Résumé of research into river channel changes conducted in the USSR
Cet article fournit des exemples soviétiques sur les changements des lits fluviaux, afin d'illustrer l'étude des processus de dynamique fluviale faite par K. J. Gregory dans son ouvrage: Changements des lits des rivières, 1977. (RF).
Après une introduction sur la nature de la végétation, l'ouvrage traite de la variabilité de la végétation dans le temps: processus des changements, fluctuations, régénération et changements cycliques, successions primaires, successions secondaires
The effect of man's activities on climatic changes in Evolution des atmosphères planétaires et climatologie de la terre=Evolution of planetary atmospheres and climatology of the earth.
Although considerable uncertainties remain, state-of-the-art climatic theories suggest that major global climatic changes due to human activities are possible as soon as the end of this century.
Geomagnetic variation during the late Pleistocene period and changes in the radiocarbon time scale
The Earth's magnetic field appears to have been weaker than it is today for much of the period 50,000-10,000yr ago. The geomagnetic record can be used to predict changes in the production of radioactive nuclides by cosmic rays interacting
Historical changes in atmospheric trace components in Evolution des atmosphères planétaires et climatologie de la terre=Evolution of planetary atmospheres and climatology of the earth.
Early analyses have not been used frequently in attempts to find changes in the trace composition of the atmosphere. In the case of rainfall analyses records stretch back more than 100 years at some sites, and a long record at Rothamsted in England
shows changes in both nitrogen and sulphur levels due to anthropogenic activity.
Paleoclimatic, paleomagnetic and paleogeoidal changes: complexity and interaction in Evolution des atmosphères planétaires et climatologie de la terre=Evolution of planetary atmospheres and climatology of the earth.
With the theory of geoid changes, sea level records can no longer be taken as a priori evidence of corresponding glacial volume changes. The Fennoscandian ice cap is found to have been 50% larger than generally assumed. The Grande Pile sequence (NE
of the geomagnetic pole: during ice ages the pole was in the Siberian-Arctic region. There is a close correlation between paleomagnetic and paleogeoid changes implying a mutual origin in core/mantle changes. The astronomical variables in the Earth/Sun constellation
have a double effect, affecting both the insolation and the Earth's rate of rotation. They therefore simultaneously generate changes in paleoclimate, paleomagnetism and paleogeodesy. It is uncertain whether the main paleoclimatic effect comes from
the insolation or geomagnetic field changes. A glaciation leads to a complex interaction of geophysical changes. Paleoclimate never has a simple and single explanation: complexity and interaction are key words.
Un des principaux traits du mouvement transitoire de l'eau souterraine est le changement du stockage souterrain de l'eau, commandé par le changement du volume vide de l'aquifère, le changement dans la saturation, le changement dans la densité de
Il y a un certain nombre de théories du changement climatique mais les météorologues n'ont pas encore fourni d'explication satisfaisante du changement climatique. Synthèse des travaux très récents, 1977-1978.
Geomorphic thresholds were defined initially as the condition at which there is a significant landform change without a change of external controls such as base level, climate and land use. Landforms evolve to a condition of incipient instability
following which change or failure occurs. Subsequently, through usage, the definition has been broadened to include abrupt landform change as a result of progressive change of external controls. Therefore, it is now appropriate to recognize both intrinsic
and to predict their change will be of value to land managers and engineers. For example, the development of gullies and fan-head trenches can be explained by the depositional steepening of valley floors and fan-heads to threshold slope. As a consequence, as yet
. Such changes can also be accomplished artificially, when it is recognized that a channel is near a pattern threshold. Sediment yield variations will be related to these periods of instability. Recognition of this will aid in the explanation of some hydrologic
which it persists. The systems and forms are subject, over 10 10 years, to perturbations caused by high magnitude low frequency events, environmental change and internal structural instabilities which initiate change. The responses to these impulses
are complex and include damped, sustained and reinforcing changes taking place by ubiquitous, linear or diffusive propagation which reflect the sensitivity of the landscape to change. This sensitivity is dependent on the path density of the process
Compte rendu des deux congrès ayant porté sur les relations entre l'homme et le climat. Celui tenu à Genève, sous les auspices de l'Organisation météorologique mondiale, a porté sur les changements climatiques récents et les relations actuelles
homme-climat. L'autre, tenu à Norwich à l'initiative du Climate Research Unit a porté sur les changements climatiques depuis la fin des glaciations, jusqu'à nos jours, et des relations entre ces changements climatiques et certains événements historiques.
Some mecanisms of climatic changes induced by encounters of solar system with an interstellar cloud in Evolution des atmosphères planétaires et climatologie de la terre=Evolution of planetary atmospheres and climatology of the earth.