how does the mantle convection hypothesis explain plate movements at divergent boundaries and subduction bound
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I'm not an expert, but just rationally thinking about this would be similar to a pot of boiling water. If something is on top of the convection wave, it is moved away from the centre of the convection current (the hottest part).\n\nLikewise, as the the convection wave moves up and outward and back down to the point of origin, the earth's plates "float" with this motion and because the plates are solid, they have to go someplace when and where they impact. The plate that contains the heavier, or more mass, subducts under the "lighter" plate.\n\nOccasionally, the thin part of a plate will slide over a "hot spot" where the magma "boils" through the plate and forms a volcano - and the rest - - -
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Plates collide in areas called subduction zones.  At these zones, oceanic crust is subducted underneath continental crust due to its higher density.  Subduction results in great amounts of heat and pressure building up in the zone.  When these factors become strong enough, they are forced to the Earth's surface in the form of volcanoes.  That is why volcanoes typically occur along plate boundaries (e.g., the ring of fire).  However, volcanoes are not exclusive to plate boundaries.  They can also form over hot spots within the interior of the Earth.  The islands of Hawaii are an example.  The islands are formed on the Pacific Plate.  The plate is moving in a northwest direction, while the hot spot underneath the crust is stationary.  As the plate moves over the hot spot, volcanic eruptions occur.  The result is a new island being created.  The islands are actually the products of a series of shield volcanoes that grow in age as one moves to the northwest.
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The interactions between tectonic plates can cause earthquakes. Plate tectonics is the theory we use to explain how lithospheric or tectonic plates move. For example, two tectonic plates will build up stress (pressure) when their movement is impeded the eventual release of this stress causes an earthquake. There is more material available via Yahoo search. The second source link will help you get a good idea of the plate boundaries.
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try this:\nhttp://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html
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Plate tectonics\nFrom Wikipedia, the free encyclopedia\nJump to: navigation, search\n    \nBridge across the Álfagjá rift valley in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates.Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology which was developed to explain the observed evidence for large scale motions within the Earth's crust. The theory encompassed and superseded the older theory of continental drift from the first half of the 20th century and the concept of sea floor spreading developed during the 1960s.\n\nThe outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere, which is a more viscous zone of the mantle. Although solid, the asthenosphere has very low shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again.\n\nThe lithosphere essentially floats on the asthenosphere. The lithosphere has broken up into what are called tectonic plates—in the case of Earth, there are ten major and many minor plates. These plates move in relation to one another at one of three types of plate boundaries: convergent, divergent, and transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates is typically at speeds of several centimetres per year.
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Earthquakes: \nIt all comes down to stress and strain from the interaction of different plates, chiefly at the boundaries. It is not 'the plates rubbing together' as many people say; or at least that's a very simplistic view.\n\nPlate tectonics causes stress on the continents and oceans, all over the surface of the earth. In some places, the stress is very small (usually within the plates). Elsewhere, the stress is high, usually where the plates meet each other. Since each plate moves, when two come in contact, the stress each other. They can push on each other and cause compressional stress, they can pull with extensional stress, and they can slide past or shear each other with tensional stress.\n\nFaulting, causing earthquakes, comes from the fact that this stress is building up all the time, but rocks and continents are strong materials. Just like hitting a rock with a small hammer, you do put stress on it, but a small amount. It would take a sledgehammer to put enough strain (effects and accumulation of stress) to build up and cause breakage. In the earth, the area around an active fault builds up strain from the stress of plate tectonics. Most faults become locked, because of this strength, and thus can not release their strain. Away from the fault, the stress produces very small and slow movement of the rock masses as a whole. Eventually, the strain is too much and the rest of the plate has moved too far and the fault releases the strain build-up all at once in a big stress release called an earthquake. This is called the elastic rebound theory, and it explains most (but not all) movements.\n\nThis is why an earthquake's size is relative to the fault size. The bigger the fault, the bigger the strain build up, and the bigger the release in an earthquake. Subduction zones and collision zones, where large portions of plates actually can rub together as a whole, have the really big earthquakes, like the 2004 Sumatra earthquake. In other plate boundaries, the entire plate boundary does not act together, so the faults become spread out and many faults take up the strain from the tectonic stress, like with the San Andreas Fault in California (it only takes up ~3/4 of the stress between the plates).\n\nEarthquakes are really tricky things; there is still so much we need to learn. As of now, there is no way to predict them, but we can say where the danger is highest and about how long between events.
