The geology of

Hampshire Hampshire (, ; abbreviated to Hants) is a ceremonial and non-metropolitan county in western South East England on the coast of the English Channel. Home to two major English cities on its south coast, Southampton and Portsmouth, Hampshire ...

in southern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

broadly comprises a gently folded succession of

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s dating from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

and

Palaeogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

periods. The lower (early) Cretaceous rocks are

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s and mudstones whilst those of the upper (late) Cretaceous are the various formations which comprise the Chalk Group and give rise to the county's

downland Downland, chalkland, chalk downs or just downs are areas of open chalk hills, such as the North Downs. This term is used to describe the characteristic landscape in southern England where chalk is exposed at the surface. The name "downs" is deriv ...

s. Overlying these rocks are the less consolidated Palaeogene

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class o ...

s, gravels and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel ...

s of the Lambeth, Thames and Bracklesham Groups which characterise the Hampshire Basin.

Hampshire Basin

In the south, along the

coast The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in ...

, soft

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

and Oligocene clays and gravels form low flat terrain, the Hampshire Basin. Protected from sea

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

by the

Isle of Purbeck The Isle of Purbeck is a peninsula in Dorset, England. It is bordered by water on three sides: the English Channel to the south and east, where steep cliffs fall to the sea; and by the marshy lands of the River Frome and Poole Harbour to the no ...

, Dorset, and the

Isle of Wight The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...

, this land supports

heathland A heath () is a shrubland habitat found mainly on free-draining infertile, acidic soils and characterised by open, low-growing woody vegetation. Moorland is generally related to high-ground heaths with—especially in Great Britain—a coole ...

and

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (se ...

habitats, a large area of which form part of the

New Forest The New Forest is one of the largest remaining tracts of unenclosed pasture land, heathland and forest in Southern England, covering southwest Hampshire and southeast Wiltshire. It was proclaimed a royal forest by William the Conqueror, fea ...

. Much of the coastal landscape of the Hampshire Basin results from

sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

in the Flandrian (after the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

) some 6000 years BP. There are several large

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...

and

ria A ria (; gl, ría) is a coastal inlet formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea. Definitions Typically rias have a dendritic, treelike outline although they ca ...

s, notably the 12 mile long

Southampton Water Southampton Water is a tidal estuary north of the Solent and the Isle of Wight in England. The city of Southampton lies at its most northerly point, where the estuaries of the River Test and River Itchen meet. Along its salt marsh-fringed wes ...

and the large convoluted

Portsmouth Harbour Portsmouth Harbour is a biological Site of Special Scientific Interest between Portsmouth and Gosport in Hampshire. It is a Ramsar site and a Special Protection Area. It is a large natural harbour in Hampshire, England. Geographically it ...

. The

Solent The Solent ( ) is a strait between the Isle of Wight and Great Britain. It is about long and varies in width between , although the Hurst Spit which projects into the Solent narrows the sea crossing between Hurst Castle and Colwell Bay t ...

, which separates the Isle of Wight from the coast of Hampshire, is itself a flooded river valley, further erosion having broken the remaining chalk link with the mainland.

Chalk Downs

In the centre and north of the county the substrate is the chalk of the

Hampshire Downs The Hampshire Downs form a large area of downland in central southern England, mainly in the county of Hampshire but with parts in Berkshire and Wiltshire. They are part of a belt of chalk downland that extends from the South Downs in the southe ...

and the

South Downs The South Downs are a range of chalk hills that extends for about across the south-eastern coastal counties of England from the Itchen valley of Hampshire in the west to Beachy Head, in the Eastbourne Downland Estate, East Sussex, in the eas ...

. These are high hills with steep slopes where they border the clays to the south. The downland supports a

calcareous grassland Calcareous grassland (or alkaline grassland) is an ecosystem associated with thin basic soil, such as that on chalk and limestone downland. Plants on calcareous grassland are typically short and hardy, and include grasses and herbs such as clover. ...

habitat, important for wild

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s and

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

, as well as arable

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...

. The hills dip steeply forming a scarp onto the

Kennet valley The Kennet is a tributary of the River Thames in Southern England. Most of the river is straddled by the North Wessex Downs AONB (Area of Outstanding Natural Beauty). The lower reaches have been made navigable as the Kennet Navigation, which � ...

to the north, and dip gently to the south. The highest point in the county is Pilot Hill, which reaches the height of 286m/938 ft. The rivers

Test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

and Itchen flow from the downland through green valleys, both supporting

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...

and other wildlife. A series of east-west trending folds in the chalk to the north of the Hampshire Basin is controlled by faults in the underlying

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

strata. From south to north these are the Winchester-East Meon Anticline, the Winchester-King's Somborne Syncline/Alderbury - Mottisfont Syncline, the Stockbridge Anticline and the Micheldever Syncline. The Winchester-East Meon Anticline in particular gives rise to many hills including Yew Hill, Compton Down,

Oliver's Battery Oliver's Battery is a civil parish in Hampshire, England, of some 700 households located just to the south of the City of Winchester. The parish was formed in 1956 (in the then Winchester Rural District, and part of the City of Winchester Dist ...

, Magdalen (Morn) Hill, Chilcomb Down, Cheesefoot Head, Telegraph Hill, Deacon Hill,

Twyford Down Twyford Down is an area of chalk downland lying directly to the southeast of Winchester, Hampshire, England next to St. Catherine's Hill and close to the South Downs National Park. It has been settled since pre-Roman times, and has housed a f ...

, St. Catherine's Hill, Beacon Hill,

Old Winchester Hill {{Infobox SSSI , image= OldWinchesterHill.JPG , image_caption = , name= Old Winchester Hill , aos= Hampshire , interest=Biological , gridref={{gbmappingsmall, SU 642 208 , area= {{convert, 66.2, ha, acre, abbr=off , notifyda ...

and Henwood Down. Around the chalk margins to the north are the Pewsey-Kingsclere Anticline and to the south the Dean Hill Anticline, Portsdown Anticline, Forest of Bere Syncline and Chichester Syncline. Further north, beyond the downs, the landscape is again lowland clay and gravel heathland, though the north is generally greener and more diverse than the south.

References

* Draper, Jo. 1990. ''Hampshire''. Wimborne: Dovecote Press. {{Geology of England , state=expanded

Hampshire Basin

Chalk Downs

See also

References