Extinction Rebellion

From Wikipedia, the free encyclopedia

Extinction Rebellion

Named after	Anthropocene extinction
Motto	Fight for life Rebel for life
Formation	31 October 2018
Type	Civil society campaign
Purpose	Climate change mitigation Nature conservation Environmental protection
Region	International
Methods	Nonviolent direct action
Fields	Conservation movement Environmental movement
Affiliations	Rising Up! The Climate Mobilization
Website	xrebellion.org

Extinction Rebellion (abbreviated as XR) is a socio-political movement which uses nonviolent resistance to avert climate breakdown, halt biodiversity loss, and minimise the risk of human extinction and ecological collapse.

Extinction Rebellion was established in the United Kingdom in May 2018 with about one hundred academics signing a call to action in support in October 2018, and launched at the end of October by Roger Hallam, Gail Bradbrook, Simon Bramwell, and other activists from the campaign group Rising Up! In November 2018 various acts of civil disobedience were carried out in London. In an ongoing action, in April 2019 XR occupied four prominent sites in central London: Oxford Circus, Marble Arch, Waterloo Bridge and the area around Parliament Square.

Citing inspiration from grassroots movements such as Occupy, Gandhi's independence movement, the suffragettes, and Martin Luther King and others in the civil rights movement, Extinction Rebellion wants to rally support worldwide around a common sense of urgency to tackle climate breakdown. A large number of activists in the movement have pledged to be arrested, and even to go to prison, similar to the mass arrest tactics of the Committee of 100 in 1961.

Its logo uses the circled hourglass extinction symbol.

Manifesto

Extinction Rebellion placard. Its logo is the extinction symbol.

Demands

Extinction Rebellion's website states its aims as:

• The Government must tell the truth about the climate and wider ecological emergency, reverse inconsistent policies and work alongside the media to communicate with citizens.
• The Government must enact legally binding policy measures to reduce carbon emissions to net zero by 2025 and to reduce consumption levels.
• A national Citizens' assembly to oversee the changes, as part of creating a democracy fit for purpose.

Stated principles

XR state the following on its website and explain in a declaration:

1. "We have a shared vision of change – creating a world that is fit for generations to come.
2. We set our mission on what is necessary – mobilising 3.5% of the population to achieve system change – using ideas such as "momentum-driven organising" to achieve this.
3. We need a regenerative culture – creating a culture which is healthy, resilient and adaptable.
4. We openly challenge ourselves and this toxic system – leaving our comfort zones to take action for change.
5. We value reflecting and learning – following a cycle of action, reflection, learning, and planning for more action. Learning from other movements and contexts as well as our own experiences.
6. We welcome everyone and every part of everyone – working actively to create safer and more accessible spaces.
7. We actively mitigate for power – breaking down hierarchies of power for more equitable participation.
8. We avoid blaming and shaming – we live in a toxic system, but no one individual is to blame.
9. We are a non-violent network – using non-violent strategy and tactics as the most effective way to bring about change.
10. We are based on autonomy and decentralisation – we collectively create the structures we need to challenge power. Anyone who follows these core principles and values can take action in the name of RisingUp!"

Support

First open letter

On 26 October 2018, approximately one hundred academics signed a call to action about the ecological crisis:

[...] The science is clear, the facts are incontrovertible, and it is unconscionable to us that our children and grandchildren should have to bear the terrifying brunt of an unprecedented disaster of our own making. [...] Our government is complicit in ignoring the precautionary principle, and in failing to acknowledge that infinite economic growth on a planet with finite resources is non-viable. [...] When a government wilfully abrogates its responsibility to protect its citizens from harm and to secure the future for generations to come, it has failed in its most essential duty of stewardship. The "social contract" has been broken, and it is therefore not only our right, but our moral duty to bypass the government's inaction and flagrant dereliction of duty, and to rebel to defend life itself. We therefore declare our support for Extinction Rebellion, launching on 31 October 2018. We fully stand behind the demands for the government to tell the hard truth to its citizens. We call for a citizens' assembly to work with scientists on the basis of the extant evidence and in accordance with the precautionary principle, to urgently develop a credible plan for rapid total decarbonisation of the economy.

Second open letter

On 9 December 2018, a second open letter of support signed by another hundred academics was published, saying:

[...] Political leaders worldwide are failing to address the environmental crisis. If global corporate capitalism continues to drive the international economy, global catastrophe is inevitable. [...] We further call on concerned global citizens to rise up and organise against current complacency in their particular contexts, including indigenous people's rights advocacy, decolonisation and reparatory justice – so joining the global movement that's now rebelling against extinction (e.g. Extinction Rebellion in the UK). We must collectively do whatever's necessary non-violently, to persuade politicians and business leaders to relinquish their complacency and denial. Their "business as usual" is no longer an option. Global citizens will no longer put up with this failure of our planetary duty. Every one of us, especially in the materially privileged world, must commit to accepting the need to live more lightly, consume far less, and to not only uphold human rights but also our stewardship responsibilities to the planet.

During the 'International Rebellion' which started on 15 April 2019, actions and messages of support arrived from various sources, including a speech by actress Emma Thompson, a planned visit by school strike leader Greta Thunberg, and statements from former Nasa scientist James Hansen and linguist and activist Noam Chomsky.

