Geography of Picardy

The Picardy covers a surface of 19.399 km including 7.369 km for the Aisne, 5.860 km for Oise and 6.170 km for the Somme.

Geology and relief

The basement of Picardy east mainly composed of cretaceous bases and tertiary sectors which occupy more than 90% of its surface, the chalk by forming with it only approximately half. From a geological point of view, the area can be subdivided in six zones: - the Western termination of the solid mass of the Ardennes calédonohercynien; - Jurassic zones with the outcrops of Lias and the Dogger in the area of Hirson and those of Malm in the Country of Bray; - nonchalky lower cretaceous zones represented by continental sediments of Wealdien and higher primarily made up by the greensands and clays of Gault (Albo-Aptien); grounds observed in edge of the Jurassic zones (Thiérache and Pays of Bray), like in the valleys of Authie and Bresle; - supracrétacées zones extending on all the basin from the Sum and a weak part of that of Oise (Marlois), like in the Country of Thelle in the south-east of the Country of Bray; most of the time, these chalky outcrops are masked by the silts of the plates and the silts with quaternary flints; - tertiary zones distributed in 4 units: - very reduced paleocene outcrops and Eocene inferiors present especially in the average area of the course of Oise (Clermontois, Noyonnais and Laonnois) but also, with the state of pilot hillocks, disseminated on the whole of the cretaceous zones; - average Eocene outcrops or plates lutétiens on both sides of the valley of Aisne (Soissonnais and Tardenois) and with the south of the valley of Viosne, in French Vexin; - higher and Oligocene outcrops Eocene lower localized on two banks of Ourcq (Valois and Multien); - higher Oligocene outcrops of the plates bordering the valley of the Marne (Brie); - quaternary zones localized in the valleys (primarily Somme, Oise and Aisne) but represented also well in the Picardy Maritime Plain. The plates established on chalk, more or less started by a network of dry valleys and deeply dissected by the principal rivers, constitute horizontal or slightly tilted surfaces. On the sides of the chalky valleys are often observed projections of a few meters, locally called “curtains”, corresponding in the majority of the cases to a correction of the slope to agricultural ends. The tertiary zones, at least near the chalky areas, have a morphology of pilot hillocks or cuestas more or less marked. Towards the center of the Paris basin, limestones draw beautiful plates cut out by the affluents of Oise and the Marne.

