The emergence of new islands:
mechanisms of their appearance

It is one of the most fascinating geological processes on our planet – islands arise through the complex interaction of tectonic, volcanic, sedimentary and climatic factors, creating unique ecosystems and geographic formations.

Volcanic activity as the main mechanism

Underwater volcanic activity remains the dominant factor in the formation of new islands. Oceanic eruptions account for approximately 70% of all volcanic activity on Earth, with the majority of underwater volcanoes forming along mid-ocean ridges. As magma erupts through the ocean floor, it accumulates layer by layer, gradually increasing the height of the seamount until it reaches the surface.

A classic example of this process is Surtsey Island off the coast of Iceland, which suddenly emerged from the ocean in November 1963. Over four years of active eruptions, the island reached an area of over a square kilometer, demonstrating how quickly new land can form. Similar processes were observed in 2023 off the coast of Japan, where an underwater volcano created a new island approximately 100 meters in diameter in less than a week.

Hydrostatic pressure at great depths has a significant impact on the nature of eruptions. At depths exceeding 3,000 meters, water pressure inhibits gas release from the magma, resulting in more sedate lava flows. At shallower depths, the interaction of hot lava with cold seawater creates explosive conditions that facilitate the rapid accumulation of volcanic material.

Hotspots and island chains

Hotspot theory explains the formation of extended island chains, such as the Hawaiian Islands. Stationary mantle plumes create rising currents of molten rock that erupt through a moving tectonic plate. As the plate moves over the hotspot, a chain of volcanoes of varying ages forms — the youngest located directly above the plume, while the oldest gradually move away from the magma source.

The Hawaiian-Emperor seamount chain stretches 6,000 kilometers across the Pacific Ocean, revealing a 70-million-year history of a single hotspot. The youngest island, the Big Island of Hawaii, continues to grow thanks to active eruptions, while islands farther from the hotspot are eroding and gradually sinking.

Tectonic processes and uplift

Collisions between tectonic plates create the conditions for the formation of island arcs through the process of subduction. When one oceanic plate subducts beneath another, the released volatiles cause the mantle above the subduction zone to melt. The resulting magma rises to the surface, forming chains of volcanic islands with characteristic arc-shaped shapes.

The Japanese islands are the result of the interaction of three tectonic plates — the Pacific, Philippine, and Eurasian. This complex subduction system has created over 200 volcanoes, 60 of which remain active. Similar processes led to the formation of the Caribbean islands, where the subduction of the South American Plate beneath the Caribbean Plate created the Lesser Antilles with their active volcanoes.

Tectonic uplift can push existing coral reefs above sea level, creating limestone islands with rocky shores. The islands of Tonga and Nauru demonstrate this formation mechanism, where ancient reefs were uplifted by tectonic forces tens of meters above modern sea level.

Coral atolls and biogenic construction

The formation of coral atolls represents a unique example of biological involvement in island creation. Charles Darwin’s theory of subsidence explains the three-stage process of atoll development: a fringing reef around a volcanic island, a barrier reef with a lagoon, and finally, a ring atoll after the original island has completely submerged.

Coral polyps build their calcium skeletons in symbiosis with zooxanthellae algae, creating massive reef structures over thousands of years. The rate of coral growth must match the rate of subsidence of the volcanic base to ensure the reef remains in the sunlit zone of the ocean. The process of atoll formation can take anywhere from 1 to 30 million years, depending on the rate of coral growth and the rate of subsidence.

The Maldives exhibit active formation of new coral islands. Research shows that many of these islands formed during periods of higher sea levels 1,600 to 4,200 years ago, when sea waves deposited coral debris on reef platforms. This process continues today, especially on shallow reefs with nearly full lagoons.

Glacial processes and land exposure

Melting glaciers due to climate change are becoming a significant factor in the emergence of new islands. Retreating glaciers expose previously hidden land masses, which become surrounded by water when completely free of ice.

Between 2015 and 2018, more than 30 new islands, capes, and bays were discovered in the Russian Arctic in the Novaya Zemlya and Franz Josef Land archipelagos. Five islands, ranging in size from 900 to 54,500 square meters, emerged near the Vylki Glacier as a result of the melting of the ice covering them. Similar processes are occurring in Greenland and Alaska, where retreating glaciers are exposing new sections of coastline.

