The geology of London, like the rest of Britain, is very complex. There are many different rock types visible at the surface, with some dating up to 145 million years ago, with many that are much more recent. The main bedrocks are Chalk and London Clay, with much of the surface geology made up of sands and gravels from the Eocene, till and gravel from glacial activity, and recent non-glacial deposits caused by wind or water action.
The London Basin area is formed from a layer of chalk accumulated on the bed of a warm sea in the Cretaceous period over 65 million years ago. Together with much of Southern Britain, at the same time the Alps were being formed around 15-20 million years ago, the area was folded to form a shallow basin (a syncline). This chalk basin is filled with other rock types, but it still surfaces today mainly in the Chiltern Hills to the north-west, and in the North Downs on the southern edge of the London area. At Westminster, it is 70 metres below ground. Chalk is porous, creating an artesian basin, and makes an alkaline soil.
Impermeable London Clay is also a sea-bed sediment, laid down 56-34 million years ago in the Eocene epoch. It lies on top of the chalk, and in some places is 150m thick. As with other clay soils, it is ‘heavy’ and not naturally good for agriculture, but two characteristics are very important for London: it is easy to be tunnelled and it makes very good bricks. Much of the London Underground system runs through tunnels dug into the London Clay, and this explains why there are few Underground lines south of the river: there is much less clay in this area. The classic yellow ‘London Stock’ brick is made from this clay, and can be seen in houses and buildings all over the capital.
Patches of other important sedimentary rocks that were laid down in the Paleogene period 65-25 million years ago include Thanet Sand, Woolwich Beds and Blackheath Beds associated with heathland and acid soils. The Bagshot Beds are old sands that lie above the clay, and create the hills of Harrow, Hampstead, Highgate and some of the heath around Esher.
The Thames did not always follow its current path, but the action of great ice sheets eventually blocked the previous route through the Vale of St Albans and caused it to break through the chalk ridge at Goring from where it then scored its way through London, carrying much glacial debris with it. At the height of the last ice age as recently as 20,000 years ago, the ice sheet, extended down to present day Finchley, and deposited boulder clay around Finchley and much of London to the north. Repeated glacial and inter-glacial periods created much erosion and fluctuation in ice and river levels. The Thames alternately deposited and then cut through, gravel terraces formed. Much of central London is built on these terraces, with extensive flat areas connected by quite steep inclines being very evident: the roads that lead from the Embankment to the Strand are connecting one terrace with another. Oxford Street is on the edge of a river terrace and St Martin's Lane slopes into Trafalgar Square past the National Portrait Gallery, moving from one terrace to the next lower one. These terraces form many of the heathlands and acid grasslands of London, including the area around Heathrow. Gravel extraction for construction has resulted in many gravel pits.
In several areas, these river gravel deposits are topped with Brickearth, a fine grained wind-borne sediment, used in brick making. The area around Pall Mall is one such deposit.
The many river valleys have deposits of recent Alluvium, and and still being formed today in some areas. Other rivers such as the Westbourne (through Hyde Park) and the Tyburn (Regent’s Park) have been lost underground in recent centuries, but have left their trace in Alluvium deposits on the surface, culminating in this case a large expanse of Alluvium at Westminster.
The soils formed from these surface geology produce a complex mosaic of different habitats, with their associated distinct flora and fauna.
London Naturalist Geology Map: A map of the surface geology of the London Area, by Colin W. Plant (1994) (The London Naturalist 73: 215-220). Map here (as a .jpg file) or here (as a downloadable PDF version).
BGS Geology of Britain viewer
BGS iGeology smartphone app
The Hemiptera is a large and diverse insect order in Britain, containing nearly 2000 species, many of which can be found in London. In fact, some are found nowhere else! Species from continental Europe or even further afield are now regularly becoming established in Britain and the London area is often where they first appear. Now is an exciting time to record these insects within the capital.
A uniformly green species, although turning brown before hibernation. The membrane at the tip of the wings is dark. Very common in many habitats including parks and gardens, feeding on a wide range of plants.
