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Four things tsunami-vulnerable countries must do to prepare for the next disaster

<p>The eruption of an underwater volcano and subsequent tsunami that hit Tonga on January 16, was one of the <a rel="noopener" href="" target="_blank">most violent natural disasters</a> in decades. While this event had <a rel="noopener" href="" target="_blank">catastrophic consequences</a>, such incidents are relatively common as volcanoes are naturally unstable, unpredictable and exist throughout the world.</p> <p>I have spent most of my career conducting post-disaster field research, improving coastal defences and supporting people to become more resilient to tsunamis and less anxious about the risk. The challenge facing countries in these naturally vulnerable parts of the world is to adapt and educate their citizens to take their own safety actions.</p> <p><a href=";q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img src=";q=45&amp;auto=format&amp;w=754&amp;fit=clip" alt="Map showing areas of the world at risk from tsunamis." /></a> <em><span class="caption">Sketch of global tsunami hazard (as of May 2009).</span> <span class="attribution"><a rel="noopener" href="" target="_blank" class="source">UN Office for Disaster Risk Reduction</a></span></em></p> <p>Here I have outlined four things that vulnerable countries must urgently do to mitigate the consequences of tsunamis:</p> <p><strong>1. Educate people to be more resilient</strong></p> <p>Education is one of the most effective defences. Regardless of the size of the wave or strength of seawalls, people are much more likely to survive a tsunami if they know exactly how to react once an alert is triggered. Vulnerable countries must therefore urgently create an educated, close-knit community that is aware that they are exposed to the risk and accept it as an aspect of their life and culture.</p> <p>I conducted focus group meetings with people, businesses and communities in Indonesia <a rel="noopener" href="" target="_blank">after the Anak Krakatoa tsunami in 2018</a>. In these groups, we established designated high ground areas and clear signage directing people to these safe zones. Evacuation events, such as mock tsunami drills, must be practised regularly so that people are familiar with safe areas and know where to go in the instance of a real tsunami.</p> <p>In Tonga specifically, where a third of the population is under the age of 15, tsunami safety must be taught at both primary and secondary school levels. Familiarising their young population with tsunamis, as well as other natural hazards such as <a rel="noopener" href="" target="_blank">cyclones and earthquakes</a>, will create a more resilient and less anxious adult population.</p> <p><strong>2. Create effective early warning systems</strong></p> <p>A decrease in ocean water surface levels is a clear sign that a tsunami is about to hit. Vulnerable countries must create early warning systems using satellites, drones and tide gauges to measure the vertical rise or fall of water to identify tsunamis before they happen.</p> <p>In light of the tsunami in Tonga, it would also help to place equipment such as <a rel="noopener" href="" target="_blank">conductivity-temperature-depth (CTD)</a> instruments, seismometers and thermal cameras near underwater volcanoes, while also observing the waters above with satellites. Buoys that measure the height and direction of waves can also be placed out at sea.</p> <p><a href=";q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img src=";q=45&amp;auto=format&amp;w=754&amp;fit=clip" alt="A yellow buoy in the ocean" /></a> <em><span class="caption">A tsunami detection buoy off the coast of Thailand.</span> <span class="attribution"><span class="source">The Mariner 4291 / shutterstock</span></span></em></p> <p>When water levels are triggered, tsunami alert messages are sent out, giving people enough time to escape the impact zones. I experienced this myself while conducting fieldwork in a small town on the southern coast of Japan in 2018. There was <a rel="noopener" href="" target="_blank">an earthquake</a> during my stay and before the ground had even stopped shaking my colleague received a text alert from the regional government with instructions. I grabbed my passport and prepared to go towards a nearby hill if he received a follow up “red alert” text – fortunately, that particular earthquake did not cause a tsunami, and we were able to stay where we were.</p> <p><strong>3. Establish a strong coastal defence scheme</strong></p> <p>Tsunami-vulnerable countries must urgently create strong coastal defence schemes of offshore breakwaters, <a rel="noopener" href="" target="_blank">tsunami walls</a> and flood levees. Tsunami waves hit hard, so ideally these foundations will be made of reinforced concrete to avoid erosion. Natural protections like <a rel="noopener" href="" target="_blank">coral reefs</a> could be strengthened with nature-based solutions such as rock armour or heavy sandbags, which will lower the cost for developing countries.