TECTONIC PLATES

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TECTONIC PLATESAND THEIR MOVEMENTS : 

TECTONIC PLATESAND THEIR MOVEMENTS By: Naveed Ahmad 2005-MS-C-STR-86

A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Plate thickness also varies greatly, ranging from less than 15 km for young oceanic lithosphere to about 200 km or more for ancient continental lithosphere (for example, the interior parts of North and South America). : 

A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Plate thickness also varies greatly, ranging from less than 15 km for young oceanic lithosphere to about 200 km or more for ancient continental lithosphere (for example, the interior parts of North and South America). WHAT IS TECTONIC PLATE?

The word tectonics comes from the Greek root "to build." Putting these two words together, we get the term plate tectonics, which refers to how the Earth's surface is built of plates. The theory of plate tectonics states that the Earth's outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another. Before the advent of plate tectonics, however, some people already believed that the present-day continents were the fragmented pieces of preexisting larger landmasses ("supercontinents"). : 

The word tectonics comes from the Greek root "to build." Putting these two words together, we get the term plate tectonics, which refers to how the Earth's surface is built of plates. The theory of plate tectonics states that the Earth's outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another. Before the advent of plate tectonics, however, some people already believed that the present-day continents were the fragmented pieces of preexisting larger landmasses ("supercontinents"). HISTROCIAL PERSPECTIVE

TECTONIC PLATE MOTION : 

TECTONIC PLATE MOTION Most movement of tectonic plate occurs along narrow zones between plates where the results of plate-tectonic forces are most evident. There are four types of plate boundaries: Divergent boundaries Convergent boundaries Transform boundaries Plate boundary zones

DIVERGENT BOUNDARIES : 

DIVERGENT BOUNDARIES Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle. Picture two giant conveyor belts, facing each other but slowly moving in opposite directions as they transport newly formed oceanic crust away from the ridge crest.

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It is the best known of the divergent boundaries is the Mid-Atlantic Ridge. This submerged mountain range, which extends from the Arctic Ocean to beyond the southern tip of Africa, is but one segment of the global mid-ocean ridge system that encircles the Earth. The rate of spreading along the Mid-Atlantic Ridge averages about 2.5 centimeters per year (cm/yr), or 25 km in a million years. This rate may seem slow by human standards, but because this process has been going on for millions of years, it has resulted in plate movement of thousands of kilometers. Seafloor spreading over the past 100 to 200 million years has caused the Atlantic Ocean to grow from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today.

CONVERGENT BOUNDARIES : 

CONVERGENT BOUNDARIES These are the boundaries where crust is destroyed as one plate dives under another. Such destruction (recycling) of crust takes place along convergent boundaries where plates are moving toward each other, and sometimes one plate sinks (is subducted) under another. The location where sinking of a plate occurs is called a subduction zone.

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OCEANIC-CONTINENTAL CONVERGENCE

OCEANIC-OCEANIC CONVERGENCE : 

OCEANIC-OCEANIC CONVERGENCE

CONTINENTAL-CONTINENTAL CONVERGENCE : 

CONTINENTAL-CONTINENTAL CONVERGENCE

TRANSFORM BOUNDARIES : 

TRANSFORM BOUNDARIES The zone between two plates sliding horizontally past one another is called a transform-fault boundary, or simply a transform boundary. Most transform faults are found on the ocean floor.

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PLATE-BOUNDARY ZONES Not all plate boundaries are as simple as the main types discussed above. In some regions, the boundaries are not well defined because the plate-movement deformation occurring there extends over a broad belt (called a plate-boundary zone). One of these zones marks the Mediterranean-Alpine region between the Eurasian and African Plates, within which several smaller fragments of plates (microplates) have been recognized. Because plate-boundary zones involve at least two large plates and one or more microplates caught up between them, they tend to have complicated geological structures and earthquake patterns.

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RATES OF MOTION We can measure how fast tectonic plates are moving today, Because the ocean-floor magnetic striping records the flip-flops in the Earth's magnetic field, scientists, knowing the approximate duration of the reversal, can calculate the average rate of plate movement during a given time span. The Arctic Ridge has the slowest rate (less than 2.5 cm/yr), and the East Pacific Rise near Easter Island, in the South Pacific about 3,400 km west of Chile, has the fastest rate (more than 15 cm/yr).

WHAT DRIVES THE PLATES? : 

WHAT DRIVES THE PLATES?

EFFECTS OF TECTONIC PLATES ON PEOPLE : 

EFFECTS OF TECTONIC PLATES ON PEOPLE Yet violent earthquakes related to plate tectonics have caused terrible catastrophes -- such as the magnitude-7.7 earthquake that struck the Chinese province of Hebei in 1976 and killed as many as 800,000 people. NATURAL HAZARDS Most earthquakes and volcanic eruptions do not strike randomly but occur in specific areas, such as along plate boundaries. One such area is the circum-Pacific Ring of Fire, where the Pacific Plate meets many surrounding plates. The Ring of Fire is the most seismically and volcanically active zone in the world

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EARTHQUAKES Because many major population centers are located near active fault zones, such as the San Andreas, millions of people have suffered personal and economic losses as a result of destructive earthquakes, and even more have experienced earthquake motions

VOLCANIC ERUPTIONS : 

VOLCANIC ERUPTIONS As with earthquakes, volcanic activity is linked to plate-tectonic processes. Most of the world's active above-sea volcanoes are located near convergent plate boundaries where subduction is occurring, particularly around the Pacific basin. TSUNAMIS Major earthquakes occurring along subduction zones are especially hazardous, because they can trigger tsunamis (from the Japanese word tsunami meaning "harbor wave")

NATURAL RESOURCES : 

NATURAL RESOURCES Many of the Earth's natural resources of energy, minerals, and soil are concentrated near past or present plate boundaries. The utilization of these readily available resources have sustained human civilizations, both now and in the past.

FERTILE SOILS : 

FERTILE SOILS

GEOTHERMAL ENERGY : 

GEOTHERMAL ENERGY

FOSSIL FUELS : 

FOSSIL FUELS