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🌤 | Rain and thunderstorms in Hokuriku and the Ogasawara Islands Is it snow in Hokkaido even on flat ground?


Rain and thunderstorms in Hokuriku and the Ogasawara Islands Is it snow in Hokkaido even on flat ground?

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The Pacific side of eastern Japan, western Japan, and the Nansei Islands, which are affected by high pressure, are generally sunny, but clouds are expected to spread in the Kanto and western Japan Sea sides.

On the 16th (Tuesday), a low pressure system near the Kamchatka Peninsula advances from the north, and a front extends from the south of Japan to the far east of Japan ... → Continue reading

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Eastern Japan Taihei

Nansei Islands

Nansei Islands(What is it)KyusyuFrom the south of the islandTaiwanLocated northeastislandsIs a group[6][11][12][13].

From north to south,Osumi Islands,Vassal archipelago,Amami archipelago,Okinawa Islands,Miyako Islands,Yaeyama IslandsIn the east of the Okinawa IslandsDaito IslandsAway north of the Yaeyama Islands尖 閣 諸島There is.

Name and scope

The name "Nansei Islands" isJapan Coast GuardIs the predecessor ofWaterwayIs central to1887 The place name was given around (Meiji 20) and issued the following yearChart"Ishigaki Anchorage Japan, Nansei Islands, Ishigaki Island"[14]Is first listed in[11][15].1894 (27th year of Meiji) Used in earnest from nautical charts after "Japan Hydrographic Magazine"[11],AlsoGeographical Survey InstituteOne of the predecessors of the Japanese Army Land Survey Department1937 It is also listed on the land map issued in (Showa 12)[16].. However, because the name "Nansei Islands" was used by a limited organization such as the waterway,Pacific WarWas never publicly known until[11].Okinawa under US military ruleHowever, only a small part of the official document mentions "Southwest Islands", and laterReturn to JapanThere are almost no use cases in Okinawa Prefecture[11].

"Nansei Islands" is used in the current Geographical Survey Institute local maps and the Coast Guard hydrographic magazine[17]. this is1965 May 10In the 4th "Communication Council on Unification of Place Names", an agreement was reached to use the "Nansei Islands"[18][19], Used as the official name in the geographical maps of the Geospatial Information Authority of Japan and the maritime information department published by the Japan Coast Guard[12].

The following names have also been agreed at the "Communication Council on Unification of Place Names".

Place name decided by "Communication Council on Unification of Place Names"
Classification and name according to the regional map of the Geographical Survey Institute[17][22]
Nansei IslandsSatsunan IslandsOsumi IslandsKagoshima
Vassal archipelago
Amami archipelago[20]
Ryukyu Islands[21]Okinawa Islands(Okinawa Island,Kumejima,Iwo TorishimaSuch)Okinawa
Kerama Islands
Sakishima IslandsMiyako Islands
Yaeyama Islands
尖 閣 諸島
Daito Islands
Classification and names according to the Japan Coast Guard hydrographic magazine[17]
Nansei Islands
(Satsunan Islands) *
Osumi archipelago
Vassal archipelago
Amami archipelago[20]
Ryukyu Islands[21]
Okinawa archipelago
Sakishima Islands (including Senkaku Islands)
Daito Islands
*The Satsunan Islands are on hold at the 65th "Communication Council on Unification of Place Names"[23].

Other designations for the Nansei Islands

The following names are sometimes used for the Nansei Islands.

  • Ryukyu Islands(Ryukyu Retto)
Ryukyu TrenchOkinawa TroughFormed betweenAnticlinePart of the archipelago (arc-shaped archipelago), which has an arc shape,East China Sea Ofcontinental shelfWith the Senkaku Islands located aboveThe Pacific OceanExcluding the Daito Islands existing on the deep sea floor[6][12][13].1907 Issued in (Meiji 40)GeologyWakimizu Tetsugoro's book "Okinawa Visits"[24]Found in[25].. Apart from the above, the Ryukyu Islands are the islands that make up the entire Okinawa Prefecture, and are explained synonymously with the Ryukyu Islands.[26][27]There is also.
It is an administrative name like the Nansei Islands and is not commonly used.Edo PeriodMid-termArai ShiroishiEven in the Meiji era, the Ryukyu Islands had been pointing to the area south of the Amami archipelago, beginning with "Minamijima-shi" written by. Even during the postwar US military rule period in Okinawa, the U.S. forces may have named the south of the Amami Islands the Ryukyu Islands until the Amami Islands returned to Japan. After the return of Amami, the area of ​​the Ryukyu Islands began to show the entire Okinawa prefecture, which had not been restored to the mainland.[28].. However, the "Communication Council on Unification of Place Names" agreed on the entire Okinawa prefecture except the Daito Islands.[21].. In addition, the islands of the Ryukyu Islands that belong to Okinawa Prefecture, that is, the Okinawa Islands and the Sakishima Islands, are included, and Daito and Senkaku Islands are not included Article[6][12]There is also. The Geographical Survey Office, one of the predecessors of the Geographical Survey Institute,1958 This name has been used for maps published by the Geospatial Information Authority of Japan since it was used in land maps issued after (Showa 33).[16].
  • South Island(What!)
It is a word that refers to the islands south of Kyushu and has been around since ancient times.Japanese calligraphy], there is a record of having interacted with the South Islanders[29].. Before the name of the Nansei Islands was used,1873 (6th year of Meiji) You can also check it in the "Minamijima Hydrographic Magazine".[11].. Although it is not an administrative or academic name,Folklore-cultureMostly seen in research materials[29].

