Island arc in the context of Plate tectonics

The Japanese archipelago (Japanese: 日本列島, Hepburn: Nippon/Nihon Rettō; Japanese pronunciation: [ɲip.pon/ɲi.hon ɾeꜜt.toː]) is an archipelago of 14,125 islands that form the country of Japan. It extends over 3,000 km (1,900 mi) from the Sea of Okhotsk in the northeast to the East China and Philippine seas in the southwest along the Pacific coast of the Eurasian continent, and consists of three island arcs from north to south: the Northeastern Japan Arc, the Southwestern Japan Arc, and the Ryukyu Island Arc. The Daitō Islands, the Izu–Bonin–Mariana Arc, and the Kuril Islands neighbor the archipelago.

Japan is the largest island country in East Asia and the fourth-largest island country in the world with 377,975.24 km (145,937.06 sq mi). It has an exclusive economic zone of 4,470,000 km (1,730,000 sq mi).

North Asia or Northern Asia (Russian: Северная Азия) is the northern region of Asia, which is defined in geographical terms and consists of three federal districts of Russia: Ural, Siberian, and the Far Eastern. North Asia is bordered by the Arctic Ocean to its north; by Eastern Europe to its west; by Central Asia and East Asia to its south; and by the Pacific Ocean and Northern America to its east. It covers an area of 13,100,000 square kilometres (5,100,000 sq mi), or 8.8% of Earth's total land area; and is the largest subregion of Asia by area, occupying approx. 29.4% of Asia's land area, but is also the least populated, with a population of around 37 million, accounting for merely 0.74% of Asia's population.

Topographically, the region is dominated by the Eurasian Plate, except for its eastern part, which lies on the North American, Amurian, and Okhotsk Plates. It is divided by three major plains: the West Siberian Plain, Central Siberian Plateau, and Verhoyansk-Chukotka collision zone. The Uralian orogeny in the west raised Ural Mountains, the informal boundary between Asia and Europe. Tectonic and volcanic activities are frequently occurred in the eastern part of the region as part of the Ring of Fire, evidenced by the formation of island arcs such as the Kuril Islands and ultra-prominent peaks such as Klyuchevskaya Sopka, Kronotsky, and Koryaksky. The central part of North Asia is a large igneous province called the Siberian Traps, formed by a massive eruption which occurred 250 million years ago. The formation of the traps coincided with the Permian–Triassic extinction event.

The Northeastern Japan Arc, also Northeastern Honshū Arc, is an island arc on the Pacific Ring of Fire. The arc runs north to south along the Tōhoku region of Honshū, Japan. It is the result of the subduction of the Pacific plate underneath the Okhotsk plate at the Japan Trench. The southern end of the arc converges with the Southwestern Japan Arc and the Izu–Bonin–Mariana Arc at the Fossa Magna (ja) at the east end of the Itoigawa-Shizuoka Tectonic Line (ITIL). This is the geologic border between eastern and western Honshū. Mount Fuji is at the point where these three arcs meet. To the north, the Northeastern Japan arc extends through the Oshima Peninsula of Hokkaidō. The arc converges in a collision zone with the Sakhalin Island Arc and the Kuril Island Arc in the volcanic Ishikari Mountains of central Hokkaidō. This collision formed the Teshio and Yūbari Mountains.

The Ōu Mountains form the backbone of the volcanic part of the inner arc that run from Natsudomari Peninsula in Aomori Prefecture south to Mount Nikkō-Shirane in Tochigi and Gunma prefectures. The volcanic front consists of four north to south lines of Quaternary volcanoes and calderas, which extend the length of the range. It also includes the Quaternary volcanoes of southwestern Hokkaido. The Dewa Mountains and the Iide Mountains are non-volcanic uplift ranges that run parallel to the west of the Ōu Mountains.

