Geography of the United Kingdom

The United Kingdom is a sovereign state located off the north-western coast of continental Europe. The United Kingdom is made up of four countries – England, Scotland, Wales and Northern Ireland. With a total area of approximately, the UK occupies the major part of the British Isles archipelago and includes the island of Great Britain, the north-eastern one-sixth of the island of Ireland and many smaller surrounding islands. It is the world's 7th largest island country. The mainland areas lie between latitudes 49°N and 59°N, and longitudes 8°W to 2°E. The Royal Observatory, Greenwich, in south-east London, is the defining point of the Prime Meridian.
The UK lies between the North Atlantic and the North Sea, and comes within of the north-west coast of France, from which it is separated by the English Channel. It shares a international land boundary with the Republic of Ireland. The Channel Tunnel bored beneath the English Channel now links the UK with France.
The British Overseas Territories and Crown Dependencies are covered in their own respective articles.

Area

The total area of the United Kingdom according to the Office for National Statistics is, comprising the island of Great Britain, the northeastern one-sixth of the island of Ireland and many smaller islands. This makes it the 7th largest island country in the world. England is the largest country of the United Kingdom, at accounting for just over half the total area of the UK. Scotland at, is second largest, accounting for about a third of the area of the UK. Wales and Northern Ireland are much smaller, covering respectively.
The area of the countries of the United Kingdom is set out in the table below. Information about the area of England, the largest country, is also broken down by region.

Rank	Name	Area
1	England ∟ South West ∟ East of England ∟ South East ∟ East Midlands ∟ Yorkshire and the Humber ∟ North West ∟ West Midlands ∟ North East ∟ London	132,938 km² 23,837 km² 19,120 km² 19,096 km² 15,627 km² 15,420 km² 14,165 km² 12,998 km² 8,592 km² 1,572 km²
2	Scotland	80,239 km²
3	Wales	21,225 km²
4	Northern Ireland	14,130 km²
	United Kingdom	248,532 km²
	Overseas territories	1,727,570 km²

The British Antarctic Territory, which covers an area of is geographically the largest of the British Overseas Territories followed by the Falkland Islands which covers an area of. The remaining twelve overseas territories cover an area.
Other countries with very similar land areas to the United Kingdom include Guinea, Uganda, Ghana and Romania. The UK is the world's 80th largest country by land area and the 10th largest in Europe.

Physical geography

The physical geography of the UK varies greatly. England consists of mostly lowland terrain, with upland or mountainous terrain only found north-west of the Tees–Exe line. The upland areas include the Lake District, the Pennines, North York Moors, Exmoor and Dartmoor. The lowland areas are typically traversed by ranges of low hills, frequently composed of chalk, and flat plains. Scotland is the most mountainous country in the UK and its physical geography is distinguished by the Highland Boundary Fault which traverses the Scottish mainland from Helensburgh to Stonehaven. The faultline separates the two distinctively different regions of the Highlands to the north and west, and the Lowlands to the south and east. The Highlands are predominantly mountainous, containing the majority of Scotland's mountainous landscape, while the Lowlands contain flatter land, especially across the Central Lowlands, with upland and mountainous terrain located at the Southern Uplands. Wales is mostly mountainous, though south Wales is less mountainous than north and mid Wales. Northern Ireland consists of mostly hilly landscape and its geography includes the Mourne Mountains as well as Lough Neagh, at, the largest body of water in the UK.
The overall geomorphology of the UK was shaped by a combination of forces including tectonics and climate change, in particular glaciation in northern and western areas.
The tallest mountain in the UK is Ben Nevis, in the Grampian Mountains, Scotland. The longest river is the River Severn which flows from Wales into England. The largest lake by surface area is Lough Neagh in Northern Ireland, though Scotland's Loch Ness has the largest volume.

Geology

The geology of the UK is complex and diverse, a result of it being subject to a variety of plate tectonic processes over a very extended period of time. Changing latitude and sea levels have been important factors in the nature of sedimentary sequences, whilst successive continental collisions have affected its geological structure with major faulting and folding being a legacy of each orogeny, often associated with volcanic activity and the metamorphism of existing rock sequences. As a result of this eventful geological history, the UK shows a rich variety of landscapes.