In addition, the names that are almost synonymous with "Nansei Islands" and not used are listed below.

  • Southern Islands(Shutansho)
Before the name "Nansei Islands" was bornMinistry of NavyNamed and nineState OfsouthIt is believed that the islands were named after the islands located in.1886 It can be seen in the Hydrographic magazine published in (Meiji 19), but it has not been used in the Hydrographic magazine in 1894 (Meiji 27) after the name was changed to the Nansei Islands.1885 When the Daito Islands were transferred to Japan in (18th year of Meiji), it is thought that this name was not suitable, probably because it is located a little further than the south of Kyushu.[30][31].
  • Hainan Islands(Kaitansho)
1887 Around (Meiji 20)Tashiro stableWas named by. After that, Tashiro continued to be used for about 30 years, but from the middle, it was treated as a synonym with the Southern Islands and used together.Kunio YanagitaThe name was mentioned in a part of the book, but it did not become popular[32][33].

Geological/topographic classification

"Nansei Islands"公共 機関Is the administrative name decided byGeography-Earth scienceIs not a term used in[6][11].

From a geological and topographical perspective, in 1885Heinrich Edmund NaumannOn the geological map ofLiukiu BogenCan be seen[17].

  • Ryukyu arc(Ryukyu)
Almost synonymous with the Ryukyu Islands, but strictly forms the Japanese IslandsIsland arcOne of theKyusyuIs located at the junction of the Southwestern Japan arc and the Ryukyu arc[34][35].. In addition to the Ryukyu Islands and Kyushu, the Ryukyu ArcTaiwanAlso includes[6][36].. Unlike the administrative name of the Nansei Islands, the Ryukyu Arc is an academic term in geography and earth sciences.[36].1870 eraToHeinrich Edmund Naumann,Toyokichi HaradaNamedGerman " Liukiu Bogen It was a word that translated "and existed before the names of the Nansei Islands and the Ryukyu Islands were established.[36].
  • Ryukyu(Ryukyuwan)
Synonymous with Ryukyu Arc in the late Meiji eraRyukyuThe term (Ryukyuwan) also appeared, but it was hardly used after the war.[37].

Geologically and topographically, it is divided into the Tokara structure strait (between Sekiishijima and Takarajima) and the Kerama Kaiseki (between Okinawajima and Miyakojima), which is a geological depression, and is divided into Tohoku Ryukyu, Chubu Ryukyu, and Southwest. It is divided into three areas such as Ryukyu, North Ryukyu, Middle Ryukyu, and South Ryukyu.[17].

Topographical overview of each island

Of the Nansei Islands, excluding the Senkaku and Daito Islands, the Ryukyu IslandsRyukyu TrenchOkinawa TroughLocated between and[38].. In addition, there are two tectonic lines that divide the Ryukyu Islands between the bad stone islands of the Tokara Islands and Kotakara Island, Okinawa Island and Miyako Island. The former is the Tokara Structure Strait (this strait isBiogeographic area OfOld Kita WardToyo WardIt is one of the boundaries of the area, and is called the Watase line), and the latter is called the Kerama Kaifuku (Miyako depression).[39][40].. The Ryukyu Arc is from the north of these tectonic lines,North Ryukyu(Osumi Islands etc.),Ryukyu(Amami archipelago, Okinawa Islands, etc.),South Ryukyu(Miyako/Yaeyama Islands)[41][42].

