(6) Earthquakes, volcanoes, meteorite impacts: risk assessment, Cassandra and Pollyanna.
Format questions:
Also, what exactly would you like for this paper on the risk assessment
of natural disasters? Do you want an explanation of the process and prediction?
Yes. What are the most dangerous geological processes (not necessarily
limited to earthquakes, volcanoes and meteorites), how do these processes
work, and how do we go about assessing and living with the risk?
I was just wondering if on the research paper you would like us to
give a history of the subject as well as answering the question provided.
I suppose it would help to know if we were answering the question for a
general audience, who essentially we could provide this information for,
or if it is more directed towards you. Regardless of the answer I
have already provided this information in my outline, however if you do
not want this information included please let me know.
Assume a general, but scientifically literate audience. Some history
is good, but you can put your own "spin" on the question.
I noticed that in the topic that I'm researching you have it as risk assessment, but does that mean risk assessment of all natural disasters, and not just earthquakes, volcanoes, and meteorite impacts? Do you want us to include tornadoes, hurricanes, and monsoons also? I was just wondering what you wanted us to do about that.
Feel free to add processes, but try to maintain the central theme of risk assessment of natural hazards, there are many common threads.
Content questions:
What is the true reason behind risk assessment if everywhere we go we're subject to some sort of natural disaster we can't control?
While it is true that natural disasters are everywhere, they are not everywhere all the time, and some intelligent risk management can significantly reduce the effects that such disasters have. There are several strategies, but the best is probably observation and avoidance. For example, real estate on the flanks of an active volcano may be cheap, but it is almost never worth building on. The science is in the definition of active, and then it gets interesting. There have been no volcanoes active in this part of Texas for about 100 million years, so it's a pretty safe bet that you don't have to worry about that type of disaster. Similarly we haven't had any significant earthquakes for about 15 million years. Hurricanes do occasionally hit south Texas, but by the time they get to San Antonio much of their energy is spent. However, we do experience serious flooding from time to time. So, building an earthquake proof house is not sensible, avoiding a house in a river flood plain is. There is some element of risk management associated with everything we do, and intelligent evaluation of risk is important - ask an insurance company.
And who are Cassandra and Pollyanna?
Cassandra is a character from Greek history/mythology.
The god Apollo taught Cassandra (a mortal) how to foresee the future. As
with most of these gods, Apollo couldn't keep his thoughts from the carnal.
Cassandra, however, wasn't interested in heavenly sex, but was interested
in knowledge and the skill of prophecy. Apollo was mad, not to say frustrated,
and in a fit of pique made sure that Cassandra would not enjoy her new-found
talent: she would have the gift of accurate prophecy, but no one would
believe her. She predicted many dire events but she was never believed.
She even predicted the result of the Trojans bringing the wooden horse
into their city.
(check out: http://www.loggia.com/myth/cassandra.html)
Pollyanna Whittier is a character from two books by Eleanor Hodgman
Porter, the first was published in 1913. Pollyanna was an orphan who went
to live with an aunt. Through many difficulties and in the face of even
the least pleasant characters Pollyanna manages to retain an optimistic
and cheerful outlook on life.
(see: http://www.bibliomania.com/0/0/39/77/frameset.html)
All hurricanes are given names. I'm assuming that's to track the hurricane and see if it comes again next year. But how do we know the next year that it's the same hurricane? What difference does that make?
Tornadoes are not named. The reason that hurricanes are given names is largely whimsy. In the North Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea, which is where we in the USA expect to see hurricanes, US Air Force and Navy meteorologists began, in the mid-1940's, to informally name hurricanes after their girlfriends or wives. In the early 1950's, tropical cyclones of the North Atlantic Ocean were identified by the phonetic alphabet (Able-Baker-Charlie-etc.), but in 1953 the US Weather Bureau switched to female names. In 1979, the World Meteorological Organization and the US National Weather Service added male names to the list. The names are for the season only and each year the list starts again in the A's. Occasionally a name is "retired" this is done when a storm has caused excessive damage or loss of life:
e.g., hurricane Andrew:
Courtesy Cambrian Systems Inc.
Hurricanes and tropical depressions typically last for about a month,
sometimes two. In the North Atlantic they usually end up expiring on the
western shores of Europe, they do not return year after year.
I understand who Cassandra and Pollyanna are, but what is their
connection with earthquakes, volcanoes, meteorite impacts, and risk assessment?
The reference is there to spark at least two points of view:
Cassandra: "We are living on a dynamic earth and earthquakes, volcanoes
and other natural disasters will kill millions of people."
Pollyanna: "Don't worry, be happy."
In reality we need to understand the risks and act to reduce them. Natural
disasters are only disasters if you get in the way. So what the topic is
all about is: What are the dangerous events? How do they threaten us? What
are the risks and how do we mitigate them?
How do volcanoes that are not along a fault form? I heard that the
North American Plate used to be pulled in both directions, resulting in
the activity in the center, is this true?
