These mountains are a set of 9 remnants of volcanic plugs, dating back around 25 milion years. They are visible from Brisbane, as well as by sea.
[Edit] Aboriginal explanation
So, you may have heard of the term 'Dreamtime'. We now use 'Creation Time', as the Aboriginal people lived their culture, not just dreamed of it. These ancestors and this time is not just in the past, it is also in the present and is very real.
The Aboriginal people believe that way way back in the beginning of everything, the earth was dark and flat and strange ancestor spirits, often half animal/human/plant in form, came up from the earth or down from the sky and roamed across the earth. And it was their adventures that carved out every mountain, river, cave and formation you see today.
They gave birth the animals, plants and the people, all Aboriginal People believing they are descendant from one of these Creation Creatures, or Totem. They believe they share their blood with both animals, and that of the sap of the trees, and the blood of the earth. And this is one reason why they are so connected to their ancestral lands, or country, as they call it. It is a visible and physical link to their ancestors, and a reminder of the laws, morals and teachings of the ancestor spirits.