Similar to the above species and best distinguished by the transparent pale wing membrane. Uncommon and usually in man-made habitats. Most frequent in allotments, where it is particularly fond of runner beans. A recent arrival in Britain and largely confined to the London area. Records are of particular interest.
This species is distinguished by the wing membrane, which is covered in dark spots. The antennae are also strongly banded. Uncommon and usually in man-made habitats. A recent arrival in Britain and so far entirely confined to the London area. Records are of particular interest.
A very large and striking bug, with characteristic leaf-like expansions on the hind legs. Native to the USA; a recent arrival in Britain and now widespread, although rarely seen in the summer months, when it lives on pines. Most records are of bugs overwintering inside buildings.
A striking red and black bug which is also rather hairy. A recent arrival in the London area and historically confined to the southern and western coasts of Britain. Now found in a range of habitats including gardens.
A large and distinctive black and yellow plant bug, most often seen in mid-summer. Widespread in parks and gardens on deciduous trees, particularly oaks and hawthorns.
An unmistakable species which is most often found in May and June. Widespread and common across much of England and Wales on a range of herbaceous plants, but rather uncommon in the LNHS recording area and largely absent from urban London.
An unmistakable species which is most often found in May and June. Widespread and common across much of England and Wales and generally associated with old woodlands. Rather uncommon in the LNHS recording area and largely absent from urban London.
The largest leafhopper in Europe, with characteristic ear-like projections on the thorax. A cryptic bark dweller, particularly on lichen-covered oaks. Rarely seen, although may come to moth traps.
A very distinctive red and green leafhopper which feeds on Rhododendron and is frequent in London’s parks. Originally native to the USA, it was introduced to Britain in the early 1900s and has since spread widely.
Some remarkable fungi of London.
Comprising over 14,000 hectares of public parks, woodland, gardens and cemeteries, London is the greenest major city in Europe, with 40% of London’s surface area comprising green space that is accessible to the public.
A wide diversity of habitats, including unimproved grassland, woodland, heathland and scrub with various water features, on various soils from Chalk to London Clay to Bagshot Sands, provides home to 1000’s of native trees and shrubs such as, oak, beech, birch, willow, poplar, Scots pine and many more. All of this glorious green space is irresistible to fungi, which thrive across the city landscape. Step into your local green space and you are likely to see fungi of some kind. Over 600 species have been recorded from Hampstead Heath alone.
Below are a just a small number of the fungi species to be found in London, some of which may be difficult to find elsewhere in Britain.
Podoscypha multizonata - Zoned Rosette
This species has its stronghold in the southern counties of England and London is one of those strongholds. The Zoned Rosette is a red data species and has a Biodiversity Action Plan (BAP) attached to it. 80% of the known world sites are in England, mostly with a southern bias. It occurs on the roots of broadleaved trees, usually oak, in open woodland or old parks.
Paxillus obscurosporus - "Fat - Lipped Roll Rim"
Commonly known as a Roll Rim, this particular species has only recently been described and was new to Britain in 2008. This is a large species, reaching 35cm across, with characteristic, persistent, in-rolled margin. A common species in London’s parks and open green spaces, often in large numbers beneath lime trees, one of the trees with which it forms a mutual symbiosis.
Grifola frondosa – Hen of the Woods
Found at the base of deciduous trees, during the autumn, this very well camouflaged, ‘leafy’ polypore was once considered quite rare. It favours old oak trees in parkland or woodland, so therefore in thrives in the London area as both are in fairly good supply. Although a root rotter, it is a splendid fungus to stumble across whilst out on an autumn stroll.
Leccinum duriusculum – Slate Bolete
Mutually symbiotic, forming a mycorrhizal relationship with poplar trees. The Slate Bolete is quite a cosmopolitan species, occurring with different species of poplar, in cemeteries, public parks and with street poplars on grass verges, right across London. A key identification feature is that the flesh will turn pink and then slate upon cutting in section.
