelmed and killed many thousands of people... some great ships were hurled by the fury of the waves onto the rooftops."
Several factors determine the height and destructiveness of a tsunami.
They include the size of the quake, the volume of displaced water, the topography of the sea floor and whether there are natural obstacles that dampen the shock.
The Pacific Ocean is particularly prone to earthquakes and therefore to tsunamis, but over the millennia tsunamis have occurred in many parts of the world.
The tsunami of December 2004 in the Indian Ocean was caused by a 9.1 magnitude earthquake off the Indonesian island of Sumatra.
It released energy equivalent to 23,000 of the atomic bombs dropped on Hiroshima, according to the US Geological Survey (USGS). Around 220,000 people in 11 nations were killed, many of them thousands of kilometres from the epicentre.--AFP
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
The Star
6 hours ago
- The Star
Cultural fallout: the impact of the atomic bombings on Japanese arts
From Godzilla's fiery atomic breath to post-apocalyptic anime and harrowing depictions of radiation sickness, the influence of the nuclear bombings of Hiroshima and Nagasaki runs deep in Japanese popular culture. In the 80 years since the World War II attacks, stories of destruction and mutation have been fused with fears around natural disasters and, more recently, the Fukushima crisis. Classic manga and anime series Astro Boy is called Mighty Atom in Japanese, while city-levelling explosions loom large in other titles such as Akira, Neon Genesis Evangelion and Attack On Titan . "Living through tremendous pain" and overcoming trauma is a recurrent theme in Japan's cultural output "that global audiences have found fascinating", said William Tsutsui, a history professor at Ottawa University. The US nuclear bombing of Hiroshima on Aug 6, 1945 left around 140,000 people dead. It was followed days later by the bombing of Nagasaki that killed around 74,000 people. Some poetry "portrays the sheer terror of the atomic bomb at the moment it was dropped", but many novels and artworks address the topic indirectly, said author Yoko Tawada. "It's very difficult for the experience of the atomic bomb, which had never existed in history before, to find a place in the human heart as a memory," she told AFP. Tawada's 2014 book The Emissary focuses on the aftermath of an unspecified terrible event. She was inspired by connections between the atomic bombs, the 2011 Fukushima nuclear disaster and "Minamata disease" - mass mercury poisoning caused by industrial pollution in southwest Japan from the 1950s. The story "is less of a warning, and more a message to say: things may get bad, but we'll find a way to survive", Tawada said. Godzilla's skin Narratives reflecting Japan's complex relationship with nuclear technologies abound, but the most famous example is Godzilla, a prehistoric creature awakened by US hydrogen bomb testing in the Pacific. "We need monsters to give a face and form to abstract fears," said professor Tsutsui, author of the book Godzilla On My Mind. "In the 1950s, Godzilla fulfilled that role for the Japanese - with atomic energy, with radiation, with memories of the A-bombs." Many people who watched Godzilla rampage through Tokyo in the original 1954 film left theatres in tears, he said. And "it's said that the special effects people working on Godzilla modelled the monster's heavily furrowed skin after the keloid scars on the survivors of Hiroshima and Nagasaki." In the nearly 40 Godzilla movies released since, nuclear themes are present but often given less prominence, partly to appease American audiences, Tsutsui said. Even so, the series remains hugely popular, with 2016 megahit Shin Godzilla seen as a critique of Japan's response to the tsunami-triggered Fukushima disaster. 'Black Rain' Black Rain , a 1965 novel by Masuji Ibuse about radiation sickness and discrimination, is one of Japan's best-known novels about the Hiroshima bombing. But the fact Ibuse was not an A-bomb survivor is part of a "big debate about who is permitted to write these stories", said Victoria Young of the University of Cambridge. "How we talk about or create literature out of real life is always going to be difficult," she said. "Are you allowed to write about it if you didn't directly experience it?" Nobel-winning author Kenzaburo Oe collected survivor accounts in Hiroshima Notes, essays written on visits to the city in the 1960s. "He's confronting reality, but tries to approach it from a personal angle" including his relationship with his disabled son, said Tawada, who has lived in Germany for four decades after growing up in Japan. "The anti-war education I received sometimes gave the impression that Japan was solely a victim" in World War II, she said. "When it comes to the bombings, Japan was a victim - no doubt" but "it's important to look at the bigger picture" including Japan's wartime atrocities, she said. As a child, illustrations of the nuclear bombings in contemporary picture books reminded her of depictions of hell in historical Japanese art. This "made me consider whether human civilisation itself harboured inherent dangers", making atomic weapons feel less like "developments in technology, and more like something latent within humanity". - AFP
