On top of the world where the rocky shards of the Karakoram mountain range pierce the blue sky, odd mushroom-shaped ice and rock formations once peppered the landscape.

In a different age there were hundreds, explains Glasgow-based photographer Colin Prior, fresh from his sixth expedition to Pakistan to capture dramatic images of the Himalayan mountains and their shifting glaciers.

Now, however, ice which for centuries raised huge rocks aloft – the more downbeat might view them resembling an atomic explosion than a mushroom – is rapidly receding.

Many of the Karakoram’s Boltaro glacier’s dramatic ‘ice sculptures’ which once added to the mountains’ unique allure, have vanished.

Prior, one of Scotland’s best-known landscape photographers whose images of our own mountains, glens and loch feature on countless calendars, has witnessed at first-hand the changes to the Karakoram’s precious landscape.

Having first trekked to its lofty heights in 2009 – fulfilling a dream which began in his youth when he picked up a library book and fell in love with the Karakoram’s rocky spires – he has seen the ice sculptures gradually shift and vanish.

Now, he says, only a few remain.

“They were once a common feature of the Karakoram glaciers, but they are now all but extinct,” he says. “Hundreds have vanished over the past ten years as temperatures have risen.

“The ice pedestals are like giant mushrooms. When you look at some of the landscapes with these ice sculptures, it could be something straight from a Tolkien novel. They are so exotic.”

Prior, 60, and a team of local guides spent six weeks in the region in June, intent on capturing the remains of the winter’s snow packed into the jagged peaks and crevices of the surrounding mountains.

They trekked first to the Charakusa Glacier and K6 Basecamp, then battled through thick snows and torrential rain to reach the Baltoro Glacier.

One of the world’s longest glaciers outside the polar regions, it stretches for almost 40 miles, overshadowed by K2 and three other 8000m mountains.

It is among a number of Karakoram glaciers are considered among the most stable in the world, retreating at a slower rate – and even growing in mass in some places - while others nearby have dramatically receded.

However, he found just seven of the odd-looking ice sculptures remain intact.

Constantly shifting, retreating and surging, in some respects change is natural. However, Prior, who has built up a collection of hundreds of images of the Karakoram glaciers over his six visits believes climate change has also played a part.

Whether any of the mushroom-like features will be left when he concludes his Karatoum project next year, is anyone’s guess.

“In just the last three or four years, it’s obvious that many of these ice tables have collapsed,” he says.

“If you look at historic pictures taken in the area 100 years ago, you can clearly see there were huge ice features. But in many areas, these ice tables have gone.”

Prior, one of the world’s leading mountain photographers, was inspired to photograph the Karakoram after picking up a library book, The Throne Room of the Mountain Gods, in his early 20s. It revealed mountain landscape of sharp, vertical rocky peaks, deep snowy crevices and vast glaciers which, he says: “Spoke to me so deeply and captivated my imagination like nothing else.

“I went in 1996 and realised I had to go back.”

His Karakoram project will eventually span seven visits over two decades, with plans for a book of images which will showcase the remarkable landscape and create a a record which could help scientists analyse change in years to come.

He believes such a long-term project is unlikely to ever be repeated due to costs, lack of interest from sponsors and a shift towards video over the art of photography.

Simply reaching the area requires careful planning, a large team of ponies, at least 20 porters and guides, several weeks of preparation and miles of trekking.

Even then, there are risks. During one visit in 2013, a group of 11 mountaineers and their porters were murdered in the Karakoram range in a brutal terrorist attack, while there are regular rock falls, loose scree to contend with and deep snow-covered crevices to be aware of.

It is physically demanding too. “We have to carry everything we need to survive. There are no teashops on the way, unlike in Nepal,” adds Prior.

“You develop close relationships - the guy who carries my camera I’ve now known since 2004. Many of the porters are related, and the leader has huge responsibility to look out for everyone’s welfare.”

His latest expedition set off in June, picking a way over a late fall of snow which created a further range of hazards before Prior was rewarded with a vista of spiky, rocky granite peaks and wide glacier valleys.

“The scenery is graphic, are towers, minarets, cathedrals of rock.

“Unlike the Himalayas, most of the mountains are so vertical that they shed snow, exposing their granite and gneiss structures below. The shapes and graphics present the photographer with the ultimate mountain landscape with myriad possibilities.

“Often when you spend time in a place it tends to diminish in size as you get used to it. But in the Karakoram, it seems to grow in stature.”

Prior, who has also published a series of Scottish landscape books, prints and calendars, is now preparing to showcase his Karakoram images and his latest expedition in a series of talks, including one for the Royal Scottish Geographical Society at Edinburgh University’s Appleton Tower, on Wednesday, November 20.

He adds: “I feel very privileged to have visited the Karakoram since 1996, but I have seen the start of changes there.

“Nowhere else has captured my imagination the way the Karakoram has.”