Butyriboletus appendiculatus – Oak Bolete
Many of the large species of Boletus such as this, are thermophilic, that is to say that they prefer the warm temperatures that a city like London has in being at least 2o C warmer than areas outside of London. It forms a mutual symbiosis (mycorrhiza) with oak and beech trees. Cold, wet summers will not favour this and other species.
Amanita phalloides -The Death Cap
This deadly mushroom is locally common across London; forming a mutual symbiosis via a mycorrhizal relationship with deciduous trees, favouring oak and hornbeam trees in parks, cemeteries or gardens, from summer to autumn. White gills, olive to white cap, white stem with greenish hue and white velar remnants, base with sac-like volva. Smell sickly sweet. Onset of poisoning can take up to 36 hours depending on the dose, with severe diarrhoea, vomiting, dehydration, false cessation followed by liver failure, kidney malfunction, coma, death.
Amanita virosa -The Destroying Angel
A much rarer species, with the same outcome as the Death Cap if ingested, occurs in woodland close to London. Pure and as white as snow, it associates with beech trees in well-established woodlands. The smooth, conical cap is often off centre, the stem shaggy looking, and the base of the stem, as with the Death Cap, is clothed in white tissue, appearing loose and bag-like.
Cortinarius nolaneiformis - "Bellita Webcap" (nolanei = small bell, formis = shaped like)
The genus Cortinarius is believed to contain the greatest number of species among any genera of mushrooms, worldwide. They are commonly known as the webcaps, as they have a web-like veil the covers the gills when young. Gills initially variable in colour but finally rust-brown. This species was recorded during a survey on Hampstead Heath; it turned out to be new to Britain.
Russula carpini - "Hornbeam Brittle Gill"
This is a very rare species that associates solely with Carpinus, Hornbeam, as the name suggests. It is one of the many species of Brittle gills, which characterises the Russula genus, among which species have many different colours in both cap, gills and stem.
This species was discovered to be new to Middlesex during a survey of Regents Park.
Laetiporus sulphureus – Chicken of the Woods
This beautiful bright yellow, salmon fringed polypore, forms large tiers that adorn lots of different trees, in many different habitats right across London. Usually appearing during late May into the summer months, it is a welcome and colourful sight. It occurs on oak, willow, beech, poplar, cherry, hawthorn, false acacia and more, in parks, gardens, cemeteries and woodlands.
Common names as per British Mycological Society where available. Otherwise in "quotes".
All photographs ©Andy Overall 2016
The London Bat Atlas was initiated during 2010 with seed funding from the Vodafone ‘World of a Difference’ fund, which helped employ the services of Richard Law, to gather together the existing data holdings, as well as investigate the type of document and layout we wanted.
It took longer to accomplish than we originally thought, but with the help of Greenspace information for Greater London, our group has produced a document, which is as accurate as possible, but easy to access the information.
It is an example of the importance of submitting biological records, especially in this time of ‘blink and you miss it’ demolition and re-development. As always it exemplifies those boroughs where there are active bat group members so absence of records doesn’t mean absence of bat species!
There has been a lot of positive feedback since the Atlas was distributed especially from London’s remaining Biodiversity Officers, who have commented on its use as reference material, to support their requests for bat surveys, especially when responding to planning applications.
The beetle fauna of the London area is about as rich as anywhere in the British Isles and more so than most places. The variety of habitats, semi-natural and man-made, the parks with veteran trees and the capital as point of introduction for foreign species, contribute towards this diversity. Some of the country’s best sites for saproxylic (dead wood feeding) beetles lie in London’s suburban parks.
Pre-eminent among London’s beetles is the Stag Beetle (Lucanus cervus) for which south London is not only a British stronghold but also a European one. The larvae feed in rotting tree stumps for 3 or 4 years before pupating in autumn to spend the winter within the tree before emerging as an adult in June. Suburban streets can the best places to spot one especially when in flight at dusk. The Lesser Stag Beetle (Dorcus parallelopipedus) is more common and widespread and occurs in some parts of inner London.