In Alaska’s Glacier Bay National Park, a new island of approximately 2 square kilometers formed in 2025 after the retreating Alsek Glacier ceased encircling Prow Knob. Alsek Lake has grown from 45 to 75 square kilometers since 1984, demonstrating the scale of the glacial retreat.

Between 2000 and 2020, retreating glaciers created 2,500 kilometers of new coastline and 35 new islands in the Arctic. The Zacharias Isstrøm glacier in northeastern Greenland alone exposed 81 kilometers of new coastline — more than any other glacier in the study.

Sedimentation processes and barrier islands

Barrier islands form through the accumulation of sand and other sediments under the action of waves, currents, and wind. Four key conditions are necessary for their formation: an abundant sand source, a gently sloping continental shelf, wave activity exceeding tidal activity, and a slowly rising sea level.

Bribie Island off the coast of Queensland, Australia, was formed by the intertidal transport of sand along the eastern Australian coast. The process began thousands of years ago during sea level fluctuations following the last ice age. The gradual accumulation of sand, stabilized by vegetation, created the long, narrow structure of today’s barrier island.

River islands form as a result of sediment accumulation in riverbeds. The interaction between pioneer vegetation and sandbars leads to vertical sediment accumulation. Plants create barriers to water flow, facilitating sedimentation and sediment fixation. This process can lead to rapid island growth over several hundred years.

Mud volcanoes and gas emanations

Mud volcanoes represent a unique mechanism of island formation associated with the ejection of a mixture of water, gases, and sediment under high pressure. Unlike magmatic volcanoes, mud volcanoes are not associated with molten rock, but are formed as a result of excess pressure from underground fluids within sedimentary strata.

In the Caspian Sea, the Kumani Bank mud volcano periodically creates temporary islands. In 2023, a new island approximately 400 meters in diameter emerged after an eruption, but by the end of 2024, it had been almost completely eroded by sea waves. Since 1861, this volcano has created islands eight times, with the largest, in 1950, reaching 700 meters in diameter and 6 meters in height.

The formation of mud volcanoes is associated with the accumulation of fine-grained, gas-saturated sediments at depths greater than 1.5-2 kilometers in an active tectonic environment. Excessive pore fluid pressure becomes the primary driving force for the eruptions of mud breccias toward the surface. Approximately 86% of the gas released is methane, with smaller amounts of carbon dioxide and nitrogen.

Hydrothermal systems and underwater springs

Hydrothermal vents form where seawater penetrates through cracks in the ocean floor, particularly along tectonic plate boundaries and underwater volcanic regions. Cold seawater is heated by magma chambers to temperatures reaching 400°C and rises back to the surface enriched with minerals and chemicals.

The Beebe Hydrothermal Field in the Caribbean Sea is the deepest known cluster of hydrothermal vents, at a depth of nearly 5,000 meters. These systems create distinctive chimneys of mineral deposits that can reach heights of up to 60 meters. While most hydrothermal vents do not result in the formation of islands, they do create localized seafloor uplifts and unique geological structures.

Near Bangka Island, hydrothermal vents heat water to 41°C, compared to an ambient sea temperature of 29°C. Geothermal activity alters the chemical composition of seawater and creates specific conditions for the development of unique ecosystems based on chemosynthesis.

Anthropogenic creation of islands

Artificial islands represent a modern method of creating new land through human activity. Technological advances make it possible to construct artificial islands at depths of up to 75 meters using reclamation and drainage methods.

The primary construction method involves dredging sand or soil from the seabed and transporting the material to the construction site via pipelines or barges. After reclamation, the soil is stabilized using geotextiles, compaction, and other engineering solutions. Vegetation is planted to prevent erosion and further stabilize the island.

Preventing the collapse of artificial islands requires a comprehensive approach, including shoring up the foundation with piles, constructing concrete or stone breakwaters or dams, soil stabilization, and regular monitoring. Engineering solutions may include geotubes, gabions, or breakwaters, depending on the specific conditions and challenges.

Climate change and sea level

Sea level changes play a critical role in the formation and disappearance of islands. Global warming is melting glaciers and ice sheets, leading to a mean sea level rise of 3.2 millimeters per year since 1993. For low-lying island states like Kiribati and Tuvalu, where the maximum elevation is less than two meters above sea level, this poses an existential threat.

