Jackson, Ian. Northumberland Rocks — 50 extraordinary rocky places that tell the story of the Northumberland landscape. Newcastle upon Tyne : Northern Heritage, 2021.
The richly illustrated and accessible book series of Northumberland, Cumbria and Durham Rocks are available to purchase from Northern Heritage.
Theme: Climate and landscape change
The pavement is on the northern shore of Broomlee Lough, which is north of Hadrian’s Wall. You can reach it by walking from Housesteads visitor centre.
On the northern shore of Broomlee Lough is a limestone pavement: a natural platform of bare limestone rock cut by fissures, like a very rough set of paving slabs.
The limestone is Carboniferous and called the Oxford Limestone. It is over 320 million years old but the “pavement” feature was mostly created after the last ice sheet left 15,000 years ago. This is a very rare feature for Northumberland. There are many limestone pavements in the Yorkshire Dales and in south Cumbria but not in our county.
It happens when an ice sheet scrapes off all the soil and loose rock and leaves the limestone exposed. That leaves the rock open to the elements. Rain absorbs carbon dioxide from the atmosphere and the weak carbonic acid eats into the joints of the limestone, which is mostly made up of calcium carbonate — creating this natural pavement. The blocks are called clints and the fissures are called grikes.
This fragment of rare limestone pavement supports lime-loving plants such as small scabious, salad burnet, common rock-rose, fairy flax and mouse-ear hawkweed.