Super volcano

Slightly digress for a moment - here in Australia the majority of the country doesn't really experience winter like the Northern Hemisphere. I was surprised when it was pointed out by many far northern hemisphere ex-pats that they freeze here in the winter!!!!!!
This completely blew me away as this was in the Riverina area of NSW I learned this - completely caught out on this I said "How can you be cold?? {I had a Norseman heater that did an awesome job heating - or so I thought} You lived in a land that bloody freezes and doesn't see the sun?" "These winters hardly get below zero!" Then it was explained that here in Australia we mostly only heat one room - over in the top part of Russia, Sweden and Finland and other similar countries - they heat the whole house/apartment. (FYI - Think I mentioned the next house we get will be our last move - which is further North - we plan to include a Maxi-Heat heater/stove, even I have noticed the change in winters since we moved to Nth Qld - perhaps I have acclimatised.

Now back on track to original post - I agree Y/Stone would make life difficult. But I see no mention of those few equally nasty volcanoes a mere stones throw from Down Under. We have 3 on our doorstep and we border the 'Ring-Of-Fire', there has been an increase of activity in Australia in recent months and some rather intense E~Quakes within this region in a close proximity to us in OZ. I'm far from any sort of an expert but just the pyroclastic flows would be enough for Australia to have a 'very bad day'.

1).Name: Lake Taupo. Country: New Zealand. Location: North Island
VEI Index: 8. Diameter: ~616 km³

Lake Taupo is a lake situated in the North Island of New Zealand. With a surface area of 616 square kilometres (238 sq mi), it is the largest lake by surface area in New Zealand, and the largest freshwater lake by surface area in Oceania. Lake Taupo has a perimeter of approximately 193 kilometres, a deepest point of 186 metres. It is drained by the Waikato River (New Zealand's longest river), while its main tributaries are the Waitahanui River, the Tongariro River, and the Tauranga-Taupo River. It is a noted trout fishery with stocks of introduced brown trout and rainbow trout. The lake lies in a caldera created following a huge volcanic eruption (see supervolcano) approximately 26,500 years ago. According to geological records, the volcano has erupted 28 times in the last 27,000 years. It has predominantly erupted rhyolitic lava although Mount Tauhara formed from dacitic lava.

The largest eruption, known as the Oruanui eruption, ejected an estimated 1,170 cubic kilometres of material and caused several hundred square kilometres of surrounding land to collapse and form the caldera. The caldera later filled with water, eventually overflowing to cause a huge outwash flood. Several later eruptions occurred over the millennia before the most recent major eruption, which occurred in 180 CE. Known as the Hatepe eruption, it is believed to have ejected 100 cubic kilometres of material, of which 30 cubic kilometres was ejected in the space of a few minutes. This was one of the most violent eruptions in the last 5,000 years (alongside the Tianchi eruption of Baekdu at around 1000 and the 1815 eruption of Tambora), with a Volcanic Explosivity Index rating of 7. The eruption column was twice as high as the eruption column from Mount St. Helens in 1980, and the ash turned the sky red over Rome and China. The eruption devastated much of the North Island and further expanded the lake. The area was uninhabited by humans at the time of the eruption, since New Zealand was not settled by the Maori until several centuries later at the earliest. Taupo's last known eruption occurred around 210 CE, with lava dome extrusion forming the Horomatangi Reefs, but that eruption was much smaller than the 11z0 CE eruption. The 180 eruption was one of the largest in recorded history. The skies and sunsets formed from this eruption were noted by Roman and Chinese observers. Any possible climatic effects of the eruption would have been concentrated on the southern hemisphere due to the southerly position of Lake Taupo. Underwater hydrothermal activity continues near the Horomatangi vent, and the volcano is currently considered to be dormant rather than extinct.


2).Name: Lake Toba. Country: Indonesia. Location: Northern Sumatra
VEI Index: 8. Diameter: ~2,800 km³

Lake Toba (Indonesian: Danau Toba) is a lake and supervolcano, 100 kilometres long and 30 kilometres wide, and 505 metres (1,666 ft) at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2°53'N 98°31'E / -2.88°N. It is the largest volcanic lake in the world. In addition, it is the site of a supervolcanic eruption that occurred about 74,000 years ago,[2] a massive climate-changing event. The eruption is believed to have had a VEI intensity of 8. This eruption is believed to have been the largest anywhere on Earth in the last 25 million years. According to the Toba catastrophe theory to which some anthropologists and archeologists subscribe, it had global consequences, killing most humans then alive and creating a population bottleneck in Central Eastern Africa and India that affected the genetic inheritance of all humans today.

