Archive for category: Other

Lab Exercise 7

In this lab, you will:

Examine datasets of topography, bathymetry (ocean depth), volcano location, earthquake location, and ocean floor age to determine the location and attributes of different plate tectonic boundaries. Examination of several study regions will reveal the variety of tectonic processes that form our amazing landscapes.

 

Materials:

Computer Workstation with Google Earth Pro Installed. Google Earth Pro is a free software that can be downloaded at: https://www.google.com/earth/versions/#earth-pro. If you have never used Google Earth, the videos provided in the two links below will introduce you to basic functions.

• Google Earth Intro Part 1
• Google Earth Intro Part 2

 

Part 1

Install Google Earth Pro if your computer does not already have it.

 

Tips

• You should uncheck datasets that you are not using for a given question because they may interfere with each other (particularly the Age-of-Ocean-Floor).
• Earthquakes and volcanos will not show up until you are somewhat zoomed in. You will probably find that an eye altitude of 4000-5000 km is best for balancing data visibility.

 

• The topography of the Earth is the result of the balance between present and past tectonic activity and exogenic forces that denude (erode) these landforms. Based on your textbook (CH13) readings, you should now be familiar with the three main types of plate boundaries.  What are they?  Provide a brief description of each. (1 points)

Atlantic Ocean
Double-click plate tectonics exercise.kmz in your lab 7 folder to open it in Google Earth. Note: Google Earth may appear to freeze here on some computers, however it is just loading the file, allow 2-3 minutes for the file to load. Do not click anywhere else after you click to open the .kmz file. You will know when the file is loaded and ready to be examined as a colorful legend with “magnitude” listed on the top will be visible on the screen.

Explore the datasets that became available including cross section profiles, ocean floor age, and locations of earthquakes and volcanoes.

Make the Atlantic cross-section visible (located in the Cross-sections folder within the loaded .kmz file on Google Earth) and show the elevation profile. To show the elevation profile, right click on the Atlantic cross section name in the legend (on the right side of Google Earth) and then click the option to show the elevation profile. As you move your mouse on the elevation profile, a corresponding arrow will be visible in the matching location on the globe.

1. On the cross-section below, mark the transitions from continental crust to oceanic crust (Hint: Use the profile line on Google Earth to determine where the drop off is located. You can also move the globe around to see specific locations. Right click on “Atlantic” in the legend and then click “show elevation profile”). Remember this is not where water meets land but rather where the actual geology changes. (1 point)
   
2. Using earthquake, bathymetry, and ocean floor age data, identify the plate boundary on the first figure (elevation profile above) (back up statements you make with good explanations). Hint: become familiar with plate boundaries and their locations by reviewing CH 13 in your textbook. You can also find additional plate boundary maps from reliable sources online. (1 point)
3. What type of earthquakes (shallow or deep) occur along the plate boundary? You can determine specific earthquake depths, by clicking on an earthquake icon (zoom in to where you can see the red X). In general, earthquakes shallower than 50 km are considered relatively shallow, while those occurring at depths greater than 50 km are considered deep. (1 point)
4. What rate (in mm/yr) are each of the plates moving relative to the boundary? (You will need to use the ocean floor age data and the Ruler tool to determine this. The numbers you see are millions of years). (1 point)
5. What type of plate boundary is it (hint: refer to your book for clues)? (1 point)

Sumatra
Make the Sumatra cross-section visible and Show the Elevation Profile.

1. Mark the boundary between the Indo-Australian and Eurasian plates at the Earth’s surface. (1 point)
2. Support your answer for the location you have chosen for the plate boundary. (1 point)
3. Describe how the earthquake depths change from southwest to northeast near the profile line. You will need to check a minimum of 10 earthquakes to determine the pattern. (1 point)
4. What type of plate boundary is it? Hint: refer to your textbook for clues. (1 point)

 

Himalaya
Make the Himalaya cross-section visible and Show the Elevation Profile.

1. This is a continent-continent convergent margin. Using topography, mark on the cross-section where you think the plate boundary is. (1 point)
2. Watch the animation IndiaAsiaCollision.mov in the lab 7 folder. If the video player that is selected does not open the file, select another one. Do you still agree with where you located the plate boundary? If you have changed your thinking, show the location of where you would put the boundary now (mark it as “new”). Support your answer with an explanation of your reasoning. (1 points)
3. How has the boundary changed over the last 60 million years? What two types of crust were involved 60 million years ago? When did it switch to being continent-continent? (1 points)
4. What depth of earthquakes are associated with the Himalayan-Tibetan region? (1 point)

 

Earthquakes in the study region
Open the part2.kmz AND BoxingDayTsunami.kmz. This contains additional earthquake data that you will need to complete the following exercise. Turn off the previous layers you were using so that only the part2.kmz and BoxingDayTsunami.kmz files are visible. Explore the datasets. Turn on the “Earth’s Tectonic Plates” file within the BoxingDayTsunami.kmz file.

Using the >6 Mag EQuake dataset, determine which type of plate boundaries are associated with bigger earthquakes and more numerous earthquakes? Support your reasoning with a detailed explanation that uses the dataset provided and plate boundary details from your textbook. (2 points)

The Boxing Day Tsunami

The Boxing Day Tsunami occurred in the Indian Ocean on December 26, 2004. Sadly, it was one of the worst natural disasters in modern history. In this exercise, you will explore the causes and effects of this event.

Open the Boxing Day Tsunami KMZ file in Google Earth. Examine the layers by turning each of them on and off. It helps to look at these individually before getting started. Be sure to specify the units for all distances, velocities, and times in the questions below. You may turn off layers that are not being utilized to limit the amount of things on the screen as it can become hard to see. Keep the “Source Event” layer turned on.

1. What were the latitude, longitude, magnitude, and depth of the source event for the tsunami? Click on the source event icon on the globe to find out. (1 point)
2. What was the closest country to the source event?  Use the data in the Countries where Deaths Occurred folder to find out.  Expand the folder. How many deaths occurred in that country as a result of the tsunami? (1 point)
3. What country in which deaths occurred was farthest from the source event? About how far was it?  How many deaths occurred there? (1 points)
4. Make the Earth’s Tectonic Plates folder visible.  This data is from the United States Geological Survey. What types of plate boundaries are represented by this data?  What two types of plate boundaries are closest to the location of the source event? (1 points)
5. Make the folder that is entitled Seismic Events, Dec 25 to 31, 2004 visible. Where did most of the seismic events represented in this folder occur?  How do these events spatially relate to the source event? (1 points)

Open the NGDC Wave Travel Time Overlay in Google Earth. This overlay documents the travel time of the waves from the location of the source event.  Each line represents an hour of travel time.  Bold lines mark 5-hour intervals.

• a) How long did it take the waves to reach Mozambique? (1 point)
• b) How fast did the tsunami wave travel as it approached Mozambique (hint: you will need to determine the distance from the source event to Mozambique)? Why do you think this happened? (1 point)

Adapted from SERC: Beth Pratt-Sitaula, UNAVCO