Notable Islands Across the World: Volcanic Origins and Living Landscapes

Five islands, five geological clocks

Islands can look like self-contained worlds, yet none is ecologically sealed. Seeds arrive on wind and ocean currents; birds carry them between coasts; people introduce crops, livestock and sometimes invasive species. The land itself keeps changing, too. Lava builds new ground, waves cut cliffs, coral grows over sinking volcanic foundations, and erosion lowers old mountains. These processes operate on clocks that range from a few years to tens of millions.

The contrast among Surtsey, Madeira, Jeju, the Galápagos and Madagascar makes those timescales unusually clear. Surtsey emerged during an eruption that began on November 14, 1963. Jeju is dominated by a volcanic shield and the 1,947-metre Hallasan. Madeira is an Atlantic volcanic island whose steep relief gathers distinct climate zones over short distances. The Galápagos sit above a hotspot whose motion relative to the Nazca Plate has left islands of different ages. Madagascar, by contrast, is a continental fragment separated from other landmasses over geological time.

These are not interchangeable examples of “island biodiversity.” Their origins establish different starting conditions: young, bare lava; rugged volcanic slopes; oceanic islands repeatedly renewed by eruptions; or an old landmass with a long record of isolation. Ecology develops within those constraints, but it does not follow a single script.

Surtsey: a new island under observation

On November 14, 1963, an underwater volcanic eruption south of Iceland broke the sea surface. The eruption continued intermittently until June 1967, building Surtsey from volcanic material. At first, the exposed surface was hot, unstable and nearly devoid of soil. Waves and weather immediately began to reshape it. The island’s early form was therefore not a finished stage but a moving boundary between volcanic construction and marine erosion.

Surtsey offers an exceptionally well-documented example of biological colonization because researchers began observing it while it was still forming. The island was protected as a nature reserve in 1965, and access has been tightly controlled. That restriction matters: researchers can study arrivals and establishment with less disturbance than would be possible on a routinely visited island. UNESCO added Surtsey to its World Heritage List in 2008, recognizing its scientific value as a natural laboratory.

Colonization did not mean that a complete ecosystem appeared at once. The first organisms faced bare surfaces, exposure to salt spray and a shortage of organic matter. Seeds and spores could arrive in wind, drift in seawater or be transported by birds. A seed landing on lava, however, is not the same as a plant becoming established. It must encounter suitable moisture and nutrients, survive disturbance and eventually reproduce. Early vegetation can alter those conditions by trapping windblown material and adding organic matter as plant tissue breaks down.

Birds help connect these steps. They can bring seeds, deposit nutrients and create nesting areas where vegetation may gain a foothold. As colonies expand or shift, their effects on soils and plants also change. Surtsey’s ecology is thus not simply a list of species that arrived after 1963; it is a record of relationships forming on a young, changing surface. The distinction is useful in island ecology more broadly: arrival, survival and establishment are separate filters.

Surtsey’s story also demonstrates why “new land” does not remain pristine in a simple sense. Erosion has reduced the island’s area since its emergence, while plant communities and animal activity have developed in places where conditions allow. Geological construction and ecological succession proceed simultaneously. The island is both a product of a volcanic event and an ongoing experiment in how life takes hold on newly exposed ground.

Madeira: steep relief, compressed climates

Madeira rises from the Atlantic west of Morocco as a rugged volcanic island shaped by successive eruptions, faulting, erosion and marine exposure. It belongs to the Madeira archipelago, which also includes Porto Santo and smaller islands. The island’s volcanic origin is clear in its steep slopes and dissected valleys, but the present landscape is not simply a stack of fresh lava. Water has cut deeply into the terrain, and coastal processes have carved cliffs from the island’s margins.

The elevation changes are ecologically consequential. Moist air carried from the Atlantic encounters high ground, producing strong differences in rainfall and exposure across relatively short distances. The island’s laurel forest, or laurisilva, is a relict subtropical forest associated with humid conditions and once more widespread across parts of southern Europe and the Atlantic region. Madeira’s surviving laurel forest is especially valuable because it preserves habitat and ecological relationships that have disappeared or contracted elsewhere.

Laurisilva is not merely a scenic label. Its evergreen trees intercept moisture, while mosses, ferns and other plants occupy damp, shaded conditions. The forest’s structure creates a habitat with its own light and humidity patterns. In Madeira’s steep terrain, catchments and slopes also shape how water moves from uplands toward the coast. A change in vegetation cover can influence soil stability and runoff, making forest conservation relevant to both biodiversity and physical landscape processes.

Madeira’s history also shows how human land use can transform an island without erasing its geological foundations. Settlement, agriculture and introduced species have altered many habitats. The steep terrain limits some forms of land use while channeling others into valleys and coastal zones. In this sense, the island’s ecology reflects both volcanic topography and a long history of human decisions. Its living landscape is not untouched nature, but neither is it reducible to human modification: old forest refuges and endemic species retain distinct ecological value.

