A geologist has written three best-selling books on Northumberland, Cumbria, and Durham for charity.

Ian Jackson's trilogy on the geology of these regions has raised more than £20,000 for local wildlife trusts.

The series began as a few web pages marking the 50th anniversary of the Northumberland Wildlife Trust and eventually expanded into fully illustrated books.

The books, praised for their accessibility, have attracted wide acclaim including from BBC presenter Iain Stewart and international author Simon Winchester.

Ian Jackson said: "Geology is a bit of a nerdy subject - not everyone loves rocks as much as us geologists.

"But the amazing number of book sales show that if you cut out technical jargon, keep it short, include lots of photos and connect the rocks to other things such as history, wildlife and society, then people are genuinely interested in the ground under their feet.

"I wanted to help people understand how the landscape they live in came to be.

"When I was a boy growing up in Cumberland, I was full of wonder about the countryside around me.

"So I thought I’d try and write a book to answer those simple questions and before I knew it one book turned into three."

The books - entitled Cumbria Rocks, Durham Rocks, and Northumberland Rocks - caters to a shared interest in geology and local walks, with some readers using it as a geological version of Wainwright's well-known list of Lake District peaks to be climbed.

Jackson visited remote locations across the three counties and took thousands of photographs for the books.

Mike Pratt, Northumberland Trust chief executive, said: "Quite apart from the boost to our income, these books do something much more important in that they explain to people why everything in nature is connected - the rocks, plants, animals, water, the atmosphere and us.

"If we want to look after our environment then making sure we all understand that is crucial (and) these books are helping people do that.

"They are a wonderful contribution and I still can’t believe Ian took all the photos with his phone, which is all it needs to capture something wonderful."