About This Item
Share This Item
ABSTRACT: Paleo-Hazard Recognition in Coastal Settings—Microfossil Determinations of the History and Precursors of Major Catastrophic Events
David B. Scott1 and Jere H. Lipps2
1Centre for Environmental and Marine Geology, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada
2Museum of Paleontology, University of California, 1101 Valley Life Sciences Bldg., Berkeley, California 94720-4780
Many catastrophic events (e.g., earthquakes, large storms) occur on or close to ocean coastlines and because over 50% of the world's population lives within 100 km of a coastline, advance notification of more than a few hours of hurricanes/typhoons, tsunami, or earthquakes is important. In this respect, the history of occurrence of these is essential in understanding and planning for such events. Cores taken in coastal areas, particularly wetlands, can provide indications of periodicity or repetitions of hurricanes/ typhoons, earthquakes, and tsunami. Around the Pacific Rim, particularly on the west coast of North America, a “precursor” event a few years before an actual megathrust earthquake in coastal sediments has been detected, suggesting a possible advance warning mechanism.
Microfossils provide accurate paleo-indications from small diameter cores that are not readily obtainable by any other means. In particular, marsh foraminifera provide an accurate paleo-measurement of former sea levels and are a key to detecting small sealevel and crustal movements prior to megathrust earthquakes. These fossils are also useful for determining the presence of tsunami layers that are re-deposited from deeper water depths and the periodicity of such events at any one site. The same is true along coasts prone to hurricane/typhoon strikes. Foraminifera from a marsh indicate the origin of sand layers—if the layer has an abundance of calcareous offshore foraminifera, it very likely resulted from a violent storm, because normal storms usually do not rework offshore material over a beach ridge and into wetland areas. These layers are rapidly buried and leave an excellent record of hurricanes in the coastal setting. With sufficient records, probabilities of hurricane strikes, tsunami occurrences, earthquakes, and precursors to megathrust earthquakes can be determined for specific areas that could save many lives with the development of early warning systems.