"We're standing on a log," the geologist said. "A coalified tree log.

"There are dozens of trees around here. You can see the density of them.

"There are trees everywhere."

The trees are embedded in the rock, and the wood has been turned to stone.

Initially, the petrified trees can be hard to see, but Roz Kerr points out the straggling lines that are fallen trunks and branches, and circular shapes indicating stumps.

"The bark has been coalified and the inside of the tree has been replaced by silica," she said.

The geologist shows fragments of leaves in the rock and gestures at the growth rings of a tree.

"The texture of the wood has been replaced by chalcedony [a mineral]," she explained. "The wider rings are summer growth, the tiny, skinny ones are when the plant almost shut down during winter. It didn't really grow."

To Roz Kerr, this platform just below the Marine Rescue station at Reid's Mistake Head, on the southern side of the lake's entrance and facing the sea, is not just a shelf of rock being constantly shaped and whittled by the waves and wind, it is a storybook for the ages.

"Geology is about imagination and stories," she said. "Interpreting the rocks, stories from the rocks. This is a good storybook."

And the story told here is one filled with drama.

While it was a blustery and rain-spattered day for the tour by the Newcastle Ramblers Bushwalking Club, the conditions were idyllic compared with what was happening here 253 million years ago, when it is believed the forest growing in a peat swamp was destroyed.

"It was a catastrophic event," Roz Kerr said.

She explained how a nearby volcano erupted, producing a sideways blast of hot gases and ash.

That blast knocked over many trees, their trunks snapped off near the base. The fallen trees were buried under the volcanic ash, which formed into the rock known as tuff coating much of this coastal platform. So the event that destroyed the forest simultaneously began the process of preserving it.

Having been buried, the remains of the forest were compacted and covered by more layers of sand, stones and silt over thousands of years. The peat bog gradually turned into coal. A seam of coal runs through the platform.

The petrified forest was revealed as the rock platform's layers were eroded by Father Time and Mother Nature.

"It's millions of years in the making," said Roz Kerr.

And what has been made, she said, was one of the most significant sites of its type in the region.

"It's probably the best exposure of a fossil forest that's annihilated by a volcanic eruption in the Hunter," she said.

"There are not many places you can see such exposure."

But that exposure and accessibility open up the site to potential risk and damage, Roz Kerr said, highlighting the need for not just governments but the community to protect it.

On the tour was Peter Downes, who, like Roz Kerr, worked for many years at the government department, Geological Survey of NSW. He said this was a very significant site.

"I think these are really important sites that need to be protected, that they tell a very clear geological story," Dr Downes said.

"They tell about climate change, paleo climate change. They tell about geological events, how quickly it can change, and how slowly it can change too. So if you understand what you're looking at, it becomes an absolutely fascinating story."

Part of that story is a reminder that the coastline used to be much further east than it is today, before the sea levels rose thousands of years ago.

"I think it's really important from a local [perspective], and understanding what happened in Newcastle, and that there used to be volcanoes off the shore," said Dr Downes.

"They [people] look at the shore and they forget that six, ten, 15 thousand years ago, you had to walk 30 kilometres to get to the bloody beach. The beach wasn't here."

Peter Downes said this geological storybook was also a crystal ball, offering lessons from the deep past to take into the future.

"The climate's always changing is one," Dr Downes said. "Geological processes are critical for ensuring that our civilisation remains stable. Understanding geological risk is really important, and that comes down to everything from engineering ... through to hazard reduction."

Part of the push to protect the site, both Dr Downes and Roz Kerr said, was educating the public about what was here, and why it was significant.

"They should realise it's really important and learn about it," said Roz Kerr, who also used to teach geology at the University of Newcastle. Which is perhaps why she hopes the site inspires the next generation to fall in love with the stories told through rocks.

"If we get one geologist out of this site, it's important," she said.

While there are geotrails at other sites in New South Wales, including along the Newcastle coastline, the Swansea Heads site is so far largely off the tourist map.

However, Lake Macquarie City Council's Senior Environmental Strategy Officer, Symon Walpole, has encouraged people to visit the site.

"We are very lucky to have such tangible reminders of an era so many millions of years ago, right here in our backyard," he said.

"Get out there, discover and enjoy them, but it's important to respect and preserve them so they are here for many generations to come."

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