Published on Bad Science on Saturday 19th of June 20010.
On the case of the Italian seismologists who failed to predict an earthquake:
http://www.badscience.net/2010/06/burn-the-scientists/
Please, circulate the following letter and sign it. Apparently, earth scientist are supposed now to have paranormal powers and to be able to see the unknown. Or, at least, that is what prosecutors and politicians in Italy believe....
http://www.mi.ingv.it/open_letter/index.php
Open letter to the President of the Republic of Italy
Two weeks ago in Italy, the L’Aquila Prosecutor’s office indicted scientists, some of them members of the “Commissione Grandi Rischi” (Commission for High Risks), and civil protection officials for manslaughter. The basis for the indictment is that these people did not provide a short-term alarm to the population after a meeting of the Commission held in L’Aquila six days before the Mw 6.3 earthquake that struck that city and the surrounding area.
The allegations against the scientists are completely unfounded. Years of research worldwide have shown that there is currently no scientifically accepted method for short-term earthquake prediction that can reliably be used by Civil Protection authorities for rapid and effective emergency actions.
The international seismological community has long recognized that the best approach to defending populations from catastrophic earthquakes is not through earthquake prediction, but through risk mitigation and the application of appropriate safety measures to prevent buildings from collapsing. In this regard, the development of seismic hazard maps, which provide estimates of the probability of occurrence of predefined values of peak ground motion in a given time period, provide the specifications required by building codes to avoid collapse of buildings and the resulting fatalities
Italy is an earthquake-prone country. An improved seismic hazard map that summarizes decades of research on earthquake occurrence and effects was completed in 2004 (see http://zonesismiche.mi.ingv.it/). It is the result of the work of many scientists, it is considered to be one of the best seismic hazard maps in Europe, and it has been used as a basis for the Italian building code beginning in 2008 (“Norme Tecniche per le Costruzioni”, GU n.29 del 04/02/2008). It should be viewed as the primary contribution of the Italian earthquake scientists to their Country.
Seismic hazard maps must also be used for conveying to the population the basic concepts of earthquake hazard, awareness, preparedness, and response. Increased consciousness of the earthquake hazard and associated risk should also foster further prevention actions by national and local authorities. Overall, earthquake preparedness and damage prevention in the form of retrofitting are not only possible but mandatory in a country affected for the most by moderate size earthquakes that often result in catastrophes for the society because of the large percentage of seismically unreinforced buildings.
Education, awareness, preparedness and retrofitting are the best tools for mitigating the impact of the catastrophic earthquakes that will inevitably affect Italy in the future.
The scientific community involved in earthquake science urges the Italian government, local authorities and decision makers in general, to be proactive in establishing and carrying out local and national programs to support earthquake preparedness and risk mitigation rather than prosecuting scientists for failing to do something they cannot do yet - predict earthquakes.
.
In the past weeks I haven't had any time to look for new and attractive websites to present them here, so my selection of "website of the month" is a bit delayed.
But never is to late, as they say, and I have in my bookmarks a very interesting link that you may find useful for yourself or your students, if that is the case: the website of Dr. Patrice Rey, from the School of Geosciences of the University of Sidney.
I guess the website is not very updated, at least in some sections, and I haven't found the way to access the following sections from his homepage, but nevermind, as here you have the direct link to them. He has two teaching modules, organised in the style of an online presentation, with very clear explanations and beautiful graphics:
"Module 1" focusses on thermo-mechanics of lithospheric deformation, with the following sections: Course Outlines, Driving Forces, Isostasy & Gravitational Forces, Heat and Temperature, Continental Geotherms, Thermal Consequences of Lithospheric Deformation, Rheology and Lithospheric Strength y References.
"Module 2" focusses on tectonics, with the following chapters: Course Outlines, Introduction, Finite Strain Analysis, Convergence & Shortening, Divergence & Extension, Gravity Driven Deformation, Transcurrent Tectonics, Finite Strain Field Interferences and References.