</p> <p><a href=";q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img src=";q=45&amp;auto=format&amp;w=754&amp;fit=clip" alt="Man walks along concrete wall" /></a><em> <span class="caption">A new coastal dyke in the city of Sendai, Japan, built after the 2011 tsunami.</span> <span class="attribution"><span class="source">Ravindra Jayaratne</span>, <span class="license">Author provided</span></span></em></p> <p>Critical infrastructure like power plants, densely populated communities and tourist hotspots must be built on higher ground, where possible. A good example of this comes from Miyagi and Iwate prefectures, Japan, which were badly hit by the 2011 Tohoku tsunami (the one which caused a nuclear disaster in neighbouring Fukushima). Some towns were <a rel="noopener" href="" target="_blank">rebuilt on elevated ground</a> that had been filled in with compacted soil.</p> <p>If space is available, coastal forests with tall trees could be planted between communities and the beach to <a rel="noopener" href="" target="_blank">act as a buffer zone</a>, limiting the impact of waves and reducing flooding, while also improving the local ecosystem.</p> <p>These defences may damage the tourist-friendly aesthetic of white sandy beaches, but they could save lives.</p> <p><strong>4. Form a regional approach to tsunamis</strong></p> <p>The effects of the underwater volcano eruption and tsunami in Tonga were felt around the Pacific in Australia, New Zealand, Japan and America. These vulnerable countries must implement a regional approach to defending and responding to tsunamis.</p> <p>Aid must be given before tsunamis hit, not just after. This can be done through sharing data, expertise, research facilities and equipment. It is vitally important that this information is specifically given to developing countries to help strengthen their own defences.</p> <p>The underwater volcano near Tonga is active. And even if the recent eruption was a one in 1,000 year event, there is still a strong chance that it will erupt again since geological deposits show that major eruptions like this one tend to involve a <a rel="noopener" href="" target="_blank">series of many individual explosive events</a>.</p> <p>Countries that are threatened by tsunamis can’t prevent these natural disasters from happening, but they can adapt to be better prepared for when they do. Foreign aid will be vital for Tonga to recover from this horrific incident. However, education and collaboration will be its most important defence in the longer term.<!-- Below is The Conversation's page counter tag. Please DO NOT REMOVE. --><img style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important; text-shadow: none !important;" src="" alt="The Conversation" width="1" height="1" /><!-- End of code. If you don't see any code above, please get new code from the Advanced tab after you click the republish button. The page counter does not collect any personal data. More info: --></p> <p><em><a rel="noopener" href="" target="_blank">Ravindra Jayaratne</a>, Reader in Coastal Engineering, <a rel="noopener" href="" target="_blank">University of East London</a></em></p> <p><em>This article is republished from <a rel="noopener" href="" target="_blank">The Conversation</a> under a Creative Commons license. Read the <a rel="noopener" href="" target="_blank">original article</a>.</em></p> <p><em>Image: Getty Images</em></p>

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First death of Tonga tsunami tragedy confirmed

<p>An animal welfare charity founder has been confirmed dead after the devastating impact of the Tonga tsunami tragedy. </p> <p>The body of British woman Angela Glover was found on Monday after she was swept away by huge swells that were caused by a massive underwater volcanic eruption. </p> <p><span>The Hunga Tonga-Hunga Haʻapai volcano, which erupted on Saturday, is located 65km from where 50-year-old Angela lived with her husband in the Tongan capital of Nuku’alofa.<br /></span></p> <p><span>Angela moved to the Pacific islands in 2015, after leaving her life in London's advertising industry behind. </span></p> <p><span>Angela's bother Nick, who resides in Sydney, confirmed the news of her death on Monday, saying his sister's body was found "in some bushes" by her husband. </span></p> <p class="css-1316j2p-StyledParagraph e4e0a020">“I’ve not even got the words in my vocabulary to describe how we’re feeling at the moment. This is just a terrible shock, that it’s happened to us,” he said.</p> <p class="css-1316j2p-StyledParagraph e4e0a020">“We’re ordinary people - stuff like this doesn’t happen to people like us, then it does."</p> <p class="css-1316j2p-StyledParagraph e4e0a020">“I understand this terrible accident came about as they tried to rescue their dogs.”