Osumi Islands

Osumi IslandsIs located in the north of the Nansei Islands,Yakushima-Tanegashima-Kuchinoerabu Island-Mage IslandIt consists of four islands, but in the broad senseMishima villageIslands belonging to (Kami MishimaAlso known as Kuchino Mishima[43]) Is also included[44].. In western Tanegashima, eastern Yakushima, etc.Coral reefAre small but well developed and are considered to be the northernmost coral reefs in the Nansei Islands[45].

The highest peak in KyushuMiyanoura TakeYakushima, which hasMioceneCaused by the subsidence of the Shikoku BasingraniteBut,UpheavalErosionIn response to this, it seems that it formed a high and steep mountain range. A steep slope over several hundred meters appears near the coast, but the slope becomes gentler toward the center of the island. The top of the mountain has a tore terrain where the bedrock is exposed. This is a long timeweatheringAndIce ageHappened toPeriglacial actionIt is thought to be due to. 4 or 5 steps on the southern and eastern coastsCoastal terraceIs developing.PleistoceneIt is thought that terraces were formed in the area, but in a very low place several meters above sea level.HoloceneYou can see the terraces of the times[46][47].

Tanegashima is a low-lying plateau island, as opposed to Yakushima, which has a steep topography. Tanegashima is an island that rises from the bottom of the sea, with coastal terraces generally developed. Especially on the northwest coast of the island, many coastal terraces are found, but on the southeastern terrace terrain is eroded,Drowning valleyStands out. This is because the northern part of the island is mainly composed of firm alternating layers of sandstone and slate, and the southern part is composed of soft geology such as conglomerate and mudstone. Also, the whole islandTephraIt is thought that the pyroclastic flow deposit called ``spread'' spread in the Holocene and had a great influence on the above-ground flora and fauna.[46][48].

Kuchinoerabujima and KamimishimaMount AsoFrom south to southKirishima volcanic beltBelong to. AlsoIwo JimaTakeshima TheOnikai CalderaIt forms part of the outer ring of the mountain, and most of the caldera is sunk on the seabed. It is an elliptical caldera with a diameter of about 20 km and the maximum depth is 500 m. Large in the pastPyroclastic flowAt least four eruptions accompanied by the occurrence of eruptions occurred, and the latest eruption was about 4 years ago. These pyroclastic flows are located on the east side of Yakushima and Tanegashima, and also on Kyushu.Osumi-Satsuma PeninsulaExtended to It has two volcanic bodies in the east and west of Kuchinoerabujima. Eruption activity of Shindake, which is located in the eastern part, is particularly active and has been erupting many times since the prehistoric times.1933 Of the village that existed at the foot of the eastern side has disappeared due to the eruption of[49][50].

Vassal archipelago

Vassal archipelagoIs Kagoshima prefectureToshima VillageIs a group of islands belonging to[51][52].. The total length of about 320 km,Volcanic islandLine up[53].. It is included in the Kirishima volcanic zone, of which Ioshima and Takeshima pass through the Tokara Islands,Iwo TorishimaIs called Tokara Volcanic Islands[54].. The Tokara Islands are a series of new volcanic islands formed in the Quaternary.TertiaryIs roughly divided into old volcanic islands that erupted in Japan and did not retain the original volcanic landform[55].. The old volcanic islands are located on the continent side of the new volcanic islands[56].

Old volcanic columnsAndesiteConsists of quality volcanic islands, some of whichTreasure island-Small treasure islandThere are also islands with developed topography derived from coral reefs.Woja Island,HirashimaThere are steep and steep cliffs that surround a part of the island, and there are places with flat and gentle slopes. Also, Takarajima and Kotakarajima occurred about 2,500 years ago.big earthquakeIt was found that the Takarajima had risen about 3m and Kotakarajima up to 8m. There are many factors such as the active Kirishima volcanic belt, the Tokara structure strait, and the expansion of the Okinawa Trough.[56][57].

The volcanic islands belonging to the new series of volcanoes form a mountainous body from the bottom of the sea about 500 m below sea level and have Mt.NakanoshimaHas a specific height of about 1,500 m from the seabed.KuchinoshimaIs in two placescalderaThere are three central craters in the relatively newly formed caldera. This caldera is located in the southeastern part of the island, has an elliptical shape with a long diameter of 3 km, and retains the original shape of the outer ring. The central crater hills are all lava domes, and fumarolic activity can be seen on one of them, Moedake.Suwa Nose IslandOf the Kirishima volcanic beltSakurajimaWith it, very active volcanic activity. At least 200 eruptions have been observed in the last 8 years,Scoria溶岩Is ejected in large quantities.1813 Around (culture(A year), scoria was deposited in the settlements with a thickness of 50 cm or more, and the residents at that time were forced to evacuate from the island.[58].

