Rare Catastrophic Events Research Articles

On the Origin of Tektites

The properties of tektites as yet afford little direct evidence of the source of their material and process of formation, but their forms strongly suggest that they arrive through the high atmosphere at small cosmic speeds. Their ages indicate a frequency of production of tektite-fields of lo6 to lo7 years and this would be consistent with some rare catastrophic event such as cometary encounter or a large meteoritic impact. Immediate formation of tektites by such processes seems not to be possible, but for encounter with a cometary dust-cloud an accretion-stream could result and tektites form secondarily within this. Similarly, a sufficiently large meteorite impacting the Earth could result in the ejection of material far beyond the atmosphere, and this material condensed into fine particles moving in elliptic orbits surrounding the Earth could form an accretion-stream depositing tektites in the antipodal regions of the planet. This last hypothesis seems the most hopeful if a terrestrial origin of the material proves essential, since it would also meet the requirement of final entry of the tektites through the high atmosphere.

Life on the Edge of Chaos

In this article we consider singularly perturbed systems of ordinary differential equations having one swift and one n (n ≥ 3) slow variable. Conditions for the existence of attractors of hard turbulence type and of on-off intermittency are formulated. It is shown that any finite-dimensional system with chaos can be complemented so that it will have one dimension more and hard turbulence will arise. In other words, we propose one possible way of taking into account rare catastrophic events in systems with complicated behavior.

Predicted Mercury Concentrations in Hair From Infant Immunizations: Cause for Concern

Mercury (Hg) is considered one of the world’s most toxic metals. Current thinking suggests that exposure to mercury occurs primarily from seafood contamination and rare catastrophic events. Recently, another common source of exposure has been identified. Thimerosal (TMS), a preservative found in many infant vaccines, contains 49.6% ethyl mercury (EtHg) by weight and typically contributes 25 μg. of EtHg per dose of infant vaccine. As part of an ongoing review, the Food and Drug Administration (FDA) announced in 1999 that infants who received multiple TMS-preserved vaccines may have been exposed to cumulative Hg in excess of Federal safety guidelines. According to the centers for disease control (CDC) recommended immunization schedule, infants may have been exposed to 12.5 μg Hg at birth, 62.5 μg EtHg at 2 months, 50 μg EtHg at 4 months, 62.5 μg EtHg at 6 months, and 50 μg EtHg at approximately 18 months, for a total of 237.5 μg EtHg during the first 18 months of life, if all TMS-containing vaccines were administered. Neurobehavioral alterations, especially to the more susceptible fetus and infant, are known to occur after relatively low dose exposures to organic mercury compounds. In effort, to further elucidate the levels of ethyl mercury resulting from exposure to vaccinal TMS, we estimated hair Hg concentrations expected to result from the recommended CDC schedule utilizing a one compartment pharmacokinetic model. This model was developed to predict hair concentrations from acute exposure to methymercury (MeHg) in fish. Modeled hair Hg concentrations in infants exposed to vaccinal TMS are in excess of the Environmental Protection Agency (EPA) safety guidelines of 1 ppm for up to 365 days, with several peak concentrations within this period. More sensitive individuals and those with additional sources of exposure would have higher Hg concentrations. Given that exposure to low levels of mercury during critical stages of development has been associated with neurological disorders in children, including ADD, learning difficulties, and speech delays, the predicted hair Hg concentration resulting from childhood immunizations is cause for concern. Based on these findings, the impact which vaccinal mercury has had on the health of American children warrants further investigation.

An Empirical Analysis of the Nature, Correlates, and Functions of Dreams.

Risk assessment has been widely adopted in mental health settings in the hope of preventing harms such as violence to others and suicide. However, risk assessment in its current form is mainly concerned with the probability of adverse events, and does not address the other component of risk – the extent of the resulting loss. Although assessments of the probability of future harm based on actuarial instruments are generally more accurate than the categorisations made by clinicians, actuarial instruments are of little assistance in clinical decision-making because there is no instrument that can estimate the probability of all the harms associated with mental illness, or estimate the extent of the resulting losses. The inability of instruments to distinguish between the risk of common but less serious harms and comparatively rare catastrophic events is a particular limitation of the value of risk categorisations. We should admit that our ability to assess risk is severely limited, and make clinical decisions in a similar way to those in other areas of medicine – by informed consideration of the potential consequences of treatment and non-treatment.

Mass Extinction——A Fundamental Indicator for Major Natural Divisions of Geological History

Abstract In the Phanerozoic, there are three major geological boundaries: Precambrian / Cambrian, Permian / Triassic and Cretaceous / Tertiary. Studies of these boundaries in China and over the world strongly suggest that they have the following similar features: mass extinctions of many, taxa, positive anomalies of platinum‐group metals, and abrupt changes of stable isotopes (δ13C). It is quite probable that these were the consequences of some rare catastrophic events of extraterrestrial origin. Hence, the three above‐mentioned mass extinction events may be regarded as key indicators for the division of the geological history of the Phanerozoic.

