User:Gerrad.caldwell/sandbox

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You made a useful addition with citation to the Gorda Plate page for your week 3 assignment William Wilcock (talk) 23:54, 16 April 2017 (UTC)

This is my sandbox. Now I'm just being bold.[1]

Evaluating Articles and Sources Look for a rating in the talk page. Good/featured vs. start/stub. Warning banners, short intro that doesn't flow, words of persuasion, no valid references, questionable references or citations, relevant sections are missing. You can add [citation needed] when a statement is made without a citation. Facts need references.

I like your evaluation of the two articles. They are quite detailed. I also think you are correct to question the reliability of this article. The links to flood basalt, hotspots and triple junctions are rather muddled. You could usefully add some comments on the article talk page William Wilcock (talk) 05:35, 10 April 2017 (UTC)

Plate tectonics Article There are a lot of links on this page as well as a reference at the end of every short paragraph. The introduction in long with a good flow between each short paragraph. The contents is very long, broken into many headers and sub-headers. These are once again linked back to main articles. There is a warning bar showing the need for more citations within a sub-header section. There is an extensive list of references including articles, books, videos, and other external links. This article was at one point a featured article, however was demoted and is now listed as "Former featured article". In the Talk page there is mention of people trying to include "other beliefs" into the plate tectonic page. I had never considered having to defend a science article against non-believers on Wikipedia, however this is good to realize now. It seems as though a lot of the talk section is back and forth disputes on either wording of the article, or why things were/were not added to the article. From this article I have learned that it was earlier believed that the globe would contract and expand as new crust was made or subducted, as opposed to the conveyor belt notion of today. I have never heard that plate movement is driven by the motion of the seafloor away from the spreading center, which is described further as differences in gravitational forces.

Divergent boundary Article First thing on this page is the warning notification for citations. The introduction is very short with very few references (only 1 for this whole section). Wording is vague "current research" without fully describing what the research says and where it is from. Sentence structure is short and as though multiple people have written sections and pieced them together. The contents is very short, with only main headings (no sub-headings), and the description section is the only section with substantial information. This section also contains no references. The images used are basic and confusing, with the article discussing images that are not displayed. There is only one reference for the entire article. This article is classified as a "Start class". The talk page of this article is embarrassing! Apparently this person created this page as a project for school, and not only did a poor job on their project, but also let everyone know how unimportant this project was to them. Have some self pride people! The article uses the word "massive" a lot, which holds no value. This should be replaced with examples of actual measurements or rates. It also talks about a lot of different ideas in the description section, none of which are referenced and backed by facts. You can tell this person did not put a lot of time into this article. From this article there was not very much new information to learn (sadly), however the list of the divergent boundaries was new to me. I had no idea there were so many. However, after reviewing this article I would double check that list before ever using it to reference a divergent boundary.

Gorda Ridge Article[edit]

It looks like you found some good sources to start with. I would be careful not to pursue too many in-depth questions. Given how little is currently on the wiki page, there are plenty of fundamental topics (such as those William listed) that need to be addressed. Erik (talk) 13:44, 24 April 2017 (UTC)


William Wilcock (talk) 04:43, 24 April 2017 (UTC)This is a good start. Just a google search for the Gorda Ridge found some more popular web articles https://volcano.si.edu/volcano.cfm?vn=331031 https://www.volcanodiscovery.com/north-gorda-ridge.html Have you searched the library Georef database. This would allow focused searches and give you links to many articles. Other questions to ponder. What are some basic facts about it (spreading rate, morphology (depth of valley). When was the ridge discovered? Does it have earthquakes? Have eruptions been observed there. William Wilcock (talk) 04:43, 24 April 2017 (UTC)


This page talks about where the Gorda Ridge is, but apart from this, it doesn't give any real information. The talk page suggests new images because the ones used are drawn incorrectly. I would like to better address the motion of the plates surrounding the ridge, the history of the ridge, the morphology of the ridge, how the ridge is changing/changed, and any associated activity with the ridge. A few sources I have found include [2], [3], [4], [5], [6], and [7]

Notes[edit]

