Seafloor Sediments in Orinoco Delta, Venezuela

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

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The Use of Drilling Solid Waste as Amendment of Acid-Sulphate Soils of the Orinoco Delta

10.2118/35880-ms ◽

1996 ◽

Author(s):

P. Vasquez ◽

J. Urich ◽

V. Gonzalez ◽

P. Silva ◽

A. Rodriguez

Keyword(s):

Solid Waste ◽

Acid Sulphate ◽

Acid Sulphate Soils ◽

Orinoco Delta

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Trade and the conservation status of the family Psittacidae in Venezuela

Bird Conservation International ◽

10.1017/s0959270900002021 ◽

1991 ◽

Vol 1 (2) ◽

pp. 153-169 ◽

Cited By ~ 17

Author(s):

Philip Desenne ◽

Stuart D. Strahl

Keyword(s):

Conservation Status ◽

Field Studies ◽

Remedial Action ◽

Trade Data ◽

Orinoco Delta ◽

The Family ◽

Priority Order ◽

Key Sites ◽

Educational Campaigns ◽

National Trade

SummaryAn assessment of trade in parrots throughout Venezuela, 1988–1989, reveals alarmingly high internal and international levels. The national trade has main outlets in major cities, but is now compounded by the use of feathers for Indian artifacts sold to tourists. International trade involves illegal export chiefly from the Orinoco Delta, the majority of such birds (65,000–75,000) destined for Guyana. The large macaws suffer badly from both types of trade, but owing to its restricted range the endemic Amazona barbadensis is perhaps the most critically threatened species. Other species are assessed and, along with key sites, identified in priority order for remedial action, which should include more detailed field studies, rigorous trade data analysis, exchange of trade data with major neighbours, census and monitoring technique improvements, educational campaigns, and strict breeding facility control.

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