The Lesser Antilles is a group of islands in the Caribbean Sea, forming part of the West Indies in Caribbean region of the Americas. They are distinguished from the larger islands of the Greater Antilles to the west. They form an arc which begins east of Puerto Rico at the archipelago of the Virgin Islands, swings southeast through the Leeward and Windward Islands towards South America, and turns westward through the Leeward Antilles along the Venezuelan coast.

Most of them are part of a long, partially volcanic island arc between the Greater Antilles to the north-west and the continent of South America. The islands of the Lesser Antilles form the eastern boundary of the Caribbean Sea where it meets the Atlantic Ocean. Together, the Lesser Antilles and the Greater Antilles make up the Antilles. The Lesser and Greater Antilles, together with the Lucayan Archipelago, are collectively known as the Caribbean islands or West Indies.

Andesite (/ˈændəzaɪt/) is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende.

Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust.

The Kuril–Kamchatka Trench or Kuril Trench (Russian: Курило-Камчатский жёлоб, Kurilo-Kamchatskii Zhyolob) is an oceanic trench in the northwest Pacific Ocean. It lies off the southeast coast of Kamchatka and parallels the Kuril Island chain to meet the Japan Trench east of Hokkaido. It extends from a triple junction with the Ulakhan Fault and the Aleutian Trench near the Commander Islands, Russia, in the northeast, to the intersection with the Japan Trench in the southwest.

The trench formed as a result of the subduction zone, which formed in the late Cretaceous, that created the Kuril island arc as well as the Kamchatka volcanic arc. The Pacific plate is being subducted beneath the Okhotsk plate along the trench, resulting in intense volcanism.

The Leeward Antilles (Dutch: Benedenwindse Eilanden; Spanish: islas de Sotavento) are a chain of islands in the Caribbean, specifically part of the southerly islands of the Lesser Antilles (and, in turn, the Antilles and the West Indies) along the southeastern fringe of the Caribbean Sea, just north of the Venezuelan coast of the South American mainland. The Leeward Antilles, while among the Lesser Antilles, are not to be confused with the Leeward Islands (also of the Lesser Antilles) to the northeast.

Largely lacking in volcanic activity, the Leeward Antilles island arc occurs along the deformed southern edge of the Caribbean Plate and was formed by the plate's subduction under the South American Plate. Recent studies indicate that the Leeward Antilles are accreting to South America.

The Burma plate is a minor tectonic plate or microplate located in Southeast Asia, sometimes considered a part of the larger Eurasian plate. The Andaman Islands, Nicobar Islands, and northwestern Sumatra are located on the plate. This island arc separates the Andaman Sea from the main Indian Ocean to the west.

To its east lies the Sunda plate, from which it is separated along a transform boundary, running in a rough north–south line through the Andaman Sea. This boundary between the Burma and Sunda plates is a marginal seafloor spreading centre, which has led to the opening up of the Andaman Sea (from a southerly direction) by "pushing out" the Andaman-Nicobar-Sumatra island arc from mainland Asia, a process which began in earnest approximately 4 million years ago.

The South Sandwich Islands (Spanish: Islas Sandwich del Sur) are a chain of uninhabited volcanic islands in the South Atlantic Ocean. They are administered as part of the British Overseas Territory of South Georgia and the South Sandwich Islands. The chain lies in the sub-Antarctic region, about 700 kilometres (430 mi) southeast of South Georgia and 1,700 kilometres (1,100 mi) northeast from the tip of the Antarctic Peninsula.

The archipelago comprises 11 main islands forming an island arc running north–south, the largest being Montagu at 110 square kilometres (42 sq mi). It is divided into four groups, from north to south: The Traversay, Candlemas and Central Islands (Saunders, Montagu, and Bristol), and Southern Thule.

The Tonga–Kermadec Ridge is an oceanic ridge in the south-west Pacific Ocean underlying the Tonga–Kermadec island arc.It is a result of the most linear, fastest converging, and seismically active subduction boundary on Earth, the Kermadec–Tonga subduction zone, and consequently has the highest density of submarine volcanoes.

