This post is about the Tarawera Kaharoa eruption, and shows that it happened in June 1306. But it is a long story, connecting places as far apart as Taiwan, Ecuador and the Antarctic Peninsula. Enjoy!
Large volcanic eruptions throw out their ash and gas into the atmosphere and forget about the mess. They are heavy smokers who have never heard about such inventions as ash trays. (Mind you, most young people will not have come across those. We have at least cleaned up some aspects of our world!) One of our house rules is ‘You make a mess, you clean it’. It is applied within limits, of course. But volcanoes couldn’t care less.
The amount of ash that major eruptions deposit is outside of our experience. Etna left a layer of ash in local villages, requiring dump trucks to collect it and take it somewhere. Cumbra Vieja buried houses up to their chimneys. A decent eruption can cover many thousands of square kilometers in ash deep enough to kill the vegetation. Much later, people will find a distinct layer in the soil and wonder what had happened.
An important layer is found over much of the North Island of New Zealand. It is called the Kaharoa tephra. An example is shown below, taken from a peat bog at the Bay of Plenty. The layer here is about 5 cm thick, and is distinctly white compared to the black peat. Above the layer the peat is blacker than below. This is thought to come from burning, evidence not of volcanic activity but of human damage. Polynesians had reached New Zealand and had begun to make it their home. The evidence for their activities is only found above the white layer, not below. The data of their arrival is disputed, but this suggest they arrived around the time of this eruption. So, when was this ash deposited? And which volcano did it?
Let’s first take a step back in time. The colonization of New Zealand was just one part in an event that changed an ocean and created a world. It was the peopling of the Pacific.
Peopling the Pacific
The Pacific Ocean is an amazing place. The expanse of water is unimaginable, stretching halfway across the world. The continents that line it are worlds apart, with completely different people, history and culture. Australia’s and Papua New Guinea’s Aboriginees, the Han Chinese, the Chuki reindeer people, and the First People in America have nothing in common. The ocean that keeps them apart is occupied by different people again. They live on the volcanic islands that pepper the Pacific. Some of these islands are isolated to the extreme. Other islands form closely linked archipelagos. In either case, the people that live there are remarkably uniform in culture, in spite of living across an area larger than any continent. New Zealand’s Maori are part of that culture. The peopling of the Pacific is the ultimate story of adventure; and exploration of the unknown, knowing there could be no going back. When and how did it happen?
The shores of the Pacific ocean were first reached by humans more than 50,000 years ago. Impressively, that had already involved an ocean crossing of 70 kilometers into New Guinea. he abilities of people of that time went well beyond tools and cave paintings. The nearest Pacific islands of Melanesia, such as Bougainville, were also reached. But here they remained, on the rim of the Pacific. They only went to islands they could see. The horizon was their limit. The island hopping brought them to Australia, but the deep Pacific was beyond them.
The true expansion into the Pacific started in Taiwan, perhaps 5000 years ago. The people grew rice and millet, and kept pigs and dogs, and they took these with them. Evidence of their presence quickly appeared on the Philippines and Sulawesi. Rice did not grow well there, and it disappeared from their basket. Instead they adopted several tropical fruits. Chickens were added to the animals they kept.
Different groups now dispersed to different regions. One of these groups settled around the Bismarck Archipelago, off the northeastern coast of New Guinea. Here they developed a distinct style of pottery called Lapita. By 3000 years ago, this pottery appeared on Fiji, Tonga and Samoa, 5000 kilometers distant. And they traveled amazing distances. Guam was colonized by the Lapita culture, and that involved a continuous sea journey of 2000 kilometers. Was that an accident? Or did they know where they were going, and did they come prepared for long-distance migration? A trade network linked their islands: obsidian (a very valuable hard volcanic rock) from New Britain (part of the Bismarck archipelago, and a dangerously volcanic place) was found across much of the newly colonized world of Melanasia. The sudden expansion may have come from improvements in their canoes (perhaps the outriggers) but this is not known.
The Lapita culture suddenly disappeared from western Melanasia. It remained at Samoa and Tonga, but it lost the characteristic pottery. The trading network had collapsed. Some seafaring remained, and over time a new type of canoe was developed, which used a double hull rather than outriggers. And sometime between 1000 and 2000 years ago they began to expand eastward into the sparser islands of the southern central Pacific. The sudden resumption may have come from new technology (the double canoe) or just from the discovery of islands beyond the horizon. The amazing journeys now reached the Marquesas islands, Easter Island and even Hawai’i. They build their empire of volcanic islands by going against the direction of the prevailing wind. This may have been deliberate: by going against the wind, if anything went wrong they could quickly go back.