The Pacific island nations are experiencing sea level rise above the global average. Sea surface temperatures in the region have risen three times faster than the global average since 1980, and marine heatwaves have roughly doubled in frequency since the same period. NASA analysis shows that countries such as Tuvalu, Kiribati, and Fiji will face sea level rise of at least 15 centimeters over the next 30 years, regardless of changes in greenhouse gas emissions.

Paradoxically, some coral islands can grow under conditions of moderate sea level rise. Research in the Maldives has shown that the islands actually formed during periods of higher sea levels in the past, when increased wave action facilitated the deposition of coral material on reef platforms. However, this process requires healthy coral reefs capable of producing sufficient sediment.

Erosion processes and island stability

Newly formed islands are subject to intense erosion, especially in the first years after their formation. Surtsey Island lost a significant portion of its original mass due to coastal erosion — in the winter of 1967-1968, the southern side of the lava fields retreated 140 meters, with an average retreat of 75 meters.

The rate of erosion decreases sharply as the volcanic material consolidates. In the first years after the eruption, the rate of coastal erosion on Surtsey was 5-6 times higher than today’s due to the less cohesive nature of the lava apron at the shelf edge. Tuff cones eroded 2-3 times faster in the first years due to the unconsolidated and unbound nature of the material.

Wind deflation and surface runoff also contribute to the erosion of tuff cones and slope deposits. The total volume loss from these processes on Surtsey amounted to 1.6 million cubic meters, with a current erosion rate of 0.03 million cubic meters per year. Extrapolation from the current erosion rate suggests that the island will become a rocky cliff in approximately 100 years.

Modern examples of island formation

Recent decades have provided numerous examples of active island formation. In 2013, a magnitude 7.8 earthquake created the island of Zalzala Koh off the coast of Pakistan, which remained until 2016. That same year, a new islet, 200 meters in diameter, formed off Nishinoshima, Japan, in less than four days after an underwater eruption.

Tonga regularly witnesses the creation of new islands as a result of underwater volcanic activity. In 2022, an eruption in the Hunga Tonga region created a new island, although most such formations in this region are relatively short-lived due to active wave erosion. An exception was the island created by the Leit-iki volcano in 1995, which lasted 25 years.

In 2023, the Zubair Island group in the Red Sea off the coast of Yemen demonstrated the cyclical nature of volcanic island formation. Jadid Island, formed in 2013, and Sholan Island, formed in 2011, demonstrated varying resistance to marine erosion depending on the composition and structure of the volcanic material.

Ecological succession on new islands

Islands formed by volcanic activity provide unique laboratories for studying ecological succession. Surtsey was declared a nature reserve in 1965 specifically to study colonization processes by plants, insects, birds, seals, and other life forms. Over the decades, diverse ecosystems have developed on the island, demonstrating how life adapts to new conditions.

Anak Krakatau, the "child of Krakatau," which emerged in 1930 in the flooded caldera of the famous Indonesian volcano, has developed rich tropical forests despite periodic destruction by frequent eruptions. A population of wildlife, including insects, birds, rats, and even monitor lizards, has successfully established itself on the island, demonstrating life’s remarkable ability to colonize new territories.

The speed of biological colonization often exceeds scientists’ expectations. Canyons, gullies, and other landforms that typically take tens of thousands or millions of years to form can appear within a few years of an island’s formation. This demonstrates that geological processes can occur much more rapidly than previously thought.

Future Prospects of Island Formation

Predicting future island formation requires taking into account multiple factors, including tectonic activity, climate change, and anthropogenic impact. Continued global warming will contribute to further glacier melt, potentially exposing new land masses in the polar regions.

Volcanic activity remains the most predictable source of new islands, especially in tectonically active regions of the Pacific Ring of Fire. Monitoring underwater seismic activity and thermal anomalies allows for partial prediction of the potential locations of new volcanic islands.

Artificial islands will continue to be created for a variety of purposes, from housing to industrial needs and strategic interests. Technological advances make construction possible at ever greater depths, expanding the potential areas for creating new land.

Coral islands face an uncertain future in the face of ocean acidification and rising water temperatures, which threaten the health of reef-building corals. However, some studies suggest that moderate sea level rise could activate island formation processes under certain conditions.