Climate

Picardy belongs to the southernmost fringe of Europe of the North-West and, like the whole of this great geographical field, it is largely occupied during the year by masses of humid air and fresh arrivals of the North Atlantic, heated however by more tepid water of the North Atlantic Drift. In winter, Picardy, generally wetter than cold, is located in western limit of advanced of cold and dry continental polar air. On the heights of Bray and in Thiérache, snow can accumulate and persist a few days. A persistent freshness, a quasi-permanent moisture and powerful winds, especially in edge of the littoral, characterize Picardy. In spring, as in autumn, even in winter, can occur of beautiful sunny days. Picardy climate present many nuances in the course of the seasons and its local varieties where combine altitudes, plains and valleys, slopes sheltered or exposed, more or less marked proximity of the littoral, etc In Picardy, the rate/rhythm of the seasons does not present great contrasts and the length of the intermediate seasons is such as the winter is in extreme cases only one period a little fresher and the summer a few weeks a little sunnier. Springs and autumn are long and almost monotonous, the moderate and fresh temperatures (12 with 15°), the rather frequent rains (15 to 20 days per month) and abundant, the sunning as varied as unforeseeable, of the radiant breaks succeeding in an unexpected way long gray or rainy meetings. These intermediate seasons are the great times of the wind which blows mainly of the west and south-west. Towards the east, these winds moderate and them those of the North-East are affirmed more and more. The summer is rather short and moderate (17 with 20° approximately). The modest sunning hardly exceeds 40% of the annual sunning (approximately 1600 h/an in Saint-Quentin, 1660 H with Abbeville and 1700 H with Creil). The breaks are more frequent than during the close seasons, the hotter sun, the rarer fog and especially less durable. In winter, the variability of the climate is even larger, and if the monthly average temperatures are positive, certain days the thermometer can remain below 0: freezing, glazes and snow are rather unforeseeable. If January and February are the most cold months, they comprise also beautiful days when the cold and dry polar air invades Picardy: the pure ciels and the contrasted temperatures settle for a few days, bringing the frost. Between September and May, only the south of Picardy can escape the risk from cold too early or too late. Inside this general framework, the climate of Picardy is only nuances. Precipitations, for example, vary from 600 mm in the valley of Oise and southernmost Santerre of Montdidier to Compiegne, with nearly 1 m in Thiérache. However from Abbeville with Méru, Castle-Thierry and Laon, it does not fall 700 mm in average year. The month comprising less days of rain (ten) is July in the west and October with Laon where the summer appears less frequently sprinkled. The days of fog are on the other hand more frequent towards the interior (Creil and Saint-Quentin) that in Abbeville. Also moderation is the character dominating of the Picardy climate: average temperatures everywhere close to 10°, soft winters (averages of the coldest month slightly higher than 0°), be hot but without excess, long and varied intermediate seasons. Sometimes the variations take the form of catastrophes: rigorous and snow-covered winters, too hot summers but especially early frosts (as from September) or late (until May), rainy periods which do not finish any more, etc Locally, the facets of the Picardy climate are multiple. The littoral climate is fresh without being cold and thus slightly hotter than inside the grounds, enough dryness, more been windy and less misty. Behind of this littoral of a few kilometers, a fringe of about fifty kilometers, fresh band, copiously sprinkled, especially in autumn and winter, and very been windy. The heart of Picardy, with Amiens to the valley of Oise and Noyonnais, less is sprinkled, more sheltered wind by the Norman high plateaus, sunnier, richer in green valleys and “cuts” sometimes mistier than the plates, and a little hotter too. These characters open out on the Brie, near to Castle-Thierry, where the summer is rather hot but, the continental influences relaying the weakened oceanic influences gradually, the winter becomes slightly colder. Higher, more sprinkled and fresher on the impermeable ground, Thiérache constitutes a small misty country where the winter is the most sprinkled season, character which is outlined already in Laon. The Picardy climate thus knows transitions according to a longitudinal gradient where the oceanic influences yield gradually in front of the more continental tonalities, and also according to an athwartship gradient where towards north the fogs continue, of short duration certainly but frequent, and the reduction in the sunning. Locally, the zones sheltered like the surroundings of Montdidier, Boundary-line or certain sunnier valleys still add to the complexity of the climate. Winter like summer, a climatic cut settles between Chantilly and Clermont, underlining, there still, the existence of southernmost Picardy, a little less misty and a little sunnier, beside septentrional Picardy, more been windy, at more unforeseeable time and the skies more animated even.

Hydrography

In Aisne, three large valleys (the Marne, Vesle and Aisne) indent the escarpment of the cuesta of Ile-de-France. The first river is an affluent of the Seine while the two last join the Oise which constitutes the geomorphological and hydrological main axe of southernmost Picardy. The Sum shares the department of the same name into two, Authie constitutes the limit with the Pas-de-Calais while Bresle makes in the same way with the Seine-Maritime.

Land use

The whole of Picardy is primarily made up of arable lands (60%) but also of wooded areas (19%), meadows (12,1%), artificialized grounds (5,2%), wetlands (1,6%), waste lands and moors (1,5%), finally of market gardenings and fruit-bearing (0,6%).

Natural districts or small countries

Picardy can be subdivided in eighteen natural areas or small countries are six in Aisne (Vermandois, Thiérache, Marlois, Laonnois, Soissonnais overflowing on Oise and Tardenois), seven in Oise (Oise Picardy, Country of Bray, the plate of Thelle, Vexin, Clermontois, Noyonnais and Valois) and five in the Sum (the Picardy Maritime Plain, Ponthieu, Vimeu, Amiénois and Santerre).

Sources

Flatrès P. (1980) Atlas and geography of North and Picardy . Flammarion, Geneva, 423 p.
Minot Mr., Méléard Mr. & Dron Mr. (1982) small countries of Picardy . CNDP, CRDP Amiens, 294 p.
Sweat F. (2007) Birds of Picardy . Picardy Ornithological group, Saint-Quentin-in-Tourmont.

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