The sweet potato was added to the foods they grew. This was very unexpected, as this is a South American plant. The word they used for the sweet potato even has a South American origin. (It is however also possible that the sweet potato had spread naturally to the eastern Polynesian islands, before any human arrival.) Contact with South America is proven by genetic studies, which found American DNA in the genome of the eastern Polynesians, but not the other way around. That makes sense, given the size of the populations: genetic contact would have been highly diluted among the 100 times larger population of South America. There is uncertainty whether the Polynesians reached South America, or that the Americans came west and met them there. The contact appears to have been with people from the region of Colombia or Ecuador: both the human genetic tracers and that of the Pacific sweet potato point at this area. The human genetic signal is limited, and suggests that the mixing of populations happened only once. The fact that they acquired a new food suggests that the contact was not caused by a American canoe caught off guard by wind and currents and accidentally driven to Polynesia. It seems more likely that Polynesians traveled to South America, as they were the ones who had the ability and were already traveling that way. The arguments get heated and are driven more by opinions than by (sparse) facts. We do know that the early contact was with people from the Tuamotu islands and not (as often argued) with Easter Island. Traces of South American DNA is not found in Easter Island populations until 100 years later, well after Easter Island was colonized.
It has been argued that this Polynesian contact, around 1200, introduced their chickens to South America. Chickens came to South America with the Spanish. There is however some evidence for chicken bones in Chile which predate Columbus. This requires confirmation and the genetic evidence for non-European chickens is currently inconclusive. If confirmed, this would strongly point at an attempt by Polynesians to establish a settlement in South America. Such an attempt could also most easily explain both the genetic mixing and the acquisition of the sweet potato. If so, the settlement failed and like the Vikings in Newfoundland, the Polynesians left again. But if neither the chicken nor the sweet potato evidence holds, then we don’t know what happened! The only solid data we have is on the date, around 1200 AD,
But when did this expansion across the Pacific happen? Early carbon dating had indicated that the Polynesians spread during the first millennium AD, perhaps from around 500 AD. But more detailed studies done later found more recent dates, and this divided the scientists in an ‘early’ and a ‘late’ camp. Genetic studies added direction to the dates. The genetic diversity indicate that the expansion occurred in two distinct colonization waves. The first wave began in Samoa, and reached the Southern Cook Islands around 800AD. The second wave began around 1100 AD, and expanded from the Southern Cook Islands. Hawai’i was settled around 1200, apparently by two different groups.
The genetic tracers that show mixing with a South American population are found in the area of the Tuomotu Islands, and in the islands settled from there, but not elsewhere. The date for the mixing agrees well with the Polynesian expansion, another indication that the contact was initiated by the Polynesians during their longest journeys. Interestingly, the islands with the American tracers are also the islands which have a tradition of stone monuments, such as the statues of Easter Island. It has been argued that this tradition also came from a South American influence.
The Polynesian expansion was not haphazard. They clearly knew where they were going. The Polynesians had recorded where the islands were, and had developed excellent navigation ability. They had explored and found the islands, returned to their homes to report and plan, and finally set out with a colonization cargo consisting of enough people to successfully settle, their crops and their animals. Even the Pacific rats which spread with the people may have been a deliberate cargo, providing another food source. They settled unoccupied locations. They left us no colonies in South America or Australia. They only went were none had gone before.
A long-distance trading network was again established, among the largest the world may have seen up to that point. Stone adzes, needed to make the canoes and which were made from basalt found in only a few islands, were traded around the entire region. This trade network was centred on the Southern Cook Islands. But over time it contracted and declined. The Marquesas dropped out of the network before 1400, and long distance trade may have ceased before 1500. In contrast, trade with nearby Samoa continued into the 1600’s. The reason for the decline in trade is not known. The 1453 eruption of Kuwae has been blamed but there is no evidence linking the two.
