Showing posts with label Luzon Island. Show all posts
Showing posts with label Luzon Island. Show all posts

Sunday, 8 September 2024

Passage of Typhoon Yagi kills at least 39 people across the Philippines, South China, and Vietnam.

Typhoon Yagi is now known to have killed at least 39 people as it swept across the  Philippines, South China, and Vietnam between 2 and 7 September 2024. The storm was initially detected as a low pressure system to the northwest of Palau by the Japan Meteorological Agency on 30 August 2024. By 1 September it has moved to the northeast, gaining in strength to become a tropical depression as it entered the Philippine Area of Responsibility (an area of the northwest Pacific monitored by the Philippine Atmospheric, Geophysical and Astronomical Services Administration. The system was identified as Tropical Depression 12W by the Joint Typhoon Warning Center, and named Enteng by red by the Philippine Atmospheric, Geophysical and Astronomical Services Administration, then as it intensified to become a tropical storm, formally named Tropical Storm Yagi by the Japan Meteorological Agency.

Typhoon Yagi made landfall in Aurora Province on Luzon Island, the Philippines, at about 2.00 pm local time on Monday 2 September, taking fifteen hours to move across the island before emerging over the South China Sea at about 3.00 am on Tuesday 3 September. During this time the storm lost considerable energy, particularly as it passed over the Cordillera Central mountain range, but still causing significant disruption. The storm raised the waters of the Marikana River, which flows through eastern Manila, to rise by 16 m, leading to flooding in the Metro Manila area, as well as in the provinces of Bulacan, Camarines Norte, Camarines Sur, Cavite, Laguna, Northern Samar, Pangasinan, and Rizal. A number of ships were driven aground in Manila Bay, with two colliding and catching fire. Twenty people are currently known to have died as a result of the storm on Luzon, nine of them in Rizal Province, with at least more 26 missing and at least eighteen injured. Around 28 000 people in Metro Manila, Calabarzon, and Bulacan, lost their electricity supplies during the storm, schools were closed for two days, and most flights to and from Luzon Island cancelled. About 80 000 people were evacuated from low-lying areas, with 459 homes destroyed and another 6128 damaged. Several dams had to be opened to prevent them being damaged by high waters, adding to the flooding in areas beneath them.

Flooding in Rizal Province, the Philippines, on 2 September 2024. AP

After passing over Luzon Tropical Storm passed across the South China Sea, merging with a smaller depression and gaining significantly in strength as it moved west towards China. By 5 September the storm had gained suficient energy that the Japan Meteorological Agency upgraded it to a Super Typhoon, which is to say a typhoon with windspeeds of 240 km per hour or above, the equivalent to a Category 4 or 5 storm on the Saffir–Simpson scale.

In preparation for this 420 000 people were evacuated from low-lying areas on Hainan Island, and 500 000 from low-lying areas in Guangdong Province, with widespread cancelation of flights, non-essential travel, and coastal activities in both provinces as well as Hong Kong.

Typhoon Yagi made landfall near the city of Wenchang on Hainan at about 4.20 pm local time on Friday 6 September, bringing with it sustained windspeeds of 195 km per hour, making it the strongest storm to hit the island since Typhoon Ramassun in 2014. It passed across the island making, and over the provincial capital, Haikou, before briefly making landfall in Xuwen County, Guangdong Province, then passing out over the Gulf of Tonkin. Four people are reported to have lost their lives on Hainan Island, with another 95 injured, and 1.2 million people losing electricity supplies. Aa further nine people were injured in Hong Kong.

Heavy rainfall and fallen trees in Wenchang City on 6 September 2024. Luo Yunfei/China News Service/VCG/Getty Images.

Typhoon Yaagi gained in strength again as it passed over the Gulf of Tonkin, reaching Vietnam as a Category 4 Typhoon (i.e. a storm with sustained winds in excess of 209 km per hour), making it one of the strongest storms ever to hit northern Vietnam. In preparation for the storm schools were closed and fishing and outdoor gatherings advised against, as well as most flights, ferry services, and sporting events cancelled. The storm made landfall over the city of Haiphong, binging high winds and extensive flooding to the Red River Valley. fifteen people are known to have died in Vietnam, including four people hit by flying debris, another four, described as a family, by a landslide in Hoa Binh, and another man in Hai Dong hit by a falling tree.

