Towards the close of Carboniferous Period and in the early Permian, some 295 million years ago (Ma), crustal extension caused by movement of the Earth's tectonic plates during the Variscan orogeny allowed the emplacement of igneous intrusions of magma across much of northern England of a suite of tholeiitic dolerite intrusions. These were largely concordant with the strata of the existing country rock.
Around 295 million years ago (Ma), during the late Carboniferous and early Permian periods, crustal expansion caused by tectonic plate movement during the Variscan orogeny resulted in the intrusion of dolerite magma into much of northern England. These intrusions were largely aligned with the existing rock layers.