Ring of Fire 1: What Volcanoes Tell Us About Plate Tectonics
|Areas of Science||
|Time Required||Long (2-4 weeks)|
|Prerequisites||Computer with Internet access. Perseverance.|
|Material Availability||Readily available|
|Cost||Very Low (under $20)|
AbstractThe Ring of Fire is a region of volcanic and earthquake activity that surrounds the Pacific Ocean. In this project you can explore the connection between plate tectonics and volcanic activity by mapping historical data.
ObjectiveThe goal of this project is to map volcanic activity and relate it to the positions of the Earth's tectonic plates.
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Last edit date: 2020-11-20
Today it is widely accepted that the Earth's crust consists of a series of huge plates that slowly move. The low parts of the plates are beneath the world's oceans, and the high parts of the plates are landmasses. New plate material is generated at deep sea ocean ridges in a process called sea-floor spreading. Material from plates is also recycled at trenches, where dense, oceanic crust dives back (subducts) underneath an adjacent plate towards the upper mantle. Figure 1 shows a map of the major tectonic plates.
The theory of plate tectonics revolutionized geology in the 1960s. Before this, geology had been a descriptive science. Mechanisms for large-scale processes such as the formation of mountain ranges were put down to vague "earth forces." Plate tectonics changed that. A series of scientific papers by Harry Hess, Robert Dietz, Fred Vine, Drummond Matthews, and others brought together a growing body of evidence that massive pieces of the earth's surface were constantly on the move. Subduction of one plate beneath another could provide the massive force to produce uplift of mountain ranges. Fifty years earlier, in 1912, Alfred Wegener had proposed his theory of continental drift, and was widely ridiculed. Wegener, like others before him, had noticed that the continents on either side of the Atlantic Ocean had complementary shapes, suggesting that they might have originated much earlier from the same landmass. He had also noted similarities in rock formations on opposite sides of the ocean, and similarities in both living and fossil animals. Wegener did not have a good explanation for how vast chunks of the earth's surface could move relative to one another, and the community of geologists was not ready to accept his ideas (McPhee, 1981-1998; WGBH, 1998).
Figure 1. Map of major tectonic plates of the earth (Tilling, date unknown).
Today we still do not know the mechanism for the motion of the plates, although it is thought that convection of heat from the earth's interior is somehow involved. The evidence that clinched the case for plate tectonics came from detailed mapping studies of paleomagnetism. Rocks containing magnetic material reveal the history of when and where they were formed. As the molten rock cooled, the magnetic particles aligned themselves with the earth's magnetic field at that time. Although the positions of the earth's magnetic poles have changed over the billions years of earth's history, geologists have been able to recreate the time line of those changes. Armed with that information, geologists have been able to map the dates of origin of the oceanic crust, and to confirm that sea-floor spreading at suboceanic ridges and subduction at trenches is a constant process.
How are volcanoes related to tectonic plates? The following paragraph from Annals of the Former World by John McPhee, summarizes the connection quite well:
A seismologist discovered that deep earthquakes under a trench had occurred on a plane that was inclined forty-five degrees into the earth. As ocean floors reach trenches and move on down into the depths to be consumed, the average angle is something like that. Take a knife and cut into an orange at forty-five degrees. To cut straight down would be to produce a straight incision in the orange. If the blade is tilted forty-five degrees, the incision becomes an arc on the surface of the orange. If the knife blade melts inside, little volcanoes will come up through the pores of the skin, and together they will form arcs, island arcs—Japan, New Zealand, the Philippines, the New Hebrides, the Lesser Antilles, the Kurils, the Aleutians (McPhee, 1981-1998, 121)
The goal of this project is to collect volcanic activity data and map it. If the plate tectonics theory of volcanic activity is true, then the great majority of volcanic activity should occur at or near boundaries between tectonic plates. What do you think you'll find?
Terms and Concepts
To do this project, you should do research that enables you to understand the following terms and concepts:
- types of volcanic formations:
- cinder cone,
- complex volcano,
- explosion crater,
- fissure vent,
- lava (or volcanic) dome,
- pyroclastic cone,
- shield volcano,
- spatter cone,
- somma volcano,
- submarine volcano,
- tuff cone.
- types of volcanic eruptions:
- pillow basalt;
- debris flows:
- debris avalanche;
- lava fountain,
- lava lake,
- pyroclastic flow,
- layers of the Earth:
- tectonic plate,
- How is subduction of oceanic crust thought to be related to volcanic activity?
- Does your mapped data of volcanic activity support this hypothesis?
BibliographyFor more information on different types of volcanic formations, volcanic eruptions and activity, and plate tectonics, see:
- Tilling, R. I. (1997, January 31). Volcanoes U.S. Geological Survey. Retrieved March 5, 2013.
- Public Broadcasting Service (PBS). (1998). Intro to Plate Tectonic Theory. WGBH. Retrieved March 5, 2013.
- Smithsonian. (n.d.). Volcanoes of the World. Global Volcanism Program, Department of Mineral Sciences, National Museum of Natural History. Retrieved March 5, 2013.
- Smithsonian / U. S. Geological Survey. (n.d.). Smithsonian / USGS Weekly Volcanic Activity Report. Global Volcanism Program, Department of Mineral Sciences, National Museum of Natural History. Retrieved March 5, 2013.
- Excel Easy. (n.d.). Excel Easy: #1 Excel tutorial on the net. Retrieved June 12, 2014.
- McPhee, J., 1981-1998. Annals of the Former World. New York, NY: Farrar, Strauss and Giroux.
Materials and EquipmentTo do this experiment you will need the following materials and equipment:
- world map or regional map with lines of latitude and longitude,
- transparency material at least as large as your map,
- computer with Internet access
- perseverance and attention to detail.
- Gather data on worldwide volcanic activity from the Smithsonian Institute/USGS Weekly Volcanic Activity Report archive (SI/USGS, 2007a).
- For each event, keep track of the following information in a table (or spreadsheet file):
- type of volcanic formation,
- type of volcanic activity.
- The more events from which you collect data, the better.
- For each event, keep track of the following information in a table (or spreadsheet file):
- Data analysis by mapping.
- Think of ways to encode the volcanic data with your map symbols. For example, you could encode the type of volcanic formation with the type of symbol, the type of volcanic activity with the color of the symbol, and the magnitude of the activity with the size of the symbol.
- Compare your volcanic activity data map with maps showing the boundaries of tectonic plates.
- Remember, correlation does not prove causation. A correlation of volcanic activity with known plate boundaries would provide supportive evidence for the plate tectonic theory. A lack of correlation would be significant evidence against the plate tectonic theory.
If you like this project, you might enjoy exploring these related careers:
- Questions to consider:
- What types of volcanic events are included in the archive?
- How representative are the data you have collected?
- Is there any correlation between the local shape of volcanic activity and the relative motion of adjacent plates?
- Use the Google Earth program to map your data and make illustrations for your display board. You can download the program from: http://earth.google.com/download-earth.html. You can find a Google Earth placemark file for Holocene (i.e., last 10,000 years) volcanoes at http://www.volcano.si.edu/world/globallists.cfm?listpage=googleearth.
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