Group Four Project (Team 9): 2011

Monday, 11 April 2011

THE ANSWER TO OUR RESEARCH QUESTION : Conclusion

HOW HAS THE JAPAN EARTHQUAKE SHORTENED DAYS ON EARTH?

From a marine scientist perspective, we can understand how the earthquake was formed and what changes took place in the tectonic plates that were involved in the quake. The movement of the plates was due to subduction of the Pacific Plate under the Philippine plate and the friction resulted in an earthquake. Because the subduction was so abrupt, everything on the plates also shifted which decreased the diameter of the earth by a very small amount but still large enough to shorten the day slightly. This is explained further lower down using diagrams to illustrate the shifting of the plates.

The earth is divided in layers of different composition so different structures. The crust is the superficial layer therefore the one we are in contact with. It is divided in two main parts the oceanic crust and the continental crust(that forms the tectonic plates), they have respectively a density of 3g.mol-1 and 2.7g.mol-1. Considering these densities and the amount of the crust; we can easily come to the conclusion that the masses involved are huge and a small movement can change a lot of things as the axis the Earth

From the physics point of view, it was explained how a change in the diameter of the solid spherical earth causes a change in the earths's period, that is, the length of the day on earth.

A lower R(new) value (new radius) will give us a lower T(new) value (new period) and vice versa. This explains how, due to the reduced radius of the earth, the length of the day, that is, the Period of the earth was also reduced.

Procedure of Investigation.

Though the content in our blog seems to be rather short and precise, the procedure through which we reached the conclusions presented in the different blog posts, was quite lengthy. We have done a lot of reading mostly from websites, all of which are cited in the bibliography in the former post.

In terms of the physics approach, the topics explaining the phenomenon was something we have never come across before. It was a completely new topic and was rather challenging for us to properly understand. However, after further research and some help from our Physics teacher, it was finally understood. Some research regarding definitions were done from various websites, all of which are cited in the bibliography as well as the individual blog post. The understanding of a completely new topic, and thus reaching a conclusion, answering a major part of our research question was truly an accomplishment.

We have also done a lot of research on plate tectonics and mass distribution of the earth from various online sources, all of which are cited in individual posts as well as in the bibliography.

We have done a lot of reading from which we may not have cited texts from however have gained valuable information which aided in our understanding of the topics. All those sources are also cited in the Bibliography.

After all the research, and complete understating of the topics we had to cover, we compiled all the information collected and wrote down our understanding of the topics, in our own words, as the posts.
We tried to simplify our text as much as possible simply for the ease of understanding of the readers.

At the end of the day, we were successful in answering our research question.

BIBLIOGRAPHY

"NASA - Japan Quake May Have Shortened Earth Days, Moved Axis." NASA - NASA.gov. Web. 12 Apr. 2011. <http://www.nasa.gov/topics/earth/features/japanquake/earth20110314.html>.

"Japan Earthquake and Tsunami: Earth's Day Length Shortened as Axis Tilted by 25cm | Mail Online." Home | Mail Online. Web. 12 Apr. 2011. <http://www.dailymail.co.uk/sciencetech/article-1365821/Japan-earthquake-tsunami-Earths-day-length-shortened-axis-tilted-25cm.html>.

"How the Japan Earthquake Shortened the Earth Day | Japan Earthquake & Tsunami | Natural Disasters, Earth Tilt & Earth's Axis | Space.com." Space, NASA Information & News | Outer Space Flight Videos & Pictures | Astronomy, Solar System Images | Space.com. Web. 12 Apr. 2011. <http://www.space.com/11115-japan-earthquake-shortened-earth-days.html>.

"Earth's Day Length Shortened by Japan Earthquake - CBS News." Breaking News Headlines: Business, Entertainment & World News - CBS News. Web. 12 Apr. 2011. <http://www.cbsnews.com/stories/2011/03/13/scitech/main20042590.shtml>.

Rice, Doyle. "NASA: Japan Quake Shortened Earthâ€™s Day, Shifted Axis - Science Fair: Science and Space News - USATODAY.com." News, Travel, Weather, Entertainment, Sports, Technology, U.S. & World - USATODAY.com. Web. 12 Apr. 2011. <http://content.usatoday.com/communities/sciencefair/post/2011/03/japan-earthquake-shifted-earth-axis-shorter-day-nasa/1>.

"Angular Momentum." Wikipedia, the Free Encyclopedia. Web. 12 Apr. 2011.
<http://en.wikipedia.org/wiki/Angular_momentum>.

"Moment of inertia." Wikipedia, the Free Encyclopedia. Web. 12 Apr 2011.
<http://en.wikipedia.org/wiki/Moment_of_inertia>.