UK actions

2018

“	Organisers say they hope the campaign of 'respectful disruption' will change the debate around climate breakdown and signal to those in power that the present course of action will lead to disaster.	”
— Damien Gayle, The Guardian

On 17 October 2018, activists from Extinction Rebellion held a sit-in at the UK headquarters of Greenpeace, the direct action environmental organisation, "to encourage their members to participate in mass civil disobedience as the only remaining alternative to avert the worst of the catastrophe" and join in future activities of Extinction Rebellion.

'Declaration of Rebellion'

An assembly took place at Parliament Square, London on 31 October 2018, and drew more than a thousand people to hear the "Declaration of Rebellion" against the UK government and speeches by Donnachadh McCarthy, 15-year-old Greta Thunberg, the Swedish schoolgirl "on strike" from school over her own government's climate inaction, Julia Bradbury, and Green MEP Molly Scott Cato in the square. After a motion was proposed and agreed, the assembly moved to occupy the road, where Green MP Caroline Lucas, environmentalist George Monbiot, and other speakers and singers, including Seize the Day, continued from the reclaimed street directly in front of the Houses of Parliament. Following this, 15 campaigners were arrested for deliberately continuing the sit-in in the roadway.

In the first two weeks of the movement in November 2018, more than 60 people were arrested for taking part in acts of civil disobedience organised by Extinction Rebellion. On 12 November 2018, activists blockaded the UK's Department for Business, Energy and Industrial Strategy and some glued their hands to the department's doors. Activists unveiled a "Climate Change... We're Fucked" banner over Westminster Bridge and glued themselves to the gates of Downing Street, near the Prime Minister's official residence, on 14 November.

'Rebellion Day'

"Rebellion Day" on Blackfriars Bridge, 17 November 2018

 

On 17 November 2018, in what was called "Rebellion Day", about 6,000 people took part in a coordinated action to block the five main bridges over the River Thames in London (Southwark, Blackfriars, Waterloo, Westminster, and Lambeth) for several hours, causing major traffic disruption; 70 arrests were made. The Guardian described it as "one of the biggest acts of peaceful civil disobedience in the UK in decades". YBA artist Gavin Turk was one of the activists arrested for obstructing the public highway. Internationally there was an action by the XR group in Stockholm, as well as rallies in Dublin, Cork, Galway, Belfast. Copenhagen, Berlin, Madrid and New York City.

Extinction Rebellion protesters in Tower Hill, 23 November 2018

 

From 21 November 2018, beginning a campaign known as 'swarming' roadblocks (repeated roadblocks of approximately 7 minutes each), small groups of Extinction Rebellion activists carried out protests by occupying road junctions at Lambeth and Vauxhall Bridges, Elephant and Castle, Tower Bridge and Earl's Court, causing serious disruption to rush-hour traffic and continuing throughout the day. Similar actions continued for the next two days in London, with one group moving to Oxford Street on the afternoon of the discount shopping day Black Friday.

On 23 November, in a first action outside London, an Extinction Rebellion group in York stopped traffic on Coppergate, Clifford Street, Pavement and Ouse Bridge, as well as holding a demo outside West Offices of the City of York Council. An Oxford XR group blocked traffic on Botley Road on the same day.

'Rebellion Day 2'

On "Rebellion Day 2", a week after the first, Extinction Rebellion blocked the roads around Parliament Square, before a mock funeral march to Downing Street and then onto Buckingham Palace. XR co-founder Gail Bradbrook read out a letter to the Queen, and one activist glued herself to the gates of the Palace, before the procession returned to Parliament Square. On 24 November there were actions outside London by XR groups in Manchester, Sheffield, Machynlleth, and Edinburgh.

On 15 December 2018, a professor of psychology was arrested for a "climate change graffiti attack" on the Bristol Department for Environment, Food and Rural Affairs (DEFRA) building, and a "die-in" was held at a local shopping center.

On 21 December 2018, actions were staged at BBC locations across the UK by Extinction Rebellion calling for a change in editorial policy, perceiving a "failure to report" on the "climate emergency." BBC headquarters in London was placed on lockdown.

2019

January council actions

On 25 January 2019, about 40 members of Extinction Rebellion staged a peaceful one-hour occupation of the Scottish Parliament's debating chamber in Holyrood, Edinburgh. Council chambers were also occupied by XR groups in Norwich on 11 February, and Gloucestershire, on 13 February, which included a mock trial of the council's "criminal negligence". A week later neighbouring Somerset County Council declared a climate emergency, citing school strikers and XR as having some input into the decision. In late February, following an XR petition, Reading Borough Council also declared a climate emergency, aiming to cut carbon emissions by 2030, a week after discussions with the XR Reading (XRR) group and a day after the warmest winter day on record in the UK.

February – London Fashion Week

An Extinction Rebellion march during the London Fashion Week in London, 22 February 2019

 

During London Fashion Week in February, Extinction Rebellion organised actions to disrupt events, calling on the British Fashion Council organisers to declare a 'climate emergency' and for the industry to take a leading role in tackling climate change. 'Swarming' roadblocks were held outside several venues; a couple of rebels wore living grass coats. Later in the week, designer and XR co-founder Clare Farrell, was barred from a fashion show by a label in which she had been involved with production.

March

Gerald Vernon-Jackson, leader of the Portsmouth City Council, joining in an Extinction Rebellion protest in Portsmouth, 19 March 2019

 

On 9 March 2019, around 400 protesters staged a "Blood of Our Children" demonstration outside No. 10 Downing Street, in which they poured buckets of fake blood on the road to represent the threatened lives of children. As Portsmouth City Council passed a climate emergency motion, the 49th in the UK, protestors confronted leader Gerald Vernon-Jackson outside Portsmouth Guildhall.