Amami archipelago

Amami archipelagoIs a group of islands located in the north-central part of the Nansei Islands and extending from the northernmost part of Amami Oshima to the southern end of Yoron Island for about 200 km.[59][60].. The land map issued by the Geospatial Information Authority of Japan has long been written as "Amami Islands",2010 May 2"Amami archipelago" was adopted as the place name at the 72nd "Communication Council on Unification of Place Names"[20].

Has the largest area in the Amami archipelagoAmami OshimaIt is,Paleozoic OfJurassicからCretaceousThe basement rocks that have been formed over the period are exposed. Most of them form steep mountain topography due to erosion, but they have a flat topography near an altitude of 300 m, and the topography of the southwestern part of the island (elevation of about 300 m to 450 m) is a ridge-like topography with little relief. Can be confirmed. They areQuasi-plainIt is said to be a small erosion surface, and a semi-plain is formed on some of the Nansei Islands. The coastline of the island has a complicated structureRias coastAnd, there are modern coral reefs on the surrounding coast. The Kasari Peninsula in the northeastern part of the island is different from the topography of the main part of Amami Oshima mentioned above. Coastal terraces are widely distributed and consist of marine sediments about 40m thick[61][62][63].

Kikai IslandIs formed by coral reef terraces. You can see four coral reef terraces formed along the island's coastline, and the altitude of this terrace becomes lower toward the northwest. Kikaijima, located in the eastern part of the Amami archipelago, is closest to the trench side,Philippine Sea PlateThe upheaval is intense due to the subduction of. In fact, the rising speed of Kikaijima is the highest in the Ryukyu Islands, and it has risen more than 7 m in about 10 years. The uplifting motion on this island is considered to be due to crustal movement due to a large earthquake[64][65].

Tokunoshima TheIgneous rockMainly on the base, the altitude of the highest peak of the island, Inogawadake, reaches 645m. For itOkinoerabujima-Yoron IslandThe whole is formed by terraces of raised coral reef, the highest altitude is relatively low at about 200 m, and the river is not well developed.[59][66].

Okinawa Islands

Okinawa IslandsIs a group of islands located in the central part of the Nansei Islands, and consists of Okinawa Island (Okinawa main island), which has the largest area in the Nansei Islands, and the neighboring remote islands, the Kerama Islands and Kume Island. As an administrative division, the Daito Islands are generally included in the Okinawa Islands.[68][69].

It is the main island of the Okinawa IslandsOkinawa IslandIs due to the geological structure,Uruma City石川It has different topography and geology in the north and south, based on the boundary (Ishikawa Gorge) that connects the area from to Zanba Cape.Motobu PeninsulaThe northern part of the island exceptCretaceousType of metamorphic rocks formed inPhylliteOccupy in the Nago layer mainly composed of. However, as seen from the northern part of the island, the southeast side (NagoFrom the eastKin Town) IssandstoneKayo Formation of accretionary prism, large depending on locationFoldYou can observe the strata formed. With the Motobu PeninsulaIheya Island-Izena IslandTo the southeast, of which the Kayo Formation isAdductIt is the most recently formed basement around the northern part of Okinawa Island that has a structure[70][71].

Motobu PeninsulaIs mainly of the late PaleozoicCrystalline limestonechart,MudstoneConsists of.KarstThe terrain is well developed and peculiar to the tropicsConical castThere are many erosion depressions called Polje.The undulations of the summit, which is located in the center of the peninsula and is about 400 m above sea level, are gentle, and the altitude decreases toward the west.Located on the sea west of Motobu PeninsulaIe IslandIs a flat terrain entirely covered with Quaternary limestone. However, Paleozoic charts project to the east of the islandShiroyama(Ie Island Tachu) rises from between the permeable limestone and impermeable chartsspringAppears[72][73][74].

Unlike the geology of the northern part of Okinawa Island, it originates from coral reefs.QuaternaryLimestone (Ryukyu limestone)When,NeogeneIt is composed of the Shimajiri Group dominated by the mudstones and sandstones. In contrast to the mountainous northern region, the central and southern regions consist of plateaus and lowlands,RiverIs less developed than the north. South island has northwest-southeast strikeFaultThere are a lot of them, but they are formed before the Ryukyu limestone is deposited. Since the weathering rate of the Shimajiri mudstone layer is higher than that of mainland Japan, there are wide basin valleys and water-soluble sandstone layers.Natural gasIt is distributed over the southern part of the country. Located in the southeastern part of the islandNakagusuku BayIs the eastern part of Okinawa Island on the west side of the plain where the land mass collapsed in the past and spreads along the coast.watershedAre thought to have been formed[75][76][77].

