African Journals Online
The Zimbabwe Science News

Volume 34 Number 3&4, December 2000

Earthquakes in Zimbabwe

R.Clark
School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK

ABSTRACT
Earthquakes are one of the most destructive natural forces, in both human and economic terms. For example, since 1900, 10 earthquakes have occurred that each killed over 50 000 people. Earthquakes in modern industrialized areas can be also be very costly, even if well designed and constructed buildings save many lives. In Zimbabwe, beginning in February 1959 prompted by fresh seismic (earthquake) activity after the Kariba Dam was sealed in December 1958, seismograph stations began to be installed in the region. Seismographs detect ground vibrations. By 1970, the network consisted of 6 stations (including 1 each in Zambia and Malawi), was operated by the Zimbabwe Meteorological Services from the Goetz Observatory in Bulawayo. Almost all earthquakes in Zimbabwe occur in the Hwange-Zambezi-Kariba or Eastern Highlands areas. Sensitive engineering structures such as the Kariba Dam and power generating facilities around Hwange lie in these areas. However, the central part of Zimbabwe (including the two main cities, Harare and Bulawayo) has almost no earthquakes, only ~1% of the total. Fortunately, most earthquakes in Zimbabwe are quite small: of the ~3 400 earthquakes recorded in a 32 year period, only 30 exceeded a magnitude of 5 on the Richter Scale. The largest earthquake recorded here was in 1963, beneath the newly filled Lake Kariba, measuring 5.8 on the Richter Scale.





Options for the recovery of Warburgia salutaris  (Pepperbark tree) populations in Zimbabwe

A. Maroyi
Department of Biological Sciences, Bindura University of Science Education, 
P Bag 1020, Bindura 

ABSTRACT
The "Pepperbark" tree, Warburgia salutaris (Bertol. f.) Chiov., is a small to medium tree (5 - 10 m) facing a high risk of extinction in the wild. It is now a critically endangered species in Zimbabwe. It has undergone a considerable decline throughout its natural habitat (range) in Zimbabwe mainly due to over-exploitation for medicinal purposes. Any part of the plant can be used for treating various ailments, fetching a very high price on the market. A full botanical description, of the species, its significance for economic use, past distribution and historical background are discussed in this paper. The options available for its cultivation and successful reintroduction to its historic range are described.


The chemistry of nickel and copper production from sulphide ores

I. Love
Department of Chemistry, University of Zimbabwe, P O Box MP 167, Mt Pleasant, Harare
Email: [email protected] 

ABSTRACT
Nickel is one of Zimbabwe's principle metallurgical exports. It is processed to a very high level of purity and hence has a high value. The economics of nickel production can be difficult, as the selling value of nickel varies tremendously with time, from a low of US$ 3 900 per ton in late 1998 to US$ 10 100 per ton in May 2000, and to US$ 8 500 less than a year later. By contrast, copper is essentially a minor product in Zimbabwe, although still of significant value. It is now produced mainly from ores which are mined and processed in order to obtain more valuable products: nickel and gold. Sulphide copper ore was mined until recently near Chinhoyi, and processed at the nearby Alaska Refinery, producing crude (blister) copper which was then electrolytically refined. These mines have since closed, but the smelter and refinery now aim to process concentrates and matte from elsewhere. As will become clear, this process, although simpler, has many similarities to that for the combined nickel copper process. Copper is also produced at the relatively new Sanyati Mine, where the process involves acidic heap leaching of oxide ore, solvent extraction to concentrate the copper solution, and subsequent electro winning of the copper.


Crop variety release notices

P. N. Nyakanda
Groundnut Breeder, Crop Breeding Institute, Department of Research and Specialist Services, P O Box CY550, Causeway, Harare

Release of a short season groundnut variety: "Jesa"
"Jesa", a short season groundnut variety was accepted for commercial release by the Crop Variety Release Committee in September, 1999. The objective in putting it up for release was to widen the choice of improved short season groundnut varieties available to farmers. Jesa was developed using the bulk selection method for phenotypically similar plants at Chitedze Research Station, Malawi by the Southern African Development Community/International Crops Research Institute for the Semi-Arid Tropics (SADC/ICRISAT) Groundnut project. The variety was first introduced into Zimbabwe through this regional groundnut project and was assessed in national breeding trials from 1990/91 to 1997/98. Results from the advanced variety trials conducted at various research stations between 1994/95 and 1997/98 are summarized in the paper.


Release of a short season groundnut variety: "Teal"
Teal, a locally bred short season groundnut variety, was accepted for commercial release by the Crop Variety Release Committee in September, 1999. The objective in proposing release of this variety was to make available a short season variety with larger seeds and improved overall seed quality, relative to existing short season varieties. Teal was selected as a single plant in 1988/89 from a segregating population of a local cross 93 made at Harare Research Station between P1/6/147 and Valencia R2. The variety was first evaluated in progeny rows in 1989/90 and in replicated trials in 1990/91. Results from the advanced variety trails conducted at various research station trials between 1994/95 and 1997/98 are summarized in the paper.