</p> <p class="css-1316j2p-StyledParagraph e4e0a020">Angela's "deep love" for canines inspired her to create the Tongan Animal Welfare Society to shelter and rehabilitate stray animals, according to her brother. </p> <p class="css-1316j2p-StyledParagraph e4e0a020"><span>“The uglier the dog, the more she loved it. She just loved them all, she was totally dedicated to it.”</span></p> <p class="css-1316j2p-StyledParagraph e4e0a020"><span>In Angela's final social media post, she shared a picture of the fiery Tongan sunset just hours after the eruption of the volcano, saying "everything's fine".</span></p> <blockquote style="background: #FFF; border: 0; border-radius: 3px; box-shadow: 0 0 1px 0 rgba(0,0,0,0.5),0 1px 10px 0 rgba(0,0,0,0.15); margin: 1px; max-width: 540px; min-width: 326px; padding: 0; width: calc(100% - 2px);" class="instagram-media" data-instgrm-permalink=";utm_campaign=loading" data-instgrm-version="14"> <div style="padding: 16px;"> <div style="display: flex; flex-direction: row; align-items: center;"> <div style="background-color: #f4f4f4; border-radius: 50%; flex-grow: 0; height: 40px; margin-right: 14px; width: 40px;"></div> <div style="display: flex; flex-direction: column; flex-grow: 1; justify-content: center;"> <div style="background-color: #f4f4f4; border-radius: 4px; flex-grow: 0; height: 14px; margin-bottom: 6px; width: 100px;"></div> <div style="background-color: #f4f4f4; border-radius: 4px; flex-grow: 0; height: 14px; width: 60px;"></div> </div> </div> <div style="padding: 19% 0;"></div> <div style="display: block; height: 50px; margin: 0 auto 12px; width: 50px;"></div> <div style="padding-top: 8px;"> <div style="color: #3897f0; font-family: Arial,sans-serif; font-size: 14px; font-style: normal; font-weight: 550; line-height: 18px;">View this post on Instagram</div> </div> <p style="color: #c9c8cd; font-family: Arial,sans-serif; font-size: 14px; line-height: 17px; margin-bottom: 0; margin-top: 8px; overflow: hidden; padding: 8px 0 7px; text-align: center; text-overflow: ellipsis; white-space: nowrap;"><a style="color: #c9c8cd; font-family: Arial,sans-serif; font-size: 14px; font-style: normal; font-weight: normal; line-height: 17px; text-decoration: none;" rel="noopener" href=";utm_campaign=loading" target="_blank">A post shared by Angela Glover (@ifthegloverfits)</a></p> </div> </blockquote> <p><span>She captioned the picture, "I’m not kidding you, this is the sunset today after the volcano exploded last night. We’ve been under tsunami warnings today. Everything’s fine... a few swells ....a few eerie silences...a wind or two...then silence...sudden stillness... electric storms.... everything looked like I was watching thru an Instagram filter."</span></p> <p class="css-1316j2p-StyledParagraph e4e0a020"><span>Angela is the first known death of the disaster, as the scale of the destruction is still unknown. </span></p> <p class="css-1316j2p-StyledParagraph e4e0a020">Experts<span> say that the volcano, which last erupted in 2014, had been puffing away for about a month before rising magma, superheated to around 1000 degrees Celsius, met with 20-degree seawater, causing an instantaneous and massive explosion.</span></p> <p class="css-1316j2p-StyledParagraph e4e0a020"><span>The impact of the eruption was felt as far away as Australia, New Zealand, Fiji and Japan. </span></p> <p class="css-1316j2p-StyledParagraph e4e0a020"><em>Image credits: Instagram @ifthegloverfits</em></p>


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Why the volcanic eruption in Tonga was so violent, and what to expect next

<p>The Kingdom of Tonga doesn’t often attract global attention, but a <a href="">violent eruption of an underwater volcano</a> on January 15 has spread shock waves, quite literally, around half the world.</p> <p>The volcano is usually not much to look at. It consists of two small uninhabited islands, Hunga-Ha’apai and Hunga-Tonga, poking about 100m above sea level 65km north of Tonga’s capital Nuku‘alofa. But hiding below the waves is a massive volcano, around 1800m high and 20km wide.</p> <p><img src=";q=45&amp;auto=format&amp;w=754&amp;fit=clip" alt="A map of the massive underwater volcano next to the Hunga-Ha’apai and Hunga-Tonga islands." /> <span class="caption">A massive underwater volcano lies next to the Hunga-Ha’apai and Hunga-Tonga islands.</span> <span class="attribution"><span class="license">Author provided</span></span></p> <p>The Hunga-Tonga-Hunga-Ha'apai volcano has erupted regularly over the past few decades. During events in 2009 and 2014/15 hot jets of magma and steam exploded through the waves. But these eruptions were small, dwarfed in scale by the January 2022 events.</p> <p>Our <a href="">research</a> into these earlier eruptions suggests this is one of the massive explosions the volcano is capable of producing roughly every thousand years.</p> <p>Why are the volcano’s eruptions so highly explosive, given that sea water should cool the magma down?</p> <p>If magma rises into sea water slowly, even at temperatures of about 1200℃, a thin film of steam forms between the magma and water. This provides a layer of insulation to allow the outer surface of the magma to cool.