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: Volcanoes and molten rock
In the Harthope Valley, southwest of Wooler
Housey Crags is another spectacular Cheviot tor but this natural rock castle is not made of granite, it was once lava from a volcano. It sticks out on a plateau on the hillside and provides great views of The Cheviot, Northumberland’s highest mountain.
The Volcanoes in this area erupted about 400 million years ago and their lava covered much of northern Northumberland. When they were erupting Britain was 30 degrees south of the Equator, not 55 degrees north like now. These crags are made of rocks that exploded violently as molten magma from volcanic vents. The rocks are called andesites, but shortly after they erupted they were heated up and hardened by the molten Cheviot granite; they are now a metamorphic rock called a hornfels.
Millions of years of erosion, especially during recent Ice Ages, has left them poking out of the ground.
Surrounding the Crags the grass and heather moorland is managed for red grouse. Skylark, meadow pipit and curlew are common in the spring and summer and you might see a common lizard. The Crags have good lichen cover and a range of mosses.