Bøger i Earth Evolution Sciences serien

Attention to the problems posed by natural hazards in West and Central Africa was brought into sharp focus by the deaths of an estimated 1700 people in the valleys to the north of Lake Nyos in 1986.

Fractures, Pseudotachylite Veins and Breccia Dikes in the Crater Floor of the Rochechouart Impact Structure, SW-France, as Indicator of Crater Forming Processes.- Impact Structures in Brazil.- The Sudbury Structure, Ontario, Canada ¿ A Review.- Continuous Deposits of the Ries Crater, Germany: Sedimentological and Micropaleontological Investigations of NASA Drill Core D.- The Rb-Sr-Age of the Rochechouart Impact Structure, France, and Geochemical Constraints on Impact Melt-Target Rock-Meteorite Compositions.- The Use of Airborne and Spaceborne Radar Images for the Detection and Investigation of Impact Structures.- The Hico Impact Structure of North-Central Texas.- Book Review.

La Reunion is an oceanic intra-plate volcanic island located at the southern-most part 0 of the Mascarene Basin at 21 0 07' S, 55 32' E (Figure 1). It lies south of the Mascarene Plateau and Mauritius Island but is a distinct topographic feature on the rather flat ocean bottom of the Mascarene Basin, whose age is paleocene in the vicinity of the island (Schlich, 1982), and whose lowest point is more than 4000m deep. La Reunion is ellip­ tical in shape (50 X 70 km) with a NW-SE elongation. It is composed of two volcanoes: Piton des Neiges and Piton de la Fournaise. A third volcanic structure has been recent­ ly discovered on the east submarine flank of the island (Unat et aI. , submitted). Piton des Neiges, a dormant and deeply eroded volcano, rises to a height of 3069 m and oc­ cupies the northwestern two-thirds of the island. Piton de la Fournaise (2630 m), one of the most active basaltic volcanoes in the world, began to grow more than 3. 5 X 1O~ years ago on the southeast flank of Piton des Neiges. The evolution of Piton de la Fournaise (Chevallier and Bachclery, 1981) is marked by the formation of three sub-concentric nested calderas (Figure 2). The boundaries of the two older calderas are more or less buried or eroded.

Within the last decade or so, the accelerated growth of Nigeria in the fields of urbanisation, population, business as well as industry has led to some attention in assessment of available water resources in various parts of the country.