House of Commons naked demonstration

On 1 April 2019, around 12 protesters were arrested after undressing and gluing themselves to the glass in the House of Commons viewing gallery during a debate on Britain's intended departure from the European Union, with two of the protesters wearing grey body paint and elephant masks to draw attention to "the elephant in the room". XR activists attributed inspiration for the direct action to a suffragette protest in Parliament in 1909, when (non-nude) protesters chained themselves to statues.

Mid-April occupations

The boat named after Berta Cáceres, with its slogan "tell the truth", which was the centrepiece of the demonstration in Oxford Circus

 

Starting from Monday 15 April 2019, Extinction Rebellion organised demonstrations in London, focusing their attention on Oxford Circus, Marble Arch, Waterloo Bridge and the area around Parliament Square. Activists fixed a pink boat named after murdered Honduran environmental activist Berta Cáceres in the middle of the busy intersection of Oxford Street and Regent Street (Oxford Circus) and glued themselves to it, and also set up several gazebos, potted plants and trees, a mobile stage and a skate ramp whilst occupying Waterloo Bridge. Five activists, including XR co-founder Simon Bramwell, were arrested for criminal damage when they targeted Shell's headquarters, near Waterloo. After the police imposed a 24-hour Section 14 condition at 18:55 requiring activists to move to Marble Arch the police tried to clear Waterloo Bridge arresting 113 people, without gaining control of the bridge.

On the second day of actions on Waterloo Bridge police began making arrests of the activists at 12.40 pm, but stopped a few hours later, after running out of holding cells. By the end of Tuesday 16 April an estimated 500,000 people had been affected by the disruptions and 290 activists had been arrested in London. In Scotland, more than 1,000 protesters occupied the North Bridge for seven hours in Edinburgh, bringing one of the main routes into the city centre to a standstill. Police said they made 29 arrests.

On the morning of Wednesday 17 April two activists climbed onto the roof of a Docklands Light Railway train at Canary Wharf station whilst another glued himself to the side, spreading disruption to railway services. The following day the three activists were charged with obstructing trains and after pleading not guilty sent to jail for four weeks, with no bail, whilst awaiting their next hearing. In response to the protests, the British Transport Police suspended access to public Wi-Fi at London Underground stations the same day. Towards the end of Wednesday a large force of police marched on the camp at Parliament Square, arresting people and partially removing roadblocks before it was retaken later the same night by protesters who arrived with a samba band and re-established the roadblocks.

At the start of the fourth day of continuous occupations at four locations the arrest figure had risen to 428, the majority for breaching public order laws and obstructing a highway. During the morning of 18 April about 20 XR activists spread traffic disruption wider with a series of swarming (short duration) roadblocks on Vauxhall Bridge.

On the fifth morning, after significant media speculation about a threat to Heathrow Airport, around a dozen teenagers, some aged 13 and 14, approached the access road holding a banner which read “Are we the last generation?” Some of the teenagers wept and hugged each other, as they were surrounded by a far larger squad of police. In the middle of the day police moved in force to surround the pink boat as Emma Thompson read poetry from the deck, eventually removing the people who were either locked-on or glued to it. After seven hours police had moved the boat without clearing Oxford Circus. By late Friday evening police were saying that 682 people had been arrested in London.

Actions elsewhere

"Declaration Day" at the Victorian State Government, 22 March 2019

 

Extinction Rebellion Australia held a 'Declaration Day' on 22 March 2019 in Melbourne, Adelaide, Sydney, and Brisbane. Demonstrators assembled and protested to demand that governments and media declare a state of climate emergency. On the eve of international Rebellion Day, 15 April, an XR group occupied the Parliament's Lower House.

Extinction Rebellion events were planned for the week starting Monday 15 April 2019, in 27 other countries including the United Kingdom, Ireland, Australia, Canada, France, Sweden, Germany, Colombia, New Zealand and in New York City for a national day of action for the United States.

On 15 April, XR activists occupied part of the International Criminal Court in The Hague, forming human chains before being arrested. Similar actions were organised by XR groups in Berlin, Heidelberg, Brussels, Lausanne, Madrid, Denver and Melbourne. In New York City, on Wednesday 17 April, an XR group of 300 gathered outside City Hall to demand that the City Council declare a climate emergency with over 60 arrested after occupying the street and hanging banners from the lamposts. On Friday 19 April XR activists disrupted a railway line in Brisbane, Australia.

Public support

A study conducted during the first two days of the mid-April London occupation found that the rebellion had more support than opposition from the UK public.

Criticism

The movement has been criticised by some for making unrealistic demands. The Energy & Climate Intelligence Unit, which supports its course of strong action and demands, said that the timeframe being urged by XR was "...an ambition that technically, economically and politically has absolutely no chance of being fulfilled." They calculated that to go net zero by 2025, flying would need to be scrapped and 38 million cars (both petrol and diesel) would need to be removed from the roads. In addition, 26 million gas boilers would need to be disconnected in six years.

American philosopher and animal rights advocate Gary L. Francione criticised the movement for refusing to promote veganism as a solution to climate change, and for adopting the "personal/political" dichotomy which he says "every progressive movement for the past 50 years has rejected because common sense tells us that you cannot ignore the role of the individual in creating and perpetuating social problems".

