Mountains I. INTRODUCTION A mountain is an elevated land mass usually higher than its surroundings. Some are isolated, but they usually appear in ranges(MsBs95W32). "A group of ranges closely related in form, origin, and alignment is a mountain system; an elongated group of systems is a chain; and a complex of ranges, systems, and chains continental in extent is a cordillera, zone, or belt."(MsBs95W32). Some mountains are remains of plateaus, mesas, and buttes, through erosion(Summerfield).
Others are cones of volcanoes formed with igneous rock. Fault-block mountains occur where blocks of the earth's surface are raised relative to other neighboring blocks. Most of the great mountains are either fold mountains or complex structures formed by many different natural activities. The ultimate cause of mountain building is only theoretical and abstract. Although, the plate tectonics is the first reasonable theory, stating that the crust of the earth breaks into several parts that eventually collide with another.
Where they collide, stresses cause deformation and uplift of the land, which forms folded and/or faulted mountain chains. The highest point on earth, Mt. Everest, is also believed to have been formed by folding when the Australian-Indian plate collided with the Eurasian plate. II. TABLE OF CONTENTS I INTRODUCTION II TABLE OF CONTENTS III. TYPES OF MOUNTAINS 1.
VOLCANOES 2. FOLDING & FAULTING 3. RESIDUAL MOUNTAINS IV. VOLCANO FORMATION 1. TYPES & NOMENCLATURE 2. PROCESS 3.
EXAMPLE V. FOLDING AND FAULTING 1. PROCESS 2. EXAMPLE VI. PLATEAUS TO MOUNTAINS 1.
TYPE 2. EXAMPLE VII. CONCLUSION VIII. BIBLIOGRAPHY III. TYPES OF MOUNTAINS M ountains can be created in many different ways. Two very well-known and quite common ones are volcanic mountains and folded mountains.
Other important ones include residual mountain formation in which a plateau is eroded away into a mountain. 1. Volcanoes Volcanoes are formed when the magma reserves underground erupts. Also There are many different types of eruptions that the Geologists have classified into, according to their location, style, and other features. These variations contribute to the different and distinct shapes of each volcanoes. 2.
Folding & Faulting According to the Microsoft Office Bookshelf 1995, the earth is changing its shape constantly every year by a few centimeters. This caused the earth to move from one huge continent called Pangea to what it looks like now in almost 200 million years(30 Boehm). When the giant pieces of landmasses move around, they tend to bump into each other some day. When they collide, they create a fold, and if the fold gets too much pressure, it breaks and becomes a fault. Fold and Fault mountains are ubiquitous throughout the world. 3.
Residual Mountains Due to the weathering, parts of the world change frequently, but slowly. This can also happen to a plateau. If a small plateaus edges are washed away by rain and wind, it forms a new mountain-like structure, which we call residual mountain, meaning that it became a mountain from the remainders of many erosions. VI. VOLCANO FORMATION V olcanoes are one of the "fastest of all the processes making the Earths relief features"(quoted from 2 Scarth).
While some eruptions are quick and powerful, others can be very slow and continue for over hundreds of thousands of years.(2 Scarth). Two thirds of the volcanoes can be found in the Pacific ring of fire(14 Scarth). Most others are usually submerged undersea, or makes up an island with cooled igneous rocks; Hawaii rises 9000m above the sea floor. Magma, which is what igneous rocks were to begin with, is formed from molten parts of asthenosphere(150-650km under ground) which is a part of the upper mantle(60-650km u.g.)(p20-21 Scarth). A.
Types & Nomenclature The volcanoes are classified by its eruptive style and by the type of magma it ejects(32 Scarth). There is almost an infinite number of kinds of volcanoes possible, but most geologists divide them into four main groups: Hawaiian, Vulcanian, Strombolian, and Pelean(33 Scarth). These names all come from famous volcanoes around the world, but not all other volcanoes always exactly fit in to one group, and there are other minor groups such as Flood basalt, Surtseyan, Plinian, Debris-avalanche(34 Scarth). Here is a table about some volcanoes and their features. B.