The Star
9 hours ago
- The Star
Japan sets record temperature of 41.8 deg C
TOKYO: Japan logged a new heat record on Tuesday (Aug 5), with the mercury hitting 41.8 deg C, the weather office said, warning temperatures may rise further still. Temperatures the world over have soared in recent years as climate change creates ever more erratic weather patterns, and Japan is no exception. The scorching temperature in the city of Isesaki on Tuesday surpassed the previous record in the Hyogo region of 41.2C, which was set only last week. Tokyo has also been struggling with extreme heat. "I'm really concerned about global warming, but when it comes to my daily life, I can't live without turning on the air conditioner," office worker Mayomi Saito told AFP. "I don't really know what I should be doing. I'm just desperately getting through each day." Last month, 38,608 people were treated in hospital for heatstroke, data showed Tuesday, down from 43,195 in July 2024. Last week there were 18 deaths. In tourist hotspot Kyoto last week the mercury hit 40C, the first time any of its observation points -- the oldest opened in 1880, the newest in 2002 -- had seen such a high, authorities said. Experts warn Japan's beloved cherry trees are blooming earlier due to the warmer climate -- or sometimes not fully blossoming -- because autumns and winters are not cold enough to trigger flowering. The famous snowcap of Mount Fuji was absent for the longest recorded period last year, not appearing until early November, compared with the average of early October. July was also the hottest since records began in 1898, the weather agency said Friday, with the average monthly temperature 2.89C above the 1991-2020 average. Japan's summer last year was the joint hottest on record, equalling 2023, and was followed by the warmest autumn since records began 126 years ago. - South Korea, Vietnam sizzle - Blistering heatwaves have also hit other parts of Asia this summer, from South Korea to Vietnam, as well as Europe. South Korea saw its second-hottest July, with an average temperature of 27.1C, according the meteorological office, which has been collecting such data since 1973. The hottest July on record in South Korea was in 1994, when the average temperature reached 27.7 degrees Celsius. In northern Vietnam, 17 places across seven provinces reported record highs for the month of August, with electricity demand spiking as people try to stay cool, authorities said Tuesday. The capital Hanoi experienced its first-ever August day above 40C on Monday. In Japan, some dams and paddies nationwide are experiencing a water shortage, with farmers complaining that the sizzling heat combined with a lack of rain is slowing rice cultivation. Precipitation in July was low over wide areas of Japan, with northern regions facing the Sea of Japan experiencing record low rainfall, it added. The rainy season ended about three weeks earlier than usual in western regions of Japan, another record. Every summer, Japanese officials urge the public to seek shelter in air-conditioned rooms to avoid heatstroke. The elderly in Japan -- which has the world's second-oldest population after Monaco -- are particularly at risk. This year, western Europe saw its hottest June on record, as extreme temperatures blasted the region in punishing back-to-back heatwaves, according to the EU climate monitor Copernicus. Dangerous weather stretched into the next month, with separate research estimating that climate change made the temperature up to 4C hotter, pushing the thermometer into deadly territory for thousands of vulnerable people and greatly worsening the projected death toll. Firefighters also battled blazes across Turkey, Bulgaria, Greece and Portugal in July following a deadly heatwave. Millions were exposed to high heat stress as daily average temperatures in western Europe climbed to levels rarely seen before -- and never so early in the summer. - AFP
The Sun
11 hours ago
- The Sun
Milan-Cortina 2026 Winter Games on track despite challenges
Six months before the Winter Olympics kick off, Italian organisers assure that preparations remain on track despite past hurdles. Andrea Varnier, CEO of the Milan-Cortina 2026 Organising Committee, stated, 'Preparations are progressing steadily and according to the timeline we have set.' The Games will begin with curling on February 4, followed by the opening ceremony on February 6. The event emphasises cost efficiency, with a budget of 5.2 billion euros ($6 billion), significantly lower than previous editions like Sochi 2014 ($40 billion) and Beijing 2022 ($38 billion). Existing venues will be prioritised, including Verona's ancient Roman amphitheatre for the closing ceremony, reducing both expenses and environmental impact. Challenges remain, such as constructing a new bobsleigh track in Cortina after political insistence, but organisers remain confident. 'We are moving forward with confidence,' Varnier said. Accommodation plans are also secured, with athlete villages set for completion by October. Medal designs were unveiled in July, with improved durability to avoid issues seen in Paris 2024. The only uncertainty? Snowfall. Italy's weather service cannot yet predict conditions, but organisers remain unfazed: 'We'll be ready.' - AFP