Tollmann's bolide hypothesis

From Wikipedia, the free encyclopedia

Tollmann's bolide hypothesis is a hypothesis presented by Austrian paleontologist Edith Kristan-Tollmann and geologist Alexander Tollmann in 1994. The hypothesis postulates that one or several bolides (asteroids or comets) struck the Earth around 7640 ± 200 years BCE, with a much smaller one approximately 3150 ± 200 BCE. The hypothesis tries to explain early Holocene extinctions and possibly legends of the Universal Deluge.

The claimed evidence for the event includes stratigraphic studies of tektites, dendrochronology, and ice cores (from Camp Century, Greenland) containing hydrochloric acid and sulfuric acid (indicating an energetic ocean strike) as well as nitric acids (caused by extreme heating of air).

Christopher Knight and Robert Lomas in their book, Uriel's Machine, argue that the 7640 BCE evidence is consistent with the dates of formation of a number of extant salt flats and lakes in dry areas of North America and Asia. They argue that these lakes are the result remains of multiple-kilometer-high waves that penetrated deeply into continents as the result of oceanic strikes that they proposed occurred. Research by Quaternary geologists, palynologists and others has been unable to confirm the validity of the hypothesis and proposes more frequently occurring geological processes for some of the data used for the hypothesis. Dating of ice cores and Australasian tektites has shown long time span differences between the proposed impact times and the impact ejecta products.

Scientific evaluation

Quaternary geologists, paleoclimatologists, and planetary geologists specializing in meteorite and comet impacts have rejected Tollmann's bolide hypothesis. They reject this hypothesis because:

1. The evidence offered to support the hypothesis can more readily be explained by more mundane and less dramatic geologic processes
2. Many of the events alleged to be associated with this impact occurred at the wrong time (i.e., many of the events occurred hundreds to thousands of years before or after the hypothesized impacts); and
3. There is a lack of any credible physical evidence for the cataclysmic environmental devastation and characteristic deposits that kilometer-high tsunamis would have created had they actually occurred.

Global sea level curve for the Late Pleistocene and Holocene

 

Evidence used by proponents of the Tollmann's bolide hypothesis to argue for catastrophic Holocene extinctions have alternative explanations by more frequently occurring geological processes. The chemical composition and presence of volcanic ash with the specific acidity spikes in the Greenland ice cores shows evidence that they result from volcanic instead of impact origins. Also, the largest acidity spikes found in Antarctica ice cores have been dated to 17,300 to 17,500 BP, which is significantly older than hypothetical Holocene impacts. The formation of modern salt lakes and salt flats is explained by the concentration of salts and other evaporite minerals by the evaporation of water from stream-fed lakes lacking external outlets, called endorheic lakes, which commonly occur in arid climates on both hemispheres on Earth. The composition of the salts and other evaporite minerals found in these lakes is consistent with their precipitation from dissolved material continually carried into the lakes by rivers and streams and subsequent concentration by evaporation, instead of evaporation of sea water. Whether a lake becomes salty or not depends on whether the lake lacks an outlet and the relative balance between the inflow and outflow of lake waters via evaporation. Ocean water accessing a continental lake as the result of a single catastrophic event, as Tollmann's hypothesis proposes, would contain an inadequate amount of dissolved minerals to produce, when evaporated, the vast quantities of salts and other evaporites found in the salt lakes, flats, and pans cited as evidence of a mega-tsunami by this hypothesis.

Geological criticism

Isostatic rebound

Isostatic rebound in the British Isles

 

Many published papers demonstrate that isostatic depression of the Earth's crust happened in the early Holocene. This process has led to submerging substantial portions of coastal areas adjacent to continental ice sheets and resulted in the accumulations of marine sediments and fossils within them. A well-documented example of flooding caused by isostatic depression is the case of Charlotte, The Vermont Whale, a fossil whale found in the deposits of the former Champlain Sea. Like many similar marine deposits, the sediments, which accumulated within the Champlain Sea lack the physical characteristics; i.e. sedimentary structures, interlayering, and textures, that characterize sediments deposited by a mega-tsunami. These deposits and the associated fossils have been dated to significantly earlier periods than the times the bolide hypothesis proposed. In case of the Champlain Sea, its sediments started to accumulate around 13,000 BP, almost 3,400 years before the oldest of the hypothesized Holocene bolide impacts.

Dating

Lake Bonneville and other ice age pluvial lakes (17,500 years BP), and modern remnants

 

A significant amount of the physical evidence used by Kristan-Tollmann and Tollmann, as supporting their hypothesis, is either too old or too young to have been created by this hypothesized impact. In many cases, it is hundreds to thousands, and in one case hundreds of thousands, of years too old to be credible evidence of a Holocene impact. The research that dates the tektites, which Tollmann's bolide hypothesis regards as indicative for the timing of the impact, is outdated. Later research, has dated the Australasian tektites to the Middle Pleistocene; about 790,000 years BP. In addition, the formation of salt lakes and salt flats is neither synchronous nor consistent with the hypothesized impacts having occurred about either 9,640 BP or 5,150 BP. For example, in case of Lake Bonneville, Lake Lahontan, Mono Lake, and other Pleistocene pluvial lakes in the western United States, the transition to salt lakes and salt flats occurred at different times between 12,000 and 16,000 BP. Thus, the change from freshwater to salty water and eventually salt flats started over 2,400 to 6,400 years before the oldest of the impacts hypothesized by the Tollmann bolide hypothesis occurred. As a result, it is impossible that the formation of these salt lakes could have been associated with the impact hypothesized by Kristan-Tollmann and Tollmann.