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The reponse is related to plate tectonics. The earth crust is composed of a larger number of plates that float, very slowly of course, over the liquid interior. Continents therefore move relative to each other. When two plates meet, generally one moves under the other and it is here that we find mountains and volcanoes.\n\nWhat relation with oceans? Well, between some of the plates there is an upwelling of new magma, new crust. This is for instance the case in the middle of the Atlantic Ocean. The new crust needs room and pushes the plates on the left and right away: the Americas are moving to the west, while Europe and Africa are moving to the east. \n\nOceans (ah, at last!) are watermasses in which such upwelling of fresh crust takes place. An ocean therefore is partly in two or more different plates. On the other hand, seas are bodies of water that are on one continental plate only, or on two plates were no new crust is formed.\n\nHere is a pictures of the different continental plates:\n http://en.wikipedia.org/wiki/Image:Plates_tect2_en.svg
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Trenches define one of the most important natural boundaries on the Earth’s solid surface, that between two lithospheric plates. There are three types of lithospheric plate boundaries: divergent (where lithosphere and oceanic crust is created at mid-ocean ridges), convergent (where one lithospheric plate sinks beneath another and returns to the mantle), and transform (where two lithospheric plates slide past each other). The deepest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench at a depth of 10,911 m (35,798 ft) below sea level\n\nFormation:\n\nThe distribution of earthquakes reveals the location on the subducted Pacific Plate beneath the Mariana Islands. From the deep Mariana trench to a depth of about 100 km the plate is subducted at a gentle angle. From about 100 to 680 km the plate is subducted at a near vertical angle. Some geologists believe that the downward gravitational force of the steeply dipping plate is enough to pull the Pacific Plate away from the mid-ocean ridge, essentially providing a driving force for plate tectonics. Other geologists believe that the plates are pushed away from the mid-ocean ridge by forces generated at the ridge. Most geologists would agree that both forces are important.
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At convergent plate boundaries two plates collide and the heavier of the two plates is forced beneath the lighter one. As the heavier plate gets pushed down deep into the earth it begins to melt and forms molten magma. This magma slowly migrates upwards through the earth's crust where it then errupts onto the earth's surface as lava, eventually forming volcanoes. \n\nAt divergent plate zones two plates move apart from each other. When this happens a crack forms in the earth's crust. Magma from below moves upwards into this crack to fill the void 'so to speak'. Once again this magma errupts onto the earth's surface as red hot lava and we have the formation of active volcanoes.
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About 1,800 miles beneath the surface, Earth's internal structure changes abruptly where the solid rock of the mantle meets the swirling molten iron of the outer core. \nBut the boundary between the core and the mantle may not be as sharply defined as scientists once thought. By analyzing earthquake waves that bounce off the core-mantle boundary, researchers have found evidence of a thin zone where the outermost core is more solid than fluid.\n\nThe existence of such "core-rigidity zones" -- small patches of rigid material within the fluid outer core -- has been suggested before, but this report marks the first time scientists have detected one.
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There is no right answer for this question. Just because the plates are moving and right now most of the land mass is in the northern hemisphere. That is just where the bulk of it is right now, and someday it will change.
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The hotspots are stationary.  As the overlying oceanic plate slowly moves over the hot spot, volcanic activity "pops" up through the plate, showing the relative direction of plate movement.  If the plate changes direction, you will see a bend in the line of volcanic features (called seamounts).  Look at the Hawiian islands and the Emperor Seamounts.