The incredible expansion happened during only a brief period lasting no more than 200 years. In this time the Polynesians colonized the Pacific, and discovered America before Columbus did. (They were not the first to do so, though. The people who lived there for 15,000 years or more (but are rarely credited with discovering America, and both the Inuit and the Vikings also got there before the Polynesians. Columbus came last in the discovery competition.)
The mammalization of New Zealand
The expansion across the Pacific took the Polynesians to the biggest prize of their empire, New Zealand. here they became the Maori. The Maori have stories about their history which tell that New Zealand had been discovered already by 800 AD, but the great fleet of canoes which brought the settlers only came after 1350. (The dates are based on counting generations.) The Polynesians knew where they were going. The original number of settlers may have been as large as 500 to a thousand. Genetic data suggests that the settlers came from more than one Polynesian island, either in a combined fleet or as separate arrivals over a century or more. The new settlers quickly spread out along the coast line.
Not everyone has agreed with these dates. Just like for the Polynesian expansion across the Pacific, there was a group advocating a ‘long’ history, where the settlement happened as early as 900 AD, and one arguing for a ‘short’ history with a settlement after 1200. The evidence for the long history came from carbon dating. However, these data have since been revised and the evidence now strongly suggests that the ‘short’ history is correct. However, a date of 1350 appears too late, for several reasons, including population growth models and the fact that Polynesia expansion had largely ended 200 years earlier. Currently, the first human arrivals to New Zealand are thought to have come between 1250 and 1325.
This migration took the Polynesians outside of their comfort zone. Polynesia is tropical, and New Zealand is not. Their tropical crops would not grow in New Zealand, with one exception: the recently acquired South American sweet potato. Without their gardens, they became hunter/gatherers. This was probably their common approach when settling in a new place, but the Pacific islands had limited resources for hunting which quickly ran out, necessitating a return to gardening for a living. New Zealand was much larger and could support hunters for many decades. But not forever. The new arrivals may have been excellent seafarers and navigators, they were not good conservationalists. It was too easy. The mammalian predators, both humans and rats, found New Zealand to be a walking buffet.
Top of the menu were the moas, flightless birds that had evolved to fill the ecological niche of grazers, and which had reached a size commensurate with that. They were as large as a small cow, and very edible. The Maori quickly established themselves as moa hunters. Their early settlements were on the coast, and shellfish and seal also became an important part of their diet. The coastal locations could be dangerous. A large tsunami in the second half of the 15th century wiped out part of the coast, and severely damaged many settlements. In places the tsunami had a run-up height of 30 meters.
New Zealand had been densely forested, and this made settlement of the interior difficult. The Maori began to burn down those forests. The hunting, the burning and the rats changed the land. All 11 species of Moas went extinct within 200 years of the arrival of humans. Even seals nearly went extinct. The hunter/gatherers now walked into a food crisis. In response, the population developed new, local crops, mainly suitable to the warmer climate of the North Island. They also moved in-land.
By the time the Europeans arrived, there were some 100,000 Maori living in New Zealand, but much of the land had become ecologically impoverished. It was a large scale change similar to what had happened on all Pacific islands, but it took much longer in New Zealand.
The Maori and the volcano
New Zealand has a unique way to date archaeology. This is a volcanic land where eruptions occur regularly. Small eruptions only have local effects, but large eruptions can leave traces across much the North Island. Over the time when the Maori lived in New Zealand, before the arrival of Europeans, there were six eruptions large enough to leave recognizable tephra layers in coastal regions where the Maori lived. The oldest of these is the Kaharoa Tephra, dated to around AD 1300. The second one is called the Loisels Pumice, a coastal pumice layer that arrived as a sea raft somewhere between AD 1305 and 1345. The third is the tephra from the Rangitoto Island eruption, which is only roughly dated to somewhere between AD 1410 and 1550. Finally, there are three tephra layers from Taranaki, namely the Newall Tephra, around 1600; the Burrell Tephra, around 1655, and the Tahurangi Tephra, around 1755. Of these six, the Kaharoa tephra and the Loisels pumice are most widespread, although the latter is only found at the coast.
