People are getting ready to hike to the summit of the volcanic mountain Ok in Iceland, where a memorial will be held for Okjökull. 

Okjökull (which also goes by the name of Ok) is not a person but a glacier. The occasion marks the passing of the first Icelandic glacier lost as a result of climate change – though experts doubt it will be the last.

Satellite imagery taken by the US Geological Survey's Landsat satellites and tweeted by NASA on Monday shows just how drastically things have changed over the last three decades, with before and after shots taken in 1986 and 2019. 

NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey.

The death of Okjökull will be immortalized with a plaque reading:

Ok is the first Icelandic glacier to lose its status as a glacier.

In the next 200 years all our glaciers are expected to follow the same path.

This monument is to acknowledge that we know what is happening and what needs to be done

Only you know if we did it

"This will be the first monument to a glacier lost to climate change anywhere in the world," Cymene Howe, producer of the 2018 film Not Ok documenting the glacier’s demise, said in a press release. 

"By marking Ok’s passing, we hope to draw attention to what is being lost as Earth’s glaciers expire."

Okjökull is thought to have occupied approximately 16 square kilometers (6.2 square miles) in 1890. A little over half a century later (1945) and it had shrunk to 7 square kilometers (2.7 square miles). 

Its rapid retreat continued through the latter half of the 20th century so that it was just 3.4 square kilometers (1.3 square miles) in 2000 and 0.7 square kilometers (0.2 square miles) in 2012. In 2014, it was declared dead.

Iceland has something close to 400 glaciers, many of which could be gone by 2200 if current global warming trends continue. These are the world's largest freshwater reserves and offer valuable information when it comes to understanding the Earth's atmosphere (present and historical).

But glacial retreat isn't unique to Iceland. It is a worldwide phenomenon, affecting every continent bar Australia (which is devoid of glaciers anyhow). Extreme ice melt is becoming a more and more common occurrence. Just last June, for example, Greenland lost more than a billion tons of ice in a day. If current trends remain unchanged, Greenland's ice sheet could be almost entirely iceless by 3000 CE.

Meanwhile, on the other side of the world, Antarctica is melting at six times the pace it was in 1979. This process is triggered by warmer temperatures, itself a product of human-driven climate change.  Last July saw record-breaking heatwaves across Europe and is likely to go down as not just the hottest July, but the hottest month on record. It follows the hottest June on record.  This year's scorching weather is not an anomaly – the last six years have been the warmest in documented history.

As for this week's memorial, Oddur Sigurðsson, a geologist in the Icelandic Meteorological Office, expects 100 people will be gathering to mourn the loss of Okjökull. Let's hope it's a one-off.