For comparison, Madeira’s volcanic origin is not identical to the Galápagos hotspot system or Jeju’s shield-volcano landscape. The precise history of volcanic construction in the Madeira region is complex, and the island should not be treated as a textbook copy of a single mechanism. The more useful lesson is that volcanic islands can develop very different forms depending on eruptive history, erosion, climate and age.

Jeju: a shield volcano and lava-tube terrain

Jeju, off the southern coast of the Korean Peninsula, is a volcanic island built largely from basaltic eruptions. Hallasan rises at its centre to 1,947 metres, making it the highest mountain in South Korea. Its broad profile reflects shield-volcano construction: relatively fluid basaltic lava can travel away from an eruption centre and accumulate in wide, overlapping flows. Later eruptions and erosion further shaped the island’s slopes and coast.

One of Jeju’s most distinctive geological features lies below ground. As the exterior of a lava flow cools and hardens, molten lava may continue moving through its interior. If the flow drains, it can leave behind a tube-like cavity. Jeju’s lava tubes include some of the longest and best-known examples in the world; the Geomunoreum lava tube system is part of the island’s UNESCO-listed volcanic landscape. These passages are not decorative caves in limestone. Their geometry records the movement and cooling of lava.

Jeju also contains numerous small volcanic cones known as oreum. Together with Hallasan, lava fields and coastal features, they create a varied landscape across an island that is compact compared with Madagascar or the Galápagos archipelago. Elevation, aspect, wind and distance from the coast produce local differences in moisture and temperature. Those gradients help explain why a single island can contain multiple habitat types without spanning a continent-sized area.

The volcanic substrate influences soils, drainage and vegetation, although the relationship is not mechanically simple. Basalt may weather into fertile soils, but slope, rainfall, age of the surface and land management affect how much soil develops and where it accumulates. Lava tubes and other formations also create underground habitats and preserve evidence of eruption sequences. Jeju is therefore an instructive place to connect a visible landform—the central shield and its cones—to less visible processes such as lava transport, soil development and groundwater movement.

Jeju’s cultural landscape is equally tied to its physical setting. Settlements, fields and coastal livelihoods have adapted to volcanic terrain, while local knowledge has developed around wind, water and stone. A geological account should not imply that people merely occupy a pre-existing natural stage: island communities shape landscapes through cultivation and infrastructure, and their histories are part of how environments function.

The Galápagos: a moving hotspot and an age gradient

The Galápagos Islands lie in the Pacific Ocean, roughly 1,000 kilometres west of mainland Ecuador. Their volcanoes formed as the Nazca Plate moved over a mantle hotspot. In simplified terms, magma rises through the moving plate, building volcanic islands; as the plate continues onward, older volcanoes are carried away from the principal source of activity. This helps produce a broad age pattern: the western islands, including Fernandina and Isabela, are among the youngest and most volcanically active, while islands farther east are generally older and more eroded.

Fernandina, one of the archipelago’s youngest major islands, is an especially clear example of ongoing volcanic construction. Isabela is the largest island and contains several large shield volcanoes. Farther east, Española is older and has experienced a longer interval of erosion and ecological change. The sequence is not a perfect conveyor belt—volcanic systems are complex, and individual islands have their own histories—but the age gradient gives researchers a way to examine how landscapes and communities change through time.

That gradient matters to ecology because a newly formed lava field offers different opportunities from an older, more weathered island. Soil development, freshwater availability, vegetation cover and habitat complexity can change as a landscape ages. Isolation then affects which organisms reach each island and whether populations persist or evolve independently. The Galápagos’ famous endemic species are part of this history, but the underlying scientific point is broader: geological age, distance between islands and dispersal ability interact to shape community composition.

Darwin’s visit to the Galápagos aboard HMS Beagle in 1835 is a well-documented moment in the archipelago’s scientific history. His observations later contributed to thinking about variation and species, but the islands’ ecological significance is not limited to that episode. Ongoing research examines volcanic activity, marine and terrestrial ecosystems, introduced species and conservation management. The archipelago is inhabited, visited and protected through complex institutions, so its ecological future is connected to human choices as well as geological processes.

It is tempting to describe the Galápagos as a natural laboratory in which isolation produces unusual species. That shorthand misses the mechanism. Isolation can reduce routine exchange with mainland populations, but it does not stop dispersal. Organisms arrive irregularly; some establish, while others fail. Populations that persist encounter local environments and may diverge over generations. The outcome depends on chance, habitat and biology—not isolation alone.

Madagascar: an ancient fragment, not an oceanic volcano

Madagascar stands apart from the four volcanic examples. It is a large continental island whose geological history is bound to the breakup of Gondwana. Madagascar separated from Africa roughly 160 million years ago and later became isolated from India around 88 million years ago, as continental plates shifted and the Indian Ocean opened. Those events long predate the island’s modern ecosystems, but they created the deep separation that has shaped its biological history.