Iheya/IzenajimaConsists of chert and sandstone, no limestone[78].. On the mountain-winning islands,Iheya IslandIs the largest in the Ryukyu IslandsAlluvial plainOne of[79].Kerama IslandsAre also mountainous islands, but with sandstoneMetamorphic rocksIt consists of (green schist and phyllite). Phyllites are distributed throughout the Kerama Islands, but green schists haveCopper oreProducedKuba IslandYakabi IslandSeen in[80].KumejimaThe northern part is composed of Tertiary volcanic rocks and reaches an altitude of more than 300m, while the southern part is predominantly Ryukyu limestone and forms a flat land.[81][82].. Remains of mines remain in various parts of KumejimaFriWas mined[82].. Also on the east coast of Kume IslandOujimaCalled tatami stoneAndesite OfColumnar jointIs formed[83].

Located in the northernmost part of Okinawa PrefectureIwo TorishimaIs the only one in this prefectureactive volcanoOn the island[Note 2], Considered to be the southernmost part of the Kirishima Volcanic Zone. It has two volcanic bodies, Mt. Iou and Mt. Gusuku, and a crater lake is formed at Mt. Continuing volcanic activity for tens of thousands of years,sulfurThe fumes including are raised.1959 After evacuating islanders to Kumejima, it has become an uninhabited island[84][85].

Miyako Islands

Miyako Islands(Miyako Islands) is located about 300 km southwest of Okinawa Island, and there is a depression called Kerama Kaifuku (Miyako Depression) with a depth of about 1,000 m. Most of the geology of the islands consists of Ryukyu limestone, with the sandstone and mudstone Shimajiri layer as the base. The terrain is a flat lowland without mountains, and the highest elevation of this island is 115m of Miyakojima.[86][87].

Main island of the main islandsMiyakojimaIs a plateau island with sea cliffs on the northeast or south coast, but sandy beaches on the west coast[88].. Faults developed along the northeast coastlineKesta TerrainForming[89]It is also said that Miyakojima took a triangular shape due to this fault[86].. There are no rivers and residents flow between the limestone and Shimajiri strata.groundwaterI have to rely on spring water (→Miyakojima water supply See).1979 First in the world on MiyakojimaUnderground damWas constructed and several underground dams are now complete. But sprayed on farmlandPesticideInfiltrate underground, thereby dams and groundwaterWater pollutionIs a problem[90].. On the sea about 15km north of MiyakojimaYaedoseForm a group of coral reefs[87].

Irabu IslandTarama IslandAll covered with Ryukyu limestone[89], Irabu Island has a karst terrain[91], Tarama Island is formed by coastal terraces[92].

Yaeyama Islands

Yaeyama Islands(Yaeyama Islands) is located in the southernmost part of the Nansei Islands, and has Yonaguni Island at the westernmost end of Japan and Hateruma Island at the southernmost end of Japan as a man-made island, and also administratively includes the Senkaku Islands.[93].

The geology of Ishigaki Island differs from north to south, and in the mountainous northern part, it is composed of late Paleozoic metamorphic rocks (Tomuru Formation), chert and sandstone complex (Tomisaki Formation) and volcanic rock-derived Nosoko Formation. Also the highest peak in OkinawaMt Odode(Elevation 526m) consists of volcanic complex rocks centered on granite, and is thought to have been formed during the Miocene. The Tomul Formation is the oldest formation in the Yaeyama Islands and is considered to be an accretionary complex of marine sediments. Southern part is called Miyara formationEoceneIs mainly limestone,ForaminiferaContains a lot[92][94].

Iriomote Island is a mountainous island with steep cliffs on the south coast. The mountaintops above 300 m above sea level are gently undulating due to erosion and form a quasi plain. The coastline of the western part of the island is intricate and complex, forming a rias coast[93].. The entire Iriomote IslandMioceneIt is composed of the Yaeyama Group of sandstone and mudstone formed in, and the Tomuru Formation is found in the northeast. Also, the Yaeyama formationcoalBefore the war, including the layers, a coal mine was developed in the western part of the island,1960 Was mining up to[95].. It is the longest river in the prefectureUrauchi RiverAnd at the mouth of the Nakama RiverTriangle river(Estuary) has developed,mangroveThe forest is clustered[96][97].