Volcanoes not associated with a plate margin - which I assume
is what you are asking about - are often associated with hotspots in the
mantle. These are regions where there is a lot of hot rock rising to the
base of the lithosphere in a fairly focussed way.
check: http://pubs.usgs.gov/publications/text/hotspots.html
Hotspots can last from 10 to 100 million years and often leave tracks as plates move over the top of them. The best known and studied of these is Hawaii. The volcanoes of Hawaii are above a mantle hotspot, a chain of extinct volcanoes stretches away to the WNW and NNW to Kamchatka. These volcanoes increase in age away from Hawaii. The Pacific plate has moved NNW and then WNW over the mantle hotspot which has left this trail of extinct volcanoes.
The North American Plate has been split on at least two occasions once
about a billion years ago and again about 15 to 20 million years ago. Both
of these events generated some volcanic activity in the continent. The
recent one was caused by the opening of the Rio Grande Rift.
Index map:
Detail map:
The tectonic conditions that created the Rio Grande Rift are still active
in the Basin and Range, and there is some volcanic activity associated
with the stretching and transform motion in California and Nevada today
(geologically speaking).
Index map:
Detail Map:
check http://tapestry.usgs.gov/ages/quaternary.html
How accurate can the process of risk assessment of natural
diasters be? Has there ever been a city or state that took action
and prepared for a hurricane or earthquake but in the end was not affected
by it and suffered quite a loss of money?
The town of Mammoth in the Owens Valley of eastern California sits
on the Long Valley caldera. This is the caldera that erupted the Bishop
tuff about 760,000 years ago which entirely buried more than 150 square
kilometers of the region under at least 100 m of ash - Bishop tuff ash
is found in the Gulf of Mexico. The area has many hot springs, experiences
small earthquakes on a regular basis, and has a large volume of molten
rock about 4 to 10 km beneath it. In the 1980's the USGS (United States
Geological Survey) predicted that there was about to be an eruption of
the caldera, based on increased levels of earthquake and hot spring activity.
Many people panicked, property prices fell. No eruption occurred.
In 1991 the volcano of Pinatubo in the Philippines showed signs of increased earthquake and vent activity. The USGS team predicted an eruption and started an evacuation, then halted it, then later restarted the evacuation. Clark US Air Force base was one of the facilities that was evacuated. The USGS team was only 2 hours off in its prediction of the eruption, very few people were killed:
Check: http://wrgis.wr.usgs.gov/fact-sheet/fs113-97/
Pinatubo eruption column over Clark Air Force Base
Ashfall deposits from Pinatubo
Pinatubo also caused a global cooling for about a year because of its large dust and aerosol cloud:
The brown colors show the extent of Pinatubo's upper atmosphere cloud
a few months after the main eruption.
In 1985 the volcano of Nevado del Ruiz in Colombia was in eruption and
a USGS team warned the city of Armero that mudflows triggered by the eruption
would engulf the town. The city ignored the warning and did not evacuate.
The photograph above is of the town after the mudflow. 23,000 people were
killed in a matter of a few hours.
Also, is there any probability of a volcano ever forming in California,
like on the movie "Volcano"?
I have not seen the movie. However, there is some chance of cinder cone activity in southern and eastern California (for example in and around Death Valley), and northern and eastern California has active volcanoes that rival the "best" in the world, e.g., Lassen Peak, Mt. Shasta, Long Valley.
Cerro Negro in Nicaragua, a cinder cone:
Lassen Peak, California in 1914:
Who makes the final decision on whether to evacuate a city in the event that a natural disaster may occur?
I think it depends on the city. In most communities it would be a combined decision by the city manager/mayor's office and police.
Scientists have discovered many large meteorite craters, such as the Barringer Meteorite Crater in the Arizona desert. If meteorites can create such a large area of damage, why do you think there are no reported human deaths (at least as far as I could find) as a result of these meteorites?
The Barringer meteorite struck the Earth about 50,000 years ago. It is possible that there were people living in North America at that time but they did not keep written records even if they lived in that area.
In 1908 above Siberia in the area of Tunguska near Kirensk, a large meteor exploded above the ground surface flattening trees for several kilometres around. (e.g., http://www.psi.edu/projects/siberia/siberia.html). There are eye witness accounts, and had this occurred in a densely populated area many thousands would have been killed. Probably the reason there are no recorded deaths from such events is that they are comparatively rare in human terms, and a glance at a globe will show that most of the Earth's surface is, even now, uninhabited.
After visiting Hawaii, I was amazed by the diversity of the islands' ecosystems. Especially knowing that Hawaii was formed by a series of volcanic eruptions. What determines the kind of vegetation that can grow on dead magma - other than climate? How can life grow out of the apparently dead rock?