Precambrian

The oldest rocks in the British Isles are the Lewisian gneisses, metamorphic rocks found in the far north-west of Scotland and in the Hebrides, which date from at least 2,700 Ma. South and east of the gneisses are a complex mixture of rocks forming the North West Highlands and Grampian Highlands in Scotland. These are essentially the remains of folded sedimentary rocks that were deposited between 1,000 Ma and 670 Ma over the gneiss on what was then the floor of the Iapetus Ocean.

Paleozoic

At 520 Ma, what is now Great Britain was split between two continents; the north of Scotland was located on the continent of Laurentia at about 20° south of the equator, while the rest of the country was on the continent of Gondwana near the Antarctic Circle. In Gondwana, England and Wales were largely submerged under a shallow sea studded with volcanic islands. The remains of these islands underlie much of central England with small outcrops visible in many places.
About 500 Ma southern Britain, the east coast of North America and south-east Newfoundland broke away from Gondwana to form the continent of Avalonia, which by 440 Ma had drifted to about 30° south. During this period north Wales was subject to volcanic activity. The remains of these volcanoes are still visible, one example of which is Rhobell Fawr dating from 510 Ma. Large quantities of volcanic lava and ash known as the Borrowdale Volcanics covered the Lake District and this can still be seen in the form of mountains such as Helvellyn and Scafell Pike.
Between 425 and 400 Ma Avalonia had joined with the continent of Baltica, and the combined landmass collided with Laurentia at about 20° south, joining the southern and northern halves of Great Britain together. The resulting Caledonian Orogeny produced an Alpine-style mountain range in much of north and west Britain.
The collision between continents continued during the Devonian period, producing uplift and subsequent erosion, resulting in the deposition of numerous sedimentary rock layers in lowlands and seas. The Old Red Sandstone and the contemporary volcanics and marine sediments found in Devon originated from these processes.
Around 360 Ma Great Britain was lying at the equator, covered by the warm shallow waters of the Rheic Ocean, during which time the Carboniferous Limestone was deposited, as found in the Mendip Hills and the Peak District of Derbyshire. Later, river deltas formed and the sediments deposited were colonised by swamps and rain forest. It was in this environment that the Coal Measures were formed, the source of the majority of Britain's extensive coal reserves.
Around 280 Ma the Variscan orogeny mountain-building period occurred, again due to collision of continental plates, causing major deformation in south-west England. The general region of Variscan folding was south of an east–west line roughly from south Pembrokeshire to Kent. Towards the end of this period granite was formed beneath the overlying rocks of Devon and Cornwall, now exposed at Dartmoor and Bodmin Moor.
By the end of the Carboniferous period the various continents of the Earth had fused to form the super-continent of Pangaea. Britain was located in the interior of Pangea where it was subject to a hot arid desert climate with frequent flash floods leaving deposits that formed beds of red sedimentary rock.

Mesozoic

As Pangaea drifted during the Triassic, Great Britain moved away from the equator until it was between 20° and 30° north. The remnants of the Variscan uplands in France to the south were eroded down, resulting in layers of the New Red Sandstone being deposited across central England.
Pangaea began to break up at the start of the Jurassic period. Sea levels rose and Britain drifted on the Eurasian Plate to between 31° and 40° north. Much of Britain was under water again, and sedimentary rocks were deposited and can now be found underlying much of England from the Cleveland Hills of Yorkshire to the Jurassic Coast in Dorset. These include sandstones, greensands, oolitic limestone of the Cotswold Hills, corallian limestone of the Vale of White Horse and the Isle of Portland. The burial of algae and bacteria below the mud of the seafloor during this time resulted in the formation of North Sea oil and natural gas.
The modern continents having formed, the Cretaceous saw the formation of the Atlantic Ocean, gradually separating northern Scotland from North America. The land underwent a series of uplifts to form a fertile plain. After 20 million years or so, the seas started to flood the land again until much of Britain was again below the sea, though sea levels frequently changed. Chalk and flints were deposited over much of Great Britain, now notably exposed at the White Cliffs of Dover and the Seven Sisters, and also forming Salisbury Plain.