Earthquakes and Volcanoes as evidence of plate tectonics
Strong supporting evidence for plate tectonics can be found in the patterns formed by mapping earthquake activity across the globe. In this exercise you will be asked use Google Earth to explore patterns in the occurrence of earthquakes and Volcanoes. You will create maps showing the occurrence and depth/magnitude of each event. You will also manually create a plot showing the patterns of earthquake depth across different types of plate boundaries
Data and Methods:
There a number of sites which provide records of global earthquake events such as the one listed below.
http://www.ncedc.org/anss/catalog-search.html (Links to an external site.)
To address the following questions, read some of the specifics of the data set and data catalog http://www.ncedc.org/anss/anss-caveats.html (Links to an external site.)
- Why do the number of earthquakes appear to increase over time?
- What was a significant driving factor for the development of global seismic recording stations?
- Why do the records show significant increases in seismic activity between the years 1965 and 1975?
- Describe the relationship between magnitude and frequency for earthquakes.
YOU SHOULD DOWNLOAD THE .KMZ FILES AND RUN THEM FROM YOUR LOCAL COMPUTER... YOU MAY NEED TO INSTALL GOOGLE EARTH (free) IF IT IS NOT ALREADY INSTALLED.
Mapping the data - Data for this exercise are for the entire Earth and include earthquake depth and magnitude that occurred over a 25-year period, and volcanoes. They have been downloaded from the website listed above and converted to a Google Earth .kmz file. You will be using Google Earth to visualize and analyze the patterns in earthquake and volcanoes around the planet. Include screen captures from Google Earth to support your analysis (you don’t have to include one for every question, but a few to illustrate your analysis).
- How do observed patterns in your mapped earthquake and volcano locations support plate tectonic theory? (hint: compare locations to the ‘ring of fire’ and plate boundaries, specifically subduction zones)
- How is frequency of earthquakes and magnitude related?
- Using the earthquake depth file, create a cross section of earthquake locations/depths across a subduction zone boundary (I suggest using an area around the Andes of Western S. America or Aleutian Trench). You will first draw an imaginary line that crosses the subduction boundary which will form the ‘X’axis of your cross section. Next, identify the depth for the points that are along or near your imaginary line and plot those depths on the ‘Y’ axis. I have included a fantastic illustration below of a professional cross section (and some graphic artistry). After you have completed the cross section, explain this pattern you see.
- How do the patterns in depth of earthquake events at this location provide support for plate tectonic theory?
- Create a cross section of earthquake depth across a transform boundary (Southern California). How is the pattern of depth of earthquake events different here?
- Explain this difference.
- Discuss how these patterns also provide support to plate tectonic theory?
- Display the volcano Google Earth file along with the earthquake data. Identify places of high correlation and low correlation (You will need a blank world map to include with the report – you can find one for free online).
- What explains the areas of low correlation (hint: look up features and characteristics of different plate boundaries)?
- Explain the term ‘ring of fire’; identify this global feature on your map.