The 230 AD Taupo tephra was the last major tephra layer before the Maori arrival. It covers 20,000 km2 on land with a thickness of more than 5 cm, to the east and north east of Taupo. A lot of the Taupo tephra ended up at sea: it can be found as a pumice layer on the beaches of both the North and the northern half of the South Island. Not surprisingly, there is no indication of any Maori activity below this layer. The Rangitoto island eruption did cover Maori settlements under its ash: New Zealand was clearly well settled by this time. The impact from the Rangitoto eruption did not spread far; even though the eruption was voluminous and lasted a long time, there was not much explosive activity apart from some water-magma interaction during its early phase. In consequence only the nearest islands were affected.
The Loisels pumice came from an underwater volcanic arc north of New Zealand. The precise origin of this eruption is not fully established: it is named after Healey volcano but it is not certain that this was the source. The pumice is rhyolitic, with a single chemical composition. Rhyolite is not so common from this area, and it makes an origin in a single volcano likely.
The Kaharoa tephra came from a large eruption at our old friend, Tarawera. The tephra covers 30,000 km2 on-land with a thickness of at least 3cm. The tephra is distributed along an arc extending both southeast and northwest from Tarawera. It extends along the coast of the Bay of Plenty to close to Auckland. Unlike Taupo, the eruption did not form significant sea pumice. The white tephra came from a series of separate explosions which can be recognized as separate layers.
The Kaharoa tephra has been dated using the remains of a tree (a celery pine) that was killed in a pyroclastic flow during the eruption. The tree rings were recognizable and gave a calendar date between 1302 and 1326 AD. The Loisels pumice has been much harder to date. There are some carbon-14 dates from shells, but these can give uncertain dates. This is because carbon can spend a long time in sea water before taking in by a shell. In contrast, carbon in the air is cycled through the soil quite rapidly. Seashells can therefore give much older dates (the age of the carbon rather than the shell). This needs to be corrected for, but this correction has a large uncertainty. The best calendar date is between 1280 and 1440. However, there are sand layers above the pumice which have been dated more accurately: these provide an upper age of around 1345 AD.
The Kaharoa tephra and the Loisels pumice are not found in the same locations, so we don’t know which one is older. However, the Kaharoa tephra layer is thought to predate the Loisels pumice. Archaeology suggests that the Loisels pumice has buried younger deposits than the Kaharoa tephra. In that case, the Loisels pumice layer must date to later than 1300. The best dates are therefore between 1300 and 1345.
It is possible that not all Loisels pumice depositis have the same age. A distinction should be made between primary deposits, which is when the pumice first arrived, and reworked deposits, which is where an event (earthquake or storm) remobilized the pumice and redeposited it on the beach.
The best dates indicate that Kaharoa and the Loisels pumice came within decades of each other, after a quiet time which had lasted for a millennium. The Maori arrived at just the wrong time. First they found their coastal settlements under thick ash which killed all the vegetation, and not long after they found the sea and beaches made impassable by thick pumice, removing fish and shellfish from the diet. They suffered a double whammy.
Or did they? What does the archaeology say?
The oldest Maori settlements were found within a kilometer or so of the coast. The people left shell middens and moa bones, leaving little doubt about their main diet, although these may have been supplemented by gardens. A typical village supported some 100 people. Remains of such villages are found both above and below the Loisels pumice: when this pumice arrived, the coast was clearly already occupied. Both the layers above and below the Loisels pumice contain moa bones. Because moas became extinct within about 150 years of the Maori’s arrival at each location, and this indicates that the settlements had been less than a century old at the time of the arrival of the pumice.
The Kaharoa tephra shows a very different picture. It covers the Bay of Plenty, a very fertile region. But there is not a single Maori settlement found below the tephra layer, and very little indication for any Maori activity. Either the coast was very sparsely populated, or the Maori had not yet arrived here. The first indications of their presence comes from carbon deposition in peat, evidence of burning. This begins at the same time as the Kaharoa tephra. In a few locations the carbon is found below the tephra, but only just. The time difference is perhaps a few decades but less than 50 years. This puts the arrival of the Maori near or very shortly before the time of the Kaharoa eruption.
After the eruption, the area would not have been attractive to the settlers. The tephra would have killed much of the forest, and would have driven off the moa. For many years, the Bay of Plenty would have had little to offer. Later the area would have recovered, as the ash fertilized the soil and encouraged new growth. But that may have taken decades.
The arrival of the Maori is therefore closely linked to the Kaharoa eruption. This was the largest eruption in New Zealand since the arrival of the Maori. If the Maori arrived just after this eruption, they would have found the Bay of Plenty a desolate landscape, and gone further south. If they had already settled the area, the eruption would have given them very good reason to relocate. What do we know about this eruption, apart from the approximate date?