Male Stag Beetle ©Stuart Cole
Belonging to the same superfamily as the stag beetles are the chafers and dung beetles. The conspicuous metallic green Rose Chafer (Cetonia aurata) is a species that has become much more common in London’s outer suburbs in recent years. It is most likely to be seen on the flowers of umbellifers from May to July. The larvae live in compost heaps and decaying wood.
Rose Chafer ©Stuart Cole
Lesser Stag Beetle ©Stuart Cole
The most distinctive of the dung beetles is the Minator Beetle, the male of which possesses prominent forward pointing horns on the thorax. This prefers sandy soil in which to excavate the burrows where rabbit or fallow deer dropping are stored for the larvae. It can be found in the deer parks in south-west London and at the LNHS survey site at Bookham Common in Surrey. Another horned dung beetle is the male of Onthophagus coenobita which prefers horse dung and may be found in suburban parks and paddocks.
male Minator Beetle ©Stuart Cole
Nicrophorus vespilloides ©Stuart Cole
The carrion beetle family Silphidae has some large red and black insects commonly called burying beetles. The species most frequently found around London is Nicrophorus vespilloides which feeds not only in the carcasses of small animals but also rotting fungi; the larvae feed on carrion sunk into the soil by the adults.
The Staphylinidae are a large family of elongated beetles characterised by their short elytra and flexible abdomen. They occur in a great variety of situations including dung, carrion, ant and hornet nests and the mud of salt and freshwater marshes. The largest of the nearly 1,000 British species and one that is very common around London is the Devil’s Coach-horse (Ocypus olens) which may be found beneath logs and rocks in gardens. The larvae are predacious.
Devil’s Coach-horse ©Mick Massie
A striking beetle, another that is more frequent now than in the 1960s, is the Black-headed Cardinal Beetle (Pyrochroa coccinea). It is about 17mm long and almost entirely scarlet. The flattish larvae live under bark of dead trees.
Black-headed Cardinal Beetle and larva ©Stuart Cole
The Rusty Click Beetle (Elater ferrugineus), the largest British member of the Elateridae, was, until recently, considered one of Britains rarest beetles, possibly restricted to Windsor Forest. That is until an artificial scent was concocted that mimics the female beetle’s sex pheromone. Using lures containing the scent entomologists have found that the species is actually resident in many localities in and around London, including Hampton, Kew Gardens and even Hyde Park in central London. E. ferrugineus preys on the larvae of other rotten-wood feeding beetles.
Rusty Click Beetle ©Stuart Cole
The attractive metallic green Oedemera nobilis is now much more frequently seen than in the past. The adults feed on flower pollen in summer. The males have enlarged thighs on the hind legs and thus are easily distinguished from the females which lack this feature.
male Oedemera nobilis ©Stuart Cole
Among our largest beetles are the longhorns of the family Cerambycidae. Britain has relatively few species of these but there are some such as the elegant Rutpela maculata that can be found not uncommonly on flowers in the London area including the suburbs. Agapanthia villosoviridescens is distinctive for its banded antennae and pale blue legs. The larvae feed inside the stems of umbellifers such as hogweed. The biggest of Britain’s longhorns is the Tanner Beetle (Prionus coriarius) which grows up to 4.5 cms. and lives in ancient oaks in Richmond Park in the south-west of the capital.
Rutpela maculata ©Stuart Cole
Agapanthia villosoviridescens ©Stuart Cole
Although they look very unlike the longhorns, the leaf beetles (Chrysomelidae) belong to the same superfamily. Wherever water mint is allowed to grow at the edge of ponds and lakes you are quite likely to come across the big, bright metallic green, Mint Leaf Beetle (Chrysolina herbacea). Both adults and the black grubs feed on the aromatic leaves. Another large and conspicuous species is Chrysomela populi which lives on the foliage of aspens as well as poplars.