Northern England district - Geology

Recent surface deposits

Schematic cross-section of the geology of Northern England extending from the Irish Sea to North Sea. The alignment of the section and key are shown in P902262. P902261.

Schematic cross-section of the geology of Northern England extending from the Solway Firth to north Lancashire. The alignment of the section and key are shown in P902262. P902259.

Schematic cross-section of the geology of Northern England extending from the Cheviot Hills to County Durham. The alignment of the section and key are shown in P902262. P902282.

Geological deposits of relatively recent origin, known as superficial deposits, formed over the past 2 to 3 million years and span the Ice Ages and Interglacial periods. The deposits occur in areas such as the Solway Lowlands and south Cumbria and are locally up to 60m thick, but elsewhere these deposits are patchy and typically less than 20 m or so thick. These deposits include layers of boulder clay, sand and gravel deposited from ice sheets and typically less than 60 m thick, which are widespread within the region but are mainly confined to the bottoms of the deep valleys cut out by glaciers in the Lake District. In lowland areas there are spectacular spreads of small whale-backed hills called drumlins that are formed of glacial materials, while clay deposits can give rise to shallow lakes and wetlands such as the Solway mosses. Spreads of silt, sand and gravel are extensive and up to 50 m thick along the major river valleys especially those of the Tyne and Tees. Upland areas and the lowlands around the Solway Firth support bogs with the accumulation of peat. Peat thicknesses are usually less than 3 m, though about 9m are present in the extensive deposit east of Cross Fell in the North Pennines. Most of the superficial deposits are soft and easily eroded, as they have not been deeply buried and consolidated to form strong rocks.

Geology at depth

Below the superficial deposits, or with just a cover of soil where such deposits are absent, are older rocks which geologists broadly split into two distinct types:

• The sedimentary bedrock geology is composed of quite hard rocks formed from a few hundreds to a few tens of millions of years ago as layers of sediments which were deposited in shallow seas, deserts and swamps in times when Britain lay closer to the Equator and the climate and landscape were very different from those of today.
• The basement geology, which underlies the bedrock, is over 360 million years old and mainly comprises harder and denser rocks which have been strongly consolidated and folded. They include both rocks originally deposited as sediments and others that are products of volcanic activity or formed from the solidification of molten rock below ancient volcanoes.

This region has been affected by several phases of earth movements that caused uplift and allowed some of the sedimentary bedrock to be removed by erosion (in some parts of the region up to several thousand metres of rocks are thought to have been removed). These processes have brought older rocks that were once deeply buried close to the surface. P902261, P902259 and P902282 provide schematic vertical sections through the geology, referred to as geological cross-sections, which illustrate the variations in geology across the region.