The Toba eruption (the Toba event) occurred at what is now Lake Toba about 67,500 to 75,500 years ago. The Toba eruption was the latest of a series of at least three caldera-forming eruptions which have occurred at the volcano, with earlier calderas having formed around 700,000 and 840,000 years ago. The last eruption had an estimated Volcanic Explosivity Index of 8 (described as "mega-colossal"), making it possibly the largest explosive volcanic eruption within the last twenty-five million years.

Bill Rose and Craig Chesner of Michigan Technological University have deduced that the total amount of erupted material was about 2,800 km3 (670 cu mi) — around 2,000 km3 (480 cu mi) of ignimbrite that flowed over the ground, and around 800 km3 (190 cu mi) that fell as ash, with the wind blowing most of it to the west. The pyroclastic flows of the eruption destroyed an area of 20,000 square kilometres (7,722 sq mi), with ash deposits as thick as 600 metres (1,969 ft) by the main vent.

To give an idea of its magnitude, consider that although the eruption took place in Indonesia, it deposited an ash layer approximately 15 centimetres thick over the entire Indian subcontinent; at one site in central India, the Toba ash layer today is up to 6 metres thick[9] and parts of Malaysia were covered with 9 m of ashfall.[10] In addition it has been calculated that 1010 metric tons of sulphuric acid[citation needed]was ejected into the atmosphere by the event, causing acid rain fallout.

The Toba caldera is the only supervolcano in existence that can be described as Yellowstone's "bigger" sister. With 2,800 km3 of ejecta, it was an even greater eruption than the supereruption (2,500 km3) of 2.1 million years ago that created the Island Park Caldera in Idaho, USA. The eruption was also about three times the size of the latest Yellowstone eruption of Lava Creek 630,000 years ago. For further comparison, the largest volcanic eruption in historic times, in 1815 at Mount Tambora (Indonesia), ejected the equivalent of around 100 km3 (24 cu mi) of dense rock and made 1816 the "Year Without a Summer" in the whole northern hemisphere, whilst the 1980 eruption of Mount St. Helens in Washington State ejected around 1.2 km3 (0.29 cu mi) of material.

The subsequent collapse formed a caldera that, after filling with water, created Lake Toba. The island in the center of the lake is formed by a resurgent dome.
Landsat photo of Sumatra surrounding Lake Toba. Though the year may never be precisely determined, the season can: only the summer monsoon could have deposited Toba ashfall in the South China Sea, implying that the eruption took place sometime during the northern summer.[12] The eruption lasted perhaps two weeks, but the ensuing "volcanic winter" resulted in a decrease in average global temperatures by 3 to 3.5 degrees Celsius for several years. Greenland ice cores record a pulse of starkly reduced levels of organic carbon sequestration. Very few plants or animals in southeast Asia would have survived, and it is possible that the eruption caused a planet-wide die-off. There is some evidence, based on mitochondrial DNA, that the human race may have passed through a genetic bottleneck around this time, reducing genetic diversity below what would be expected from the age of the species. According to the Toba catastrophe theory proposed by Stanley H. Ambrose of the University of Illinois at Urbana-Champaign in 1998, human populations may have been reduced to only a few tens of thousands of individuals by the Toba eruption.

Smaller eruptions have occurred at Toba since. The small cone of Pusukbukit has formed on the southwestern margin of the caldera and lava domes. The most recent eruption may have been at Tandukbenua on the northwestern caldera edge, since the present lack of vegetation could be due to an eruption within the last few hundred years. Some parts of the caldera have experienced uplift due to partial refilling of the magma chamber, for example pushing Samosir Island and the Uluan Peninsula above the surface of the lake. The lake sediments on Samosir Island show that it has been uplifted by at least 450 metres[7] since the cataclysmic eruption. Such uplifts are common in very large calderas, apparently due to the upward pressure of unerupted magma. Toba is probably the largest resurgent caldera on Earth. Large earthquakes have occurred in the vicinity of the volcano more recently, notably in 1987 along the southern shore of the lake at a depth of 11 km.[15] Other earthquakes have occurred in the area in 1892, 1916, and 1920-1922.

