Relationship Between Volcanoes & Plate Boundaries by Shelby Soto on Prezi
I chose to compare the relationship between plate boundaries, volcanoes and earthquakes. The layers I chose satisfied the fact that magma. world map with plate boundaries and volcanoes designated Their relationship (or lack of one) to the plate tectonic cycle is still being debated. My advice when reading is to try to focus on the space-time sequence of events, rather than . With this new map, we can begin to assess how plate tectonics affect Earth's The modern Earth's tectonic plate boundaries are mapped in The new map and associated work is the result of a couple of At different periods in Earth history there were more mid-ocean volcanoes than there are today.
Which volcanoes in this activity are the most active in terms of the numbers of number of confirmed eruptions? You may have to look at a map for this one. Can you tell which volcanoes are hot spot volcanoes and which ones are subduction zone volcanoes? What are the clues besides looking at a map that will tell you.
Discuss whether there is a relationship between type of lava, magnitude of eruption, and volume of eruption for the volcanoes in this exercise. Feel free to supplement with other volcanoes if it helps to make your point.
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Figure out how to make a plot that illustrates your point. I know that I'm asking you to compare three things: Post to Questions if you are stuck. It also may help to refer back to lesson 5 in which we discussed the characteristics of different types of lava and their compositions and viscosities relative to each other. Submitting your work not yet -- there's a part 2 Save your word processing document as either a Microsoft Word or PDF file in the following format: Grading criteria I will use my general grading rubric for problem sets to grade this activity.
How Long does an Eruption Last? Volcanoes are dormant for a very long time, suddenly erupt, and then become dormant again. There are a wide variety of eruption lengths. Stromboli volcano off the coast of Italy has been erupting more or less continuously for over years!
Volcano - Volcanoes related to plate boundaries | triplexxx.info
Other volcanoes have eruptions that last less than a day. According to the Smithsonian Institute's Global Volcanism Program, the median length of time for a single eruption is seven weeks. Two curious kids and their father sitting on the beach at Stromboli in October The white haze above the peak of the volcano is actually a small ash plume from the volcano's nearly continous "Strombolian" eruptions.
There are two timescales of interest where erupting volcanoes are concerned: How long does a volcano stay active and what controls this? The main factor controlling volcanic activity in an area is the timescale over which melt is produced. For example, in a subduction zone setting, volcanism goes on for as long as the subduction zone is active. Remember, from a couple of pages ago, the overall timescale for the lifetime of a caldera.
Subduction is a process that generally lasts for millions of years. It shuts off when an entire plate has disappeared, or something causes the plate to change its direction so that it is no longer subducting. For an ocean island volcano, the timescale for activity is the lifetime of the mantle plume or other source of melt. For a single eruption, the controlling factor is the volume of melt present in the magma chamber and the degree to which the magma chamber is over-pressurized.
An eruption will usually last until the local melt has been depleted, or until the gas pressure inside the magma chamber falls to a level at which gas is no longer trying to escape. Certainly this is a fairly simplified overview. The internal plumbing of a volcano can be quite complicated, though recent monitoring efforts involving GPS, local seismometers, and tiltmeters are getting better and better at capturing the size, depth, and activity of magma chambers under active volcanoes.
The project lasted for about 5 years from The project goal was to make available a subset of volcano monitoring data from the Hawaiian Volcano Observatory HVO for educational purposes. The Web site—with data streams from the Hawaiian Volcano Observatory —provided a means for students to experience and interpret current volcano-monitoring data. The blurb above was cribbed directly from the now-sunsetted Volcanoes Exploration Program at Pu'u O'o web site and explains the point of the project.
Even though the project is over we are still able to use its data for the second part of the problem set in this lesson. The data provided by the VEPP program comes from the Pu'u O'o vent, which is on the east flank of Kilauea, so it represents just a subset of the many monitoring activities of the Hawaiian Volcano Observatory. See the map below to find the location of Pu'u O'o. It is one of the vents in the East Rift zone, the source of most of Kilauea's recent lava flows.
Map of Kilauea volcano on the island of Hawaii. The Pu'u O'o vent is the easternmost crater in an east-west trending line of craters southeast of the main summit of Kilauea. The general purpose of these measurements is to alert the scientists who receive the data about whether an eruption is imminent. This goal is worthy enough, but there is also the overarching scientific goal of getting a better understanding of how the plumbing system of a volcano works in the short-term and in the long-term.
Here is a list of the types of instruments that record the data we'll explore, and a brief description of each one. Tiltmeters Tiltmeters are installed to measure any change in the angle of the ground with respect to horizontal. The goal is to make an observation of any bulge or inflation of the ground around a vent, which could be indicative of rising magma.
Once an eruption has begun, tiltmeters can also measure deflation as the source of the eruption escapes from the ground. Below is a map of the three tiltmeters installed at Pu'u O'o.
The Hawaiin Volcano Observatory web site also has some detailed information about tiltmeters and what their data look like.
Map of tiltmeter stations installed near the Pu'u O'o vent on Kilauea. Different map colors represent different recent lava flow fields. You will recall from the New Madrid lesson in Earththat GPS stations are routinely used to monitor the movement across faults and to confirm the magnitude and direction of plate motions inferred from magnetic sea-floor anomalies.
At active volcanoes, GPS data is used to keep track of any surface deformation of the volcano. One of them is a "short-period" seismometer, which is sensitive to higher frequencies, such as the harmonic tremor that is often associated with the movement of magma at active volcanoes.
