In terms of plate tectonics, 1) How was the Western Cordillera formed and what is happening there? (-is it the Juan de Fuca Plate and Pacific Plate subducting under North American Plate, creating volcanoes along coastlines??? I was told that the Rockies, or western cordillera is the oldest mountain range, is this true?) 2) How was the Mediterranean formed and what is happening there? (-I only know that the African Plate is subducting under Eurasian Plate creating the Alps...) 3) How was the Appalachians formed and what is happening there? (-I can't see any plate boundaries in that area...) 4) How was the Mexico formed and what is happening there? (The Cocos Plate (and partly Pacific plate too) is colliding with Caribbean and N. American Plate, but is that how Mexico was formed?) 5) Are the Alps, Appalachians and Western Cordillera actually volcanoes (the Rockies don't look like volcanoes to me...) formed by oceanic-continental collision? I have to get these things clear before the test, can someone briefly explain? I would appreciate Please Register or Log in to view the hidden image!
The Rockies are older than the Appalachians. The Mediterranean was formed by the departure and spreading apart of the original land masses that were tied together. I'm not sure, but I don't think that anything is happening with the Appalachians now, but I have heard of techtonic activity in the Adirondacs in Arkansas. Mexico is part of the North American continent that originally branched off from Pangea. The upper parts of the Rockies show distinct evidence of geological plate convergene but I have not heard or seen of any volcanic activity in any of those three areas that you mention.
The rockies were old extinct volcanoes, there are quite alot of lava chambers one kilometer under sea level, where there is the most friction between Juan de Fuca Plate and the pacific plate. the friction causes the rocks to melt, creating a lava chamber that might come to the peak of the rockies fast enough to make a volcanic explsion, or it might turn into lava streams like in hawaii, or it might create pyroclastic flows. inclusion, i went way off topic and the rockies are extincted volcanoes.
Where seperate tectonic plates are moving, there are three things that can happen: they can diverge (move apart), converge (come closer together), or transform (slide past one another). Large-scale mountain building generally occurrs because of convergent plates coming together where one is subducted (slides under or over the other) or through direct continental plate collision. Sometimes these convergences involve more than one plate and many of the smaller plates. These smaller plates are generally not listed in introductory plate tectonic books, t.v. shows, or in class. Direct continental collision is what formed the Appalchian Mountains some 300 million years ago when North America collided with Africa. The most spectacular example of plate convergence is, of course, the Himalya Mountains and the more inland Tibetan Plateau. This is a result of the Indian Plate colliding with the Asian Plate. These plates are still converging and as a result the Himalayas increase in height by an inch or so - maybe more? - each year. Surprising to me is that this convergent plate mountain construction extends all the way from the Himalayas to the Alpine Mountains (north and northeast of the Mediterrian). They are linked together and are a result of the convergence of many plates. The Southern Alps northeast of the Mediterrian were caused by the African Plate overriding (sliding on top) of the European Plate. But this convergence does not seem to be active today, as it is in the Himalayas. The creation of the Sierra Nevada and the Rocky Mountains occurred between 40 to 80 million years ago and is perhaps the most least understood. It involved a convergence of the Pacific Ocean Plate subducting under the North American plate, but this subduction occurred 745 miles (1,500 kilometers) to the east in Colorado. It is thought that either the subducted slab was so thin that it was able to slide inward that far and still thrust upward, or that the Oceanic Plate and the North American Plate collided so fast (in relative geological time-frame terms) that these mountain construction forces were transmitted and occurred that far inland. Wherever you have plate convergence, you have volcanic activity. In the case of the Rockies, there are lots of volcanic sedimentary deposits throughout the range but because they formed so long ago, there are no longer any active volcanoes, although there might be some mountain ranges in the Rockies that still resemble the circular ring patterns that the top of a volcanoe forms. This I do not know. Also, wherever there is plate convergence, there has to be a corresponding plate divergence at the opposite end, and these divergences usually occur at the depths of the ocean bottoms. At great depths in the Pacific and Atlantic these divergences form lava erruptions that can spread out for miles forming trenches and huge underwater ridges and thermal hot spots. In the United States our greatest concern over the last hundred years or so has been the earthquakes caused by the San Andreas fault along the Pacific coast. This fault is caused by three main plates: the Pacific Plate moving northwest, the Juan de Fuca place moving northwest and northeast, and the North American Plate. The Juan de Fuca plate is located north of the Pacific Plate and since it is moving northeast in Northern America, this is why there are still active volcanoes in Washington and Oregon, while in California, where the Pacific Plate is diverging outward towards the nothwest, it causes earthquakes instead of volcanoes. The convergence of the Juan de Fuca Plate with the North American Plate also has to do with the existence of ancient "island arcs" in the area. In contrast to all this, the Hawaiin Islands were formed in a completely different way and are actually a series of volcanoes that uplifted from the ocean floor as a result of lava eruptions on the sea floor from the Pacific Plate moving northwest and the descending oceanic crust. It is an interesting fact that the Hawaiin Islands, if considered as mountains, and if the height of a mountain is measured from its base to its top, then the Hawaiin "mountains" are actually higher than Mt. Everest. But traditionally, for practical reasons, we normally measure the height of a mountain from its base on land and not from the ocean's floor.