The Ryukyu limestone that is widely distributed in the Ryukyu IslandsHateruma IslandKuroshima,Yonaguni IslandPresent in the northern part, not developed on Ishigaki Island and Iriomote Island[98].. Hateruma Island and Kuroshima Island are islands formed by coral reef terraces, but since Yonaguni Island is close to the Okinawa Trough, small-scale faults are caused by it.Tilting blockThere are many. In the waters of Ishigaki Island and Iriomote IslandSekisei Lagoonと 呼 ば れ るBarrier reefAre formed. In the Ryukyu IslandsFoot reefThere are many lakes, but the water depth of Sekisei Lagoon is a little deep, about 10m.[99].

1924 May 10, From the northeastern sea of ​​Iriomote IslandpumiceScoriaErupted. Temporarily fill the coast and harbor of the Yaeyama Islands and spend a yearHokkaido OfRebun IslandThere were some pumice stones ashore. Although the detailed location of the crater has not been specified, it is thought that it is located at a shallow seabed with a water depth of about 200 m. It is unknown whether this volcano corresponds to the southwest extension of the Kirishima volcanic belt.[100][101].

Daito Islands

Daito IslandsIs located about 400 km east of Okinawa Island. In addition to North Daito Island and Minami Daito Island, there is Okito Daito Island about 140 km south of the sea.[102].The Pacific OceanThis upper island is not included in the Ryukyu Islands formed on the anticline between the Ryukyu Trench and the Okinawa Trough[103].

North and South Daito Island is a unique uplift in the worldAtollIs an island. The central part is a lowland with an altitude of 10 m or less, but the surrounding area is surrounded by hills with a height of several tens of meters, and the residents call it "hagu".1934 ToTohoku UniversityGeologists visited Kitadaito Island,ボ ー リ ン グI conducted a survey. It was dug as deep as 430m from the ground, and the depth was comparable to the world's deepest record at that time, but it did not reach the volcanic rock that was thought to be the base. And1980 eraA bowling on the Daito Ridge inbasaltIt was discovered that the age of the limestone that had deposited on its basement was at least about 4800 million years ago. Further remains of bedrockMagneticAs a result of investigatingequatorialIt is thought to have developed as an atoll in the vicinity and moved north due to the movement of the Philippine Sea Plate. Also, when the Philippine Sea plate sinks into the Ryukyu Trench, the plate bends like a wrinkle in front of it, forming a raised portion. This is called the "trench marginal uplift zone", and it is said that about 400 to 600 million years ago, the island approached the uplift zone and changed from subsidence to uplift.[104][105][106][107].

North and South Daito Island is the southernmost tip of JapanLakeA densely populated area, Minami Daito Island has the largestOikeThere is[108].. Karst terrain has developed,UvaleRainwater gathered in the depression and a lake was formed. The water level is 1 m, which is almost the same as the sea level and the depth is over 7 m. Due to the limestone topography with many gaps, it was thought that seawater might have invaded the lake at first. HoweverconductivityFrom the measurement results, it is considered that seawater is not mixed with lake water.[109].

Oki Daito Island is composed of uplift atolls, like North and Minami Daito Island. However, since the highest altitude is 30m, which is lower than that of North/Minami Daito Island, it is considered that it started later than the rising time of North/Minami Daito Island.MeijiFrom the end of the period to the prewar period, the entire island was privately owned by companies,Phosphate rockWas being mined. After the warU.S. ForcesUsed as a training ground forUninhabited islandIs[110][111].

尖 閣 諸島

尖 閣 諸島Is located about 150 km north of the Yaeyama Islands, and consists of small islands and reefs.East China Sea Ofcontinental shelfBecause it is a group of islands formed in Japan, it does not belong to the Ryukyu Islands like the Daito Islands[112].

Most of the Senkaku Islands have Miocene gravel and andesite geology,Kuba IslandIs the only volcanic island in the Islands and is composed of basalt. Although a coral reef can be seen around the island, it is surrounded by steep rocks as a whole, forming an almost vertical sea cliff. The name "Senkaku" comes from these steep terrain[112][113].

1968 On the seabed off the Senkaku IslandsoilThe sedimentary layer, which is thought to be a storage layer, has an area of ​​approximately 20 km2Exists over a thickness of about 3 km,Submarine resourcesIt was reported that there is a high possibility that[114].. After receiving the announcement,1970 ToPeople's Republic of ChinaTaiwanAsserts sovereignty over the islands and disagrees (→Senkaku Islands Dispute (See)[115][116].