High winds caused by Typhoon Yagi on the shore of Phuong Luu Lake in Haiphong. Nhac Nguyen/AFP.

Tropical storms are caused by the warming effect of the Sun over tropical seas. As the air warms it expands, causing a drop in air pressure, and rises, causing air from outside the area to rush in to replace it. If this happens over a sufficiently wide area, then the inrushing winds will be affected by centrifugal forces caused by the Earth's rotation (the Coriolis effect). This means that winds will be deflected clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere, eventually creating a large, rotating Tropical Storm. They have different names in different parts of the world, with those in the northwest Pacific being referred to as typhoons.

The structure of a tropical cyclone. Wikimedia Commons.

Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate 1 cm rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms. 

The formation and impact of a storm surge. eSchoolToday.

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Saturday, 7 September 2024

Asteroid 2024 RW1 impacts the Earth.

On the morning of Wednesday 4 September 2024, planetary scientist Jacqueline Fazekas working at the University of Arizona's Catalina Sky Survey detected a fast moving object, which she interpreted as a potential Near Earth Asteroid. She reported this to the International Astronomical Union's Minor Planet Center, where it was given the provisional designation CAQTDL2. This initial discovery was followed by a series of further sightings from other observatories, confirming that the object was an asteroid, which was then named 2024 RW1, and that it was on a collision course with the Earth.

Discovery images of Asteroid 2024, within purple circles. Catalina Sky Survey.

The designation 2024 RW1 implies that the asteroid was the 47th asteroid  (asteroid W1 - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 26, A2 = 51, etc., which means that W1 = (25 x 1) + 22 = 47) discovered in the first half of September 2024 (period 2024 R - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).

Asteroid 2024 RW1 is calculated to have had a 1450 day (3.97 year) orbital period, with an elliptical orbit tilted at an angle of 0.53° to the plain of the Solar System which took in to 0.74 AU from the Sun (74% of the distance at which the Earth orbits the Sun) and out to 4.23 AU (4.23 times the distance at which the Earth orbits the Sun, and almost three times the distance at which the planet Mars orbits). It is therefore classed as having been an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). 

The calculated orbit of asteroid 2024 RW1. JPL Small Body Database.

Asteroid 2024 BX1 is calculated to have had four close encounters with the Earth before finally impacting, with the first in August 1912, and the most recent in October 2020. It has also had close encounters with Venus in June 1966 and January 2009, and Jupiter in November 2006 and September 2018. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.

By 11.00 am GMT on 4 September 2024, the European Space Agency had calculated that Asteroid 2024 RW1 would impact the Earth, entering the atmosphere at about 5.08 pm over or close to northern Luzon Island, the Philippines. In the event the asteroid entered the atmosphere at 4.46 pm GMT (0.46 am on 5 September, Philippines time) over the Pacific Ocean to the east of Luzon, producing a bright fireball meteor, with a distinct green colour, which probably indicates that it had a high magnesium content. 

A bright fireball meteor observed from Tuguegarao City in the Philippines on 5 September 2024, thought to have been caused by the impact of Asteroid 2024 RW1. Marvin Coloma/American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. It is possible on this occasion the object is known to have produced meteorites that reached the surface (an object visible in the sky is a meteor, a rock that falls from the sky and can be physically held and examined is a meteorite).

Based upon observations in space and on entry to the Earth's atmosphere, 2024 RW1 is calculated to have been about a metre in diameter, and to have had a high magnesium content, something which in turn implies a stony meteorite rich in the mineral olivine (counter to possible expectations, metallic meteorites seldom contain much magnesium). However, as it fell to Earth over the Pacific Ocean, it is unlikely that any fragments of the asteroid will be recovered to test this hypothesis. 2024 RW1 is the eighth asteroid ever to have been discovered before impacting the Earth.

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Friday, 28 July 2023

Typhoon Doksuri makes landfall in China, after leaving at least 39 people dead in the Philippines.

