The birth of an island is normally a process that requires the movement of vast tectonic plates over centuries, if not millennia.
But in Alaska, a new island has popped up in just four decades.
The two-square-mile (five sq km) landmass, known as Prow Knob, was once entirely surrounded by the deep ice of the Alsek Glacier.
But NASA has revealed that the small mountain has now been entirely surrounded by water, cutting it off from the mainland.
An image taken by the Landsat 8 satellite in August shows that the mountain has now lost all contact with the Alsek Glacier.
According to NASA’s Earth Observatory, this landmass likely transformed into an island sometime between July 13 and August 6.
NASA says that the rapid warming of the planet by human-caused climate change is to blame.
Lindsey Doermann, a science writer at the NASA Earth Observatory, said in a statement: ‘Along the coastal plain of southeastern Alaska, water is rapidly replacing ice.’
Satellite images show how a new island has formed in Alaska over just four years as the Alsek Glacier retreats, and NASA says climate change is to blame
In the early 1900s, the Alsek glacier extended some three miles (five km) further west of the island.
In the earliest recorded observations of the Alsek Glacier, which date back to 1894, the glacier was described as covering the entirety of what is now the Alsek Lake.
Follow-up reports made in 1907 describe the glacier as being ‘anchored to a nunatak’, a rocky outcrop surrounded by flowing glacial ice on all sides.
This nunatak, which came to be known as Prow Knob due to its resemblance to a ship’s prow, was surrounded by an ice face as much as 50 metres (164ft) high.
Even in the 1960s, when aerial photos were made of the glacier, Prow Knob was still noted as a nunatak with ice on all sides.
However, as the climate has warmed due to increased concentrations of greenhouse gases, the once-stable glacier has begun to weaken.
Ms Doermann says: ‘Glaciers in this area are thinning and retreating, with meltwater proglacial lakes forming off their fronts.’
In 1984, NASA took a photo of the glacier using the Landsat 5 satellite, revealing that its westernmost edge had been converted to lake shore.
Between 1984 (pictured) and 2025, the Alsek Glacier has rapidly retreated eastward, covering less and less of the nearby lake
This retreat has left the small mountain, known as Prow Knob, completely exposed on all sides. Experts think the landmass became an island between July 13 and August 6
Over the coming decades, the glacier continued to retreat further and exposed even more of the mountain.
That process became even faster in the 1990s when the glacier’s northerly arm detached from a small island in the middle of the lake.
This made the glacier vulnerable to a process known as calving, in which the front of the glacier becomes unstable and breaks off into icebergs, speeding up the retreat.
Eventually, two glacial tributaries to the north and the south retreated so far that they stopped providing the glacier with any new ice to sustain itself.
Finally, between 2018 and the present day, the glacial retreat began to rapidly accelerate and soon left Prow Knob surrounded by water on all sides.
In addition to creating a new island, this sudden change in the glacier’s limits has also had a profound effect on Alsek Lake.
Since 1984, the lake has grown from 17 square miles (45 sq km) to 30 square miles (75 sq km).
Combined with the nearby glacial Harlequin and Grand Plateau lakes, the three have more than doubled in size in those 40 years.
All across Alaska, glaciers are retreating at a rapid pace. These images show the Yakutat Glacier, Alsek Glacier, and Grand Plateau Glacier in July 1984
By 2024 (pictured), satellite images show that many of the glaciers have rapidly retreated and a the lakes have doubled in size
Glacial retreat has led to the rapid growth of ‘proglacial’ lakes such as Mendenhall Lake (pictured). Scientists say that Alaska is now becoming a ‘new lake district’
All around Alaska, and the world in general, glacial lakes are growing at an alarming rate.
Last year, Mauri Pelto, a glaciologist at Nichols College, warned NASA that Alaska was fast becoming a ‘new lake district’.
This is alarming many scientists because glacial lakes can trigger devastating flash floods.
As glaciers melt, the water drains into depressions once occupied by the glacier, forming huge lakes.
Many of these lakes are only held in place by fragile natural dams made of rock and ice, which were deposited by the glacier over centuries.
If that barrier falls, it can release a wave of water and debris rushing downstream at speeds of 20-60 mph (30-100 kph), destroying everything in its path.
In a study published last year, scientists warned that 10 million people around the world are now at risk of devastating glacial floods.
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