  1. ^ Be bold guidline. "Wikipedia. The Free Encyclopedia". Retrieved April 4, 2017.
  2. ^ Koski, R. A., Benninger, L. M., Zierenberg, R. A., & Jonasson, I. R. (1994). Composition and growth history of hydrothermal deposits in Escanaba Trough, southern Gorda Ridge. US Geological Survey Bulletin, 2022, 293-324.
  3. ^ Church, S. E., & Tatsumoto, M. (1975). Lead isotope relations in oceanic ridge basalts from the Juan de Fuca-Gorda Ridge area NE Pacific Ocean. Contributions to Mineralogy and Petrology, 53(4), 253-279.
  4. ^ Hooft, E. E., & Detrick, R. S. (1995). Relationship between axial morphology, crustal thickness, and mantle temperature along the Juan de Fuca and Gorda Ridges. Journal of Geophysical Research: Solid Earth, 100(B11), 22499-22508. Chicago
  5. ^ Chadwick, W. W., Embley, R. W., & Shank, T. M. (1998). The 1996 Gorda Ridge eruption: Geologic mapping, sidescan sonar, and SeaBeam comparison results. Deep Sea Research Part II: Topical Studies in Oceanography, 45(12), 2547-2569.
  6. ^ Davis, A. S., Clague, D. A., Cousens, B. L., Keaten, R., & Paduan, J. B. (2008). Geochemistry of basalt from the North Gorda segment of the Gorda Ridge: Evolution toward ultraslow spreading ridge lavas due to decreasing magma supply. Geochemistry, Geophysics, Geosystems, 9(4).
  7. ^ Cooper, K. M., Goldstein, S. J., Sims, K. W., & Murrell, M. T. (2003). Uranium-series chronology of Gorda Ridge volcanism: new evidence from the 1996 eruption. Earth and Planetary Science Letters, 206(3), 459-475.


Gorda Ridge[edit]

The regional setting of the Gorda Ridge.
Bathymetric image of the Gorda Ridge - Geomap

The Gorda Ridge (41°36'19.6"N 127°22'03.1"W), a tectonic spreading center, is located roughly 200 km off the northern coast of California and southern Oregon. Running NE - SW it is roughly 300 km in length[1]. The ridge is broken into three segments[2]; the northern ridge, central ridge, and the southern ridge, which contains the Escanaba Trough.

Regional Setting[edit]

The Gorda Ridge runs in a north-easterly direction, bounded at both ends by transform faults. At the southern end, the ridge meets the Mendocino transform fault, while the northern end butts against the Blanco transform fault. To its east is the Gorda Plate, which together with the Juan de Fuca Plate to its north, is what remains of the once-vast Farallon Plate. These two oceanic plates are currently moving east, subducting underneath the North American Plate in what is known as the Cascadia Subduction Zone[3]. To the west and south of the ridge is the Pacific Plate, which is currently moving west diverging from the Gorda Plate[3]. The divergence of the Pacific Plate and the Gorda Plate is what has lead to the creation of the Gorda Ridge. On the Pacific Plate, roughly 50 km west of the northern portion of the ridge, sit 8 seamounts (underwater volcanoes), known as the President Jackson Seamounts.

The history of the Gorda Ridge formation.

Geological History[edit]

Roughly 30 Mya the Farallon Plate subducted beneath the North American Plate, segmenting the Pacific Farallon Ridge[4]. This subduction created new microplates and new ridges, including the Juan de Fuca Plate and Juan de Fuca Ridge. As the Juan de Fuca Plate continued to subduct underneath the North American Plate it also segmented, creating the Gorda Plate and Gorda Ridge.

Spreading Rate[edit]

The Pacific Plate is moving in a northwest direction, creating a divergence with the Gorda Plate at a speed of 5 cm per year[5]. The Juan de Fuca Plate (including the Gorda Plate) is moving east-northeast, subducting under the North America Plate at a much slower rate of 2.5-3 cm per year[6]. Due to the ridge being segmented into three distinct parts, each section has its own spreading rate, caused by the slab-pull and ridge-push of the surrounding tectonic plates. The northern segment is the narrowest, with portions as narrow as 3 km across, and has the fastest spreading rate of 2.9 cm per year (half-rate)[2]. The central segment is roughly 10 km wide with a spreading rate of 2.4 cm per year (half-rate)[2]. The southern segment has sections as wide as 18 km, and has the slowest spreading rate of 1.2 cm per year (half-rate)[2].

Seismic events near the Gorda Ridge.

