Bathymetry Labbbbbbb2
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Wayne State University *
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Feb 20, 2024
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Uploaded by ProfessorToad1038
Introductory Oceanography Lab EARTH 223/ENVIRON 233 Seafloor Bathymetry Part 1 - Topography/Bathymetry Maps 1.
What is the difference between topographic and bathymetric maps? (2 point) Topographic maps have contour lines that express elevation, while bathymetric maps have color scales that are used to express depth. Topographic maps include local infrastructure while bathymetric maps include info used for sailing. 2.
What do the concentric lines on a topographic map represent? (2 point) They represent a specific elevation/depth. 3.
What does it mean if topographical lines are close together? Far apart? (2 points) If the lines are closer together then the depth or elevation is very steep and vice versa. 4.
Locate the following points on the topographic map and describe the type of topography or landscape that you would find there. (3 points) A.cliff C. Gentle slope J. flat 5.
Which area has a steeper slope, O or M? (2 point) M For questions 4 and 5, you may confirm your answers with the 3D model of the topographic map.
Part 2 - Lead Line Activity In this activity you will learn how early hydrographic surveys were able to create bathymetric maps of the seafloor without being able to observe it directly. In addition you will learn how decision-making can affect the results that your research team will produce. Instructions: ●
Each group will be given a cardboard box with 176 holes. The bottom of the box has some sort of 3D topography that you will measure indirectly. First, you will need to choose how many measurements you want to take and where they should be located. ●
Once you have chosen the measurements that you will take, insert the metal stick into the hole and measure how far the stick can travel into the box before touching the bottom. Record this in the appropriate box. ●
Now that you have all of your measurements, you will create a bathymetric map. To do this you can connect the boxes of similar depth with topographic lines or color boxes of similar depth with similar colors. If you choose to color in the boxes, make sure you include a color-key (8 points for your map) 1.
Describe your topographic map. What kind of seafloor features can you identify based on the map that you have created? (4 points) Some points in our map have a higher elevation than others. The elevation fluctuates on our map. A
B
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D
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I
J
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M
N
O
P
1
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2.
Does this map have high resolution or low resolution? How much detail can be expressed using this method? How would you increase the resolution? (3 points) Our map has low resolution, just because we did not plot that many points.There is still a lot of detail even though there is not that many points plotted. I would increase the resolution by adding more points. 3.
How did your choice of where to take measurements affect your results? How does this relate to how real scientific surveys must balance quality of results vs. cost, resources, or time? (3 points) We decided to spread out our points. This relates to scientific surveys because just like in scientific surveys, we had to choose our points, but also work with the materials we had with us. We only had certain materials, and that is similar to how scientists only have certain instruments to do their experiments. Part 3 - Sonar and Travel Time 1.
Now, let’s think about acoustics in the ocean and how SONAR is used to map the seafloor. a.
What is a typical velocity of sound in seawater? (2 point) The typical velocity is 1507. b.
What is the depth of the deepest point of the Earth’s Oceans and where is it located? (2 point) The depth of the deepest point is in the Mariana Trench and is 10,929 meters below sea level. c.
Use your answer from part a and b to determine how long it would take a sound wave to travel from a ship at the surface to the deepest part of the ocean and back? (please show your work) (4 points) Depth/velocity=10929/1507=7.25 Sound travel time=7.25secs d.
How long would it take a sound wave to travel from a ship at the surface to a location with a depth equal to the average depth of the world’s oceans? (4 points) 3,688/507=2.46 2.46/2=1.23secs for sound wave to travel 2.
Now that you have calculated the amount of time that it will take a sound wave to travel from a ship to the bottom of the ocean and back, we will next explore how this data would be useful for studying seafloor bathymetry. a.
Imagine that a ship sailed across an ocean basin from the coast of one continent to the coast of another continent collecting acoustic data every 100km near the
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coast and every 200km in the middle of the basin. The travel time data that they collected is recorded in the table below. Instead of calculating each water depth value independently, scientists usually use computer programs to analyze data more quickly. For this calculation you will use Excel. Copy the values below into the first two columns of an Excel spreadsheet. (.5 points for each correct depth +.5 free - total 10pts.) Distance Traveled (km) Travel Time (s) Water Depth (m) 0
0.060
100
0.066
200
0.073
300
1.324
400
3.962
500
5.375
700
5.375
b.