Typhoon Doksuri made landfall in Fujian Province, China, on the morning of Friday 28 July 2023, after claiming at least 39 lives as it passed across the Philippines earlier this week. The dead in the Philippines include a mother, her child, and two other children that were in the same house when it was buried by a landslide at Baguis in Benguet Province, on Wednesday 26 July. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. These combined often lead to catastrophic flooding in areas hit by tropical storms.. Also in Benguit Province a 17-year-old was killed in a lamdslip triggered by heavy rains. In Isabela Province, a woman selling bread from a bicycle cart was killed by a falling tree. The majority of those who lost their lives, however, were on a ferry travelling town of Binangonan on Luzon Island and the smaller island of Talim, which capsized about 50 m after setting sail. Thirty people have now been confirmed dead following this incident, with many more still missing.

The MV Princess Aya, which capsized shortly after leaving the port of Binangonan on Luzon Island on Thursday 27 July 2023. The vessel overturned after encountering strong winds associated with Typhoon Doksuri, killing at least 30 passengers. The ferry is believed to have had about 70 people onboard when it sank, despite being licenced for only 40. The captain and engineer of the vessel have been arrested and may face charges. Rappler.

After passing over the Philippines Typhoon Doksuri swept to the south of Taiwan, brining with it winds gusting at up to 191 km per hour, and rains of up to 70 mm. Around 4000 people were evacuated from vulnerable areas as a precaution, and all internal and most international flights were grounded as a precaution. In the event there have been no major damage or casualties reported, although about 15 700 houssholds temporarily lost their power. In Fujian Province around 400 000 people were evacuated from areas deemed at risk, all boats were required to return to port as a precaution, and almost all transport services were suspended. No casualties have been reported in Fujian, and the only significant damage was to a sports stadium, which lost part of its roof.

Waves associated with Typhoon Doksuri battering the coast of Fujian Province, China, on Thursday 27 July 2023. Wei Peiquan/Xinhau/AP.

Tropical storms are caused by the warming effect of the Sun over tropical seas. As the air warms it expands, causing a drop in air pressure, and rises, causing air from outside the area to rush in to replace it. If this happens over a sufficiently wide area then the inrushing winds will be affected by centrifugal forces caused by the Earth's rotation (the Coriolis effect). This means that winds will be deflected clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere, eventually creating a large, rotating Tropical Storm. They have different names in different parts of the world, with those in the northwest Pacific being referred to as typhoons.

The formation of a tropical cyclone. Natural Disaster Management.

Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate 1 cm rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms. 

The formation and impact of a storm surge. eSchoolToday.

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Wednesday, 14 June 2023

Around 15 000 people evacuated from their homes following eruptions on Mount Mayon, the Philippines.

About 15 000 people have been forced to leave their homes after the Philippine Institute of Volcanology and Seismology ordered an evacuation of villages within 6 km of Mount Mayon, a 2463 m stratovolcano (cone shaped volcano) on southern Luzon Island. The evacuations were ordered on Sunday 11 June 2023, when the volcano began a new eruption, although a warning that such an evacuation might be ordered has been in place since an upsurge in seismic activity beneath the volcano a week previously. Such seismic activity can be a sign of liquid magma moving into chambers beneath the volcano, itself often a precursor of eruptions. On Sunday 11 June lava was seen oozing from the volcano's crater and descending the mountain's flanks.

Lava flows on the flanks of Mount Mayon on 11 June 2023. Nehemiah Manzanilla Sitiar/Reuters.

Mayon is considered to be a particularly due to the dense population in the area surrounding it. It has a long history of causing fatalities, most recently in 7 May 2013, when a sudden eruption caught a party of tourists by surprise, leading to five fatalities. As well as the direct danger from volcanic eruptions, Mayon has been the cause of numerous lahars (ash-laden flash foods). These tend to occur when ash from the volcano builds up across the path of seasonal waterways during the dry season, leading to temporary damming of water courses then flash floods at the start of the rainy season.

The location of Mount Mayon. Google Maps.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process. Material from the subducting Philippine Plate is heated by the temperature of the Earth's interior, causing lighter minerals to melt and the resultant magma to rise through the overlying Sunda Plate, fuelling the volcanoes of the Philippines.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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Friday, 5 August 2022

The first Neolithic farmers on Luzon Island, the Philippines.

