Can you guess how old the oldest part of Ireland is?

Inishtrahull, an island off the coast of Co Donegal, has the oldest rocks in Ireland, according to one scientist on the new RTÉ One series “The Island.”

In the debut episode of the new Irish series "The Island," presenter and biologist Liz Bonnin speaks with Dr. Brian McConnell of Geological Survey Ireland about the Donegal island which has rocks that date back some 1.8 billion years.

“This is the oldest part of Ireland,” Dr. Brian McConnell tells Bonnin while on Inishtrahull in the debut episode, entitled "Land," of the three-part series.

“These rocks are 1,779 million years old, nearly 1.8 billion, which is an unimaginable amount of time in the human time scale.”

Inishtrahull, about about 10km off of Malin Head and the most northerly island of Ireland, was once a thriving inshore fishing community, according to What's On Donegal. While the island saw an almost 100% population increase between 1881 and 1901, a combination of factors in the early 1900s compelled islanders to evacuate; no one lives on the island today. The island is now designated a Special Area of Conservation and a Special Protection Area by Ireland's National Parks and Wildlife Service.

Elsewhere in the show's debut episode, Bonnin learns about the Iapetus Suture in Clogherhead, Co Louth, which, as Irish geologist John Walsh explains, is "probably the most formative thing in Irish geology."

Walsh says that the Iapetus Suture is "the boundary between a continent that used to be to the north, and a continent that used to be to the south, and the join is the Iapetus Suture.

"We've had a collision. So the north and south of Ireland have collided with each other and all these layers deposited in a deep ocean ... they've all been squeezed and folded and we're looking at, I suppose, we're effectively looking at the collisional smoking gun."

Ahead of the premiere of the "The Island," Bonnin told RTÉ: “I don’t think I could ever have imagined just how much the island has gone through since its first rocks formed 1.8 billion years ago, on the other side of the planet. Just how many different climates, ice ages, collisions, and intense volcanic episodes it has survived - and that’s just the half of it!”

She added: “It’s incredibly humbling to understand the extent of geological activity that has gone into the formation of our home, as you stand on its weathered rocks and think about its history.”

The second episode of "The Island," entitled "Water," airs this Sunday, September 18 on RTÉ One in Ireland, while the third episode, entitled "Life," airs on RTÉ One in Ireland Sunday, September 25.