The Hazardous Earth
We have discussed the Theory of Plate Tectonics in class. In this exercise, you will explore how natural hazards such as volcanoes and earthquakes relate to the earth’s plates. We will be using a web GIS run by the UNAVCO Facility in Boulder, CO.
Materials: Before you get started make sure that you have the following materials:
Goodes World Atlas
A ruler
A calculator or Microsoft Excel
Earthquakes
Go to the Jules Verne Voyager Jr. website at http://jules.unavco.org/VoyagerJr/Earth.(note, clicking on the link will open a new window) Select the basemap Face of the Earth & Releif and add features Earthquakes. Click on ‘Make Changes’. Turn the legend on by clicking on the ‘Legend On/Off’ button. Your legend is a popup window. If it does not show up immediately, try minimizing your other windows to make sure that it is not hidden behind one, or try turning your popup blocker off.
Questions:
1) 2 pts List 4 regions that have very deep (greater than 500 km) earthquakes. Describe these 4 locations to the best of your ability.
2) 2 pts For each region listed above, what type of plate boundary is found there? You may need to use another map, like the one in your textbook, to answer this.
Plate Tectonics and Sea Floor Spreading
Next, on the JVV site, change the basemap to Ocean Floor Age and add features Tectonic Plates (uncheck earthquakes). Click on ‘Make Changes’ If the JVV site is not working you can view the ocean floor age with a map from Rice University as PDF or GIF.
Answer the following questions in complete sentences You may want to use your atlas to find geographic locations metioned. Note that in describing the geographic locations you need to be specific. For example, if you were asked to located the Mississippi river, an acceptable answer would be ‘running north/south in the central United States’. An unacceptable answer would be ‘in the middle of the United States’.
3) 1 pts Where is the youngest tectonic plate material found in the Atlantic Ocean?
4) 1 pts Where is the oldest tectonic plate material found in the Atlantic Ocean? How old is it?
5) 1 pts Where is the youngest tectonic plate material found in the Pacific Ocean?
6) 1 pts Where is the oldest tectonic plate material found in the Pacific Ocean? How old is it?
Plate Motion
To complete this section you will need a ruler, Goodes World atlas and a calculator or Microsoft Excel.
Keeping the previous selections (Grey Topography, Tectonic Plates), under ‘Velocities’ select ‘No Net Rotation’ and leave the radio button selected on Model (obs or observed just adds a lot more arrows). Again, click the ‘Make Changes’ button. The blue arrows on the map show you the direction and speed of the earth’s tectonic plates as they move.
The Global Plate Motion Calculator can be found at http://sps.unavco.org/crustal_motion/dxdt/nnrcalc/ In this section you will first calculate the distance a present-day city will move in 500 and 5 million years. Next you will calculate the amount of time it will take for two cities to meet each other.
Use the index of Goodes World atlas to look up the latitude and longitude of Honolulu, Hawaii. Enter the latitude and longitude (just degrees and minutes, leave the seconds blank) in the Global Plate Motion Calculator .
Note that when you enter a latitude that is south of the equator you will need to enter the degrees as a negative (eg. -30, instead of 30S), and when you enter a longitude that is west of the prime meridian you need to enter the degrees as a negative (e.g. -120 instead of 120W).
Basic math refresher:
tenths = 1 number after the decimal point: 1.2
hundredths = 2 numbers after the decimal point: 1.22
thousandths = 3 numbers after the decimal point: 1.222
Note that zeros are places too. So if you were to round 1.20351 to the nearest hundredth it would be 1.20
You can calculate how far a point will move in a given number of years by multiplying the speed in mm/yr times the number of years.
This can be converted into kilometers by dividing the result by 1 million (round to three decimal places).
If the numbers are too big for your pocket calculator to deal with, you can use Microsoft Excel to do the calculations. For example, if the speed of a location was 21.1 mm/yr and you were calculating how many kilometers it would move in 5 million years, you would simply enter =(21.1*5000000)/1000000 into a cell in the Excel spreadsheet.
Round the following answers as specified. If you are not sure how to round decimals, see this link. If you are not sure what a ‘hundreth or thousandth’ in decimals is, see this link. Please note that this is approximately 5th grade math… so it is okay if you are a little rusty, but you should be able to do this in a college course. Points will be deducted for incorrect rounding or inaccurate decimals.
7) (2 points) How far (in kilometers) will Honolulu move in 2000 years? Show your work (round your answer to the nearest thousandth)
8) (2 points) How far (in kilometers) will Honolulu move in 2 million years? Show your work (round your answer to the nearest thousandth)
Next we will use Goodes Atlas and the Plate Motion Calculator to determine how long it will take for two cities to meet each other. Use Goode’s Atlas to look up the latitude and longitude of San Francisco CA and Los Angeles, CA. Go to the plate motion calculator and enter the values (just degrees and minutes, leave the seconds blank). Remember that for longitudes in the western hemisphere and the southern hemisphere to enter the values as negative.
9) (2 points) What is the speed of San Francisco? (round your answer to the nearest hundreth)
10) (2 points) What is the speed of Los Angeles? (round your answer to the nearest hundreth)
11) (2 points) Using page 118 in your atlas, how many miles apart are San Francisco and Anaheim (in LA)? Show your work (round your answer to the nearest whole number)
You can calculate how fast the two cities are moving toward each other by adding up the absoloute value of their speeds. Based on the distance that you calculated in #11, and the speed at which the two cities are moving toward each other, how many years will it take for San Francisco and Los Angeles to meet? Note that 25mm = 1 inch, 12 inches = 1 foot, 5280 feet = 1 mile.
12) (2 points) Based on your measurement in #9, how many years will it take San Francisco and Los Angeles to meet? (round your answer to the nearest whole number). Show your work.