Seismicity[edit]

Due to the Gorda Ridge's proximity to the Mendocino Triple Junction, the area experiences a significant amount of seismic activity. The majority of activity is seen on the Gorda Plate, however some occurs on the ridge itself. Most events are generated by the divergence of the Pacific Plate and the Gorda Plate. Since 1983 there have been approximately 80 magnitude 3 earthquakes happening at this location every year[3].

1996 Eruption[edit]

On 28 February 1996 the northern segment of the Gorda Ridge (42 40'N 126 48'W) experienced a burst of seismic activity, which lasted roughly three weeks[7]. Concurrent with seismicity were a series of slow volcanic eruptions (1-10 m3/sec), forming thick flows of pillow basalt. These pillow basalts are thickest to the north, indicating this region's activity lasted longer than the other portions of the ridge. The estimated volume of erupted magma during this event is 18x106 m3, forming a blanket of new oceanic crust, averaging 75 m thick[7].

Axial Valley[edit]

Unlike other intermediate spreading centers, the Gorda Ridge has a large rift valley, which is typically seen in areas of slow spreading centers[7]. This is caused by the oceanic crust beneath the ridge being thinner and mantle temperatures being cooler than most intermediate spreading centers[8]. The Gorda Ridge has an average depth of 3000 m, with a few locations reaching depths of 3500 m. The walls of this valley are steep, in most cases giving a vertical relief of over 1000 m[9]. The floor of the southern ridge valley has been filled in with roughly 1000 m of sediment from the continental margin, mostly delivered by turbidity currents. The central ridge valley contains exposed basalt, and the northern ridge valley has a light sediment covering[1].

See also[edit]


References[edit]

  1. ^ a b Carey, Stein, & Rona. (1990). Benthos of the Gorda Ridge axial valley (NE Pacific Ocean): Taxonomic composition and trends in distribution. Progress in Oceanography, 24(1), 47-57.
  2. ^ a b c d Sverdrup, K. (1986). Multiple-event relocation of earthquakes on and near the Gorda Ridge. Geophysical Research Letters., 13(7), 674-677.
  3. ^ a b c "Juan de Fuca, Explorer and Gorda Plates". Americas:
    Tectonics    . Retrieved 2017-06-07.
  4. ^ MacLeod, C. J.; Tyler, Paul A.; Walker, C. L. (228). Tectonic, Magmatic, Hydrothermal and Biological Segmentation of Mid-ocean Ridges. Geological Society of London. ISBN 9781897799727.
  5. ^ webmaster-woodshole@usgs.gov. "Mendocino Triple Junction Offshore Northern California". woodshole.er.usgs.gov. Retrieved 2017-06-07.
  6. ^ Oppenheimer, David. "Mendocino Triple Junction Offshore Northern California". Retrieved 6 June 2017.
  7. ^ a b c Chadwick, Embley, & Shank. (1998). The 1996 Gorda Ridge eruption: Geologic mapping, sidescan sonar, and SeaBeam comparison results. Deep-Sea Research Part II, 45(12), 2547-2569.
  8. ^ Hooft, E.E.E., Detrick, R.S., 1995. Relationship between axial morphology, crustal thickness, and mantle temperature along the Juan de Fuca and Gorda Ridges. Journal of Geophysical Research 100,22 499—22 508
  9. ^ "The Escanaba Trough of Gorda Ridge: A Laboratory for Mineral-forming Processes". Retrieved 6 June 2017.

Peer Review by Chanelle Cadot[edit]

This looks good so far! I think if you were looking for more content you could do another section on history of the ridge so like when it first came about, how it has evolved with time, that sort of thing. This wouldn't necessarily need its own section, though, so you could just add a sentence or two in the introduction about its history. Overall though I think the intro paragraph is good with a nice overview of the Gorda ridge, just add some historical context.

I like the content of your spreading rate section but I think this section could benefit from some more organization by splitting up this section into smaller subsections that are each of the different segments of the ridge. So having a seperate subsection for the northern ridge, central ridge, and southern one. This may split up all the information better and make it more easy to follow.

I think that you can expand your last section. You mention that the bottom of the southern ridge has been filled with sediment but what about the other two ridge segments?

It looks like you have some good references but you could use some more and maybe more varied ones too. For potential pictures I would recommend a general diagram of a spreading ridge and a map of where the Gorda ridge is located. Cadotc (talk) 04:04, 22 May 2017 (UTC)

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