|Department of Earth and Atmospheric Sciences
Hazards and Disasters
Last updated October 18, 2005
Studying and understanding the worst that nature can throw at us is one of the most interesting parts of being an Earth scientist. Defining 'worst' is, of course, subjective, and leads to a choice over whether the number of deaths, or $$ property damage, is the statistic to use. Here is a representative collection of some of the 'big ones', organized in more or less inverse chronological order.
1. The October 8, 2005 magnitude 7.6 earthquake in Pakistan was not especially large, but the more than 40,000 victims has raised it to the level of a major catastrophe. Without doubt, however, the most devastating loss of life in recent years was the much larger 9.3 Sumatra-Andaman earthquake (the third largest ever recorded) / tsunami in late 2004 that is now estimated to have claimed 275,000 lives. The tsunami was responsible for the bulk of the damage and casualties. The total costs of these events are still to early to measure, but probably won't exceed the property damage caused by the 1995 Kobe earthquake, now estimated at more than $150 billion. Within the US (excluding earthquake-prone Alaska), neither the Los Angeles Quake (1994) nor even the great San Francisco event of 1906, were nearly as damaging.
2. Hurricane Katrina, however, was a major international story. It struck the vulnerable US Gulf Coast in August 2005 and brings the still-rising death count to over 1,000, which is serious but not remarkable for a major disaster. But together with extensive urban flooding that was a secondary effect, damage estimates from insurance costs alone are at $30 billion, with total rebuilding likely to exceed Kobe. This is easily the most expensive disaster ever to hit the US, eclipsing Andrew in 1992. Interestingly both hurricanes landed twice, first in Florida, then in Louisiana. From Andrew the death toll was 'only' 26, but the property damage added up to (what was then) a staggering $25 billion.
3. The list contains several volcanoes. That of the Nevado del Ruiz (Columbia) in 1985 ended the lives of 25,000 people, most of them caught in a massive mudflow that poured down the stricken mountain. By comparison the Mount St. Helens eruption (1980) shattered the peak but had few victims.
4. The most devastating earthquake in modern times was the famous 1976 Tangshan magnitude 8 event in China, whose toll varies between the official 255,000, and a possible 655,000. This event truly began the modern era of intense seismic hazard monitoring in China and the West. Little is known of an earlier lethal earthquake that struck the Chinese city of Shaanzi in 1556. No magnitudes are quoted, and of course no recordings exist, but it is said to have taken the lives of 830,000 people.
5. This choice again highlights volcano-related disasters. Should I choose the Tambora, Indonesia volcano of 1815, in which 80,000 people died of the subsequent famine, or the famous Krakatoa explosion, again in Indonesia, in 1883 in which more than 50,000 people perished, many of them like Sumatra engulfed in a tsunami? Well, you see I did both!
6. Very close to home here, the New Madrid earthquakes of 1811-12 in southern Missouri remain the largest (3) earthquakes ever to hit the contiguous U.S. The main event is now estimated at a magnitude 7.8, although some earlier reports placed it higher (>8). Damage was relatively light due to the sparse population at that time in the Mid-West. Not so if it would happen today!
7. The event in 1737 that may have killed some 300,000 people around Calcutta, India, is now ascribed to a typhoon (the Asian equivalent of a hurricane) combined with massive flooding. Originally thought to be an earthquake, this is unlikely from a tectonics point of view - the major Himalayan seismicity is well to the north. This could be the most catastrophic atmospheric event ever recorded in terms of casualties.
8. Sounded by the bright blue Mediterranean Sea is the remnant of Stroggli, an island that literally blew up somewhere around 1500 B.C. Now known as Santorini, the volcanic explosion (and the undoubted associated tsunami) virtually eradicated the wonderful Minoan civilization. Unlike Pompeii, the population may have been warned of the impending disaster because few bodies have been found. Plato himself clearly referred to Santorini as the site where the city of Atlantis disappeared under the waves.
9. Considerable evidence exists for a major global paleoclimate event that happened around 3000B.C. It appears to have affected sea-level changes, vegetation and much surface chemistry. There is speculation that this event is in fact the Biblical Flood of the Old Testament. Scientists naturally avoid equating 'natural' disasters with 'Acts of God', but in this case the time coincidence is very suggestive.
10. Perhaps the most devastating known mass extinction occurred at the Cretaceous-Tertiary Stratigraphic Boundary, 65 million years ago, and ended not only the dinosaurs but countless thousands of other species. The evidence now strongly favors an asteroid impact (off the Yucatan peninsula), rather than a volcanic eruption. Both of course are popular box office material.
The future? As modern disasters generate ever increasing news coverage, we might naturally ask whether things are getting worse. For hurricanes in the Gulf of Mexico, the answer is yes because of the apparent 30 year cycle in ocean / atmospheric conditions that is currently favorable. For volcanoes and earthquakes we say no - there is no evidence of worsening. The processes that are driving plate tectonics will continue unabated, and in the same locations, for tens of thousands of years!
Selection by David Crossley, Professor of Geophysics.