The island of Taiwan, 125 km from the southeast coast of China, is thought to be the first island to the south of China to have been settled by Neolithic farmers, with the Dabenkeng Culture appearing here between 5500 and 5000 years before the present. Taiwan is also thought to have been the origin point of the first Neolithic settlers to arrive in the northern Philippines, more than 4000 years ago. Work on ancient DNA from archaeological sites on Luzon, the Mariana Islands, and the islands of the southwest Pacific has concluded that much of the genetic heritage of the non-Melanesian peoples of the islands of Southeast Asia and the Pacific Islands derives from an ancient migration from China via Taiwan and the Philippines.

All of this makes Luzon Island, the first major landmass likely to have been reached by Neolithic sailors heading south from Taiwan, likely to have been an important staging post in this migration, quite possibly the place in which many important cultural developments occurred. The Austronesian language family, for example, has two major divisions, one including the indigenous Formosan language of Taiwan, the other all the other significant languages of the Malay-Polynesian world, from the Philippines to Madagascar to Rapa Nui (Easter Island). The Proto-Austronesian language from which all these languages are descended is thought to have originated somewhere in the northern Philippines, probably Luzon or the Batanes Islands, or possibly on eastern Taiwan.

Northern Luzon Island is also likely to have been the first place were migrating proto-Malayo-Polynesians would have encountered people different from themselves. This island had long before been settled by the Melanesian Negrito people of the Philippines, who lived as hunter-gatherers on the island prior to the arrival of Neolithic settlers with domestic Dogs and Pigs, and a culture built around Rice-farming, between about 4200 and 4000 years ago. 

The Cagayan Valley on northern Luzon Island is the longest and widest river valley in the Philippines, with a broad alluvial plain extensively settled by Rice farmers. However, the area is still home to populations of Negrito foragers, particularly in the Sierra Madre hills to the east of the river. These people can be shown to be genetically related to the earliest, pre-Neolithic settlers in the region, though many parts of their culture are clearly more recent, including speaking a Malayo-Polynesian language and living only in remote forested areas unsuitable for Rice farming.

During the past two decades the Cagayan Valley has become a centre of great interest to archaeologists, with the uncovering of a series of shell middens which cover much of the history of settlement on the island, including the transition from a strictly foraging culture to one based around farming with foraging occurring as a supplementary activity.

In a paper published in the journal Antiquity on 1 June 2022, Hsiao-chun Hung of the Department of Archaeology and Natural History at the Australian National UniversityCheng-hwa Tsang of the Institute of Anthropology at the National Tsing Hua University, Zhenhua Deng of the Center for the Study of Chinese Archaeology and School of Archaeology and Museology at Peking University, Mary Jane Louise Bolunia and Rey Santiago of the Archaeology Division at the National Museum of the PhilippinesMike Carson of the Micronesian Area Research Center at the University of Guam, and Peter Bellwood of the School of Archaeology and Anthropology at the Australian National University, present a time-frame for the settlement of the valley based upon the radiocarbon dating of material from these shell middens, and a revised cultural and historical hypothesis based upon this.

The most westerly Pacific island chain, running from Taiwan southwards through the Philippines, has long been central in debates about the origins and early migrations of Austronesian-speaking peoples from the Asian mainland into the islands of Southeast Asia and Oceania. Hung et al. (2022).

Hung et al. identify three historical phases within the shell middens, which they term Preceramic (i.e. before the advent of ceramics), Neolithic (where ceramics have appeared), and Metal Age (where both ceramics and metal are present). The River Cagayan flows about 446 km from its headwaters in the Caraballo Mountains of central Luzon to the Babuyan Chanel where it enters the sea. The Cagayan coastal alluvial plain first formed about 7000 years ago, when rising post-glacial sealevels turned the area from a remote mountain valley into a coastal riverplain. Because Luzon is an volcanic oceanic island (albeit a rather large one), it has no surrounding continental shelf, instead rising sharply from the deep ocean. At the Last Glacial Maximum (between about 24 000 and 18 000 years ago) the sea level would have been about 120 m lower, with the Cagayan Estuary extending inwards about 100 km. It is quite possible that there are coastal and riverplain settlements lower down in the valley, but these would now be submerged and covered by metres of sediment.

(1) The Cagayan River in the Lal-Lo area; (2) part of the Magapit shell midden; (3) archaeological excavation of square P15 at Nagsabaran; (4) the Nagsabaran site, viewed from a distance. Hsiao-chun Hung in Hung et al. (2022).