In the third column, create an equation to calculate water depth from travel time. To do this, select the top box in the third column and enter an equal sign (=); this tells the Excel program that it should make a calculation. If you want your equation to include a value from another cell, you can either type in the name of the call or click on the cell. For example if you wanted to figure out the difference between the first two water depths in the data table below, you would type “=A3-
A2”. (Hint: remember that the travel time accounts for the sound wave to travel to the ocean floor and back to the ship) c.
Now that you have calculated the water depth for each ship measurement, use excel to make a graph that shows the bathymetry. Here, the x-axis should be distance traveled and the y-axis should be water depth. To illustrate how deep the water is, you will want to reverse the values on the y-axis so that 0 m is at the top. (8 points for the correct shape of the graph) d.
Make sure to include axis labels and a title on your graph. (2 points for labels, 2 points for style and readability) e.
Upload your completed excel file to Canvas along with your lab submission. 3.
What kind of features can you identify on the bathymetry profile that you have created? (2 points) This Chart also fluctuates in elevation. Some parts are higher than others. 900
5.289
1100
3.824
1300
2.362
1500
4.147
1700
5.590
1900
5.043
2100
5.395
2300
4.200
2500
1.360
2700
0.088
2900
0.077
3000
0.072
Part 4 - Satellite Altimetry
Now, let’s look more closely at satellite altimetry, specifically let’s use the following link: https://
sealevel.jpl.nasa.gov/missions/technology/ (and/or other internet sources) to learn about the JASON satellite altimeters. 1.
What is the JASON -1 satellite and what does it do? (2 points) The Jason-3 takes measurements of the oceans surface. The jason-3 is a satellite. 2.
What is the approximate altitude of the JASON-1 satellite (in kilometers) above the Earth? (2 points) 1336 kilometers 3.
What is the approximate accuracy of sea level measurements made from the JASON altimeters? (3 points) Accuracy within several millimeters. 4.
What type of electromagnetic radiation was generated by the JASON satellite: radio, microwaves, infrared (like the xbox kinect), optical, ultraviolet, x-rays, or gamma-rays? What is the speed at which the electromagnetic waves travel? (2 points) Microwave 5.
Briefly describe how the JASON satellite altimeter measurements are independently verified using a different source of data – a procedure known as “ground truthing”. (4 points) Every 10 days the Jason flies above the ocean and two measurements of the sea level (satellite and ground truth) are compared in something called “closure”. With careful monitoring, any thing unexpected fro, the satellite and ground truth measurements can be be pointed to a error in the satellite measurements. Part 5 - Seamounts The following article describes a new discovery of over 19,000 previously unmapped seamounts! Please read the article and answer the following questions. (
https://www.science.org/content/article/it-s-just-mind-boggling-more-19-000-undersea-
volcanoes-discovered
) 1.
What is a seamount and how are they formed? (2 points)
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A seamount is a underwater volcano. Seamounts form in chains formed as tectonic plates go over stationary plumes of hot rock that rise from the mantle. 2.
How much of the seafloor is currently mapped with sonar? (2 points) One Quarter. 3.
What are two reasons that scientists or industry want to know where seamounts may be located? (2 points) One reason is to see the effects of the seamounts on the climate. Another reason is to find out if deep ocean waters defying gravity and rising upward is because of seamounts. 4.
Why were so many seamounts missed by previous technology? (2 points) Because of the limited sonar coverage. 5.
Why does the location of seamounts matter for scientists that are studying climate change? (2 points) The location matter because the locations pertains to the biodiversity of the location, and the locations will allow scientists to see how the seamounts act in different locations with different life/factors in each location. 6.
How do seamounts affect biodiversity and marine life? (2 points) Seamounts are crucial oases for marine life and biodiversity. Are seamounts home to certain species of sea life? This is a question scientists are trying to answer.