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(m)\n\nAustralian and American researchers investigating forces exerted on the Indo-Australian tectonic plate have discovered that the considerable stresses being exerted on the plate could be leading to its breaking up.\n\nARC Professorial Fellow, Mike Sandiford, from the University of Melbourne’s School of Earth Sciences was recently awarded ARC funding for research aimed at understanding the forces that drive the motion of the Earth’s tectonic plates and the distribution of stresses in the Earth’s crust that give rise to great earthquakes such as the magnitude 9 Boxing Day Sumatran quake.\n\nProfessor Sandiford says the research shows that as much as 10 per cent of the huge amounts of energy being created at plate connection points at Sumatra and Java are being transferred back into our plate and causing major stresses.\n\n“This is enough stress to contribute to mild earthquake activity in the central regions of the plate, such as in the Australian continent or central Indian Ocean, and provides us with clues as to why our plate has been slowly breaking up,” he says.\n\n“The Indian Ocean quakes are, in effect, leading to the active rupture of the Indo-Australian plate into separate Indian and Australian plates. This new research provides us with important information about the stresses that are driving this drawn out tectonic plate divorce.”\n\nThe research, which was conducted in collaboration with Wouter Pieter Schellart of the Australian National University and David Coblentz of the Los Alamos National Laboratory in the US, will be published in the journal Geology (27 January).\n\nThe research is also important for understanding why smaller intra-plate earthquakes such as the 1989 Newcastle quake, which occurred nowhere near the edge of the plate, take place. Up to now, why earthquakes occur in apparently safe zones in the centre of plates has not been very well understood.\n\nProfessor Sandiford says, “Earthquakes such as the 1989 Newcastle quake that killed 13 people and caused more than $1 billion in damages are just one manifestation of mild tectonic activity that has been affecting the Australian continent for the last 5-10 million years.”\n\nThe new research shows that stresses originating at points of collision between two plates are being dissipated back into our plate and generating enormous internal stresses.\n\nThe ARC funded project will map the spatial and temporal pattern of this tectonic activity and relate it to the factors that drive the motion of the Indo-Australian plate.\n\n“This research will contribute to our understanding of the factors that drive plate motion, to earthquake risk assessment in Australia and other comparatively stable continental regions, and to the factors that have shaped our distinctive Australian landscapes,” he says.\n\nBACKGROUND INFORMATION\n\nWhat causes tectonic plates to move?\nThe Earth is made up of a series of layers. The outermost layer is called the crust and the innermost is the core. In between lies an area called the mantle (in turn made up of upper and lower mantle), which is arguably the most important when it comes to understanding where big earthquakes occur.\n\nThe outer part of the Earth, comprising the crust and top 100 or so kilometres of the mantle (together called the lithosphere), consists of a collection of eight major plates which almost fit perfectly together. The continents and oceans all lie on these plates, the major ones referred to as the African, Eurasian, Indo-Australian, Antarctic, Philippine, Pacific, Nazca, North American and South American, depending on their geographic location.\n\nThese plates (also referred to as tectonic plates) float on the softer mantle underneath. Convection currents within the upper mantle layer are a major driving force driving plate motion and therefore behind earthquake activity.\n\nThe lower sections of the mantle closest to the molten core of the earth are also the hottest parts of this la
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OK, first of all, inhale. Your body needs oxygen crisis or no crisis.\n\nIt's not that this plate movement re-awakens a bunch of volcanoes, these volcanoes exist in the first place because of the process of subduction, which has been going on--[gasp]--for your entire lifetime and a few billion years before your birth.\n\nThere are several tectonic plates at play in the Pacific. The Pacific Plate seems to be moving in a northwesterly direction, judging by the formation and erosion of the Hawaiian Islands over a hot spot that stays stationary under the moving plate. This plate apparently changed direction abruptly many millions of years ago, judging by the direction of the Emperor Seamounts in relation to the Hawaiian Islands. The first link below shows the other oceanic and continental plates in the world, including those on the Pacific side.\n\nAs a general rule, the oceanic plates in the Pacific are subducted under the surrounding continental plates and into the mantle. If you placed a couple of tables edge to edge and seated a few kindergarten students around each one, the kindergarten students would push on the tables (it's just a thing that they do) until the edge of one managed to slip over or under the edge of the other. \n\nThat's similar to what happens with continental and oceanic plates, too. If an oceanic plate and a continental plate come edge to edge, it's usually the denser seafloor that will go under the other plate. The odds are closer to even if two continental plates collide (as in the collision of the Indian subcontinent with Asia that created the Himalayas) or if two ocean plates are pushing up against each other.\n\nAs far as giant or tsunami waves, we are unable to predict exactly where the next tsunami will come from, but here are three possibilities to keep us up at night:\n\n1) Huge earthquake off the coast of British Columbia/ Washington State/Oregon/ northern California. Such an earthquake hit along 600 miles in January of 1700, and it was about the magnitude of the one that created the Indian Ocean tsunamis in 2004. The 1700 quake also caused devastating tsunamis that did hit Japan and probably hit other places as well. Computer models have shown a series of tsunamis from such a quake hitting the Hawaiian islands on their way across the Pacific, and again on the way back, a "ricochet" effect, if you will. Unfortunately, I think that animation was taken off the web a year or two ago, or I would share it with you here.\n\n2) A volcano on the island of La Palma may collapse, creating a megatsunami hundreds of meters high to scour the coast of Africa and tsunamis of 10-25 meters to batter the eastern coast of the US.\n\n3) A 4,760 cubic mile chunk of the Big Island (Hawaii) falls into the ocean, creating a devastating tsunami around the Pacific. The island of Hawaii suffered two deadly tsunamis in the middle of the last century from earthquakes around the Pacific Rim (Alaska and Chile). The Pacific Rim would be just as vulnerable to tsunami's originating in Hawaii. \n\nSuch "slumps" have occured in Hawaii before. I live on the lower slopes of an extinct volcano that lost half its mass to a landslide a million and a half years ago.
