1
Geological Sciences 0050
I am aware of the Brown University Honor Code [see the Student Handbook, which can be accessed through the Geo0050 web site], understand that this exercise falls under that code, and know the penalties that exist for violating the code.
Signature:
Name:Banner ID#:
Exercise 1 (15 points): Earth’s Dynamic Nature, Visible at its Surface
Due by Monday, September 15th, 2014
This exercise requires downloading Google Earth, which we will use several times during this semester. The current version can be obtained at “earth.google.com”. If you have trouble setting Google Earth up, need access to a computer in Geological Sciences to complete this exercise, or need any other help, talk to your TAs. Hints for first-time users of Google Earth at the end of the handout.
Please make sure all your measurements and answers are in the metric system (kilometers, meters, or centimeters) [If elevations are not showing up as metric, look under Tools-Options-3D View, or on a Mac, Google Earth-Preferences-3D View].
For many of these questions, it is easier if you have ‘terrain’ turned on, which it is by default (again, look at the 3D View preferences).
You will need the file “Geo-50_exercise1.kmz”, which was sent to you via e-mail and is also available on the class website ( Depending on the settings of your computer, you may need to open the .kmz file directly in Google Earth, instead of double-clicking the file. To get used to exploring using Google Earth, it might be valuable to first double-click on the MacMillan Hall layer and look around.
I. Geological Process: Plate Tectonics (6 points, 1 for each question)
A. Creation of new crust at a mid-ocean ridge (divergent plate boundary)
(Earth’s Dynamic Systems, Ch. 19).
Load “Geo-50_exercise1.kmz” into Google Earth (Go to File-Open). Expand the tab for “Exercise 1” and turn on the Seafloor Age Map layer by clicking the checkbox next to this layer.Double-click on the Seafloor Age Map Layer or navigate to the Mid-Atlantic Ridge by flying to 22N, 45W.
1. The boundary between yellow and orangedata in the seafloor age overlay is 40 Myr old crust (e.g., at approximately 20N, 51W). This means that oceanic crust was formed at the mid-ocean ridge 40 million years (Myr) ago, and it has been moving away from the ridge ever since (west of the ridge, moving west). What is the distance that this plate has travelled over 40 million years, moving west from the ridge?
(Click on the ruler tool and measure the distance from the 40 Myr crust on the west side of the Mid-Atlantic Ridge. Make sure you measure close to perpendicular to the ridge).
2. What is the average seafloor spreading rate at this part of the Mid-Atlantic Ridge (in cm/yr)? (Take the number you measured in pt. 1, divide by 40 Myr, and multiply by 2 (since crust spreads away from the ridge to both the east and west). Be careful with units. How does this compare with the rate of fingernail growth (~4 cm/yr)? At this rate how long would it take for this new piece of crust to travel laterally entirely around the circumference of the Earth (i.e., the equatorial circumference)?
B. Plate motion on the North American continent
(Earth’s Dynamic Systems, Ch. 20).
First, you might want to turn off the Seafloor Age Map layer, since you won’t need it again.
Then, turn on the San Andreas Fault layer and double click on this layer to zoom to it (or fly to 35.27173 N, 119.82761 W). The San Andreas Fault, a segment of which is shown here, cuts across much of southern California all the way to the San Francisco Bay. Note that there are many other known (and unknown!) faults in California, and only some of the plate motion between the Pacific Plate and North American plate occurs along this fault.
3. There is a noticeable offset of Wallace Creek along the fault at the location. What is the length of this offset in meters?
4. Geologists have figured out that it took about 3000 years for this offset to occur. Using this information, what has been the average slip rate along the fault in mm/yr?
5. What kind of fault is the San Andreas?
6. What is the sense of motion along this fault (right lateral or left lateral)?
(You can figure this out by looking at the offset of the stream from either direction. If the block on the opposite side of the fault moves to your right, this is a “right lateral” (or dextral) slip system. If it moves to the left, it is “left lateral” (or sinistral) slip system. The sense of this fault is controlled by global-scale plate motions!)
II. Geologic Process: Volcanism (5 points, one for each question)
(See Earth’s Dynamic Systems, Ch. 4).