So, run to visit the website, and write Patrice if you like it. Surely he likes to see that his online work is not only useful for his students!
_
But never is to late, as they say, and I have in my bookmarks a very interesting link that you may find useful for yourself or your students, if that is the case: the website of Dr. Patrice Rey, from the School of Geosciences of the University of Sidney.
I guess the website is not very updated, at least in some sections, and I haven't found the way to access the following sections from his homepage, but nevermind, as here you have the direct link to them. He has two teaching modules, organised in the style of an online presentation, with very clear explanations and beautiful graphics:
"Module 1" focusses on thermo-mechanics of lithospheric deformation, with the following sections: Course Outlines, Driving Forces, Isostasy & Gravitational Forces, Heat and Temperature, Continental Geotherms, Thermal Consequences of Lithospheric Deformation, Rheology and Lithospheric Strength y References.
"Module 2" focusses on tectonics, with the following chapters: Course Outlines, Introduction, Finite Strain Analysis, Convergence & Shortening, Divergence & Extension, Gravity Driven Deformation, Transcurrent Tectonics, Finite Strain Field Interferences and References.
So, run to visit the website, and write Patrice if you like it. Surely he likes to see that his online work is not only useful for his students!
_
So, here it goes the first Small Geological Fact: Volcanic and plutonic activity in a island arc.
What is the point of this article? I am working right now on a project in western Java. I find the geology in there very complex and obscure, and I realise that understanding more about the type of volcanic and plutonic materials, would help me to understand more the evolution of the volcanic arc. This article won't deal with Java itself, but with a generic volcanic arc.
The main source of information is a nice, affordable and simple (but very useful!) book by Kearey and Vine: Global Tectonics. So, if you want to know more, just read it (full reference at the bottom)
An island arc is created by plutonic and volcanic activity at ca. 150-200 km from the trench axis when the subducting lithosphere reaches a depth of 80 km. The majority of aisland arcs are found in the Pacific Ocean, and some in the Atlantic.
Young arcs are relatively simple to understand, and they are underlain by a crust no thicker than 20 km (i.e. Tonga-Kermadec, New Hebrides, Aleutians and Lesser Antilles). Older and mature island arcs are far more complex, usually build upon previous generations of subducting plate margins. Generally, they are underlain by thicker crust, 20 to 35 km, and they occur in Japan and Indonesia.
Baker(1982) identified three series of volcanic rocks in island arcs:
Now, how is that related with the evolution, structure and zonation of an island arc? How is that relevant for this blog?
The tholeiitic series are found in young arcs, as the are due to magmas formed at 80-120 km depth. The calc-alkali and alkaline series are formed in more mature arcs, because their originating magmas are formed at a deeper depth. In some mature arcs there seem to be a compsitional trend, from the trench, where a tholeiite - calc-alkaline - alkaline volcanis suite developes, representing magmas from progressive deeper levels.
In mature island arcs, plutonic rocks are exposed, which represent the residua of magma chambers which have crystallised at depth. They are generally granodiorites and related igneous rocks and exhibit similar variations to the volcanic rocks.
Sources:
- Philip Keary and Frederick Vine, Global Tectonics, Blackwell Science, 1996.pp 161-163
- Baker, P.E. (1982) Evolution and classification of orogenic volcanic rocks. in Thorpe, R.S. (ed.) Andesites, pp. 11-23, Wiley, New York.
.
What is the point of this article? I am working right now on a project in western Java. I find the geology in there very complex and obscure, and I realise that understanding more about the type of volcanic and plutonic materials, would help me to understand more the evolution of the volcanic arc. This article won't deal with Java itself, but with a generic volcanic arc.