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It is a divergent plate boundary found running down the middle of the Atlantic Ocean. Hence the name "Mid Atlantic Ridge".\n\nThis is where two lithospheric plates are moving apart from each other.\n\nWhere they spread apart, new continental crust is being created. It is said that the US & the UK move about 1 - 2 inches apart every year. The US is getting further from Europe all the time!
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Sea floor spreading is the driving force behind continental drift as it forces the crust apart.  The hot mantle rises to the surface weakening the crust until it splits and moves apart to allow the new material to form.  This rifting creates new oceanic basaltic crust rather than granitic continental crust so the continents stay roughly the same. \n\nHowever, rifting does occur within continents and eventually will split a continent, as is happening in the Red Sea today, the East African Rift being a failed offshoot of that rift system.\n\nAll this happens slowly at a rate of about 11cm a centuary and if you want to see an active spreading ridge take a trip to Iceland where the Mid Atlantic ridge is on surface.  Don't worry it is perfectly safe and you won't end up on the wrong side.
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Really, the answer to your question is simply: Plate Tectonics. Read below for details.\n\nEarthquakes: \nIt all comes down to stress and strain from the interaction of different plates, chiefly at the boundaries. It is not 'the plates rubbing together' as many people say; or at least that's a very simplistic view.\n\nPlate tectonics causes stress on the continents and oceans, all over the surface of the earth. In some places, the stress is very small (usually within the plates). Elsewhere, the stress is high, usually where the plates meet each other. Since each plate moves, when two come in contact, the stress each other. They can push on each other and cause compressional stress, they can pull with extensional stress, and they can slide past or shear each other with tensional stress.\n\nFaulting, causing earthquakes, comes from the fact that this stress is building up all the time, but rocks and continents are strong materials. Just like hitting a rock with a small hammer, you do put stress on it, but a small amount. It would take a sledgehammer to put enough strain (effects and accumulation of stress) to build up and cause breakage. In the earth, the area around an active fault builds up strain from the stress of plate tectonics. Most faults become locked, because of this strength, and thus can not release their strain. Away from the fault, the stress produces very small and slow movement of the rock masses as a whole. Eventually, the strain is too much and the rest of the plate has moved too far and the fault releases the strain build-up all at once in a big stress release called an earthquake. This is called the elastic rebound theory, and it explains most (but not all) movements.\n\nThis is why an earthquake's size is relative to the fault size. The bigger the fault, the bigger the strain build up, and the bigger the release in an earthquake. Subduction zones and collision zones, where large portions of plates actually can rub together as a whole, have the really big earthquakes, like the 2004 Sumatra earthquake. In other plate boundaries, the entire plate boundary does not act together, so the faults become spread out and many faults take up the strain from the tectonic stress, like with the San Andreas Fault in California (it only takes up ~3/4 of the stress between the plates).\n\nEarthquakes are really tricky things; there is still so much we need to learn. As of now, there is no way to predict them, but we can say where the danger is highest and about how long between events.\n\nVolcanoes:\nThere are several processes in Plate Tectonics that cause volcanism, but they result in two main types of volcanism.\n\nVolcanism in subduction is caused by volitals, like H2O, CO2. These are carried down by the plate, mainly in the form of weak minerals. These minerals break down with pressure and temperature into stronger minerals that don't contain water and carbon dioxide. The leftover gases and liquids travel into the mantle (the mantle wedge) and hydrate the mantle, causing melting. The melt rises and then... volcano!\n\nThe other main cause is from rising mantle material, which forms decompression melting. Basically, hot mantle is kept from melting by the pressure of the earth at depth. When this material rises, the pressure drops much faster than the temperature, and thus it partially melts. This mainly occurs at divergent boundaries and hot spots, which are areas in plate tectonics that have rising materials or spreading.\n\nMountain Belts:\n\nNon-volcanic mountain belts are caused by compressive stress in plate tectonics. This can be 1. fold and thrust belts in highly compressive subduction zones (almost always from oceanic beneath continental subduction, e.g. east Andes, Rockies) or 2. continental-continental collisions (e.g. Himalaya, Appalachian).