Megatsunami

The megatsunami-producing Storegga Slide in Norway has been dated to approximately 6225–6170 BCE

 

There exists a lack of credible physical evidence of either multiple-kilometer-high tsunami waves penetrating deeply into continents, and the ecological devastation these would have caused. Thousands of paleoenvironmental records constructed from the study of lakes, bogs, mires, and river valleys all over the world by palynologists have not shown the existence of such a megatsunami. In the case of North America, research published by various authors, provide detailed records of paleoenvironmental changes that have occurred throughout the last 10,000 to 15,000 years as reconstructed from pollen and other paleoenvironmental data from over a thousand sites throughout North America. These records do not recognize indications of either a resulting catastrophic environmental devastation or layers of tsunami deposits, which the mega-tsunamis postulated by Tollmann's bolide hypothesis would have created. Paleovegetation maps illustrate a distinct lack of the dramatic changes in North American paleovegetation during the Holocene, which would be expected from the cataclysmic ecological and physical destruction that a continental-wide mega-tsunamis would have certainly have caused. 

Grimm et al. in a paper published in Science in 1993, documented a 50,000-year-long record of environmental change by the analysis of pollen from an 18.5 m (61 ft) core from Lake Tulane in Highland county, Florida. Because of the low-lying nature of the peninsula, in which this part of Florida lies, this lake and the area around it would have been flooded and covered by tsunami deposits along with many of the other lakes and bogs described in their, and other publications. The forests and associated ecosystems of these areas would have been flooded and completely destroyed by the mega-tsunamis proposed by Kristan-Tollmann and Tollmann. Despite its location, both the core and the pollen record recovered from Lake Tulane lacks any indication of an abrupt, catastrophic environmental disruption, which the mega-tsunamis proposed by Tollmann's bolide hypothesis would have caused. Sedimentary cores obtained from Florida and other locations also lack sedimentary layers that have the characteristics of sediments deposited by either tsunamis or mega-tsunamis.

The cataclysmic scale of physical and ecological destruction that a megatsunami, like the one proposed by Kristan-Tollmann and Tollmann, would have caused, has not been recognized within the majority of long-term environmental records. Over a thousand cores from North America for which Holocene paleoclimatic and paleoenvironmental records have been reconstructed do not show evidence for the drastic environmental changes resulting from a large Holocene impact. There is a similar lack of evidence for mega-tsunami related, Holocene, catastrophic environmental disruptions and deposits reported from environmental records reconstructed from thousands of locations from all over the world. Other megatsunamis have been shown in coastal sediments analyzed by geologists and palynologists and point to tsunamis locally caused by either earthquakes, volcanic eruptions, or submarine slides. These non-impact related tsunamis show abundant records of their environmental effects through the study of pollen from cores and exposures.

Members of the Holocene Impact Working Group have published papers advocating the occurrence of mega-tsunamis created by extraterrestrial impacts at various times during the Holocene and Late Pleistocene. However, none of these proposed impacts match either the cataclysmic scale or timing proposed by Kristan-Tollmann and Tollmann for their hypothesized bolide.

Megatsunami

From Wikipedia, the free encyclopedia

Diagram of the 1958 Lituya Bay megatsunami, which proved the existence of megatsunamis.

 

A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water. 

Megatsunamis have quite different features from other, more usual types of tsunamis. Most tsunamis are caused by underwater tectonic activity (movement of the earth's plates) and therefore occur along plate boundaries and as a result of earthquake and rise or fall in the sea floor, causing water to be displaced. Ordinary tsunamis have shallow waves out at sea, and the water piles up to a wave height of up to about 10 metres (33 feet) as the sea floor becomes shallow near land. By contrast, megatsunamis occur when a very large amount of material suddenly falls into water or anywhere near water (such as via a meteor impact), or are caused by volcanic activity. They can have extremely high initial wave heights of hundreds and possibly thousands of metres, far beyond any ordinary tsunami, as the water is "splashed" upwards and outwards by the impact or displacement. As a result, two heights are sometimes quoted for megatsunamis – the height of the wave itself (in water), and the height to which it surges when it reaches land, which depending upon the locale, can be several times larger. 

Modern megatsunamis include the one associated with the 1883 eruption of Krakatoa (volcanic eruption), the 1958 Lituya Bay megatsunami (landslide into a bay), and the wave resulting from the Vajont Dam landslide (caused by human activity destabilizing sides of valley). Prehistoric examples include the Storegga Slide (landslide), and the Chicxulub, Chesapeake Bay and Eltanin meteor impacts.

Overview

A megatsunami is a tsunami—a large wave due to displacement of a body of water—with an initial wave amplitude (height) measured in several tens, hundreds, or possibly thousands of metres. 

Normal tsunamis generated at sea result from movement of the sea floor. They have a small wave height offshore, are very long (often hundreds of kilometres), and generally pass unnoticed at sea, forming only a slight swell usually of the order of 30 cm (12 in) above the normal sea surface. When they reach land, the wave height increases dramatically as the base of the wave pushes the water column above it upwards. 