Lake Toba lies near the Great Sumatran fault which runs along the centre of Sumatra in the Sumatra Fracture Zone. The volcanoes of Sumatra and Java are part of the Sunda Arc, a result of the northeasterly movement of the Indo-Australian Plate which is sliding under the eastward-moving Eurasian Plate. The subduction zone in this area is very active: the seabed near the west coast of Sumatra has had several major earthquakes since 1995, including the 9.3 2004 Indian Ocean Earthquake and the 8.7 2005 Sumatra earthquake, the epicenters of which were around 300 km from Toba.

On 12 September 2007, a magnitude 8.5 Earthquake shook the ground in Sumatra and was felt in the Indonesian capital, Jakarta. The epicenter for this earthquake was not as close as the previous two earthquakes, but it was in the same vicinity. Most of the people who live around Lake Toba are ethnically Bataks. Traditional Batak houses are noted for their distinctive roofs (which curve upwards at each end, as a boat's hull does) and their colorful decor.

3).Name: Whakamaru. Country: New Zealand. Location: North Island
VEI Index: 8 Diameter: 1,200-2,000 km³

Whakamaru is a town in the central region of the North Island of New Zealand. The Maori words 'whaka' and 'maru' literally mean to give shelter to, or safeguard. The town was originally established as accommodation for the Whakamaru Hydro Power Station in New Zealand. As well as being a significant contributor of electricity, the Whakamaru complex is the main switching station for the upper Waikato hydropower stations and manages the transmission system for Auckland. Transpower are in the process of applying for consent to build a new transmission line between Whakamaru and Auckland. During the summer months Lake Whakamaru is used extensively for water skiing. The Whakamaru Water Ski Club is very busy during the Christmas holidays, although water skiing courses are normally available all year round.

4).Name: Mount Tambora. Country: Indonesia. Location: Sumbawa Island
VEI Index: 7. Diameter: 160 km³

Mount Tambora (or Tomboro) is an active stratovolcano, also known as a composite volcano, on the Sumbawa islands, Indonesia. Sumbawa is flanked both to the north and south by oceanic crust, and Tambora was formed by the active subduction zones beneath it. This raised Mount Tambora as high as 4,300 m (14,000 ft), making it one of the tallest peaks in the Indonesian archipelago, and drained off a large magma chamber inside the mountain. It took decades to refill the magma chamber, its volcanic activity reaching its peak in April 1815. Tambora erupted in 1815 with a rating of seven on the Volcanic Explosivity Index, making it the largest eruption since the Lake Taupo eruption in about 180 CE. The 1815 eruption of Tambora was the largest volcanic eruption in recorded history. The explosion was heard on Sumatra island (more than 2,000 km (1,200 mi) away). Heavy volcanic ash falls were observed as far away as Borneo, Sulawesi, Java and Maluku islands. Most deaths from the eruption were from starvation and disease, as the eruptive fallout ruined agricultural productivity in the local region. The death toll was at least 71,000 people (perhaps the most deadly eruption in history), of whom 11,000–12,000 were killed directly by the eruption; the often-cited figure of 92,000 people killed is believed to be an overestimate. The eruption created global climate anomalies; 1816 became known as the "Year Without a Summer" because of the effect on North American and European weather. Agricultural crops failed and livestock died in much of the Northern Hemisphere, resulting in the worst famine of the 19th century. During an excavation in 2004, a team of archaeologists discovered cultural remains buried by the 1815 eruption.[6] They were kept intact beneath the 3 m (9.8 ft) deep pyroclastic deposits. At the site, dubbed the Pompeii of the East, the artifacts were preserved in the positions they had occupied in 1815.

5). Name: Reporoa Caldera. Country: New Zealand. Location: Taupo Volcanic Zone
VEI Index: 7. Diameter: ~100 km³

The Reporoa caldera is a 10 km by 15 km caldera in New Zealand's Taupo Volcanic Zone. It formed some 230,000 years ago, in a large eruption that deposited the approximately 100 km3 Kaingaroa Ignimbrites. It contains three rhyolitic lava domes (Deer Hill, Kairuru and Pukekahu) and the active Reporoa geothermal field. The Waiotapu geothermal area lies just north of the caldera rim, while the Broadlands thermal area lies to the south. The Waikato River runs through the southern half of the caldera. In April 2005, a large hydrothermal explosion occurred in a cow paddock within the caldera, creating a 50-metre crater. A similar explosion took place in the area in 1948, and smaller explosions have occurred in the intervening years.