Process Every volcano has a different style just as they have different names. They sometimes look similar, but most of the times, they are very distinct from the other. The usual process volcanoes go through are, although, quite similar. The lower part of the upper mantle and the transition zone between the two mantles, called asthenosphere, is very hot(1200C-1300C), and moves around(26 Scarth). It turns into magma as it melts, but not all of it becomes magma, because of the difference in boiling points of the minerals.
As the magma moves upward, it cools down a little(700C-1200C)(22-23 Scarth). If it goes too close to the surface where there is less pressure, its volume increases, and requires more space. Since there is no space under the crust, it breaks a portion of the crust, and gets out. Right before an eruption occurs, there is an explosion that triggers this eruption. Magma erupts as lava, and usually it forms an elevated area, because it soon become hard solid ob! ject. From here each volcano takes its own way, and there are some pictures on page x.
Some volcanoes, as they lose magma, sink to the ground, and form a big gorge. It sometimes forms a Crater Lake in wet regions(123 Summerfield). A. Example Examples of a volcanic mountains can be found around the boundaries of the Pacific Ocean. It includes, from SE to NW (hemispherically), Sakurajima(Jap.), Klyuchevskoy(Rus.), Augustine(US), Yellowstone(US), El Chichn(Mex.), etc.
Others include Hawaiian volcanoes, many famous European, and the igneous islands in the Atlantic Ocean. V. FOLDING AND FAULTING W hen the plates bump into each other as they move around, the colliding part gets such an intense pressure, that it moves upwards. Since they do not collide in one small specific area, this action makes more than one part to go up, and thats why most big mountain occur in groups of mountain chains A. Process The continental crust moves on the lithospheric mantle. The crust itself is also a part of the lithosphere.
Usually it is the oceanic crust that move in front of the continental crust. As one cont. crust collides with another, the oceanic crust sinks into the mantle. The two colliding crusts can cause the landmass to lift up, or fold. If there are two very strong forces pushing one plate, sometimes the plate breaks, making a fault. If the fault is big, it can cause an earthquake. The earthquake in L.A. in 1993 was also caused by a fault underground.
B. Example The Himalayas is a fold mountain system made when the Australian-Indian plate collided with the lower part of the Eurasian plate(74 Summerfield). This had been in process for more than 80 million years, and it is believed that this collision also formed the Tibetan plateau(72-73 Summerfield). VI. PLATEAUS TO MOUNTAINS P lateaus are large flat landmasses just like mesas and buttes except bigger. These plateaus can become residual mountains by weathering and erosion.
There are also names for different erosion styles. The names for erosion of a region is similar to the names of volcanic eruptions. First, there is dry flow, in which the materials flow downhill without the aid of water. Earth flow is similar to dry flow except it is usually much bigger in size. A debris flow is when very small pieces flow down the stream or a valley, but in debris avalanche, these little debris form what may look like an avalanche, and come downhill very abruptly.
These erosions cause plateaus to form different mountains as it ages. VII. CONCLUSION M ountains have important effects on the climate, population, economics, and civilization of the regions depending on where they form. Weather on one side of a big mountain can be very much different from the other side. Excess of mountains would limit the population growth and civilization. Mountains sometimes provide us natural resources and good view. Major mountain ranges include the Alps, the Andes, the Caucasus, the Himalayas, the Pyrenes, and the Rocky Mountains.
VIII. BIBLIOGRAPHY Boehm, Richard G., World Geography, Mission Hills, CA: Glencoe. 1995. Cooke and Doornkamp, Geomorphology in Environmental Management : A New Introduction, Oxford: Clarendon Press. 1990 ed. Hs, Kenneth J., Mountain Building Processes, Austin: Academic Press.
1982 ed. Lambeck, Kurt, Geophysical Geodesy : The Slow Deformations of the Earth, Oxford: Clarendon Press. 1988. Scarth, Alwyn, Volcanoes, College Station, TX: Texas A & M University Press. 1994. "Plate Tectonics" Microsoft Bookshelf 95(WIN32).
1995 ed. Summerfield, Michael A., Global Geomorphology, Yew York: Longman Scientific & Technical. 1993.