By contrast, megatsunamis are caused by giant landslides and other impact events. This could also refer to a meteorite hitting an ocean. Underwater earthquakes or volcanic eruptions do not normally generate such large tsunamis, but landslides next to bodies of water resulting from earthquakes can, since they cause a large amount of displacement. If the landslide or impact occurs in a limited body of water, as happened at the Vajont Dam (1963) and Lituya Bay (1958) then the water may be unable to disperse and one or more exceedingly large waves may result. 

A way to visualize the difference, is that an ordinary tsunami is caused by sea floor changes, somewhat like pushing up on the floor of a large tub of water to the point it overflows, and causing a surge of water to "run off" at the sides. In this analogy, a megatsunami would be more similar to dropping a large rock from a considerable height into the tub, at one end, causing water to splash up and out, and overflow at the other end. 

Two heights are sometimes quoted for megatsunamis – the height of the wave itself (in water), and the height to which it surges when it reaches land, which depending upon the locale, can be several times larger.

Recognition of the concept of megatsunami

Geologists searching for oil in Alaska in 1953 observed that in Lituya Bay, mature tree growth did not extend to the shoreline as it did in many other bays in the region. Rather, there was a band of younger trees closer to the shore. Forestry workers, glaciologists, and geographers call the boundary between these bands a trim line. Trees just above the trim line showed severe scarring on their seaward side, whilst those from below the trim line did not. The scientists hypothesized that there had been an unusually large wave or waves in the deep inlet. Because this is a recently deglaciated fjord with steep slopes and crossed by a major fault, one possibility was a landslide-generated tsunami.

On 9 July 1958, a 7.8 M_w  strike-slip earthquake in southeast Alaska caused 90 million tonnes of rock and ice to drop into the deep water at the head of Lituya Bay. The block fell almost vertically and hit the water with sufficient force to create a wave that surged up the opposite side of the head of the bay to a height of 1720 feet (524 m), and was still many tens of metres high further down the bay, when it carried eyewitnesses Howard Ulrich and his son Howard Jr. over the trees in their fishing boat. They were washed back into the bay and both survived.

Analysis of mechanism

The mechanism giving rise to megatsunamis was analysed for the Lituya Bay event in a study presented at the Tsunami Society in 1999; this model was considerably developed and modified by a second study in 2010. 

Although the earthquake which caused the megatsunami was considered very energetic, and involving strong ground movements, several possible mechanisms were not likely or able to have caused the resulting megatsunami. Neither water drainage from a lake, nor landslide, nor the force of the earthquake itself led to the megatsunami, although all of these may have contributed.

Instead, the megatsunami was caused by a massive and sudden impulsive impact when about 40 million cubic yards of rock several hundred metres above the bay was fractured from the side of the bay, by the earthquake, and fell "practically as a monolithic unit" down the almost vertical slope and into the bay. The rockfall also caused air to be "dragged along" due to viscosity effects, which added to the volume of displacement, and further impacted the sediment on the floor of the bay, creating a large crater. The study concluded that:

The giant wave runup of 1,720 feet (524 m.) at the head of the Bay and the subsequent huge wave along the main body of Lituya Bay which occurred on July 9, 1958, were caused primarily by an enormous subaerial rockfall into Gilbert Inlet at the head of Lituya Bay, triggered by dynamic earthquake ground motions along the Fairweather Fault.

The large mass of rock, acted as a monolith (thus resembling high-angle asteroid impact), struck with great force the sediments at bottom of Gilbert Inlet at the head of the bay. The impact created a large crater and displaced and folded recent and Tertiary deposits and sedimentary layers to an unknown depth. The displaced water and the displacement and folding of the sediments broke and uplifted 1,300 feet of ice along the entire front of the Lituya Glacier at the north end of Gilbert Inlet. Also, the impact and the sediment displacement by the rockfall resulted in an air bubble and in water splashing action that reached the 1,720 foot (524 m.) elevation on the other side of the head of Gilbert Inlet. The same rockfall impact, in combination with the strong ground movements, the net vertical crustal uplift of about 3.5 feet, and an overall tilting seaward of the entire crustal block on which Lituya Bay was situated, generated the giant solitary gravity wave which swept the main body of the bay.

This was the most likely scenario of the event – the "PC model" that was adopted for subsequent mathematical modeling studies with source dimensions and parameters provided as input. Subsequent mathematical modeling at the Los Alamos National Laboratory (Mader, 1999, Mader & Gittings, 2002) supported the proposed mechanism – as there was indeed sufficient volume of water and an adequately deep layer of sediments in the Lituya Bay inlet to account for the giant wave runup and the subsequent inundation. The modeling reproduced the documented physical observations of runup.

A 2010 model examined the amount of infill on the floor of the bay, which was many times larger than that of the rockfall alone, and also the energy and height of the waves, and the accounts given by eyewitnesses, concluded that there had been a "dual slide" involving a rockfall, which also triggered a release of 5 to 10 times its volume of sediment trapped by the adjacent Lituya Glacier, as an almost immediate and many times larger second slide, a ratio comparable with other events where this "dual slide" effect is known to have happened.