Turn on and double-click the Kilauea volcano layer.
7. Based on what you see, was Kilauea actively erupting when the latest images were added to Google Earth? How can you tell?
8. Examine the basaltic flow labeled ‘dark flow’. Is it younger or older than the flowsthat surround it? How can you tell? (Scientists commonly make this sort of determination, called examining stratigraphic relationships, when looking at other planets as well!) Measure the distance of this dark flow
Head to Mauna Loa volcano (19.4686 N, 155.5949W) by clicking on the layer, entering coordinates, or navigating up the slope from Kilauea.
9. Find the height of Mauna Loa above sea level by putting your cursor at the top of the volcano and reading the elevation at the bottom of the window (The "Terrain" layer must be turned on). Then, measure the shortest distance from the top of Mauna Loa to the ocean (elevation=0) using the ruler tool. With this information, calculate the average slope (in degrees) of the volcano along this transect.
(Hint: Be mindful that your elevation and distance are in the same units!)
Go to Mount Rainier by double-clicking on the layer or by entering 46.8529 N, 121.7604 W
10. In a similar manner to how you measured the slope for Mauna Loa, find the elevation at the top of Mount Rainier and the distance from the summit to the 1000-m elevation waypoint marked in Google Earth. What is the average slope (in degrees) of this volcano from the waypoint to the summit?
(Hint: Be sure that the “height” you use to calculate the average slope on this transect is calculated by subtracting the 1000-m elevation of the waypoint, since unlike at Mauna Loa, the waypoint is not at sea level!)
11. Are the flanks of Mount Rainier steeper or shallower than Mauna Loa? What is the reason for this? (Hint: what type of volcanoes are these? See EDS Ch. 4, 94-102).Glacial ice lies at the peak of Mt. Rainier; periodic melting of this glacial ice generates a heated volcanic mudflow of water and tephra know as a lahar. Lahars have flowed down the slopes of Mt. Rainier ~50 times in the past 10,000 years and are known to have traveled up to some ~110 km from their source; 300,000 people live in the area covered by past lahars generated by Mt. Rainier. What is the closest airport and major city to Mt. Rainier? How far away is it?
III. Geologic Processes: Flooding, Disaster, and the Geological Hazards for Human Life: (4 points)
(Earth’s Dynamic Systems, Ch. 11, see p. 292; and Earth’s Dynamic Systems, Ch. 12).
The Katrina disaster, which killed almost 1500 people in New Orleans alone (closer to 2000 total) was due to a combination of factors, including
(1) The geological environment: The city is in the delta region of the Mississippi river. Deltas are naturally prone to floods. (See EDS, Ch. 12, 328-329).
(2)Humans have engineered the river and delta: The systems of levees and flood control that humans have developed for the river prevent sediment from being distributed across the land surface. The delta itself acts as a tremendous weight on the Earth’s lithosphere, causing the land surface to subside, and the human control of the river means there is no mechanism for replenishing the surface; sediments are now instead mostly be carried out to the Gulf. Coastal erosion and drainage of wetlands (primarily during oil and gas exploration) also has helped contribute to subsidence (see EDS, Ch. 11, p. 292) and a loss of coastal protection during storms.
(3) Flood protection and engineering: Some of the levees that were built were poorly engineered; some allowed water to seep through under the ground, ultimately destabilizing them. Often, the weak points in the city’s flood protection system were in relatively poor areas of the city, many of which are also at low elevations. ~50% of the city of New Orleans is at an elevation below sea level, which makes it challenging to keep water out of the city or to remove water when the city floods.
For this exercise, turn on the historical imagery by clicking on the clock icon or go to view menu and selecting ‘historical imagery”.
12. Expand the folder labeled New Orleans pictures and double-click on 8/17/05. The pin is located in the ninth ward, which was the part of the city that was hardest hit by Katrina (whose path did not directly strike the city, but passed east of the city on August 29). Look around at the city, and then double-click on the layer labeled 9/2/05. (Note that you can use the historical image slider to get a broader view if you wish). Some aerial and satellite images (like these) were used in the immediate aftermath of the flooding to help first responders locate the areas that were worst affected.
