Alumnae Bulletin
August 2010

Taking measure of disasters
Geology 209: Natural Hazards

By Alicia Bessette

The what, why, and how surrounding devastating natural phenomena

Geology 209: Natural Hazards scours “big picture” issues: why, for example, an earthquake of a certain intensity may cause more deaths in a developing nation than in an industrial nation, and how earthquake hazard maps could mitigate damages.

The course takes a quantitative approach to studying the causes and impact of floods, volcanic eruptions, storms, landslides, and other extreme natural hazards on the lives of people and communities, and the geology behind these often-devastating phenomena. Case studies are drawn from contemporary and ancient societies.

“Natural hazards are a big part of life in countries around the world,” says Associate Professor of Geology and Department Chair Arlo B. Weil. “More students are coming to Bryn Mawr with an anecdotal understanding of natural hazards, which they get from following the media coverage. The idea is to deepen that understanding.”

Natural Hazards is one of Bryn Mawr’s most popular classes; the last time it was offered, more than 70 students enrolled.

Weil often shows news clips of recent events such as Hurricane Katrina and the Sumatra tsunami. He and his students analyze related data and discuss what went wrong and why: the social, economic and policy contexts within which natural geologic processes become hazards.

“Because some students go on to pursue careers in government, policy, and business, many of the implications for natural hazards can be applied to the professional aspects of their lives,” Weil says. “Natural Hazards emphasizes the actual risk that natural disasters pose, versus the perceived risk that people associate with them. We also look at the geographical distribution of natural hazards, and various methods of response.”

A complete understanding of natural disasters requires concepts from mathematics (algebra and geometry), physics and chemistry. Weil assigns weekly problem sets to emphasize the quantitative aspects of the lecture topics; those problem sets make up the majority of the final grade. Many of the problem sets demand Microsoft Excel, and they cover everything from celestial mechanics and weather analysis to sand transport and plate tectonics.

“The main inspiration for why the class was developed, from the geology department’s standpoint, is to provide students with a different way to satisfy their quantitative requirement,” Weil says. “We use rigorous quantitative techniques in an applied way.”

His teaching goal is to develop students’ fundamental quantitative literacy. To that end, students plot data, make correlations between different factors, study linear and exponential relationships, and get acquainted with statistical measurements and graphs.

In addition to his regular office hours, Weil sets aside time each week to be available for students who might need extra help solving the weekly problem set.

The quantitative aspect allowed Haverford graduate and chemistry major Casper Hu ’10 to view his senior thesis—on organic contaminants in marine sediment—from an environmental geology perspective.

“I didn’t really have any idea what geology was when I first came to Haverford,” Hu says. “I just thought geology meant rocks. I heard good things from my friends and so I took the class and really liked it. It’s one of the best, if not the best class I’ve taken so far. And it’s pretty accessible, even to non-science majors.”

Students also keep journals in which they document five significant natural hazard events that make media headlines during the semester. Each entry should discuss the event’s implications or consequences, and how damages were, or might have been, mitigated.

The journal requirement makes students pay attention to world events, says Weil. “When students are really interested in the class, they’ll ask me questions about what they saw on the news, or they’ll tell me about the Nova special they caught. The journal allows them to really think about the events that occur, within the context of the class. Students seem to enjoy it because it empowers them to speak intelligently about something they might not have been able to speak intelligently about before.”

“Now when reading news articles that discuss these hazards, I can analyze them and use the background I gained from this class to achieve a better understanding,” says geology major Sarah Matteson ’11, who is concentrating in environmental studies and has a special interest in the relationship between humans and the environment.

In addition to the journal and weekly problem sets, students take two one-hour midterm examinations and one final exam. A combination of problem solving and short answer questions, the exams test students’ grasp of theoretical concepts from homework, as well as their qualitative understanding of topics discussed in lecture.

“Including the earthquakes in Chile and Haiti, I will likely start this fall’s Natural Hazards class with a dialogue about hazard mitigation and the importance of culture and resources on the impact of natural disasters,” Weil says.

An example of a weekly problem set:

In a volcanic eruption the tephra (a collective term for all material ejected from a volcano and transported through the air) reaches a maximum elevation (ho) of 10000 feet from the vent of the volcano.

a) What was the initial velocity of the tephra as it was ejected from the volcano (assume the elevation of the volcano is 2500 meters)? To find the velocity use the kinetic energy equation and set the kinetic energy of the tephra as it explodes equal to the total potential energy the tephra has as it stops at its maximum elevation.



KE = (1/2)mv2
PE = mgh

b) Once the tephra starts flowing down the side of the volcano, it will start to lose its total energy through friction as a function of the horizontal distance (x) away from its starting point. The total energy, as a function of horizontal distance, decreases as:

Etotal (x) = mg (ho - Ax) = KE + PE

where x is the horizontal distance away from the summit, and A is the friction coefficient, A = 0.2. What is the maximum horizontal distance the tephra can travel? (Hint: the maximum distance is reached when the tephra’s velocity is zero).

A journal entry from the NH journal of Sarah Matteson ’11

Dam Bursts In Indonesia

At around 2 a.m. on Friday, March 27, a large dam ruptured in Indonesia on the outskirts of the city Jakarta. Prolonged heavy rains on Thursday March 26 are believed to be the cause of the broken dam. This event caused a wall of water and mud to hurtle down through an urban area located in a low-lying valley. At least 77 people are dead, some still missing, and hundreds of houses are flooded and damaged. On Friday evening, debris was cleared so that the water levels would lower and search and rescue teams were sent out to find the stranded victims (searching through mud and water). The dam was built in 1933 and there has been a lack of maintenance of the dam (as well as other dams in Indonesia) since then. The flooded city also has a lack of maintenance with their drainage system, which also contributed to the major flooding. The dam is planned to be rebuilt with new modifications.

This event could have been easily prevented through better maintenance, warning techniques, education, and more efficient mitigation. First of all, the dam was not kept in good condition; therefore, it was just a matter of time before it was going to burst. It was unfortunate timing that the dam gave way in the middle of the night when most people were asleep. That is one reason that so many people died. However, fewer lives may have been lost if an early warning system was set up in the city (also because the area experienced other flooding events). There was also confusion with evacuation, which added to the death toll. The citizens should have been warned of the impending danger that could occur during heavy rain periods. Even with a new and improved dam being built, the same dangers still exist for any towns/cities built downslope from the dam. Streams always desire to be at equilibrium (dynamic equilibrium), so the stream works to remove anything that’s in its path (dams) preventing it from being at equilibrium. The safest route for the future would be to not rebuild the town right below the dam if they do decide to rebuild the dam. But, if they do rebuild both, keeping up with maintenance, better education for the citizens about evacuation and the status of the dam, as well as the addition of an early warning system, will all prevent against another devastating event.