Earthquakes & Subduction Zones Lab Report Essay Example

and Defined:
- Subduction zone: where two lithospheric plates come together and one rides over the other
- Density: mass per unit volume
- Earthquake: the result of a sudden release of energy in the Earth's crust, creating seismic waves
- Subduction: the process where one plate is pushed downward beneath another plate into the underlying mantle when plates move towards each other
- Plate boundaries: found at the edge of lithospheric plates, with three types: convergent, divergent, and transform
- Deep ocean trench: a portion of the Earth's crust where a tectonic plate is being sub-ducted (pushed down) below another plate
- Shallow earthquake: more damaging than deeper earthquakes due to less rock absorption
- Deep focus earthquakes: occur within subducting oceanic plates as they move beneath continental plates

Hypothesis:
The East Pacific Rise Material at the two convergent boundaries, the Tonga Trench and the Peru-Chile Trench, is older than the crust created at the East Pacific Rise. However, the material in the Tonga Trench is older than the material in the Peru-Chile Trench.Prepare the following materials for this task: a sharpened pencil with eraser, graphing paper, a ruler, and a calculator. Additionally, retrieve the earthquakes and subduction zones lab from your teacher.

Start by reading the background and hypothesis information. Next, examine Figure 1 at the top of the Lab to form a hypothesis regarding the relative ages of the East Pacific Rise material at both convergent boundaries: the Tonga Trench and the Peru-Chile Trench.

Following that, divide your graph paper into two sections and label them as Tonga Trench on the left side and Peru-Chile Trench on the right side. On each section of the graph paper, draw a vertical line (y-axis) and a

horizontal line (x-axis).

Both sections of the graph paper should have the y-axis labeled as Focus Depth (km) and the x-axis labeled as Longitude (°W). The vertical axis (focus depth) should have a scale ranging from 0-700 km, with intervals of 50 km. Zero should be placed at the top of the y-axis and 700 at the bottom. On the left section of the graph paper, specifically for Tonga Trench, create a scale for the horizontal axis (longitude) ranging from 173-180 °W.

Label the right end of the x-axis as 173 and the left end as 180, going by intervals of 1°W. For the Peru-Chile Trench section, create a scale for the horizontal axis from 61-71 °W. Label the right end of the x-axis as 61 and the left end as 71, using intervals of 1°W. On the left section of the graph paper, plot earthquake data from Table 1 associated with the Tonga Trench using dots. Similarly, on the right section, plot earthquake data from Table 1 associated with the Peru-Chile Trench using dots.

Please draw a best-fit line for the Tonga Trench and another one for the Peru-Chili Trench. The Tonga Trench graph should have the Pacific Plate labeled to the right of the best-fit line, and the Indian Australian Plate labeled on its left side. Draw an arrow to show the motion of the Pacific Plate (subducting under the Indian Australian Plate). On the Peru-Chile Trench graph, label the Nazca Plate on its left side and the South American Plate on its right side. Draw an arrow to show the motion of the Nazca Plate (subducting under the South American Plate). Also, answer analyze questions

#1-5 (questions 4 ; 5 in steps 20-23).

Check and analyze your hypothesis

Please answer conclude and apply questions #1-2. When preparing your lab report, please follow a format similar to that used in scientific publications.

There should be at least five sections in the report. These sections should be labeled as Introduction, Methods, Results, Discussion, and Literature Cited. The report must be created using a word processor and printed with double spacing, Times New Roman font, and 12 pt. font size. The metric system should be used throughout the report.

The lab report must be written in paragraph format and consist of full sentences. The initial part, named "Introduction," offers background information necessary for comprehending the remainder of the report. Within this section, a hypothesis is presented as an explanation for an observation. The subsequent section, titled "Methods," includes sufficient details to allow readers to replicate the experiment if desired.

The lab report should include the necessary procedures and materials for conducting the experiment. The section after that should be labeled "Results," where you should include all findings, statistical analyses, graphs, and tables. In this section, describe overall patterns and summarize the tables and graphs using sentences and paragraphs. The next section should be titled "Discussion." In this section, assess whether the hypotheses are accepted or rejected and give explanations for your conclusions.

When rejecting a hypothesis, it is crucial to present an alternative explanation and justify the results. If the obtained results deviate from expectations, it is necessary to explain the reasons behind this discrepancy and what should have occurred instead. Moreover, interpreting the significance of the findings is vital. The final section of the document

is dedicated to "Literature Cited."

The importance of confirming the validity of all information presented in a scientific publication cannot be overstated, as it is vital for both reader comprehension and accuracy. The literature cited section serves to provide a comprehensive list of publications that have been referenced within the report.

To initiate the utilization of a table, establish its structure, and prepare a graph, begin with an empty sheet of graph paper. Consult Table 1 to obtain longitude and focus depths data for earthquakes occurring at both the Tonga Trench and Peru-Chile Trench. Divide the graph paper into two distinct sections by labeling the left side as Tonga Trench and the right side as Peru-Chile Trench.

The graph paper should contain a vertical line (y-axis) and a horizontal line (x-axis) in each section. The y-axes should be titled "Focus Depth (km)" while the x-axes should be titled "Longitude (°W)". Both sections, Tonga Trench and Peru Chile Trench, require a scale for the vertical axes (focus depth). This scale must span from 0 to 700 km with labels at every 50 units. The labeling begins at zero on the top of the y-axis and extends up to 700 at the bottom of the y-axis.

