Australian Defence Force (ADF) personnel have rehabilitated a tsunami-damaged monument that marks where Tonga's first Catholic mass was conducted in 1842 on Pangaimotu Island.

HMAS Adelaide ship's crew have been undertaking general clearing tasks on the island and took the time to clear debris from the monument because of its importance to the island's community.

Navy padre Chaplain Kate Lord said a dozen Navy and Army personnel scrubbed the cross clean and cut back overgrown vegetation around it.

"The cross was covered in black dirt, sand and ash since the tsunami last month, and the vegetation was obscuring the view," Chaplain Lord said.

"It was lovely to see everyone pulling together, picking up a broom, spade or saw.

"Hopefully when the sun shines on it, it can be seen from the main island and inspire the people in their faith."

The ADF team also cleaned a thick rope decorating a low wall around the monument.

The first Catholic mass in Tonga was conducted by Father Joseph Chevron under a large banyan tree.

"Christian faith is very important to the people of Tonga," Chaplain Lord said.

Navy sailors Seaman Harrison Southern-Gale, left, and Seaman Georgia Wild help restore the Catholic monument on Pangaimotu Island, Tonga. Photo: Corporal Robert Whitmore

Rehabilitating the monument also meant a lot to Army soldier Sergeant Alefosio Kakala.

"Coming from a Catholic background, the Pangiamotu cross has a special place in my heart," Tonga-born Sergeant Kakala said.

Navy sailor Petty Officer Jacob Machen led the clean-up team and said it was a rewarding task.

"There was a really good vibe as we worked on the monument," Petty Officer Machen said.

"When we sailed to Tonga for Operation Tonga Assist it was unknown what we were coming in to.

"It was unfortunate what happened to Tonga, but hopefully we can give a little back to the people by lending a hand with recovery operations."

The ADF is deployed on Operation Tonga Assist 2022 as part of the Australian Government's support to the Tongan Government following the eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano.

For more Operation Tonga Assist 2022 imagery, go to the Defence image gallery.