Some volcanic islands increase in size year after year due to the accumulation of lava emitted by underwater or terrestrial volcanoes present on these islands. This process of volcanism allows for the long-term growth and expansion of volcanic islands.
Beneath the Earth's crust, the mantle, a deep semi-fluid layer located beneath our feet, is always in motion. In certain places, warm currents slowly bring up a molten rock called magma to the Earth's surface. When this magma reaches an opening through the Earth's crust, it fuels volcanic activity, constantly supplying the volcanoes with fresh lava. As long as this "feeding" from the depths is regular, the lava gradually accumulates after each eruption, enlarging the volcanic island, much like continually adding material to an already existing pile. Some islands, such as Hawaii, benefit from this phenomenon: situated just above a hotspot in the Earth's mantle, they enjoy a constant upward flow of magma, allowing them to expand their surface year after year.
When a volcano is actively erupting, each eruption releases an impressive amount of lava and volcanic materials that cool on the surface. These successive flows gradually stack up and form new layers of solid rock, slowly increasing the entire surface of the island. With each surge of lava flowing toward the sea, the contact with water causes rapid cooling: as a result, the lava hardens almost immediately, thus creating additional land. Over the years, accumulation after accumulation, these new layers allow the island to expand and rise regularly, gaining in size and height.
Volcanic rock, like basalt, often exhibits high resistance to erosion due to its high density and natural strength. These rocks cool quickly after a volcanic eruption, forming thick and compact layers that are more resistant to the repeated action of waves, winds, and rains. By solidifying quickly, lava leaves little space for water or frost to enter the cracks, limiting the mechanical fragmentation of the rocks. This very hard and compact characteristic makes these islands robust terrains that gradually increase in size, as the new volcanic layers take time to erode away.
Volcanic islands can grow due to earthquakes and ground movements known as tectonic uplift. When two pieces of the Earth's crust push against each other, they sometimes cause a gradual elevation of certain areas. This phenomenon slowly increases the altitude of the island or creates new emerged land from the sea floor. Essentially, these tremors and uplifts reposition the land upwards, slowly enlarging the affected islands. Although it can take time, it works like a sort of very slow and subtle elevator of the Earth's crust!
Over time, plants, algae, and other organisms eventually settle on the still-cool volcanic rocks. Gradually, as they grow and then die, these organisms leave a deposit of organic matter on the island. This matter decomposes slowly and forms the beginning of fertile soil, which in turn promotes new plant and animal species. Little by little, this biological process enriches the upper layer of the island and also slightly expands its boundaries, thanks to the coral reefs or the accumulation of vegetation along the coasts. In this way, the island gains in habitable and fertile surface area, which enhances its long-term development.
Pumice, formed by the rapid cooling of gas-rich lava, can float on water for several years, allowing the transport of plants and small organisms to distant islands, thereby facilitating their biological colonization.
The underwater volcano Hunga Tonga-Hunga Ha'apai, located in the Pacific Ocean, created a new island in 2015, whose initial appearance was expected to be very temporary; however, due to the rapid solidification of its volcanic rock, it has stabilized enough to persist for several years.
The Mauna Loa in Hawaii is the largest volcano in the world by volume. When considering its submerged volume, it even far exceeds Mount Everest in height, including the slope.
Hawaii is home to one of the most active volcanic islands on the planet: the Big Island, also known as the Big Island, is regularly expanding due to the lava produced by the continuous eruptions of Kīlauea.
Yes, notably, the island of Hawaii in the archipelago of the same name continues to grow due to the regular activity of volcanoes such as Kīlauea. Another recent emblematic example is the island of Nishinoshima in Japan, which is experiencing consistent growth due to repeated eruptions.
Some recent volcanic islands, especially when they remain poorly supplied with lava after their formation, are likely to be quickly eroded by waves, ocean currents, or extreme weather conditions, leading to their rapid disappearance.
Generally no, new volcanic lands are initially deserted and barren. However, over time, pioneering organisms such as lichens, mosses, and hardy plants gradually establish themselves, allowing for the gradual development of more complex ecosystems.
Mainly, successive lava flows, deposits from explosive eruptions, repeated emissions of volcanic ash, as well as certain tectonic phenomena, lead to a gradual increase in the size of a volcanic island.
No, only islands with regular volcanic activity and a constant supply of magma from the Earth's mantle can grow. Inactive or extinct islands, on the other hand, are more significantly affected by natural erosion, which gradually reduces their size.
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