The first shell midden in the Cagayan Valley was discovered at Magapit in 1971. Since this time a further 30 such shell middens have been discovered in the area, the densest concentration of shell middens anywhere in Island Southeast Asia, a reflection of the abundant shellfish available in the area in the Middle Holocene.

Most of these sites are located along a 30 km stretch of the valley between the cities of Gattaran and Lal-lo. To the north of Lal-lo the alluvium is to young to contain Neolithic sites. All of the Neolithic shell middens have been located either because they were exposed by the river cutting into them, or because they formed distinct, visible mounds. The middens are made up predominantly of shells of the Kabibe Clam, Batissa childreni, with smaller numbers of other Molluscs present, including the freshwater Snails Thiara rudisThiara winteri, Melanoides tuberculata, Melanoides granifera, and Melanoides maculata, the freshwater Clam Corbicula fluminea and the marine Clam Nitidotellina minuta. The largest shell middens are more than 5 m deep, and many overlie layers containing pottery or other Neolithic artifacts.

As well as the shell middens, there are a number of other archaeological sites in the region, particularly in the limestone hills to the east. These include deposits which run from the Preceramic to Metal Age periods, including evidence of interactions between foraging and farming communities. The largest of these sites is at Callao Cave, and includes remains attributed the Hominin Homo luzenonsis, which lived in the area more than 50 000 years ago.

The shell middens contain layers covering time intervals from the Preceramic to the Metal age, although no midden covers the whole of this period. The Gaerlan Midden, on the east side of the river 45 km upstream of its mouth, contains Preceramic and Neolithic layers, the latter containing potsherds, while the Lal-lo, Catugan, Irigayen, and Nagsabaran middens contain Neolithic and Metal Age layers, with the Neolithic layer, including red-slipped and incised pottery, extends downwards beyond the shell middens.

While none of the middens record the full 7000 years of occupation in the valley, some of the other archaeological sites might. For example the Pintú Rockshelter, 250 km to the south of Lal-lo, has a sequence of core-and-flake stone tools which appear to span the whole sequence, with pottery fragments in the middle and upper layers. Tadiocarbon dates obtained from the Pintú Rockshelter give dates from the Preceramic layers, of roughly 4960-3683 years ago, while layers containing 'reddish-orange ware' with stamped circles on the interior of the rims, similar to that found in the Cagayan Valley, appear between 4100 and 2949 years ago.

The oldest, Preceramic, shell midden layers are found at four sites, Ulet, Leodivico Capiña, Miguel Supnet and Gaerlan. These sites would have been close to a broader Cagayan Estuary between 7000 and 4200 (the estuary has moved northwards since this time as more sediment has been washed down the river and deposited). 

The oldest site, at Ulet, has yielded stone flakes but no pottery from a layer dated to between 6745 and 6495 years before the present. The Gaerlan site has a lower layer from which chert and andesite flakes have been recovered, which has been dated to 4295-4090 years before the present, overlain by a younger layer with red-slipped pottery fragments, dated to 4092-3687 years before the present.

The major archaeological sites and landscape changes through time in the lower Cagayan Valley: (1) Ulet; (2) Leodivico Capiña; (3) Callao Cave; (4) Musang Cave; (5) Arku Cave; (6) Miguel Supnet; (7) Gaerlan; (8) Nagsabaran; (9) Irigayen; (10) Magapit; (11) Pamittan; (12) Andarayan. Mike Carson in Hung et al. (2022).

The Leodivico Capiña and Miguel Supnet sites are 1.5 and 3 m deep shell middens on the west bank of the river which have yielded chert flakes and bones attributed to Wild Pigs, Deer, Rats, Birds, Turtles, and Fish, and Plant remains including nuts and tubers, but no evidence for cereals. When first discovered in the 1990s these sites were interpreted as Neolithic, due to the large amounts of pottery found in the topsoil above the middens, but neither has produced any pottery or other material associated with the Philippines Neolithic from the midden layers, and the sites are now considered to be Preceramic. Dates produced from material from the midden layers range from 7074 to 4514 years before the present.

Shell middens dating from over 7000 years ago to about 4500 years ago have been found in Vietnam, Thailand, Peninsula Malaysia, Sumatra, Sulawesi, Mindanao, and southern China. Many of these are associated with the skeletal remains of people thought to be of Melanesian affinities, and some sites in southern China and Vietnam have also included pottery. However, none of the Cagayan Valley sites of this age have produced either pottery or Human remains.