List of megatsunamis

Prehistoric

• The asteroid linked to the extinction of dinosaurs, which created the Chicxulub crater in Yucatán approximately 66 million years ago, would have caused an over 100 metres (330 ft) tall megatsunami. The height of the tsunami was limited due to relatively shallow sea in the area of the impact; in deep sea it would be 4.6 kilometres (2.9 mi) tall.. A more recent simulation of the global effects of the megatsunami showed initial wave height of 1.5 kilometres (0.93 mi), with later waves up to 100 metres (330 ft) height in the Gulf of Mexico, and up to 14 metres (46 ft) in the North Atlantic and South Pacific.
• A series of megatsunamis were generated by the bolide impact that created the Chesapeake Bay impact crater, about 35.5 million years ago.
• During the Messinian the coasts of northern Chile were likely struck by various megatsunamis.
• A megatsunami affected the coast of south–central Chile in the Pliocene as evidenced by the sedimentary record of Ranquil Formation.
• The Eltanin impact in the southeast Pacific Ocean 2.5 million years ago caused a megatsunami that was over 200 m (660 ft) high in southern Chile and the Antarctic Peninsula; the wave swept across much of the Pacific Ocean.
• The northern half of the East Molokai Volcano suffered a catastrophic collapse and likely megatsunami about 1.5 million years ago and now lies as a debris field scattered northward across the ocean bottom, while what remains on the island are the highest sea cliffs in the world.
• The existence of large scattered boulders in only one of the four marine terraces of Herradura Bay south of the Chilean city of Coquimbo has been interpreted by Roland Paskoff as the result of a mega-tsunami that occurred in the Middle Pleistocene.
• A massive collapse of the western edge of the Lake Tahoe basin, which formed McKinney Bay around 50,000 years ago, is thought to have generated a tsunami/seiche wave with a height approaching 330 ft (100 m).
• In the North Sea, the Storegga Slide caused a megatsunami approximately 8,200 years ago. It is estimated to have completely flooded the remainder of Doggerland.
• Approximately 8,000 years ago, a massive volcanic landslide off Mt. Etna, Sicily caused a megatsunami which devastated the eastern Mediterranean coastline on three continents. Wave heights on the coast of Calabria are estimated to have reached a maximum of 40m.

Historic

c. 2000 BC: Réunion

• A landslide on Réunion island, to the east of Madagascar, may have caused a megatsunami.

c. 1600 BC: Santorini

• The Thera volcano erupted, the force of the eruption causing megatsunamis which affected the whole Aegean Sea and the eastern Mediterranean Sea.

Modern

1792: Mount Unzen, Japan

In 1792, Mount Unzen in Japan erupted, causing part of the volcano to collapse into the sea. The landslide caused a megatsunami that reached 100 metres (330 ft) high and killed 15,000 people in the local fishing villages.

1883: Krakatoa

The eruption of Krakatoa created pyroclastic flows which generated megatsunamis when they hit the waters of the Sunda Strait on 27 August 1883. The waves reached heights of up to 24 metres (79 feet) along the south coast of Sumatra and up to 42 metres (138 feet) along the west coast of Java.

1958: Lituya Bay, Alaska, US

Damage from the 1958 Lituya Bay megatsunami can be seen in this oblique aerial photograph of Lituya Bay, Alaska as the lighter areas at the shore where trees have been stripped away. The red arrow shows the location of the landslide, and the yellow arrow shows the location of the high point of the wave sweeping over the headland.

 

On July 9, 1958, a giant landslide at the head of Lituya Bay in Alaska, caused by an earthquake, generated a wave that washed out trees to a maximum altitude of 520 metres (1,710 ft) at the entrance of Gilbert Inlet. The wave surged over the headland, stripping trees and soil down to bedrock, and surged along the fjord which forms Lituya Bay, destroying a fishing boat anchored there and killing two people.

1963: Vajont Dam, Italy

On October 9, 1963, a landslide above Vajont Dam in Italy produced a 250 m (820 ft) surge that overtopped the dam and destroyed the villages of Longarone, Pirago, Rivalta, Villanova and Faè, killing nearly 2,000 people.

1980: Spirit Lake, Washington, US

On May 18, 1980, the upper 460 metres (1,509 feet) of Mount St. Helens collapsed, creating a massive landslide. This released the pressure on the magma trapped beneath the summit bulge which exploded as a lateral blast, which then released the pressure on the magma chamber and resulted in a plinian eruption. 

One lobe of the avalanche surged onto Spirit Lake, causing a megatsunami which pushed the lake waters in a series of surges, which reached a maximum height of 260 metres (853 feet) above the pre-eruption water level (~975 m asl/3,199 ft). Above the upper limit of the tsunami, trees lie where they were knocked down by the pyroclastic surge; below the limit, the fallen trees and the surge deposits were removed by the megatsunami and deposited in Spirit Lake.

Potential future megatsunamis

In a BBC television documentary broadcast in 2000, experts said that they thought that a massive landslide on a volcanic ocean island is the most likely future cause of a megatsunami. The size and power of a wave generated by such means could produce devastating effects, travelling across oceans and inundating up to 25 kilometres (16 mi) inland from the coast. This research, however, was later found to be flawed. The documentary was produced before the experts' scientific paper was published and before responses were given by other geologists. There have been megatsunamis in the past, and future megatsunamis are possible but current geological consensus is that these are only local. A megatsunami in the Canary Islands would diminish to a normal tsunami by the time it reached the continents. Also, the current consensus for La Palma is that the region conjectured to collapse is too small and too geologically stable to do so in the next 10,000 years, although there is evidence for past megatsunamis local to the Canary Isles thousands of years ago. Similar remarks apply to the suggestion of a megatsunami in Hawaii.