The Nansei Islands are scattered about 1,200km between southern Kyushu and Taiwan[5].. Among them, the Satsunan Islands belong to Kagoshima Prefecture, and the islands in Okinawa are said to be Ryukyu Islands.[117].. Area belonging to the Nansei Islands 0.01km2The total number of the above islands is 198, 38 in the Satsunan Islands and 160 in the Ryukyu Islands.[1].


SouthwesternclimateIt is,Köppen climate classificationaccording toWest JapanSame asWarm and humid climate Belongs to (Cfa)[119].. But surrounded by the sea,Warm currentIsKuroshioIs greatly affected byNahaThe average annual temperature is 23 ° C, which is warmer than half of the year, warmer in winter than in other parts of Japan, and the changes in the four seasons are unclear.Therefore, the climate is intermediate between the tropics and the temperate zone.Subtropical climate[Note 3]It is generally said that[120].


SouthwesternAnnual rangeIs 9-12 ℃,Daily rangeIt is the smallest value in Japan along with 4-5℃, and it shows the characteristics of oceanic climate.[121].. In the summer North PacificNorth Pacific HighThe western edge of theOgasawara Highと 呼 ば れ る[120][122].. The summer when it is covered by the Ogasawara high pressure has a hot and humid climate, but since it is located on the sea, the maximum temperature is not so high compared to Honshu.Ikema Island36.7℃, as of 2009)[123][124].. The warmest month is July, one month earlier than August in Honshu. This will take Honshu around Julyrainy seasonOn the south side of the front, it is considered that the Ogasawara High that expands northward covers the Nansei Islands and creates a significant downdraft.[123][125].. On the contrary, in winterEurasiaSiberian high pressureFrom the continentHimalayasCold stopped southward by(I.e.Goes around the Nansei Islands[123][126].. The average temperature during this period is 16℃, which is at least about 10℃, but the lowest temperature in the history of observation in Okinawa Prefecture was observed on January 1963, 1.Kumejima2.7 ℃ (January 2016, 1 24:11 pm(Japan Standard TimeNow[127]), the freezing point does not reach below freezing[123][124].. The coldest month is January like Honshu[123].


Okinawa Prefecture from mid-May to late Junerainy seasonseason(Okinawa Meteorological Observatory[128]According to the report, the average season for the rainy season from 1981 to 2010 is May 5, and the end of the rainy season is June 9. ) And a large amount of precipitation during the typhoon approach period from July to October, accounting for about 6% of the annual precipitation[123].Indochina PeninsulafrommonsoonReaches near the Nansei Islands, increases the frequency of cumulonimbus with contact with the cold air mass in the north, and begins the Baiu front in the south of the Nansei Islands.[129].. Furthermore, due to the generation of low pressure,Warm and humid flowBrings heavy rain to the Nansei Islands[123].. However, the 20-30 degree north latitude where the Nansei Islands are locatedMid-latitude high pressure zoneExists,DesertThere are many dry areas. As the location and power of the high-pressure zone fluctuate depending on the season, the Nansei Islands are affected by light rain.Drought,DroughtMay be hit by[120][130].. Actually Okinawa Prefecture1963 Drought, limited water supply due to drought for about one year from July 1981 (Showa 56-57 Okinawa droughtExperience)[131].

In the Nansei Islands, snowfall is limited to the northernmost Osumi Islands[132].1977 May 2ToJapanese Meteorological AgencyIs the first time in OkinawaSnowfallWas observed on Kumejima[133],this is"SleetIt is not an official record of the so-called "snow"[134].2016 May 1In Amami Oshima1901 May 2Since the snow[135]I also observed the second sleet on Kumejima and the first on Okinawa Island.[136].

From December to late June after the rainy season, the total cloud amount in Naha is 12-6%[137]And, it is easy to continue on a very cloudy day. From around December in winter, the cloud amount becomes large due to the generation of streak cumulus when the dry cold air of the continent passes through the East China Sea where the water temperature is relatively high. From February to March spring, warm air pushes the front to the north, and low pressure (East China Sea low) is likely to occur in the East China Sea, causing snowfall on the Pacific side of Honshu.[134][138].. In addition, a stagnation front occurred due to the passage of low pressure throughout Japan in April, causing long rain called “rapeseed rainy season”.[139], The Nansei Islands also pass through mobile high pressure, so it may be fine day[140][141].. In May, the so-called “Mainland Japan”May clear,” but the rainy season front begins to form in the sea near the Nansei Islands.[142][143].. And in July, when the rainy season is over, the most stable sunny day of the year continues, and it is a period of low rainfall with high temperature dryness.[124][125].