Frequency‐Cost Curves and Derivative Risk Profiles

Frequency‐cost curves (used to describe risks and to prescribe limits on “acceptable risks”) are examined with regard to their information content. Frequency density functions, expected cost density functions and cumulative expected cost distribution functions (analogous to probability distribution functions) are proposed to describe explicitly the distributions of frequency and expected cost which are implicit in frequency‐cost curves. It is shown that frequency‐cost curves can conceal rare catastrophic events that are critically important with regard to expected costs. Therefore, curves of frequency density, expected cost density, and cumulative expected cost are recommended (instead of frequency‐cost curves) for the description of risks.

Storm Deposits (Tempestites) in Ordovician Cratonic Carbonates (Arbuckle Group, South-Central Oklahoma): ABSTRACT

The Early Ordovician Kindblade Formation (Arbuckle Group), exposed in the Arbuckle Mountains of south-central Oklahoma, is a shallow marine epicontinental carbonate sequence that contains numerous storm deposits. Similar deposits also occur in other Arbukle Group units, although not as abundantly as in the Kindblade Formation. The storm deposits (tempestites) are of two types, proximal and distal; the latter dominates in terms of both number and aggregate thickness. Distal tempestites consist of a fining upward sequence, 5 to 50 cm (2 to 20 in.) thick, that overlies an eroded hardground or firmground. The sequence consists of a lag lithoclastic grainstone that grades up into a laminated peloidal grainstone and then into mudstone. Firmgrounds are characterized by hummocky, sharp, and erosional contacts (relief 2 to 7 cm, 0.75 to 2.75 in.) with grainstone-filled erosive pockets. Hardgrounds are characterized by sharp hummocky-to-convolute surfaces (relief < 4 cm, 1.5 in.), which are mineralized and bored. Primary sedimentary features such as laminations, burrows, and allochems are truncated at the surfaces, and borings are filled with unsorted lithoclasts. The lithoclasts at the base of the sequence are bored, generally well rounded, discoid in shape, and consist of mudstone, peloidal packstone, and oolitic grainstone. Infiltration fabrics within the lithoclastic grainstone include cement-filled shelter voids beneath large clasts and internal sediment perched on the upper surfaces of lithoclasts. The overlying peloidal grainstones contain ripple cross-la inations, plane-laminations, and hummocky cross-stratification as well as rare escape burrows. The overlying mudstone is sparsely fossiliferous and bioturbated with burrows either selectively dolomitized or infilled with lithoclastic grainstone. Although there are many examples of the ideal sequence described above, complex composite or amalgamated beds are also common. Proximal tempestites consist of coarse lithoclastic flat pebble conglomerate beds approximately 1 m (3.25 ft) thick that are interbedded with ooid grainstone and overlie mudstone. The contact between the units is sharp and erosional. The lithoclasts are of variable composition and may be up to 20 cm (7.75 in.) in diameter. The two types of tempestites occur in crude cycles, which consist of distal deposits overlain by proximal tempestites and ooid grainstones. The cycles are interpreted as shallowing-upward progradational sequences. The abundance of the storm deposits in the section, approximately one every 20 cm (7.75 in.), indicates that hundreds of storm-induced events are recorded in the Kindblade Formation. The tempestites represent rare catastrophic events, while the hardgrounds-firmgrounds are discontinuity surfaces that represent gaps in the sequence. End_of_Article - Last_Page 471------------

Holocene stratigraphy in flood frequency analysis

The risk of rare catastrophic flood events is extremely difficult to evaluate by using conventional flood frequency analyses. The true return period may be so long compared to gaging station or historical records that the stratigraphic record of the Holocene (0–10,000 years B.P.) may be the best method for assessing the risk of outstanding floods. Several geologic methods applicable to flood frequency analysis are (1) tree ring analysis of floodplain trees destroyed or scarred by floodwaters, (2) radiocarbon dating of organics in deposits (landforms) eroded by recent floods, (3) radiocarbon dating of organic materials in older flood deposits, (4) pollen analysis and radiocarbon dating of organic materials in lenses of fine‐grained alluvium buried by coarse flood deposits, (5) radiocarbon dating of soil horizons or organic material in slack‐water deposits, (6) radiocarbon or archaeological dating of soils developed in older flood deposits, and (7) dating of landforms eroded or buried by floods based on changes in quantitative soil properties versus time. Using one or more of the above geologic techniques, return periods of some recent catastrophic floods in the United States are: 1976 Big Thompson River, Colorado, 5000 years (?); 1964 Klamath River, California, 100 years (?); 1972 Western Run, Maryland, 2100 years (?); and 1972 Elm Creek, Texas, 400 years (?).