The main source of information is a nice, affordable and simple (but very useful!) book by Kearey and Vine: Global Tectonics. So, if you want to know more, just read it (full reference at the bottom)
An island arc is created by plutonic and volcanic activity at ca. 150-200 km from the trench axis when the subducting lithosphere reaches a depth of 80 km. The majority of aisland arcs are found in the Pacific Ocean, and some in the Atlantic.
Young arcs are relatively simple to understand, and they are underlain by a crust no thicker than 20 km (i.e. Tonga-Kermadec, New Hebrides, Aleutians and Lesser Antilles). Older and mature island arcs are far more complex, usually build upon previous generations of subducting plate margins. Generally, they are underlain by thicker crust, 20 to 35 km, and they occur in Japan and Indonesia.
Baker(1982) identified three series of volcanic rocks in island arcs:
- The low potassium tholeiitic series, dominated by basaltic lavasand lesser volumes or Fe-rich basaltic andesites and andesites.
- The calc-alkaline series, dominated by andesites, more enriched in potassium other incompatible elements and rare earth elements than the andesites mentioned above(in an Andean-type belt, dacites and rhyolites are more abundant).
- The alkaline series, including subgroups of alkaline basalts and shoshonitic lavas.
Now, how is that related with the evolution, structure and zonation of an island arc? How is that relevant for this blog?
The tholeiitic series are found in young arcs, as the are due to magmas formed at 80-120 km depth. The calc-alkali and alkaline series are formed in more mature arcs, because their originating magmas are formed at a deeper depth. In some mature arcs there seem to be a compsitional trend, from the trench, where a tholeiite - calc-alkaline - alkaline volcanis suite developes, representing magmas from progressive deeper levels.
In mature island arcs, plutonic rocks are exposed, which represent the residua of magma chambers which have crystallised at depth. They are generally granodiorites and related igneous rocks and exhibit similar variations to the volcanic rocks.
Sources:
- Philip Keary and Frederick Vine, Global Tectonics, Blackwell Science, 1996.pp 161-163
- Baker, P.E. (1982) Evolution and classification of orogenic volcanic rocks. in Thorpe, R.S. (ed.) Andesites, pp. 11-23, Wiley, New York.
.
In my daily activity as geologist I find many small facts that I have learnt in the past (i.e. during my degree or even before, in secondary school) but, after many years not using them, they simply vanish in the caves of memory.
So, why not a type of entries in the blog, "Small Geological Facts", about things I know are useful in my job at the moment or will be in the future?
Doing a blog requires time. I have many ideas, but not time enough. The result is that no matter how enthusiastic you are, if writing the entries you like takes longer that you expected, finally you will have big time gaps where no articles are created.
Small Geological Facts, that is the answer!
So, soon (very soon!) the first one... Thanks for your understanding!
So, why not a type of entries in the blog, "Small Geological Facts", about things I know are useful in my job at the moment or will be in the future?
Doing a blog requires time. I have many ideas, but not time enough. The result is that no matter how enthusiastic you are, if writing the entries you like takes longer that you expected, finally you will have big time gaps where no articles are created.
Small Geological Facts, that is the answer!
So, soon (very soon!) the first one... Thanks for your understanding!
The Geological Society of London has made freely available two sets of papers at their website, related with the earthquakes ocurred in Haiti and Chile in the past weeks and months. Together with these papers, you can also download a series of publications related with the bicentenary of Charles Darwin:
http://www.geolsoc.org.uk/gsl/publications/lyellcollection/page7188.html
These papers will be available for free until the end of March (Darwin and Haiti topics) and until the end of April, in the case of Chile.
http://www.geolsoc.org.uk/gsl/publications/lyellcollection/page7188.html
These papers will be available for free until the end of March (Darwin and Haiti topics) and until the end of April, in the case of Chile.
If you want to help contributing online, use the Google Crisis Response site dedicated to this earthquake:
http://www.google.com/relief/chileearthquake/
You can also visit your local/national Red Cross organisation:
http://www.icrc.org/
Please, help and forward this message to your contacts and friends.