Since when! No. The Mediterranean is the remains (along with the Black Sea, the Caspian sea and the Aral Sea) of the Tethys Ocean which has been closed off by the collision of Europe with Africa and southern Asia. That's why the Trudos massive, sitting in the middle of it all, is composed of scraped up ocean floor, known, conveniently enough as ophiolite. I am now frightened to look at your other posts to see how many errors they may contain. Ophiolite
Yes, the Appalachians are older than the Rockies, and I hope that my more accurate datings of this in my last post proved that I knew better; but just like a person's heart may skip a beat, I guess my brain skipped a beat on that one too. You'll find errors in every textbook amongst even the greatest of authors but no one would consider that a cause to throw the book out? I'm looking at five pictures of the splitting up of Pangaea in a geo book dating from the Permian period (250 mya) to the Cretaceous period (65 mya). During the Permian there is a large enclosed body of water right smack dab in the middle of Pangaea directly above the section that became Africa exactly where the Mediterranean is today. Then during the Cretacious Pangaea splits into Laurasia and Godwana and that same enclosed body of water now develops three channels into the other oceans. This is probably when you start to refer to it as the Tethys Ocean. But the section that later is called Europe is still there - as it was when it was part of Pangaea - right above it.
http://en.wikipedia.org/wiki/Tethys_Ocean The above makes my case more succinctly and elegantly than I could.
Great! We're in total agreement. The map shows the Tethys Sea located between Gondwana and Laurasia when Pangaea started to split (100 mya). Then when they fully split and began to reform about 15 mya, "the Tethys ocean contiued to shrink, becoming the Tethys Seaway...." But as it says, before this time during the Permean period (250 mya) when the land masses were still connected as Pangaea, it was called the "Paleo-Tethys Ocean." "Paleo" means "ancient." Then when they just started to split (200 mya) between what is now present-day Northern Africa and Southern Europe it was called the "Tethys Ocean." There map of Pangaea (on another page - Pangaea) is dated 300 mya during the Carboniferous period and does not show it then, but the map of Pangaea that I have in my book shows Pangaea during the Permian period (250 mya), and you can clearly see that enclosed body of water above the Northern tip of Africa that they call the "Paleo-Tethys Ocean." You're absolutely correct!
I love the past tense use of 'was called'. Someone ought to edit that page to refelct that the names are modern day appelations. The dinosaurs didn't call it anything. Err. Maybe I'm wrong and the dinosaurs were the ones who came up with the name then. If you're reading a geography book that is that old, it must be written by dinosaurs... (Kidding, of course. Sorry.) Rim of fire. Think Mt. St. Helens. Also, Mt. Ranier. Mt. Baker. How many other sleeping volcanoes threaten my doorstep? (I live in Seattle.)
Oh come on now, your dealing with symantics and the way I worded it "was" and "is" correct. The "was" can refer to either the name used or the past tense of the land mass. In this case I am referring to the fact that that land masses is no longer the same land mass (size, shape, height, location, climate, habitation of life, geographic time, etc.). It is predicted that Mt. St. Helen will probably errupt again and as of late there is smoke coming out of it and lava within. At least that's what they have been saying in the news. In what way are your deriding comments contributing to the educational benefit of this forum: "Plate Tectonics."?
Thanks! 1) Why parts of the Western Cordillera are volcanoes while other parts are not? For example, the Rockies are not volcanoes but for the Cascade Range, there are volcanoes? 2) Why aren't the Alps volcanoes? I was taught that oceanic-continental collision (African-Eurasian collision, in this case) will form an volcanoic arc on the land! 4) How is the Gulf of Mexico created? I was told that deposits from rivers on the ocean floor cause it to sink because of isostatic adjustment........but is this what causes a part of the ocean floor to sink while the other parts are kept the same, creating the Gulf of Mexico?
The Rocky Mountains are no longer active because the deep underlying thin plate that supposedly formed them has shown no activety for a very long time. The Cascade Range is still being affected by the Northwesterly convergent movement of the Juan de Fuca plate. The Gulf of Mexico was formed by the splitting of Pangaea into Laurasia and Godwana. The ocean back then between these two continents was called the Jurassic ocean which later became the central Atlantic. At this time the Gulf of Mexico was part of the Atlantic ocean and the Florida Peninsula did not exist. Florida was actually part of the Gulf of Mexico's Northern edge attached to North America. It then split away and formed the southerly projecting peninsula that it is today, although it is still moving eastward. The Atlantic Ocean is also to widening, while the Pacific Ocean basin is narrowing..