In 1963 off the SW coast of Iceland a brand new volcanic island formed. Surtsey, as it is called, was initially a volcanic wasteland. In only 40 years the island has been colonized by a variety of plants and microorgansims that have blown in on the wind, washed in on waves. Hawaii, or at least islands in that vicinity have been in existence for about 80 million years with ample opportunity for life to colonize the volcanic soils. Another factor is that volcanic soils are very productive, they have high levels of nutrients - witness Vesuvius, Etna, and the Canary Islands.
Other interesting volcanic islands with remarkable flora and fauna are the Galapagos Islands in the Pacific.
Check: http://www.vulkaner.no/n/surtsey/esurtmenu.html
What happened to the Guagua Pichincha volcano in Ecuador in 1999?
Why the huge cloud of ashes and no magma (relatively). How can that be
possible?
Guagua Pichincha is a stratovolcano at a mature convergent margin.
As such it is fed by silicic magma. Silicic magma is very viscous (flows
slowly), high in silica (as the name suggests) and has a high volatile
content (high here means 1 to 4%, and volatile means things like water,
and other gases). This is a combination that generates very explosive eruptions
with very small volumes of actual lava. To figure out why lavas at convergent
margins are silicic and volatile-rich refer to the lecture notes on rock
melting.
A good analogy for this is a carbonated drink (water, soda, beer, champagne).
When the cap is on a carbonated drink, the drink is under pressure and
the gas (carbon dioxide) is dissolved in the drink. Once the cap is off,
the gas bubbles out, if the bottle is shaken or bumped (or if the pressure
is released suddenly, in the case of champagne) the gas foams out carrying
the liquid with it. During eruptions of silicic, volatile rich lava, the
gases (water, carbon dioxide, sulfur oxides etc.) foam out of the lava,
but the lava is slow flowing and so large explosions occur and the lava
is blown into small fragments which solidify in the air and fall as ash.
Very little flowing lava is formed.
For more information on Guagua Pichincha:
http://volcano.und.nodak.edu/vwdocs/current_volcs/ecuador/guagua_pichincha.html
You mentioned meteorites as a natural disaster risk. however
since meteorites can strike anywhere and are almost impossible to predict
how do you asess the risk of it striking any given location? Also, how
often do meteorites large enough to be a threat strike the Earth? I don't
remember any in recent history.
On December 15 1996 a meteorite hit Honduras and made a 165-foot wide
crater:
http://www.mcsa.ac.ru/others/iipah/neo/neo96/961216.htm
For some general comments on meteorites and their dangers go to:
http://planet.ou.edu/impacts/
What was the major cause of death in the 1980 Mt. St. Helens eruption?
There were 57 deaths from the lateral blast, ashfall, and lahars (hot mud flows).
Source: http://volcano.und.nodak.edu/vwdocs/frequent_questions/top_101/Helen/Helen5.html
How many different types of volcanoes are there?
1. Cinder cones
2. shield
3. composite
4. ??
There are many types of volcanoes, and many types of eruptive styles. Most volcanoes will display several styles over their active lifespan and even during a single eruptive period. Even though Mt. St. Helens is a stratovolcano that has erupted very violently in the past (pelean to vulcanian), at the moment it is generating a lot of steam and some ash, more akin to a Hawaiian style eruption (minus the lava).
In general basaltic volcanoes will have "gentler", less explosive eruptions,
and the more silicic volcanoes (andesite to rhyolite) will be more explosive.
However, the details will depend on the actual volatile content of the
magma during the eruption, its temperature and volume.
Courtesy Cambrian Systems Inc.
Courtesy Cambrian Systems Inc.
Do either probabilistic or deterministic methods work when trying to predict a meteorite?
Once a meteorite is spotted heading for the Earth the prediction becomes
deterministic, we can calculate its trajectory very accurately. However,
estimating how many such objects there might be in a given time period,
and how big they are is a probabilistic exercise based on past observations.
Could the missile defense program that Bush was talking about a
while back be used to deflect or destroy meteors headed towards earth?
I don't know for sure, but I would be surprised if this technology had any real application here. A meteorite that could be "shot down" wouldn't do much damage and would probably burn up on atmospheric entry. The dangerous objects are several kilometers across and would need to be intercepted well outside Earth orbit and then nudged out of their original trajectory.
During my research of natural disasters many websites have mentioned using SAR ( Synthetic Aperture Radar) to detect different events. Could you elaborate on exactly how SAR works to detect natural disasters and what are its limitations?
What is the primary method scientists use to locate meteorites?
I was reading on this website, http://www.spaceweather.com/glossary/forwardscatter.html,
that NASA scientists use radio meteor listening to locate them, but is
this the only real method?
This method works only for meteors and meteorites once they interact with the atmosphere - that is when they generate radio frequency (and other) radiation. It is cool and it helps us to understand how numerous these things are. This technique does not work for objects further out, but which may strike the earth.
Try: http://impact.arc.nasa.gov/related/FAQ.html
Fairly standard telescopes can be used to look for earth crossing objects that may pose a threat (1 to 2 km across).