Its size and varied environments distinguish it from small oceanic islands. Madagascar stretches across tropical latitudes and contains humid eastern forests, drier western landscapes and distinctive southern habitats. Elevation and rainfall patterns create strong regional contrasts. The island’s geology is also varied, with ancient crystalline rocks across much of the east and central highlands, alongside sedimentary basins and younger volcanic features in some areas. Calling Madagascar “volcanic” without qualification would obscure the continental foundation that makes its history so different from Surtsey or the Galápagos.

Long isolation has helped produce high endemism: many species occur naturally only in Madagascar. Lemurs are among the best-known examples, but the island’s distinctive biodiversity includes many other mammals, reptiles, amphibians and plants. Endemism does not mean that species evolved in complete isolation from all outside influence. Ancestors arrived at different times, and dispersal across water has occurred. Rather, it describes the present geographic range of a species and reflects a long history of arrival, survival, diversification and extinction.

Madagascar also makes clear that geological age alone cannot explain ecological richness. Its large area provides room for varied habitats and populations, while isolation limits routine exchange with continental communities. Climate gradients and topographic barriers create further divisions. At the same time, human settlement and land use have transformed ecosystems over many centuries, and contemporary pressures—including habitat loss—affect the survival of endemic species. The island’s biological distinctiveness is therefore both a product of deep time and a conservation challenge in the present.

Compared with Surtsey, Madagascar offers an almost opposite view of island history. Surtsey’s biological record begins with a precisely dated eruption in the twentieth century. Madagascar’s ecosystems reflect a far longer sequence of continental separation, dispersal and evolution. One can observe colonization on Surtsey over decades; Madagascar requires geological and evolutionary evidence to reconstruct events spanning millions of years.

Reading geology through living landscapes

Comparing these islands is most useful when geology is treated as a set of conditions, not a direct blueprint for every species. A volcanic surface can offer mineral-rich material, but plant establishment depends on climate, soil formation and dispersal. An old island may have deep soils and varied habitats, yet its ecology also depends on extinction, human land use and connections to other landmasses. Geology shapes the stage; ecological history determines what happens there.

The species-area relationship offers one way to frame a comparison. In island biogeography, species richness often rises with area, commonly represented as S = cA^z, where S is the number of species, A is area, and c and z are fitted constants. The equation is a pattern, not a promise that every larger island has more species than every smaller one. Madagascar’s vast area and habitat range differ radically from Surtsey’s small, young surface. But area alone cannot explain their contrasting communities: island age, isolation, climate and evolutionary history matter too.

These cases also demonstrate why island boundaries are ecological filters rather than walls. Ocean currents and prevailing winds affect the direction and likelihood of dispersal. Birds can carry seeds across water. Human transport may move organisms much more rapidly than natural processes, sometimes with damaging consequences. Once a species arrives, the island’s geology and climate influence whether it can establish. The sequence—from transport, to arrival, to survival, to reproduction—helps make sense of why some islands acquire distinctive communities while others remain relatively species-poor.

For students, a useful comparison begins with a map and a timescale. Locate each island relative to the nearest continent and tectonic plate boundary. Then ask what built its land, how old its exposed surface is, and what processes are still changing it. On Surtsey, the key date is the 1963–1967 eruption. In the Galápagos, plate motion over a hotspot helps explain the west-to-east age pattern. On Jeju, basaltic shield construction and lava tubes reveal how flows moved. In Madeira, relief and Atlantic moisture help organize habitats. In Madagascar, continental separation and vast environmental variation frame a much older biogeographic story.

None of these landscapes is static. Surtsey continues to erode; volcanic activity remains part of the Galápagos; Madeira’s slopes channel water and support forest refuges; Jeju preserves lava features beneath and above ground; and Madagascar’s habitats continue to respond to climate and human pressure. The islands’ differences are not just a catalogue of origins. They are evidence of how landforms, time and living communities continually shape one another.

A comparative field-notes summary

• Surtsey, Iceland: emerged during an eruption beginning November 14, 1963; a protected site for studying colonization and ecological succession on young volcanic land.
• Madeira, Portugal: a rugged Atlantic volcanic island where elevation, rainfall and surviving laurel forest create sharply differentiated habitats.
• Jeju, South Korea: a basaltic volcanic island dominated by 1,947-metre Hallasan, with shield-volcano landforms, oreum cones and lava tubes.
• The Galápagos, Ecuador: oceanic volcanoes formed over a hotspot beneath the moving Nazca Plate, with younger, more active islands generally to the west.
• Madagascar: a continental island isolated through Gondwanan breakup, with long evolutionary histories and exceptionally high endemism.

Together, these examples show why “island” is a geographic category, not a single geological or ecological condition. A new volcanic cone, a weathered Atlantic mountain, a hotspot archipelago and an ancient continental fragment all meet the sea, yet each carries a different record of formation and life. Reading those records side by side turns islands into more than isolated points on a map: they become precise accounts of change, written in rock, habitat and time.