One of Nova Scotia's best-known landmarks is gone but a local museum wants the public to share their memories and photographs of the Long Island arch, in the hope it can reconstruct what happened.

The sea arch in the Five Islands area in the Minas Basin collapsed overnight on Monday.

Tim Fedak, curator of the Fundy Geological Museum wants to remember the arch and find out what everyone in the community knows about it.

"The Five Islands is one of the most stunning vistas along the Parrsboro shore," he told CBC's Maritime Noon. "As people drive along the northern shore of the Minas Basin, these five islands provide really stunning scenery.

"The arch is in one of the larger islands — Long Island — or was in one of these islands and it was quite a hole you could actually see through to the other side of the shore." 

Fedak called it an iconic image for this part of the province. 
 
"People return to them year after year and capture more and more images and develop a relationship with the place. It's a powerful place to experience."

He said he has received reports from people who heard the collapse through the night on Monday. Many people have been sending in their photos to the museum over social media, especially from the days leading up to the collapse.

"It might be neat to reconstruct the 'scene of the crime' and gather that photographic evidence of the process of losing the arch," he said. 

Long Island sea arch

The photo on the left shows the Long Island sea arch before it collapsed overnight Monday. The one on the right shows Long Island minus its sea arch. (Michel Lajoie (left)/ Harold Nesbitt (right))

So, how did it happen?

Fedak said he doesn't believe the collapse was gradual. 

"It seems to be one of these, what we call, cataclysmic failures," he said.

"The rocks of the island are made of what is called basalt, which is cooled magma. It's a very hard rock but the basalt also has traces of ancient earthquakes that cut through them.

"They formed when Pangea, the supercontinent, was ripping apart 200 million years ago as dinosaurs were walking the area." 

He said the faults cause weaknesses in the rock and it's difficult to predict when this type of failure will happen. 

A dead giveaway of an eroding cliff is if boulders or sediment are seen at the base of the cliff. 

"That might not be an area you want to spend a lot of time directly in front of. Cliff erosion can be slow but it can also be very, very quick — like has happened here," said Fedak.  

On Nov. 1, the museum is hosting a community session, called Remember the Five Islands Arch, between 1 p.m. and 4 p.m. AT.

Fedak said it will be interesting for people to gather and discuss when the arch first formed, who has the earliest picture, and who captured the last photo of the arch before its catastrophic collapse. 

"The landscape here is constantly evolving," he said.

"These are the world's highest tides that do cause tremendous erosion along the shore, so people are aware that the landscape changes, and it's sad when we lose something as dramatic as the Long Island arch. But we now, perhaps, will soon have a sixth island which will be kind of a neat thing."