The Tarawera Kaharoa eruption
The Kaharoa tephra came from Tarawera. The mountain is not particularly pretty (unlike the surrounding lakes) but deceptively dangerous. Taupo, to the south, is well known for the size of its eruptions. But Tarawera has history too. The overlapping calderas, each from a slightly different location, show that its behaviour is similar to nearby Taupo. The figure below compares the volume of the large eruptions from both regions. (The bars give the magma (or DRE) volumes: to get the VEI values, multiply by 2.5.) The Tarawera area (Okataina) never did anything as bad as the Taupo Oruanui eruption, 26,000 years ago, which reached VEI-8. But it has reached VEI-6 on many occasions, and managed at least one VEI-7.
Tarawera is mostly a rhyolitic volcano, albeit one where basaltic and rhyolitic magma can mix. The Kaharoa tephra is seen as a white, rhyolitic layer. On the slope of the mountain the tephra is 40 meters thick. Even 60 kilometers away it is still 10 cm thick, and it can be seen beyond 100 km distance.
The eruption that caused it occurred over many distinct phases. The tephra forms 13 separate layers from 11 explosive events, with the ash blown into different directions, mainly to the northwest and to the southeast. The eruptions were plinian to sub-plinian. As all Tarawera eruptions, it occured along different vents along a roughly northwest-southeast rift: for this eruption the rift was 8 kilometers long with at least four major vents. Each separate event may have lasted hours to days, based on the thickness of each tephra layer. There is no evidence for any erosion between the layers. Pyroclastic density currents and ashfall between the layers shows that there was a little time between some of the explosions, but this may only have been a few days. The explosive phase may have lasted in total as long as a month or two, or as little as two weeks. In either case, this was not a singular 4-hour event like the 1886 eruption.
The carbonized tree stump used for the dating showed a fully formed year ring below the bark, which indicates that it died during the New Zealand winter, between May and September. The burned trees are found at the bottom of the deposits, and it appears they were killed during a pyroclastic flow from the first of the explosions. The debris from the first set of explosions were blown to the southeast by a constant high-altitude wind. High-altitude winds in New Zealand are normally westerly, and southeasterly winds tend to be brief. This suggests that this winter eruption did not last long. The following layer (H in the alphabetical ordering of the layers) shows evidence for a changing wind during the eruption. The layers above that, which were ejected later, were blown into a north to northeasterly high-altitude wind. These wind directions are more common in early spring (September-October).
After the explosive phase ended, four large lava domes and one lava plug were formed. This will have taken much longer. A typical eruption rate for silicic lava eruptions is 5-10 m3/s, and at these rates the domes may have taken several years to form. These domes survive as the three peaks on the flat summit of Tarawera, and were split apart in the 1886 eruption. (The fourth dome was buried by the other ones, and revealed only by the 1886 rift.) The domes obliterated the craters formed by the earlier explosions. The explosions were probably the openings of the conduits that subsequently formed the domes.
How large was the eruption? Studies have yielded surprising answers. The distribution of the tephra suggest that for the largest two or three of the explosions, part of the ejecta fell into the sea. Indeed, Kaharoa ejecta have been found in sea sediment. The thickness of the ejecta layers are measured at different distances from the volcano, and a function is fitted to determine how quickly it falls off with distance. That function gives the total volume for each layer, and includes the part that ended up at sea. There are many uncertainties. The thickness may have been measured at the most obvious places, which is where the layer is most clearly seen. But that may just be where it was a bit thicker, perhaps due to wind or movement by water. And different layers have different distributions, as the wind changed, perhaps even during the eruption.
The measurements indicated that the total erupted volume was around 5km3 DRE which included the lava domes and the tephra. (Note that ‘DRE’ stand for Dense Rock Equivalent, and is the volume of the crater that forms. The ejecta have a large volume because tephra has a low density.) This was a substantial eruption, where the explosions together were a high VEI-5, with a tephra volume not far below 10 km3.