</p> <p>But this process doesn’t work when magma is blasted out of the ground full of volcanic gas. When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.</p> <p>Volcano researchers call this “fuel-coolant interaction” and it is akin to weapons-grade chemical explosions. Extremely violent blasts tear the magma apart. A chain reaction begins, with new magma fragments exposing fresh hot interior surfaces to water, and the explosions repeat, ultimately jetting out volcanic particles and causing blasts with supersonic speeds.</p> <h2>Two scales of Hunga eruptions</h2> <p>The 2014/15 eruption created a volcanic cone, joining the two old Hunga islands to create a combined island about 5km long. We visited in 2016, and discovered these historical eruptions were merely <a href="">curtain raisers to the main event</a>.</p> <p>Mapping the sea floor, we discovered a hidden “caldera” 150m below the waves.</p> <p><img src=";q=45&amp;auto=format&amp;w=754&amp;fit=clip" alt="A map of the seafloor shows the volcanic cones and caldera." /> <span class="caption">A map of the seafloor shows the volcanic cones and massive caldera.</span> <span class="attribution"><span class="license">Author provided</span></span></p> <p>The caldera is a crater-like depression around 5km across. Small eruptions (such as in 2009 and 2014/15) occur mainly at the edge of the caldera, but very big ones come from the caldera itself. These big eruptions are so large the top of the erupting magma collapses inward, deepening the caldera.</p> <p>Looking at the chemistry of past eruptions, we now think the small eruptions represent the magma system slowly recharging itself to prepare for a big event.</p> <p>We found evidence of two huge past eruptions from the Hunga caldera in deposits on the old islands. We matched these chemically to volcanic ash deposits on the largest inhabited island of Tongatapu, 65km away, and then used radiocarbon dates to show that big caldera eruptions occur about ever 1000 years, with the last one at AD1100.</p> <p>With this knowledge, the eruption on January 15 seems to be right on schedule for a “big one”.</p> <h2>What we can expect to happen now</h2> <p>We’re still in the middle of this major eruptive sequence and many aspects remain unclear, partly because the island is currently obscured by ash clouds.</p> <p>The two earlier eruptions on December 20 2021 and January 13 2022 were of moderate size. They produced clouds of up to 17km elevation and added new land to the 2014/15 combined island.</p> <p>The latest eruption has stepped up the scale in terms of violence. The ash plume is already about 20km high. Most remarkably, it spread out almost concentrically over a distance of about 130km from the volcano, creating a plume with a 260km diameter, before it was distorted by the wind.</p> <p><img src="" alt="" width="100%" /></p> <p>This demonstrates a huge explosive power – one that cannot be explained by magma-water interaction alone. It shows instead that large amounts of fresh, gas-charged magma have erupted from the caldera.</p> <p>The eruption also produced a <a href="">tsunami throughout Tonga</a> and neighbouring Fiji and Samoa. Shock waves traversed many thousands of kilometres, were seen from space, and recorded in New Zealand some 2000km away. Soon after the eruption started, the sky was blocked out on Tongatapu, with ash beginning to fall.</p> <p>All these signs suggest the large Hunga caldera has awoken. Tsunami are generated by coupled atmospheric and ocean shock waves during an explosions, but they are also readily caused by submarine landslides and caldera collapses.</p> <p>It remains unclear if this is the climax of the eruption. It represents a major magma pressure release, which may settle the system.</p> <p>A warning, however, lies in geological deposits from the volcano’s previous eruptions. These complex sequences show each of the 1000-year major caldera eruption episodes involved many separate explosion events.</p> <p>Hence we could be in for several weeks or even years of major volcanic unrest from the Hunga-Tonga-Hunga-Ha'apai volcano. For the sake of the people of Tonga I hope not.<!-- Below is The Conversation's page counter tag. Please DO NOT REMOVE. --><img style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important; text-shadow: none !important;" src="" alt="The Conversation" width="1" height="1" /><!-- End of code. If you don't see any code above, please get new code from the Advanced tab after you click the republish button. The page counter does not collect any personal data. More info: --></p> <p><span><a href="">Shane Cronin</a>, Professor of Earth Sciences, <em><a href="">University of Auckland</a></em></span></p> <p>This article is republished from <a href="">The Conversation</a> under a Creative Commons license. Read the <a href="">original article</a>.</p>

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