Plate Tectonics CPR Paper
by
The Professor
Introduction
The theory of plate tectonics is able to describe many of the most striking features on the earth's surface. Long mountain ranges, deep ocean trenches and high ocean ridges are caused by plate tectonic motions. In addition, earthquake patterns are explained by motion across plate boundaries. The majority of volcanoes also occur as a result of plate motion.Region A is a subduction zone at a convergent boundary and Region B is a spreading ridge at a divergent plate boundary [:(Cmnt by William Prothero: Shortcomings here are that the student has not mentioned enough about the theory of plate tectonics. Also, the conclusion is given here before any supporting data are shown. ):] .
Methods
The data that I will use for this study comes from the "Our Dynamic Planet" module of the EarthEd Online software provided for GS-4W, Introduction for Oceanography, by Prof. William Prothero. The kinds of data I will use are:1) Elevation data from the ETOPO5 elevation database.
2) Earthquake data from the "Our Dynamic Planet" CDROM provided for the oceanography course.
3) Volcano data from the "Our Dynamic Planet" CDRO [:(Cmnt by William Prothero: Data accuracy is not mentioned. The reader would get the impression that the data came from the "Our Dynamic Planet" CDROM, which is not the primary data source. The lab manual gives this information. ):] M.
Observations
{link: ptCPR_LocMapF.jpg}Figure 1 show a world map with the two regions of study marked as A and B.Region A is named the Tonga-Kermadec Trench on world maps. {link: ptcpr_LocMapF2.jpg}Figure 2 shows a detailed map of region A. Figure 3 shows an elevation profiles across the trench. The trench with a depth of 7,000 to 8000 meters.
{link: ptcpr_Tonvol.jpg}Figure 3 shows a plot of volcanoes in the region. The volcanoes lie on a line parallel to the trench.
{link: ptcprqks_prof3.jpg}Figure 4 show an earthquake profile along at the location of profile 3 shown in figure 2. The earthquakes lie along a descending line.
Region B is in the Pacific Ocean in a region centered on 50S latitude,115W longitude.. {link: ptcpr_elqk2.jpg}Figure 5 is a detailed map of this region. Two profiles were made across what appears to be a linear rise. The earthquakes are on features that are perpendicular to this linear rise. {link: ptEP_2pronolab.jpg}Figure 6 shows the 2 elevation and age profiles [:(Cmnt by William Prothero: This section is not too bad at displaying the data, but there is no description of the data and minimal discussions of how data relate to each other. ):] .
Interpretations
Region A
Region B
The data show that this region is a divergent plate boundary, or "spreading center." The strongest data is shown in {link: pt_epr2Profiles.jpg}figure 6, where the age profiles show zero (or very young) ages at the peak of the ridgecrest and nearly linearly increasing ages as distance from the ridgecrest increases. Where the ridge has offsets, perpendicular boundaries called "transform faults" connect the ridge segments.
Therefore, region A is a convergent boundary, or subduction zone, and region B is a divergent boundary, or spreading center. [:(Cmnt by William Prothero: This section is quite weak in describing how the data conform to what is expected in the model. The interpretation is also minimal. More could have been said about the earthquakes that do show up in Region B. ):]
References
Prothero, W, 2004. Introduction to Oceanography Lab Manual, pub by UCSB Bookstore, p 3-21. [:(Cmnt by William Prothero: The references are fine, given that the lab book contains all the references for the data sources on "Our Dynamic Planet." ):]
Figure 1: Location map of the two regions for this study. Region A is the Tonga-Kermadecc trench region and Region B is the East Pacific Rise region. {fig: ptCPR_LocMapF.jpg}
Reagion A detailed map. The arrows point to the approximate endpoints of the Tonga-Kermadec trench. {fig: ptcpr_LocMapF2.jpg}
Volcano plot of the Tonga-Kermadec trench region. Notice that the volcanoes lie on a line approximately parallel to the trench. {fig: ptcpr_Tonvol.jpg}
Cross section of earthquake locations along profile 3. {fig: ptcprqks_prof3.jpg}
Map of the East Pacific Rise, centered at 50S, 115W. Three elevation profiles and the earthquake epicenters are shown. {fig: ptcpr_elqk2.jpg}
Two profiles across the ridge of region B {fig: ptEP_2pronolab.jpg}
Model of Region A, the Tonga-Kermadec trench region. This shows the subducting slab with a descending pattern of quakes, a topographic trench, and the volcanoes that are a result of melting of ocean crust on the slab. {fig: cartoon1.jpg}
Two elevation and age profiles across the crest of the East Pacific Rise. {fig: pt_epr2Profiles.jpg}