A re-measurement in 2014 increased the number substantially. This study measured and fitted each layer separately, and derived volumes for each of them. The numbers are in the table. The authors calculated a DRE volume of over 7 km3 in the explosive ejecta only. Adding in the volume of the lava domes, the total became 9 km3 DRE. The explosive phase had a tephra volume of 15 km3! The means that the explosions together added up to a VEI-6. The individual explosion were of course smaller, with the largest ones producing between 2 and 3 km3 of tephra.
Where had all this material come from? Explosions this size should leave substantial craters. But in this case instead of a single VEI-6 there were 11 VEI 4 to 5’s spread out over an 8 kilometer rift. This makes the individual craters much smaller. They were later buried by the growing lava domes. Still, 9 km3 DRE even over an 8 km rift should leave a hole of 1 kilometer wide and 1 kilometer deep. But the mountain is only 1 kilometer tall. There may have been a series of older domes, blown apart by the explosions, but even so it remains hard to accommodate this much material. The older value of 5 km3 DRE is easier to understand. (In comparison, the Taupo eruption of around 230 AD produced about 30 km3 DRE.) The large proposed volume of the Kaharoa tephra requires confirmation.
In either case, this eruption was the largest one seen in New Zealand since the arrival of the Maori. It covered Tarawera’s slopes in 40 meters of lapilli, and devastated some of the best coastal land of New Zealand, within decades of the Maori arrival. It must have made the South Island, in spite of its colder climate, seem very attractive compared to the ruins of the North Island. Once burned, twice shy. Perhaps this is why for the first 200 years of the Maori presence, most of their settlements were on the South Island: New Zealand’s volcanoes are all on the North Island whilst the South Island is volcano-free – but it is, of course, earthquake-prone. In New Zealand you can’t win. Unless you are a rugby fan.
Perhaps the haka is really a Maori chalenge to the volcanoes of the north, in memory of Tarawera?
An ice core date
We can try to further narrow down the date for the Kaharoa eruption. An eruption this size should show up in the ice cores of Antarctica. Does it? Strangely, no one has looked. They should have.
The plot shows the monthly sulphate profile obtained from the ice cores. The blue line is for Antarctica (WDC06A, from Stigl et al.) and the red line is for Greenland. Tropical eruptions should show up in both ice cores, but eruptions in temperate regions tend to be only be seen in their own ice core. The tropics with its high troposphere forms an effective barrier to sulphate put in the stratosphere at high latitude. For a large eruption in New Zealand, the sulphate should show in Antarctica but not in Greenland.
There is only one sulphate peak within the allowed time period of the eruption, and it is seen in Antarctica only. The peak is not clearly seen in the annual data, where the sulphate in the ice core is averaged over each year. There is a peak but it is far from obvious and not certain. When I first looked at the ice cores, my detection algorithm rejected it. But here I am plotting the monthly data and this picks up the peak much better. It indicates that this eruption was a brief one, lasting only a fraction of a year. The sulphur declined within 1-2 months, and was gone completely after 5 months. The eruption had reached the stratosphere, otherwise it would have lasted no more than a few days. Over the next few months, the sulphur slowly came back down to the troposphere and rained (or snowed) out, and the ice signal ceased.
The peak occurred in the early (southern) winter of 1306. The sulphate began to increase in May or June 1306, peaked in July, and declined, with a second peak in September. This is consistent with what is known about the Tarawera eruption. As one interpretation, it could put the first set of explosions, when the wind was to the southeast, in May/June, and the second set, when the wind was northwest, in August/September. However, this may be optimistic as weather patterns also play a role in determining when the sulphate could have arrived in Antarctica. It is difficult to distinguish eruption patterns from weather patterns.
In any case, the ice core provides a solid date for the eruption. Tarawera exploded around June of 1306.
The ice core does not only show the volcano. It also shows the activities of the freshly arrived Maori. After their arrival, New Zealand suffered forest fires on a scale it never had before. The country is in principle not highly flammable, as it does not have the extreme weather patterns of Australia. Now, the trees went up in flames as the Maori saw them as surplus to requirements. The smoke reached into the sky, and was blown all the way to Antarctica. It too ended up in the ice.
The black soot from forest fires normally drops out of the atmosphere within a few days. In the southern hemisphere, much of it ends up in the oceans. However, some can reach Antarctica. The large annual fires of the subtropical regions of South America and Africa can dump a small amount of soot over the coast of Antarctica. Fires in Patagonia and New Zealand can also do that, but much more of their soot reached the Antarctic Peninsula, blown there in just a few days by the roaring westerlies of the Southern ocean.