The location of the study area (lower Cagayan Valley, North Luzon), and the locations of representative (pre-farming) shell middens in southern China and Southeast Asia during the Middle Holocene, roughly 7000–4500 years before present. Hung et al. (2022).

The arrival of the Neolithic in the Cagayan Valley can be marked by the appearance of a complete new tool-set including pottery, baked clay spindle whorls, polished stone adzes, bark-cloth beakers, and a range of body ornaments including ear-pendants, bracelets, and beads made from shells, clay, schist, and semi-precious stones, including jade from Fegtian in eastern Taiwan. Stone tools from this period include few chert flakes, with most tools being highly polished.

Nagsabaran Metal Age Indo-Pacific glass beads (1), bronze bell-shaped ornaments (2), iron knife (3) and black pottery (4)–(12); Neolithic red-slipped pottery (13)–(14), clay spindle whorls (15)–(16), clay object (17), flaked chert (18)–(19), polished andesite adze (20), tuffaceous sandstone stepped-adze preform (21), green quartz schist beads (22) and Taiwan nephrite bracelet fragment (23). Scale bars are in centimetres. Hsiao-chun Hung in Hung et al. (2022).

The earliest of these sites can be dated to about 4200-4000 years before the present, with culturally similar sites of the same age also appearing in the Batanes Islands to the north. The Batanes Islands and Luzon are thought to have been settled at roughly the same time by people with a common linguistic and cultural heritage; however the two areas differ in that these were (as far as we can tell) the first people to settle the Batanes Islands, whereas the new arrivals on Luzon were entering a landscape already inhabited by an earlier, and culturally different, population.

The middens at Nagsbaran and Magapit contain layers assigned to the Neolithic contain the bones of Domestic Pigs, which have been dated to between 4448 and 4246 years before the present. These layers also contain remains of Rice, and Job's Tears (Adlay Millet or Chinese Pear Barley). Foxtail Millet is also present at Magapit - but does not appear till the Metal Age. A Rice grain from Magapit produced a radiocarbon date of 3200-3000 years before the present. Possible phytoliths (mineral grains that develop inside the leaves of a Plant) from Bananas were also found at Magapit.

Plant remains from Nagsabaran (a)–(c) and Magapit (d)–(f): (a) & (d) Rice, Oryza sativa, grains; (b) Foxtail Millet, Setaria italica, grain; (c) Job’s Tear, Coix lacryma-jobi, grain; (e) Rice spikelet base; (f) phytolith of cf. Musa sp.; item (b) is Metal Age, while all others are from Neolithic layers. Zenhua Deng in Hung et al. (2022).

Recent studies have uncovered evidence for mixed Rice and Millet agriculture during the Neolithic, from sites on the Pearl River Delta in Guangdong Province, China (dated to 4800-4600 years before the present), and Nanguanglidong in southern Taiwan (dated to more than 4500 years before the present).

The Andarayan site, which is about 80 km to the south of Magapit, has produced Neolithic red-slipped pottery from a layer which has yielded dates of 3935-3378 years before the present (from a Rice inclusion) and 3890-3060 years before the present (from a charcoal fragment). This provides three examples of Neolithic Rice production from separate sites within the Cagayan Valley, despite the alluvial plains being much smaller and less well developed at this time.

The Neolithic pottery fragments recovered from shell middens in the Cagayan Valley can be distinguished by the use of sand as a tempering agent (something added to clay to prevent pottery from cracking as it cools after baking) and the use of a red slip (a slurry added as an outer layer to form a sort of glaze). Similar pottery has been found at the Andarayan site, and at Chaolaiqiao in southeastern Taiwan, at Minanga Sipakko in West Sulawesi, and at Yinian on southeastern Hainan Island, where it has been dated to 3560-3380 years before the present. 

The presence of this distinctive pottery on Hainan is interesting, as Hainan has not previously considered to have been part of the Neolithic Austronesian expansion. The Tsat language spoken on Hainan was brought to the island by a population from northern Cham, in what is now Vietnam, fled to the island in 982 AD, following the fall of their capital to the Vietnamese. The minority Hlai people of the island speak a language called  Kra-Dai, which some linguists have suggested is related to Austronesian languages, and in particular languages from the Malayo-Polynesian branch of Austronesia, which are spoken across Island Southeast Asia. 