And for comparison with our top 3 that I listed, everybody's favourite;

**) Name: Yellowstone Caldera. Country: United States of America. Location: State of Wyoming.
VEI Index: 8. Diameter: 1,000 km³

The Yellowstone Caldera is the volcanic caldera in Yellowstone National Park in the United States. The caldera is located in the northwest corner of Wyoming, in which the vast majority of the park is contained. The major features of the caldera measure about 55 kilometers (34 mi) by 72 kilometers (45 mi) as determined by geological field work conducted by Bob Christiansen of the United States Geological Survey in the 1960s and 1970s. After a BBC television science program coined the term supervolcano in 2000, it has often been referred to as the Yellowstone Supervolcano. Yellowstone, like Hawaii, is believed to lie on top of an area called a hotspot where light, hot, molten mantle rock rises towards the surface. While the Yellowstone hotspot is now under the Yellowstone Plateau, it previously helped create the eastern Snake River Plain (to the west of Yellowstone) through a series of huge volcanic eruptions. Although the hotspot's apparent motion is to the east-northeast, the North American Plate is really moving west-southwest over the stationary hotspot deep underneath.

Over the past 17 million years or so, this hotspot has generated a succession of violent eruptions and less violent floods of basaltic lava. Together these eruptions have helped create the eastern part of the Snake River Plain from a once-mountainous region. At least a dozen or so of these eruptions were so massive that they are classified as supereruptions. Volcanic eruptions sometimes empty their stores of magma so swiftly that they cause the overlying land to collapse into the emptied magma chamber, forming a geographic depression called a caldera. Calderas formed from explosive supereruptions can be as wide and deep as mid- to large-sized lakes and can be responsible for destroying broad swaths of mountain ranges.

The oldest identified caldera remnant straddles the border near McDermitt, Nevada-Oregon. Progressively younger caldera remnants, most grouped in several overlapping volcanic fields, extend from the Nevada-Oregon border through the eastern Snake River Plain and terminate in the Yellowstone Plateau. One such caldera, the Bruneau-Jarbidge caldera in southern Idaho, was formed between 10 and 12 million years ago, and the event dropped ash to the depth of a foot 1,000 miles (1,600 km) away in northeastern Nebraska and killed a large herd of rhinoceroses, camels, and other animals at Ashfall Fossil Beds State Historical Park. Within the past 17 million years, 142 or more caldera-forming eruptions have occurred from the Yellowstone hotspot . The loosely defined term 'supervolcano' has been used to describe volcanic fields that produce exceptionally large volcanic eruptions. Thus defined, the Yellowstone Supervolcano is the volcanic field which produced the latest three supereruptions from the Yellowstone hotspot. The three super eruptions occurred 2.1 million, 1.3 million, and 640,000 years ago; forming the Island Park Caldera, the Henry's Fork Caldera, and Yellowstone calderas, respectively. The Island Park Caldera supereruption (2.1 million years ago), which produced the Huckleberry Ridge Tuff, was the largest and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption. The next biggest supereruption formed the Yellowstone Caldera (630,000 years ago) and produced the Lava Creek Tuff. The Henry's Fork Caldera (1.2 million years ago) produced the smaller Mesa Falls Tuff but is the only caldera from the SRP-Y hotspot that is plainly visible today.

Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption. The most recent lava flow occurred about 70,000 years ago, while the largest violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well; an explosion 13,800 years ago left a 5 kilometer diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera). Currently, volcanic activity is exhibited via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, plus recorded ground swelling indicating ongoing inflation of the underlying magma chamber.

The volcanic eruptions, as well as the continuing geothermal activity, are a result of a great cove of magma located below the caldera's surface. The magma in this cove contains gases that are kept dissolved only by the immense pressure that the magma is under. If the pressure is released to a sufficient degree by some geological shift, then some of the gases bubble out and cause the magma to expand. This can cause a runaway reaction. If the expansion results in further relief of pressure, for example, by blowing crust material off the top of the chamber, the result is a very big gas explosion.
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Which of the above that I listed is the greater threat??
I really hope we never find out.