A recent paper looked at carbon in the ice cores from Antarctica. The data is shown in the plot, with black for the Antarctic peninsula (nAP) and red for the coast of Antarctica (DML). The time runs from 1AD to 2000 AD. The approximate time of the arrival of the Maori is indicated by the dashed line. The annual amount of soot at DML was relatively constant over that time. It is a little lower after 1500 AD, perhaps due to less burning in South America after the arrival of Europeans. That is an interesting problem in itself. The peninsula record, in contrast, is very different. It spiked around 500 AD and again around 1100-1200AD, followed by a large increase starting around 1300 AD. The early spikes are attributed to burning in Tasmania. The big increase and the higher level afterwards are from New Zealand. The Maori were clearing their new land.
The sharp sudden increase is consistent with the arrival of a significant human population. If only a few tens of Polynesians had colonized, the increase of burning would have been much slower. Instead they arrived in much larger numbers, in a planned settling of the new land. It was indeed a ‘great fleet’. And the onset of the fires can also be measured from the increase. It started in 1297+-30 AD.
The onset of the fires agrees well with the evidence from the Tarawera Kaharoa eruption. It doesn’t answer the question wether the Polynesians arrived before or after this eruption. However, an arrival a few decades before Kaharoa, perhaps around 1280 AD, fits perfectly well with the evidence from the carbon soot of Antarctica.
The story has brought us a long way, from the shores of Taiwan 5000 years ago and the shores of South America 900 years ago, to the arrival of humanity (and mammality) in New Zealand and finally to the shores of Antarctica. It gave us a precise date for the largest eruption in New Zealand during the presence of the Maori: May/June 1306 (you read it here first!). The Maori did not find an island paradise. During their first decades in the new land they suffered not just one major eruption, but two, when the destructive Kaharoa eruption was followed by the Loisels pumice. The Bay of Plenty would have looked very different and distinctly uninviting during those years. But the Maori too played their part. Just as the volcano spread its ash across the land and beyond to Antarctica, so the Maori spread their soot equally wide. Neither volcanoes nor people cleaned up the mess they made.
New Zealand has changed forever. New Zealand was the last major land mass ruled by the birds. I regret not being able to see the moa, or the gigantic eagles which hunted them. These birds had created a land akin to the world of the dinosaurs, which we have lost. The past is in the past, and people needed to live. But New Zealand is not just shaped by humanity. Volcanoes too have played their part, and their legacy can be seen in many places. The soil of New Zealand is the ashtray of the country, which still contains the ash of volcanoes past. That 700-year-old white band in the black soil tells us a story from a forgotten time, when people traveled halfway across the globe into the unknown, to go where none had gone before, to explore new worlds and to build new civilizations. We have seen nothing like it since. Tarawera is forever part of that adventure.
Albert, December 2021
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Paths and timings of the peopling of Polynesia inferred from genomic networks. Alexander G. Ioannidis et al, Nature 59, 522–526 (2021)
Hemispheric black carbon increase after the 13th-century Māori arrival in New Zealand. Joseph R. McConnell et al. Nature 598, 82–85 (2021)
Deposition and generation of multiple widespread fall units from the c. AD 1314 Kaharoa rhyolitic eruption, Tarawera, New Zealand. Steve Sahetapy-Engel et al., Bull Volcanol 76, 836 (2014)
An ashy septingentenarian: the Kaharoa tephra turns 700. David J. Lowe and Adrian Pittari, Geoscience Society of New Zealand Newsletter 11, 1-13 (2014)
Distribution, stratigraphy, and history of proximal deposits from the c. AD 1305 Kaharoa eruptive episode at Tarawera Volcano, New Zealand. Iain Nairn e al., New Zealand Journal of Geology and Geophysics, 44, 467-484 (2001)
Chronology and Evolution of Caldera-forming and Post-caldera Magma Systems at Okataina Volcano, New Zealand from Zircon U–Th Model-age Spectra. B. Charlier & C. Wilson, Journal of Petrology, Volume 51, Pages 1121–1141 (2010)
A post on Taranaki, the most frequent New Zealand eruptor during Maori times, can be found at https://volcanohotspot.wordpress.com/2021/11/15/mount-taranaki-new-zealand/