About 1% of the red-slipped ware from sites in the Cagayan Valley is also marked with incised and impressed decorations, and stamped geometric shapes. The most common patterns are rows of rounded or pointed impressions, intermixed with round stamps, sometimes within fields outlined with incised lines. These patterns are most common around the rims, shoulders, and feet of the vessels, where they form strait or zigzagged lines, or sometimes other geometric patterns. Some of the impressions contain traces of a white infill.

Examples of this pottery have been found in the shell middens at Gaerlan, Irigayen, Nagsabaran, and Magapit. The precise date at which such pottery appears is impossible to determine, but based upon stratigraphic extrapolation from radiocarbon dated material, Hung et al. place this somewhere between 3700 and 3500 years before the present. 

Pottery with similar patterns, including the presence of white infill material, has been found at the Neolithic sites of Man Bac and Xom Ren in Vietnam, where it has been dated to between 3900 and 3500 years before the present, although this pottery lacks the red slip seen on the pottery from Luzon and elsewhere in Island Southeast Asia. Baked clay earings of similar form have also been found in both Cagayan sites and northern Vietnam, further supporting the idea of contact between these areas in the Neolithic.

Red-slipped pottery (1)–(5), (7)–(9) & (11)–(14) and associated Rice, Oryza sativa, remains (6) & (15) phytoliths, (10) grain, from Chaolaiqiao, Nagsabaran, Yinian and Minanga Sipakko. Incised and impressed red-slipped pottery from Magapit: (16) open-mouthed pot on a pedestal, shown upside-down to reveal the stamped circles and possible fingernail impression decoration; (17) punctate-stamped sherd with lime or white clay infill in decoration; (18) sherd also displaying traces of white infill in incised lozenge motif with punctate infilling and impressed circles. Similarly decorated, red-slipped pottery from Nagsabaran (19)–(20) and Xom Ren (26)–(30) but without red slip. Baked clay earrings from Nagsabaran (21)–(25) and similar from Thach Lac (31)–(34). Hung et al. (2022).

Overlaying the Neolithic layers with red-slipped pottery at many of the Cagayan Valley sites, are later layers with black-slipped pottery. This can be achieved by firing the clay in an oxygen-deprived environment, possibly beneath Rice husks. This pottery is associated with metal objects, including iron blades and bronze ornaments, as well as monochrome glass beads. The origin of these metal objects is uncertain, but the glass beads, and similar glass beads from elsewhere in the Indo-Pacific, are thought to originate from South Asia or Mainland Southeast Asia.

Although the black-slipped and red-slipped potteries are distinct in form, the Magapit and Nagsabaran sites contain transitional layers, with both types of pottery present, suggesting that one did not suddenly displace the other. In addition, studies of DNA obtained from skeletal remains at Nagsabaran show affinities with the modern Ami people of eastern Taiwan, supporting the idea that there was a genetic continuity from the Neolithic into the metal age, despite the cultural change, although no DNA has been recovered from Neolithic skeletons in the area. 

The shell middens of the lower Cagayan Valley provide a unique archaeological resource within the Philippines, giving a more-or-less continuous record from the Preceramic hunter-gatherers of the Middle Holocene (roughly 7000 years ago), through the Neolithic and Metal Age periods into recent times; modern villagers in the area still consume shellfish and contribute to shell middens.

By the advent of the Neolithic, many of these shell middens were already covered large areas and were several metres deep. Similar shell middens are also known from other sites in South China, Vietnam, and Malaysia, but these were largely abandoned during the Neolithic, following the adoption of a Rice-farming lifestyle, whereas those in the Cagayan Valley continued to grow.

The Neolithic inhabitants of Luzon Island are known to have been highly skilled in the production and use of canoes, and to have produced a type of red-slipped pottery also found far from the island; examples have been found on Hainan Island 1000 km to the west, in the Mariana Islands, 2500 km to the east, on Sulawesi 1200 km to the south, and in the Bismark Archipelago, 3500 km to the southeast. This strongly supports the idea that, while Taiwan is still the undisputed ancestral homeland of the Austronesian language family and Malayo-Polynesian peoples, the island of Luzon, and in particular the Cagayan Valley, were very important steps in their early dispersal.

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