"Moment of Inertia, Sphere" Test Page for Apache Installation. Web. 12 Apr 2011.
<http://hyperphysics.phy-astr.gsu.edu/hbase/isph.html>.

" The Science Behind Japan's Earthquake and Tsunami | Seismology & Disaster | LiveScience " Current News on Space, Animals, Technology, Health, Environment, Culture and History | LiveScience Web. 12 Apr 2011.
<http://www.livescience.com/13187-japan-earthquake-tsunami-science-faq.html>.

Civil Engineer. Web. 12 Apr. 2011.
<http://www.civilengineergroup.com/earthquake-knowledge.html>.

"Earthquake Animations." John C Lahr Fun with Science. Web. 12 Apr. 2011. <http://www.jclahr.com/science/earth_science/animate/>.

"Crust." University of Wisconsin-Stevens Point. Web. 12 Apr. 2011. <http://www.uwsp.edu/geo/faculty/ritter/glossary/a_d/crust.html>.

"Care2.com: the Page You Have Requested Is Not Available." Web. 12 Apr. 2011. <http://dingo.care2.com/pictures/c2c/>.

"Chile Earthquake Altered Earth Axis, Shortened Day." Daily Nature and Science News and Headlines | National Geographic News. Web. 12 Apr. 2011. <http://news.nationalgeographic.com/news/2010/03/100302-chile-earthquake-earth-axis-shortened-day/>.

"Japan's Earthquake Moves the Earth's Axis 15 Cm - English." Ultimas Noticias En Toda Noticia. Web. 12 Apr. 2011. <http://www.todanoticia.com/24893/terremoto-japon-desplaza-eje-tierra/?lang=en>.

"Tsunami Increased the Speed of Our Planet." Physics Help and Math Help - Physics Forums. Web. 12 Apr. 2011. <http://www.physicsforums.com/showthread.php?t=58249>.

"Japanâ€™s Earthquake Changed Earthâ€™s Rotation - Anything Goes!" Acid Pixels. Web. 12 Apr. 2011.<http://acidpixels.com/blog/japan/japans-earthquake-changed-earths-rotation/>.

Friday, 1 April 2011

How the Earth's mass is redistributed after an earthquake

The information presented below were all obtained from various internet sources (all of which are listed below) and this post is a compilation and a summary, in simple words for ease of understanding of the readers, of the whole process taken into consideration for the research.) Nothing has been directly pasted from a single source.

The Earth is spherical shaped and count a number of layers. The internal structure of the Earth is as shown

http://www.uwsp.edu/geo/faculty/ritter/glossary/a_d/crust.html

Each layer has specific properties as temperature and pressure (increasing as we go to the core of the earth). When we talk about moving plates so tectonic of plates, the concerned layer is the Lithosphere made of the Mantle plus the Oceanic and Continental crusts; one thing to be known this plate are heavy. There all types of movements occur, as the convergent and divergent boundaries between plates.

The Japanese Earthquake happened at a subduction zone what is basically a type of convergent boundaries between two tectonic plates. These plates can both be Oceanic ones or one of them is Continental. One of the plates, always an Oceanic plate goes under the other ones due to many factors as the temperature, the pressure and the weight, because the Oceanic crust is really heavy compared to Continental crust. As a result, the Oceanic crust is destroyed. As mentioned in the previous articles it moves 3.5 inches annually and at the divergent boundaries are produced basalt for a renewal of the Plates.
(Source: http://news.nationalgeographic.com/news/2010/03/100302-chile-earthquake-earth-axis-shortened-day/)

http://csmres.jmu.edu/geollab/fichter/PlateTect/igevol.html

What happens during a subduction zone earthquake is that the plate that is going down, after a certain time is stuck and as a result the Oceanic plate goes up instead of down. For it to go back again, energy is release and lift up the Continental plate. This energy is released in a small amount of time and that causes an earthquake and after a tsunami. But it also moves the plates, as a result and knowing that the plates are heavy, the Earth’s mass distribution has changed. The following link is an animation of an earthquake in a subduction zone
(Source: http://news.nationalgeographic.com/news/2010/03/100302-chile-earthquake-earth-axis-shortened-day/)
Animation Sourse: http://www.jclahr.com/science/earth_science/animate/ .

Wednesday, 30 March 2011

MORE PHYSICS BEHIND THE CHANGE: Relating Radius with Period

Specific to this post, its just an interpretation of the former post using physics and algebra to prove the theory right.

We can show more clearly how a change in the radius of the earth would effect the period (the length of the day) :

Photo:This photo has not been acquired from any online source and is created using Microsoft Word and Micro Soft Paint by the group.