Next double click on the layer labeled “Riviere Frorse”, or fly to 18.554 N, 72.417 W to look at the changes in the Riviere Frorse fan in Port-Au-Prince Bay in Haiti over the last decade. Use the historical image slider to observe the change in size of the fan from the earliest image, taken on 9/19/2002, to the most recent image, taken on 9/10/2013. Note the dramatic changes in construction that has occurred in this area since the earliest image. The historical images also include photos from before and after the January 10, 2010 earthquake.
In a paragraph or two, consider the damage that you observe in Google Earth in New Orleans and reflect on your own view on how we interact (as humans) with the natural world. Was Katrina a “natural disaster” that was unavoidable, or not? Based on what you know, should we expect another Katrina-like disaster to strike the US again soon? Was Hurricane Sandy such a disaster? What lessons should we learn as a society from Katrina? Was Irene just another Katrina? What are the issues associated with continuing to build on deltas and fans such as in New Orleans and on the Riviere Frorse fan in Haiti?
------
On Friday, March 11, 2011, there was a huge underwater earthquake (magnitude of 9.0) off the coast of Japan, leading soon thereafter to monster tsunami waves (up to 40.5 meters high) that came ashore along the Japanese coast and traveled as far as ten kilometers inland, causing over 16,000 deaths. Some of the many videos of the tsunami waves can be seen at:
More details on the magnitude of this disaster can be found at:
This event reveals the differences between the behavior of rock under stress (brittle deformation) and water under stress (liquid flow) and shows the interrelationships between the two. It also illustrates the difficultyof preparingfor such events, and the short memory of humans for such types of disasters.
For this exercise, turn on the historical imagery by clicking on the clock icon or go to view menu and selecting ‘historical imagery”.
13. Expand the folder labeled Japan pictures and double click on “2011 Tōhoku earthquake epicenter.” The pin is located 100 km east of the coast of Japan. Now, double click on the layer named “Soma, Japan.” Use the historical image slider that you used for New Orleans to see the terrain and damage both before and after the tsunami. Note that pre-existing topography helped control the flooding, with flat areas being broadly inundated, and mountain valleys being filled more deeply.
What are the characteristics of a magnitude 9 earthquake and how often do they occur? Were the Japanese earthquake and tsunami related or unrelated? Compare the magnitude of this tsunami to others that have occurred in recorded history. What was the next most recent earthquake and tsunami? What was the previous most recent one to hit this same area? Address these questions in a few sentences.
If you were the Prime Minister of Japan, how would you ensure that this type of disaster would not happen again? If you could not avoid another event such as this, how would you prepare the population to deal with a similar future event?
Instructions, Tricks, and Hints for Using Google Earth
The “Fly To” tabs allow you to put in specific coordinates and it will center your view on that location.
- You might want to turn on or off background layers – do so in the “Primary Database”, at the bottom left of your screen.
- The ruler tool is located under "Tools-Ruler", or you can select the icon. After making a measurement, you can reset the tool by hitting the clear button at the bottom of the ruler dialog box.
- You can zoom in and out by holding the right mouse button on your computer (or by flicking the scroll wheel). Or you can use the Google Earth controls on the upper right hand portion of the screen (the bar with a + and – at its ends)
- You can change the perspective of your view by mousing over the compass in the upper right-hand corner and using the horizontal bar (or by holding down the scroll wheel button and moving the mouse, at least on a PC). You can also use these tools to rotate the direction that you are looking.
- If you are on a relatively new computer, you may want to consider turning the terrain quality up to the maximum amount in the slide under Tools-Options-Terrain Quality.
- Sometimes it takes a few seconds for the best resolution data to load. Be patient.
- The Primary Database has multiple features in it, each of which can be turned on and off(click the plus to expand this or any other layer). If certain features are making it difficult to see what you are looking at, turn them off! Also, you may want to turn off exercise layers (such as the sea-floor age layer) if they are obscuring your view of the surface.
- Be careful not to confuse the "eye alt" and ground "elev" if making measurements of surface elevation.
- Useful shortcuts:
Reset view to “north-up”: N key (for “north”)
Reset tilt to “top-down” view: U key (for “up”)