The Tonga–Kermadec Ridge stretches more than 3,000 km (1,900 mi) north-northeast from New Zealand's North Island. The Pacific Plate subducts westward beneath the Australian Plate along the ridge. It is divided into two segments, the northern Tonga Ridge and southern Kermadec Ridge, by the Louisville Seamount Chain. On its western side, the ridge is flanked by two back-arc basins, the Lau Basin and Havre Trough, that began opening at 6 Ma and 2 Ma respectively. Beyound the basins is the Lau-Colville Ridge. Together with these seafloor structures the ridge forms the eastward-migrating, 100  million year old Lau–Tonga–Havre–Kermadec arc/back-arc system or complex.

The Scotia Sea is a sea located at the northern edge of the Southern Ocean at its boundary with the South Atlantic Ocean. It is bounded on the west by the Drake Passage and on the north, east, and south by the Scotia Arc, an undersea ridge and island arc system supporting various islands. The sea sits atop the Scotia Plate. It is named after the expedition ship Scotia. Many icebergs melt there.

Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Volcanism is the surface expression of magmatism.

Magmatism is one of the main processes responsible for mountain formation. The nature of magmatism depends on the tectonic setting. For example, andesitic magmatism is associated with the formation of island arcs at convergent plate boundaries while basaltic magmatism is found at mid-ocean ridges during sea-floor spreading at divergent plate boundaries.

The Krakatoa Archipelago is a small uninhabited archipelago of volcanic islands formed by the Krakatoa stratovolcano located in the Sunda Strait, nestled between the much larger islands of Java and Sumatra. As of 2018, the archipelago consists of four main islands: Verlaten (a.k.a. Sertung) to the northwest, Lang (a.k.a. Rakata Kecil, or Panjang) to the northeast, Rakata (what remains the main island) to the south, and the currently volcanically active Anak Krakatoa in the north-centre. Together, the islands are a part of the Indonesian island arc system, created by the northeastward subduction of the Indo-Australian Plate. As part of a dynamic volcanic system, the islands have been continuously reshaped throughout recorded history, most notably in the 1883 eruption of Krakatoa.

Administratively, the Krakatoa Archipelago lies entirely within Lampung, Indonesia and forms a part of Ujung Kulon National Park.

The Kermadec Islands (/ˈkɜːrmədɛk/ KUR-mə-dek; Māori: Rangitāhua) are a subtropical island arc in the South Pacific Ocean 800–1,000 km (500–620 mi; 430–540 nmi) northeast of New Zealand's North Island, and a similar distance southwest of Tonga. The islands are part of New Zealand. They are 33.6 km (13.0 sq mi) in total area and uninhabited, except for the permanently staffed Raoul Island Station, the northernmost outpost of New Zealand.

The islands are listed with the New Zealand outlying islands. The islands are an immediate part of New Zealand, but not part of any region or district, but instead an Area Outside Territorial Authority.

The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.

Most of the rock now exposed in the park is granitic, having been formed 210 to 80 million years ago as igneous diapirs 6 miles (10 km) below the surface. Over time, most of the overlying rock was uplifted along with the rest of the Sierra Nevada and was removed from the area by erosion. This exposed the granitic rock to much lower pressure, and it was also subjected to erosion in the forms of exfoliation and mass wasting.

The back-arc region is the area behind a volcanic arc. In island volcanic arcs, it consists of back-arc basins of oceanic crust with abyssal depths, which may be separated by remnant arcs, similar to island arcs. In continental arcs, the back-arc region is part of the continental platform, either dry land (subaerial) or forming shallow marine basins.

An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust, but in some cases the wedge includes the erosional products of volcanic island arcs formed on the overriding plate.

An accretionary complex is a current (in modern use) or former accretionary wedge. Accretionary complexes are typically made up of a mix of turbidites of terrestrial material, basalts from the ocean floor, and pelagic and hemipelagic sediments. For example, most of the geological basement of Japan is made up of accretionary complexes.