These temporary pieces of real estate are more than just geographical curiosities. They are dynamic natural laboratories, windows into the powerful forces that shape our planet. They are also geopolitical wildcards, capable of creating international disputes over territory and resources that may not exist by next year. Let’s dive into the world of land that comes and goes.

Forged in Fire: The Rise of Volcanic Islands

The most dramatic ephemeral islands are born from the planet’s molten heart. When a submarine volcano, hidden deep beneath the waves, erupts with enough force and persistence, it can breach the ocean’s surface. What follows is a spectacular battle between fire and water.

Initially, these eruptions are often what geologists call Surtseyan eruptions, named after the famous Icelandic island of Surtsey. Explosive interactions between hot magma and cold seawater create colossal plumes of steam, ash, and volcanic rock fragments called tephra. If the eruption continues, this loose material can pile up, forming a cone that rises above the waves. Over time, if lava flows begin to cap this loose pile, the new island gets a protective, rocky shield, giving it a fighting chance against the erosive power of the ocean.

Hunga Tonga-Hunga Ha’apai: A Modern Saga

Perhaps the most famous recent example is Hunga Tonga-Hunga Ha’apai in the Kingdom of Tonga. In late 2014, a submarine eruption began, and by January 2015, it had built a new cone of land that connected two small, pre-existing islands (Hunga Tonga and Hunga Ha’apai). Scientists initially predicted it would erode away within months. Instead, chemical reactions in the warm, salty environment helped cement the volcanic ash into a more durable rock, and the island survived for seven years. It became a priceless site for science, offering a pristine environment to study how life—from microbes to plants and birds—colonizes new land.

Its end was even more spectacular than its birth. In January 2022, the volcano produced one of the most powerful eruptions in modern history, a blast that sent shockwaves around the globe. The event obliterated the new landmass and much of the two older islands, proving just how ephemeral this type of land can be.

Other Fleeting Volcanic Lands

• Surtsey, Iceland: The classic case study. Formed between 1963 and 1967 off the coast of Iceland, Surtsey has been a protected UNESCO World Heritage site since its birth, allowing scientists a unique view of biocolonization. While it has eroded significantly, its core is made of durable lava, and it is expected to last for centuries.
• Zalzala Koh, Pakistan: Not all volcanic islands are made of hot magma. In 2013, a powerful earthquake off the coast of Pakistan pushed a large pocket of methane gas and mud to the surface, forming a “mud volcano” island dubbed Zalzala Koh (“Earthquake Island”). This soft, muddy landmass was no match for the Arabian Sea and had completely washed away by 2016.

Islands of Sand and Silt: The Shifting Coastline

Not all ephemeral islands are born in a fiery spectacle. Many are quietly built by the patient, relentless work of water. These sedimentary islands are formed from sand, silt, and gravel deposited by ocean currents, tides, and rivers.

Barrier islands, sandbars, and river delta islands (known as “chars” in South Asia) are in a constant state of flux. They are built up by accretion, where currents deposit more material than they remove, and worn down by erosion from storms and changing tides. They can migrate, change shape, or disappear entirely over seasons or decades.

The Wandering Islands of the World

The Wadden Sea, stretching along the coasts of the Netherlands, Germany, and Denmark, is a perfect example of this dynamic environment. It is home to a chain of barrier islands that protect the mainland, but also to countless smaller sandbanks and shoals that appear and disappear with the tides and storms. Some, like the Dutch sandbank Noorderhaaks, are large enough to be considered semi-permanent islands, while others are truly ephemeral.

In Bangladesh, the vast Ganges-Brahmaputra delta is home to hundreds of chars. These fertile silt islands support millions of people, but their existence is precarious. A single monsoon flood can wash an entire village’s land away, while new land may form elsewhere. This creates immense challenges for human geography, as communities are forced to become nomadic, following the land as it shifts.

Who Owns Land That Doesn’t Last? The Geopolitical Quagmire

The appearance of a new island isn’t just a matter for geologists and biologists; it’s a major event for international lawyers. According to the United Nations Convention on the Law of the Sea (UNCLOS), a country’s territory includes its islands. Crucially, owning an island grants a nation not only a 12-nautical-mile territorial sea around it but also a massive 200-nautical-mile Exclusive Economic Zone (EEZ). This zone gives the country exclusive rights to all resources in the water and seabed, including fish, oil, and gas.

But what are the rules when the island itself is temporary? UNCLOS defines an island as a “naturally formed area of land, surrounded by water, which is above water at high tide.” A feature that is only visible at low tide (a “low-tide elevation”) doesn’t count. This raises tricky questions:

• How long must an island exist to be claimable?
• What happens to the EEZ if the island that generated it sinks back beneath the waves?
• Can a country artificially reinforce a disappearing island to maintain its claim?

History provides a comical example. In 1831, a volcanic island named Ferdinandea emerged in the Mediterranean Sea, in a strategic spot between Sicily and Tunisia. The British were the first to land and claim it, naming it Graham Island. The King of the Two Sicilies (a precursor to Italy) sent ships to claim it as Ferdinandea. The French and Spanish also prepared their own claims. Before warships could be dispatched, however, the loosely-packed volcanic island eroded away and vanished beneath the waves just a few months later, peacefully resolving the multi-national standoff.

Today, the issue is more acute. Japan, for instance, spends millions reinforcing the tiny, remote atoll of Okinotorishima with concrete and titanium to prevent it from disappearing and taking its vast EEZ with it. China and South Korea argue it’s merely a “rock”, not an “island”, and therefore shouldn’t generate an EEZ, highlighting the immense stakes involved.

A World in Motion

Ephemeral islands are a profound reminder that the Earth’s surface is not static. They demonstrate that coastlines are not fixed lines but dynamic zones of creation and destruction. From the fiery birth of a Surtseyan island to the silent shifting of a sandbar, these fleeting lands offer a unique glimpse into the powerful forces that govern our world. They are where geology, biology, and geopolitics collide—a fascinating, ever-changing frontier on our planet’s map.