By Adrian Pitches
BBC environment correspondent
What have Changing the Guard at Buckingham Palace, the Scottish Parliament and your TV screen all got in common?
The Northumberland National Park Authority hopes to find out what lies beneath its protected landscapes
They are all linked by the geodiversity of Northumberland in north-east England.
Geodiversity? Well, just as biodiversity means the range of living things present in a particular ecosystem, geodiversity represents the spectrum of rock types in a particular location.
And in Northumberland it is a very wide spectrum indeed. This is why the Northumberland National Park Authority has launched a geodiversity audit to find out what lies beneath its protected landscapes.
The two-and-a-half year study is a collaboration between the park, English Nature and the British Geological Survey (BGS).
It is a first for a national park and has attracted £200,000 of funding from the Aggregates Levy Sustainability Fund.
The Fund is a pot of money accrued from the taxation on every tonne of rock mined or quarried in the UK - and plenty of that rock has come from Northumberland.
Brian Young of the BGS, who is a member of the team conducting the geodiversity audit, enthuses about the county's rocks: "Northumberland is probably the county in England most shaped by its geology.
"You can see the skeleton of the landscape sticking out at places like Steel Rigg where Hadrian's Wall climbs along the Whin Sill."
The Romans who built the coast-to-coast Wall in AD 120 from Bowness-on-Solway in Cumbria to Wallsend on the River Tyne were astute geologists.
"They used the escarpment of the Whin Sill for the route of the Wall, but they knew they couldn't make square building blocks from the hard whinstone," Brian told BBC News.
"They had a particular spec for the bricks which they used all along the Wall so they would quarry sandstone up to three miles away and transport it to the site as they could more easily fashion this into square bricks."
And subsequent rulers of Britain have looked to Northumberland for their building needs.
The distinctive red roadstone used in the Mall in front of Buckingham Palace comes from the Harden quarry near Alwinton. And the honey-coloured sandstone used to make modern-day repairs to Edinburgh's Georgian New Town is quarried at West Woodburn.
This is due to its similarity to the original stone used in the buildings, which was mainly obtained from Edinburgh.
This stone was used to repair St Andrew's House, the suggested home for the Scottish Parliament before an all-new building was approved at Holyrood instead.
And if you watched the Queen's official opening of the Scottish Parliament in October, you may have made use of another very special Northumberland mineral, witherite.
Witherite (barium carbonate) powder is used in ceramic glazes and glassmaking, including the glass used for TV screens.
Brian Young again: "The Settlingstones mine near Hexham had more witherite than the rest of the planet combined."
Northumberland's geodiversity also includes two rather important deposits from the Carboniferous Period - about 320 million years ago: fossil-bearing shale, and coal.
The mineral which fuelled the Industrial Revolution was mined across north-east England.
Indeed, the last deep mine in the region which once produced most of the world's coal is at Ellington on the Northumberland coast.
The limestone laid down in the same period as the coal is quarried as aggregate for the construction industry. And in the shale that overlies the limestone - the overburden as its styled - can be found some fine fossils including trilobites and crinoids.
Brian says: "There are some excellent fossil sites in working quarries with wonderfully preserved fossils. But maybe I'd better not be specific about locations."
Dozens of Sites of Special Scientific Interest (SSSIs) have been designated in the Northumberland National Park by English Nature for their fossil or other geological value. The new geodiversity audit will no doubt uncover more. But it has a wider purpose.
"We're taking stock of what makes Northumberland such a special landscape. There's an intimate connection between the countryside you see and the rocks that lie beneath," Brian says.
"People who visit the countryside are demanding more than views - they want interpretation, to understand what they're seeing. Hopefully we can help the national park assess the quality of its landscapes so they can better inform their visitors."
So geodiversity may well stimulate geotourism. The Northumberland National Park Authority need only look just to the south-west and the North Pennines Area of Outstanding Natural Beauty (AONB) centred on Alston in Cumbria.
In June 2003, the North Pennines AONB was awarded European Geopark Status, a Unesco backed designation for areas with world-class geology. On this evidence, Northumberland National Park could well follow it.