The Pacific-Farallon Ridge was a spreading ridge during the Late Cretaceous that extended 10,000 km in length and separated the Pacific Plate to the west and the Farallon Plate to the east. It ran south from the Pacific-Farallon-Kula triple junction at 51°N to the Pacific-Farallon-Antarctic triple junction at 43°S. As the Farallon Plate subducted obliquely under the North American Plate , the Pacific-Farallon Ridge approached and eventually made contact with the North American Plate about 30 million years ago. On average, this ridge had an equatorial spreading rate of 13.5 cm per year until its eventual collision with the North American Plate. In present day, the Pacific-Farallon Ridge no longer formally exists since the Farallon Plate has been broken up or subducted beneath the North American Plate, and the ridge has segmented, having been mostly subducted as well. The most notable remnant of the Pacific-Farallon Ridge is the 4000 km Pacific-Nazca segment of the East Pacific Rise .
45-551: As a spreading ridge, the Pacific-Farallon Ridge was a divergent plate boundary, which is where the two plates are moving away from each other. Partial mantle melting occurs beneath such ridges, which forms new oceanic crust . The Pacific-Farallon Ridge was thought to be a particularly productive spreading ridge, and there are estimates that the ridge and its remnants have formed up to 45% of all oceanic lithosphere since 83 million years ago. The spreading rate of
90-427: A the acceleration of the object and the distance traveled by the accelerated object in time t , we find with v = a t {\displaystyle v=at} for the velocity v of the object The work done in accelerating a particle with mass m during the infinitesimal time interval dt is given by the dot product of force F and the infinitesimal displacement d x where we have assumed
135-410: A body's mass, inertia, and total energy. In fluid dynamics , the kinetic energy per unit volume at each point in an incompressible fluid flow field is called the dynamic pressure at that point. Dividing by V, the unit of volume: where q {\displaystyle q} is the dynamic pressure, and ρ is the density of the incompressible fluid. The speed, and thus the kinetic energy of
180-402: A major source of submarine earthquakes . A seafloor map will show a rather strange pattern of blocky structures that are separated by linear features perpendicular to the ridge axis. If one views the seafloor between the fracture zones as conveyor belts carrying the ridge on each side of the rift away from the spreading center the action becomes clear. Crest depths of the old ridges, parallel to
225-459: A map in time and space of both spreading rate and polar reversals. Kinetic energy In physics , the kinetic energy of an object is the form of energy that it possesses due to its motion . In classical mechanics , the kinetic energy of a non-rotating object of mass m traveling at a speed v is 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} . The kinetic energy of an object
270-402: A single object is frame-dependent (relative): it can take any non-negative value, by choosing a suitable inertial frame of reference . For example, a bullet passing an observer has kinetic energy in the reference frame of this observer. The same bullet is stationary to an observer moving with the same velocity as the bullet, and so has zero kinetic energy. By contrast, the total kinetic energy of
315-449: A system of objects cannot be reduced to zero by a suitable choice of the inertial reference frame, unless all the objects have the same velocity. In any other case, the total kinetic energy has a non-zero minimum, as no inertial reference frame can be chosen in which all the objects are stationary. This minimum kinetic energy contributes to the system's invariant mass , which is independent of the reference frame. The total kinetic energy of
360-515: A transition of the Pacific-Farallon Ridge from being a globally oriented spreading ridge system to a locally oriented one. The distinction between these systems is that slab pull and gravitational gliding forces determine the characteristics of the globally oriented whereas those of the locally oriented are influenced by the contact of the ridge with the North American Plate. As the Pacific-Farallon Ridge began its subduction underneath
405-514: Is conserved was first developed by Gottfried Leibniz and Johann Bernoulli , who described kinetic energy as the living force or vis viva . Willem 's Gravesande of the Netherlands provided experimental evidence of this relationship in 1722. By dropping weights from different heights into a block of clay, Gravesande determined that their penetration depth was proportional to the square of their impact speed. Émilie du Châtelet recognized
450-421: Is dissipated in various forms of energy, such as heat, sound and binding energy (breaking bound structures). Flywheels have been developed as a method of energy storage . This illustrates that kinetic energy is also stored in rotational motion. Several mathematical descriptions of kinetic energy exist that describe it in the appropriate physical situation. For objects and processes in common human experience,
495-446: Is equal to where: The kinetic energy of any entity depends on the reference frame in which it is measured. However, the total energy of an isolated system, i.e. one in which energy can neither enter nor leave, does not change over time in the reference frame in which it is measured. Thus, the chemical energy converted to kinetic energy by a rocket engine is divided differently between the rocket ship and its exhaust stream depending upon