British Columbia

Some geologists consider an unstable rock face at Mount Breakenridge, above the north end of the giant fresh-water fjord of Harrison Lake in the Fraser Valley of southwestern British Columbia, Canada, to be unstable enough to collapse into the lake, generating a megatsunami that might destroy the town of Harrison Hot Springs (located at its south end).

Canary Islands

Geologists Dr. Simon Day and Dr. Steven Neal Ward consider that a megatsunami could be generated during an eruption of Cumbre Vieja on the volcanic ocean island of La Palma, in the Canary Islands, Spain.

In 1949, this volcano erupted at its Duraznero, Hoyo Negro and Llano del Banco vents, and there was an earthquake with an epicentre near the village of Jedey. The next day Juan Bonelli Rubio, a local geologist, visited the summit area and found that a fissure about 2.5 kilometres (1.6 mi) long had opened on the east side of the summit. As a result, the west half of the volcano (which is the volcanically active arm of a triple-armed rift) had slipped about 2 metres (6.6 ft) downwards and 1 metre (3.3 ft) westwards towards the Atlantic Ocean.

Cumbre Vieja is currently dormant, but will almost certainly erupt again. Day and Ward hypothesize that if such an eruption causes the western flank to fail, a mega-tsunami could be generated. 

La Palma is currently the most volcanically active island in the Canary Islands Archipelago. It is likely that several eruptions would be required before failure would occur on Cumbre Vieja. However, the western half of the volcano has an approximate volume of 500 cubic kilometres (120 cu mi) and an estimated mass of 1.5 trillion metric tons (1.7×10¹² short tons). If it were to catastrophically slide into the ocean, it could generate a wave with an initial height of about 1,000 metres (3,300 ft) at the island, and a likely height of around 50 metres (164 ft) at the Caribbean and the Eastern North American seaboard when it runs ashore eight or more hours later. Tens of millions of lives could be lost in the cities and/or towns of St. John's, Halifax, Boston, New York, Baltimore, Washington, D.C., Miami, Havana and the rest of the Eastern Coasts of the United States and Canada, as well as many other cities on the Atlantic coast in Europe, South America and Africa. The likelihood of this happening is a matter of vigorous debate.

The last eruption on the Cumbre Vieja occurred in 1971 at the Teneguia vent at the southern end of the sub-aerial section without any movement. The section affected by the 1949 eruption is currently stationary and does not appear to have moved since the initial rupture.

Geologists and volcanologists are in general agreement that the initial study was flawed. The current geology does not suggest that a collapse is imminent. Indeed, it seems to be geologically impossible right now, the region conjectured as prone to collapse is too small and too stable to collapse within the next 10,000 years. They also concluded that a landslide is likely to happen as a series of smaller collapses rather than a single landslide from closer study of deposits left in the ocean by previous landslides. A megatsunami does seem possible locally in the distant future as there is geological evidence from past deposits suggesting that a megatsunami occurred with marine material deposited 41 to 188 meters above sea level between 32,000 and 1.75 million years ago. This seems to have been local to Gran Canaria. 

Day and Ward have admitted that their original analysis of the danger was based on several worst case assumptions. A 2008 paper looked into this very worst-case scenario, the most massive slide that could happen (though unlikely and probably impossible right now with the present day geology). Although it would be a megatsunami locally in the Canary Isles, it would diminish in height to a regular tsunami when it reaches the continents as the waves interfere and spread across the oceans.

Hawaii

Sharp cliffs and associated ocean debris at the Kohala Volcano, Lanai and Molokai indicate that landslides from the flank of the Kilauea and Mauna Loa volcanoes in Hawaii may have triggered past megatsunamis, most recently at 120,000 BP. A tsunami event is also possible, with the tsunami potentially reaching up to about 1 kilometre (3,300 ft) in height According to the documentary National Geographic's Ultimate Disaster: Tsunami, if a big landslide occurred at Mauna Loa or the Hilina Slump, a 30-metre (98 ft) tsunami would take only thirty minutes to reach Honolulu. There, hundreds of thousands of people could be killed as the tsunami could level Honolulu and travel 25 kilometres (16 mi) inland. Also, the West Coast of America and the entire Pacific Rim could potentially be affected. 

However, other research suggests that such a single large landslide is not likely. Instead, it would collapse as a series of smaller landslides.

In 2018, shortly after the beginning of the 2018 lower Puna eruption, a National Geographic article responded to such claims with "Will a monstrous landslide off the side of Kilauea trigger a monster tsunami bound for California? Short answer: No."

In the same article, geologist Mika McKinnon stated

there are submarine landslides, and submarine landslides do trigger tsunamis, but these are really small, localized tsunamis. They don't produce tsunamis that move across the ocean. In all likelihood, it wouldn't even impact the other Hawaiian islands.

Another volcanologist, Janine Krippner, added:

People are worried about the catastrophic crashing of the volcano into the ocean. There's no evidence that this will happen. It is slowly—really slowly—moving toward the ocean, but it's been happening for a very long time.

Despite this, evidence suggests that catastrophic collapses do occur on Hawaiian volcanoes and generate massive, yet local tsunamis. 

Cape Verde Islands

Steep cliffs on the Cape Verde Islands have been caused by catastrophic debris avalanches. These have been common on the submerged flanks of ocean island volcanoes and more can be expected in the future.