Becca Hedges
Geo 3210
Dr. Kaiser
15 Dec. 2016
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Proposal
The Pacific plate is moving in a northwest direction. So why is the Hawaiian Island chain appearing to move southward? Mantle flow models for Hawaii estimate its location to be at 17°N (Kodama, 165). However, the current position is located at 19°N (Tarduno 1064). My hypothesis is the southern movement of the Hawaiian Island chain is due to apparent polar wandering (APW). APW is of great importance to the populations of Earth because of the effects it can have on the physical world. Plate movement can result in destructive events. It is known that the pacific plate is flowing in a northwesterly direction (Steinberger, 168). If my hypothesis proves correct, understanding this concept could enhance long term projections or forecasts of cataclysmic events. I plan to use this evidence to prove that the Hawaii Island chain has a more southern latitude than it should if it were a fixed location within the pacific plate (Steinberger, 167). I will test my hypothesis that the location of Hawaii does not fit the current models and predictions (Steinberger, 167). I propose that magnetite and paleomagnetism will show how polar wandering affects the earth’s crust during crystallization.
Magnetite, Fe2+Fe3+O4 exhibits a variety of characteristics dependent on its temperature. There are three ranges of temperature where magnetite behaves differently. The Curie temperature span of 120K to 840K are the temperatures important to this study. This is the temperature where the magnetite will orient parallel to the earth’s magnetic field. Crystallographically, magnetite is a member of the Spinel family. The oxygen ions form a close packed cubic lattice with the iron ions located at the intersections between the oxygen ions. There are two different locations that the ions can take, tetrahedral and octahedral sites. Magnetite is magnetic because it is ferromagnetic, this is the spinning of unpaired electrons that are aligned in the same direction. The more unpaired electrons there are, the more magnetic the mineral is. Magnetite is not the only mineral that has magnetic properties. However, it is the strongest and most abundant. The Fe3+ ions are located in both sites and are anti parallel so, the magnetic moment of the unit cell only comes from the Fe2+ ions, which will fill in the octahedral sites (Nesse 394-396).
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Magnetite was a major contributor in the development of paleomagnetism and the acceptance of the continental drift theory (Nesse, 396). Magnetite and paleomagnetism interactions have left a history of Earth’s Paleomagnetic history. Pole reversals have no finite switching pattern and the mechanism which initiates the shift itself is still unknown. The Paleomagnetic poles are based on rocks that move with the plates of the earth. Hotspots like Hawaii are simply markers of the APW. The best Paleolatitude indicators are found in basaltic rocks. A good location to conduct this study would be in the seamounts around Hawaii because we can find both older and newer basalts (Tarduno, 1064). Being able to compare the orientation of the magnetite within these various aged basalts helps show how the hotspot of Hawaii has been affected by APW.
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Collecting data and comparing it to the magnetic pole history can aid in reconstructing latitudinal profiles of where the deposits were created. (Gordon, 575). Understanding the processes of tectonic movements are important because it allows us to predict or forecast potential hazards such as earthquakes, tsunamis, volcanic activities and even climate change. Any advantage we can gain through the information gathered during this study will better prepare people for unanticipated events, could save lives, and reduce infrastructure damage. Information gathered here could give us insights into to how long it takes for the poles to complete a reversal. The pacific plate moves approximately 1 cm yr-1 (Steinberger, 168). The APW is also a relatively slow movement and it is said that we are currently experiencing APW (Gordon, 573). It has been found that during certain periods of time these movements occurred at a much faster rate, some over 40 mm a year (Tarduno, 1064).
The known bend of the Hawaiian Island chain has been explained as the change in motion of the Pacific plate. However, plate reconstruction models have failed to show this bend. This bend said to have begun roughly 47 Myr during the late cretaceous early period, but there is some debate on this age (Steinberger 167). The study site we will be focused on is located within the Emperor Seamount chain near Hawaii. With the help of the Ocean Drilling Program (ODP) we will collect two to three core samples from four to six different locations of the seamount chain. Prior seamount drilling operations have gone to depths between 150-250 m. This should be a sufficient depth to gather the age range of the crust needed (Tarduno, 1066). These cores will allow us to gather the Paleomagnetic history of the area. They will also give us radiometric ages, as well as geochemical data. Using this data, we can compare the Paleomagnetic alignment to the age of each deposit. Specific ages of the crust we will focus on include 81 Myr, 61 Myr, 47 Myr, and 20 Myr. We will use high-resolution Paleomagnetic measurements on small, continuous subsamples that are taken from the center of split cores. They will be placed in u-shaped plastic liners known as u-channels. We will compare the data collected with known Paleomagnetic reversals (Tarduno 1067). This will aid us in determining the latitude at which the deposits were created, giving us their composition, and at what age of the Earth the Curie temperature was reached.
We will also use the predicted mantle flow models in order to compare and contrast the data collected against the current models. These predictions track hotspot plumes and convection currents in order to produce these current models. Some of these models assume hotspots to be in fixed locations and lack predicted bends in the Hawaiian chain which should be located farther west. The direction of multiple plate movements are then added. In one model, the Pacific and African plate interactions do not match the current behaviors observed. No bend of the Hawaiian chain is predicted. Yet, another model looks at the interaction of Australia and the Pacific plates. This model does predict the Hawaiian bend at 65 Myr. That is a large time difference of when this bend could have begun occurring. It also shows that the location of the islands should be much farther west. These models were created using GMT software. The results of the current models compared with current locations support that Hawaii has a motion that is in a southern direction which does not match the model’s predictions (Steinberger, 168-171). This supports my hypothesis that the APW during the cretaceous period is what initiated the bend. Once the data is collected from the ODP we will use the same GMT software to correlate our findings. Our new models will include hotspot motion rather than a fixed location.
Works Cited
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Gordon, R. "Polar Wandering and Paleomagnetism." Annual Review of Earth and Planetary Sciences 15.1 (1987): 567-93. GeoRef. Web. 9 Dec. 2016.
Kodama, K., S. Uyeda, and N. Isezaki. "Paleomagnetism of Suiko Seamount, Emperor Seamount Chain." Geophysical Research Letters 5.3 (1978): 165-68. GeoRef. Web. 9 Dec. 2016.
Nesse, William D. Introduction to mineralogy. New York: Oxford U Press, 2012. Print.
Steinberger, Bernard, Rupert Sutherland, and Richard J O’Connell. “Prediction of Emperor-Hawaii Seamount Locations from a Revised Model of Global Plate Motion and Mantle Flow”. Natur. 430.6996 (2004): 167-173. Academic Search Premiere. Web. 8 Dec. 2016.
Tarduno, John A., et al. “The Emperor Seamounts: Southward Motion of the Hawaiian Hotspot Plume in Earth’s Mantle”. Science 301.5636 (2003): 1064-1069. Academic Search Premiere. Web. 8 Dec. 2016.