Cheviot Hills

Only three rise 150 metres (490 ft) or more above the surrounding terrain: The Cheviot itself, Shillhope Law and Housedon Hill, a small northern outlier (see Marilyn).

These are in turn intruded by a swarm of igneous dykes with a predominantly calc-alkaline chemistry arranged radially around the pluton.

[4] Both the pluton and the volcanic rocks owe their origin to the northward subduction of the oceanic crust attached to the former micro-continent of Avalonia beneath the Laurentian plate in the course of the Caledonian orogeny during the Ordovician and Silurian periods.

[5][6] The surrounding lower ground is formed from Carboniferous Limestone, though much of it is obscured by superficial deposits of Quaternary age.

In addition, a sparse network of public bridleways and footpaths stretches around the area, often providing useful means of access from the lower ground onto the open hills.

[7] Many walking routes have been established, such as: The Otterburn Army Training Estate (ATE) covers about 230 square kilometres (90 sq mi) of the Southern Cheviots, approximately 23% of the Northumberland National Park.

Otterburn is the UK's largest firing range, and is in frequent use — artillery can be clearly heard from Lindisfarne to the north-east and Fontburn Reservoir in the south.

[11][12][13] The peaks marked with a warning sign () lie within the danger area of the ATE Otterburn artillery range.

Hedgehope Hill and overlooking the Breamish Valley
The Cheviot Burn
College Valley in the northern Cheviots, near Hethpool