Two sections of graph paper should be created. On the left section, which represents the Tonga Trench, a scale for longitude ranging from 173-180 °W should be made. The right end of this axis is labeled 173 and the left end is labeled 180, with intervals of 1. On the right section, representing the Peru-Chile Trench, a scale for longitude ranging from 61-71 °W should be made. The right end of this axis is labeled

61 and the left end is labeled 71, with intervals of 1.

The earthquake data associated with Tonga Trench should be plotted on the left section of the graph paper using dots to represent each point. Similarly, the earthquake data associated with Peru-Chile Trench should be plotted on the right section using dots as well.

The data and results pertain to movements involving three plates - Pacific Plate, Indian-Australian Plate, and South American Plate.

South American Plate Nazca Plate Nazca Plate Analysis and Synthesis:

Question: What is the distance between Tonga Trench and East Pacific Rise? Keep in mind that one degree longitude equals approximately 100 km.

If the seafloor spreads at a rate of 3 cm/year, how long would it take for material on the plate to travel this distance?
Answer:
The Tonga Trench is located 6,500 km away from the East Pacific Rise. If the seafloor spreads at a rate of 3 cm/year, it would take approximately 216.67 million years for material to travel this distance. Calculation: 65°W = 65 x 100 km = 6,500 km. 6,500 km x 100,000 cm = 650,000,000 cm. 650,000,000 cm / 3 cm/year = 216,666,667 years.
Question:
What is the depth of the deepest earthquake in the Tonga data set? Please estimate the rate of descent of the East Pacific Rise material at the Tonga Trench in centimeters per year.

Answer: The depth of the deepest earthquake in the Tonga data set is 675 km. The rate of descent of the East Pacific Rise material at the Tonga Trench in centimeters per year is 0.312 cm/year. Work: 675 km x 100,000 cm = 67,500,000 R = 67,500,000 cm / 216,666,667 years R = 0.312 cm/year

Question:

Estimate the rate of descent of East Pacific Rise material into the Peru-Chile Trench in centimeters per year.

Answer: 5°W = 45 x 100 km = 4,500 km;
4,500 km x 100,000 cm = 45,000,000 cm;
450,000,000 km /3 cm/year =150 ,000 ,000 years;
540 km x100 ,00cm=54 ,00 ,00cm ;
R=54 ,00 ,00cm/150 ,00 ,00years ;
R=0.

The data provided shows the focus depths and longitudes (°W) of earthquakes at the subduction zones of Peru-Chile Trench and Tonga Trench. In the case of the Tonga Trench, there is a correlation between increasing longitude (°W) and increasing focus depth, resulting in an upward slope. Conversely, for the Peru-Chile Trench, increasing longitude (°W) corresponds to decreasing focus depth, creating a downward slope.

The estimated boundary location of the Pacific Plate and the Indian-Australian Plate can be seen on the Tonga Trench graph, represented by a best-fit line. The Pacific Plate is subducting beneath the Indian-Australian Plate while overriding it. Similarly, on the Peru-Chile Trench graph, there is also a best-fit line indicating the boundary between the Nazca Plate and the South American Plate. In this case, the Nazca Plate is moving under the South American Plate as it overrides it. Both trenches have similar earthquake focus depths measured in km but differ in longitude measured in °W. To summarize, when two tectonic plates converge with at least one being oceanic lithosphere, a subduction zone will form.

The Tonga Trench and the Peru-Chile Trench can be compared to observe that the former has a steeper profile due to its older and denser crust. The charts also show this steeper profile of the Tonga Trench, indicating its age and density. Consequently, subduction occurs at a

faster and steeper rate in the Tonga Trench. The behavior of a plate is determined by the composition of rock.

The speed and angle of subduction in the mantle vary depending on the density of the plate. Plates with higher density subduct more quickly and at a steeper angle compared to plates with lower density. The rate of subduction is also influenced by the age of the crust. Older crust, which is cooler and denser, subducts faster and at a sharper angle in a subduction zone than new crust. To verify this hypothesis, it is suggested to analyze the data as it provides support for the hypothesis.

According to my prediction, the East Pacific Rise crust is younger than the material at two convergent boundaries - the Tonga Trench and the Peru-Chile Trench. However, the material at the Tonga Trench is older than that at the Peru-Chile Trench. The reason for this can be attributed to the fact that the Tonga Trench and the Peru-Chile Trench are farther away from the crust creation location, resulting in older material. Additionally, the Tonga Trench has older material compared to the Peru-Chile Trench due to its steeper slope, indicating its greater age and density.

To enhance my understanding of the topic, I conducted further research on background information and addressed any errors. Moreover, I thoroughly explained and analyzed my data to provide a clear understanding of trends and their implications. Additionally, I included instructions on utilizing a table of data, setting up equipment, preparing a graph, and crafting a comprehensive lab report.

My lab report contained errors in the math work of the first three analyze questions, the direction of subduction of

the plates, and a lack of clarity in my hypothesis. To rectify these mistakes, I paid attention in class during the review of the math problems, which improved my understanding and enabled me to solve them correctly. Additionally, I previously believed that the Pacific Plate moved upwards against the Indian-Australian plate, but I revised this belief after realizing that it actually subducts under the Indian-Australian plate, changing the direction to downwards. Lastly, I modified my hypothesis to accurately address the question, which was to compare the relative ages of the East Pacific Rise material at two convergent boundaries: the Tonga Trench and the Peru-Chile Trench. In my original hypothesis, I only mentioned the relative age of the East Pacific Rise material.