The other seismometer is a "broadband" instrument, which is sensitive to a wider range of frequencies than the short-period instrument, and to generally lower frequencies.
Lesson 6: Volcanic Eruptions
Broadband seismometers are installed all over the world to monitor ordinary earthquakes, but short-period seismometers are usually only for measuring what is going on in a small locality.
If you want to see recent earthquakes recorded in Hawaii, you can check out HVO's seimicity map. Location of the co-located short-period and broadband seimometers near Pu'u O'o. One of them is mounted on the north rim of the crater and looks southward into the crater.
The other one is installed on the southeast flank of Pu'u O'o. It looks east across the currently active vent. Map of the two webcams at Pu'u O'o. Arrows indicate direction of view.
I found this event by searching month-by-month using the software package the HVO scientists use, which used to be available to educators when the VEPP project was going on. I looked for distinctive jumps in the seismic amplitude data. Watch the three videos below to hear my explanation of what is going on in these plots because these plots tell us about the behavior of the volcano's inner workings.
So you click this little thing here and then over here you can choose which station to search for. I am going to use station STC and the short-period data from that station. I am going to leave everything else over here alone.
To make the exact plot I made, these are the time periods. It starts March 17 and ended on March Then I click submit and a little plot pops up. The x axis of this plot is days. It does not say the year but we know what year it is because we typed in right here. Over here is basically a sort of arbitrary amplitude scale.
Plate Tectonic, Volcanoes and Earthquakes
What this plot is showing you is recordings of the background seismic amplitude. This is different from a normal seismogram where you would actually see waveform arrivals of individual events. This is just kind of telling you what the background level of chatter is.
You can think of it that way. So the background level is basically nothing, but there is the occasional big excursion which could be anything, such as cultural noise or a sudden windstorm or a helicopter landing nearby, things like that. You can ignore those because they don't have anything to do with the volcano. When you see a sustained higher amplitude thing in the data, then you might start to think something is actually going on with the volcano.
It is a good idea to narrow in on this little thing and then check the tilt data and the GPS data to see if there is a real event happening there recorded by those instruments, too.
Video 2 Transcript of Video 2 Now that we have the seismic data, let us check the tilt data to see if we can find this event there, too. The way I am going to do that is I am going to click Tilt. I am going to choose this station. I am going to choose the Radial and Tangential components. And I am also going to choose to see rainfall because we know that sometimes when there is a lot of rainfall that can lead to a spurious signal in the tilt data, so we want to make sure there is no rainfall correlated with this thing we are looking for.
The start time and the end time are the same as what I had in there before so all I have to do is click Submit here. Up pops the tilt time series data for the same time period as the seismic data that we looked at before. Let us scroll down so we can see both of them at the same time. This plot has time in days on the x axis again and on the y axis is tilt in micro radians.
On the y axis on the right side is rainfall in millimeters. There are three different lines plotted here so it is a little more complicated than the seismic data. The black data is the rainfall data. That means we have to use the y axis that is over on the right side to see what is going on.
The blue and the green are the two different components of tilt for the same station.Plate Tectonics Explained
They are oriented with respect to degrees. Let us check what is going on. I can see that this blue line is showing deflation, so that is negative motion, that is towards the caldera, down to about this time.
Interestingly enough, right here is where inflation begins and that inflation begins exactly at the same time as the seismic signal. The inflation that ends with this little peak corresponds very well in time to the seismic signal. I can also see that there is not a big rainfall event associated with this. I think we can convince ourselves that rainfall is not causing this. There is something going on at the volcano that is causing both a tilt and a seismic signature at the same time.
That is pretty cool. Video 3 Transcript of Video 3 Let us see if the GPS data confirms our suspicions that there is something interesting going on that we already saw in the seismic and the tilt data.
I am going to select GPS here. The Cascade volcanoes in the northwestern United States and the volcanoes in Mexico and Central America are related to the subduction under the North American Plate of the small Juan de Fuca and Cocos plates, which are on the east side of the Pacific Plate.
Similarly, the volcanoes of the Andes are related to the subduction of the Nazca Plate beneath the South American Plate. Conceptual models of how subduction and rift volcanoes may form are shown schematically in the diagram and in the video. Of the 1, volcanoes listed in the table of landform types, 80 percent occur along subduction zones, and 15 percent occur along rift zones.
At those depths active submarine volcanoes have yet to be observed, though many hydrothermal areas have been found along submarine rift zones by research submersibles. Icelanda segment of the Mid-Atlantic Ridge that emerges above sea level, has 70 volcanoes that have erupted during the past 10, years. If this is a typical number for a rift system, there may be several thousand potentially active volcanoes along the oceanic ridges that are the surface expressions of the world rift system.
Subduction volcanoes As an oceanic plate is subducted beneath a continental plate, seafloor sediments rich in water and carbon dioxide are carried beneath the overriding plate. These compounds may act as fluxes, reducing the melting temperature of magma. Although the process is not clearly understood, magma apparently forms and rises by buoyancy from a depth of to km 60 to miles. Subduction-zone volcanoes occur on the overriding plate and are offset inland from the actual plate boundary along the ocean trench.
The rising subduction-zone magma is probably basaltic in composition and is formed by the partial melting of mantle rocks. As the rising magma moves slowly up through the continental crust of the overriding plate, however, two things may occur to increase significantly the silica content of the magma.
Crystallization of olivine and pyroxene minerals from the basalt can leave the residual melt enriched in silica and depleted in magnesiumiron, and calcium. This process is called fractional crystallization. Also, basaltic magmas have enough excess heat to partially melt the continental host rocks through which they are ascending.