The Nansei IslandsTyphoon ginza'[120][145]Is calledtyphoonApproaching/passing through[Note 4]Is a region with a lot of. According to the Japan Meteorological Agency, during the period from 1981 to 2010, the annual number of typhoons was 25.6, while the number of annual approaches to the mainland was 5.5, and the southwestern islands south of the Tokara Islands were 7.6.[146].. In addition, the number of typhoons increases from July to October and reaches the maximum in August. Along with that, the number of approaches is highest in August. However, the maximum number of records of the maximum wind speed and the daily minimum sea level pressure within the top 7 observations (from the beginning of the observation to 10) is highest in September. In other words, a strong typhoon can easily approach the Nansei Islands around September. Around August, the northern limit of the typhoon generation areaフィリピンAlthough it will be on the northern sea, typhoons reaching Okinawa are often under development. Around September, the typhoon generation area moves southward compared to August, and the typhoon at its peak tends to attack when approaching. In addition, there is a point where the course of the typhoon changes from the west to the east (referred to as the turning point of the typhoon), and in August it is near Honshu and in September it moves southward to the Nansei Islands. Since the typhoon has the maximum power at this turning point and the traveling speed is often small,[147], It is thought that the frequency of low-speed typhoons invading Okinawa around September will increase with the typhoon holding the most power.[145].

Words that represent the seasons

In Okinawa, the rain and wind that appear at the transition of the seasons from a long time ago are expressed in a unique way. For example, Ningachikajimai (““February (Old calendar)Of the wind'), Kurchibeh ()Summer solstice south wind.. Strong winds blow from the south during this time. ), in the autumn of October to November, Nininishi (new north wind, the first north wind that blows in late summer) and Takanu Shibai (hawk OfPee.SashibaIt is a time for a flock of birds to winter in Okinawa, and it is easy to get light rain when the north wind blows. ), the cold wave in late December was Tungy Bisa (winter solsticeThe cold wave around February is the Moochybysa (MoochyIs said to beMoon peachWrapped in leavesMochiTheLunar calendar November 12Because of the custom of eating and eating (late January-early February of the new calendar)[148].. ) And many other words[124][134][149][150].

Major cities

List major cities in the Nansei Islands. Data as of July 2021, 12.

Naha(315,344 people)
Okinawa City(142,816 people)Uruma City(125,965 people)Urasoe City(116,023 people)Ginowan City(100,181 people)Miyakojima City(52,848 people)Ishigaki(47,715 people)Amami(40,930 people)Nishinoomote(14,508 people)


[How to use footnotes]

注 釈

  1. ^ a b KagoshimaNishinoomote,Amami,Kagoshima District,Kumage,Oshima-gunAnd the whole Okinawa prefecture.
  2. ^ According to Kato (1995) p.166, the volcanic islands belonging to Okinawa Prefecture are Iototorijima and Senkaku Islands.Kuba IslandIn addition to Iwo Torishima, the active volcano of this prefecture isIriomote Submarine VolcanoIs mentioned.
  3. ^ According to Kazuo Nakamura et al., “Natural Areas of Japan, 8 Southern Islands” (1996), pp.1-6, there is no “subtropical zone” in the ocean. It may be called this because the Nansei Islands in the summer have a long period of entering the tropical convergence zone, but unlike the atmospheric circulationOcean currentExplains that cold and warm currents do not interchange depending on the season. Furthermore, the atmospheric circulation mechanism is fundamentally different between tropical and non-tropical,WesternThen tropical (tropical ) And outside the tropics (extra-tropical )weatherSome institutions are researching. See also Toshio Kawana "Series of Okinawa, Topography of the Ryukyu Islands" (1988) pp.17-28.VegetationThere is no term "subtropical" in Köppen's climate classification based on the difference in the distribution ofair massBased on the different nature ofAlisov's climate classificationHas a climate classification called "subtropical zone", but it belongs to other than the Nansei Islands.HokkaidoAll over Japan, exceptContinental United StatesIt is said that it is not appropriate to call it "Ryukyu Islands = "subtropical"" because it covers most of the area.
  4. ^ JMA Typhoon termsAccording to the typhoonClose toMeans that the center of the typhoon should be within a radius of 300 km centered on the geographical boundary (coastline, prefectural border, etc.) of the area.通過Means "when the center of a typhoon crosses a small island or a small peninsula and then resurfaces in a short time". By the way, the typhoonlandingMeans "when the center of the typhoon reaches the coast of Hokkaido, Honshu, Shikoku, and Kyushu", and this term is not used for the Nansei Islands including Okinawa and Amami.


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