Therefore, we can see that, a lower R(new) value will give us a lower T(new value) and vice versa. This explains how, due to the reduced radius of the earth, the length of the day, that is, the Period of the earth was also reduced.

THE PHYSICS BEHIND THE CHANGE

A quantity that can be used to describe the overall state of a physical system is said to be Angular Momentum. . Angular momentum is always conserved in a system where there is no net external moment of force.

For a rigid body rotating around an axis of symmetry (e.g. the fins of a ceiling fan, or the earth), the angular momentum can be expressed as the product of the body's moment of inertia (a measure of an object's resistance to changes in its rotation rate) and its angular velocity ω:

Photo:This photo has not been acquired from any online source and is created using Microsoft Word and Micro Soft Paint by the group.

The earth has its own Angular Momentum which is conserved. This means, that if either part of its product, i.e. the moment of inertia or the angular velocity rises, the other value of the other will fall and vice versa, in order to maintain a constant value for the Angular Momentum of the earth.

The earth can be considered a Solid Sphere, and the moment of inertia of a Solid Sphere is given by the formula :

Photo:This photo has not been acquired from any online source and is created using Microsoft Word and Micro Soft Paint by the group.

So we can say that the Earth’s Angular Momentum can be calculated by the following formula:

Photo:This photo has not been acquired from any online source and is created using Microsoft Word and Micro Soft Paint by the group.

The earthquake in Japan caused a change,a slight decrease, in the Earth’s radius as a result of the subduction of the Tectonic plates. This decrease in the radius however is very very very small in comparison to the earth’s radius before the change. This will cause the value of R in our formula will reduce. The total mass of earth still remains constant ensuring that the M value remains unchanged. Therefore, in order to keep the value of L constant (conservation of Angular Momentum), the value of the angular velocity ω will rise (by a very small amount), thus slightly speeding up the velocity at which the earth rotates and in turns shortening the 24 hour day in earth by a few micro seconds, 1.8 micro seconds to be more specific.

Picture Source: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvGGXhE2p8Gp20I_FEYH3ZiFQevkf3gNf1mNCNbzC3QZYbXqJ25m91JnP6uI79sJck1HrM4AZ4idYJ7KVFm4_r9Fq1r7Wup2sxrA8DTE80a3Q8IRLl9oejDQkOovb9UuKEcXBJzSGME-Yv/s1600/Ang_mom.gif

Source : http://en.wikipedia.org/wiki/Angular_momentum,
http://en.wikipedia.org/wiki/Moment_of_inertia.
http://hyperphysics.phy-astr.gsu.edu/hbase/isph.html

Plate Tectonics

The information presented below were all obtained fro various internet sources (all of which are listed below) and this post is a compilation and a summary, in simple words for ease of understanding of the readers, of the whole process taken into consideration for the research.) Nothing has been directly pasted from a single source.

Picture Source: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCY8FhUeignbaJAHkRlv5x3PKHJ5_03XTQQG7_U0Wb6_3b9XWeWB7VL7KByYUI5lqCEPHpCNgNH7xteZVK7l7SDt8UbZXahrt4qegX1OlskLd9cSEU_ERB4r91YEUl9LqPGeW571M6xVBk/s1600/earth-plates.jpg

Before getting into the technicalities of exactly how the earthquake caused the day to shorten we first need to obtain basic knowledge of how the earthquake was formed.

Japan is situated on the brinks of 4 plates: the Eurasian plate, the Philippine plate, the North American plate and the Pacific plate. Some earthquakes occur as a result of there being a movement between plates which makes Japan an earthquake prone island. This area is called the Pacific Ring of Fire and is the world's most active earthquake belt where rigid plates in the Earth's crust collide along the rim of the Pacific Ocean.
Source of Information :http://www.livescience.com/13187-japan-earthquake-tsunami-science-faq.html

http://www.civilengineergroup.com/earthquake-knowledge.html

The Japanese earthquake on March 11th was the result was the result of a type of converging plate boundary (subduction boundary) which is where oceanic lithosphere is pushed beneath either oceanic or continental lithosphere and in this case the denser Pacific plate was subducted under the less dense Philippine plate. It is not irregular for the Pacific Plate to move as a result of its mass and as a matter of fact it is said that it moves 3.5 inches annually. However, this move is not done gradually; at times the friction between plates causes the plate to stand at rest while building up energy so that when it finally moves the distance is greater and the force is large enough to generate an earthquake. The subduction was great enough to cause Japan to move 8 ft. eastward redistributing matter on earth and as a result it decreased the earth's radius by a minuscule amount. The following image shows what was observed of the shift of the island:
(Sources of information: http://www.livescience.com/13187-japan-earthquake-tsunami-science-faq.html

http://www.civilengineergroup.com/earthquake-knowledge.html)