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#1732771916267540-419: Is equal to 1/2 the product of the mass and the square of the speed. In formula form: where m {\displaystyle m} is the mass and v {\displaystyle v} is the speed (magnitude of the velocity) of the body. In SI units, mass is measured in kilograms , speed in metres per second , and the resulting kinetic energy is in joules . For example, one would calculate
585-479: Is equal to the work , force ( F ) times displacement ( s ), needed to achieve its stated velocity . Having gained this energy during its acceleration , the mass maintains this kinetic energy unless its speed changes. The same amount of work is done by the object when decelerating from its current speed to a state of rest . The SI unit of kinetic energy is the joule , while the English unit of kinetic energy
630-418: Is simply the sum of the kinetic energies of its moving parts, and is thus given by: where: (In this equation the moment of inertia must be taken about an axis through the center of mass and the rotation measured by ω must be around that axis; more general equations exist for systems where the object is subject to wobble due to its eccentric shape). A system of bodies may have internal kinetic energy due to
675-493: Is sometimes thought to be associated with the phenomenon known as hotspots . Here, exceedingly large convective cells bring very large quantities of hot asthenospheric material near the surface, and the kinetic energy is thought to be sufficient to break apart the lithosphere. Divergent boundaries are typified in the oceanic lithosphere by the rifts of the oceanic ridge system, including the Mid-Atlantic Ridge and
720-591: Is the foot-pound . In relativistic mechanics , 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} is a good approximation of kinetic energy only when v is much less than the speed of light . The adjective kinetic has its roots in the Greek word κίνησις kinesis , meaning "motion". The dichotomy between kinetic energy and potential energy can be traced back to Aristotle 's concepts of actuality and potentiality . The principle of classical mechanics that E ∝ mv
765-550: Is the movement energy of an object. Kinetic energy can be transferred between objects and transformed into other kinds of energy. Kinetic energy may be best understood by examples that demonstrate how it is transformed to and from other forms of energy. For example, a cyclist uses chemical energy provided by food to accelerate a bicycle to a chosen speed. On a level surface, this speed can be maintained without further work, except to overcome air resistance and friction . The chemical energy has been converted into kinetic energy,
810-487: The Earth's mantle allows material to rise to the base of the lithosphere beneath each divergent plate boundary. This supplies the area with huge amounts of heat and a reduction in pressure that melts rock from the asthenosphere (or upper mantle ) beneath the rift area, forming large flood basalt or lava flows. Each eruption occurs in only a part of the plate boundary at any one time, but when it does occur, it fills in
855-472: The East Pacific Rise , and in the continental lithosphere by rift valleys such as the famous East African Great Rift Valley . Divergent boundaries can create massive fault zones in the oceanic ridge system. Spreading is generally not uniform, so where spreading rates of adjacent ridge blocks are different, massive transform faults occur. These are the fracture zones , many bearing names, that are
900-690: The Central and South Pacific. Divergent boundary This is an accepted version of this page In plate tectonics , a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary ) is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts , which eventually become rift valleys . Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges . Current research indicates that complex convection within
945-653: The Juan de Fuca Plate and Cocos Plate , and then later fragmented further to form the Rivera Plate . Once the Pacific-Farallon Ridge began subducting beneath the North American Plate, the remains of the Farallon Plate broke apart to form the Monterey, Arguello, Magdalena, and Guadelupe Microplates, and the southern portion of the ridge rotated in a clockwise manner. The contact of the ridge with North America marked
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#1732771916267990-596: The North American plate 30 million years ago, its southern segment, the East Pacific Rise continued spreading. The East Pacific Rise did not begin its subduction under the North American Plate until 20 million years ago, and the presently surviving portion of the East Pacific Rise is the Pacific-Nazca segment. The present-day spreading from the East Pacific Rise dominates the spreading regime in
1035-540: The Pacific-Farallon Ridge has varied throughout its lifetime with an acceleration of its spreading rate occurring 55 to 48 million years ago, around the same time that a significant portion of the Farallon Plate broke to form the Vancouver Plate. The spreading rate decreased once the ridge made contact with the North American Plate 16 million years ago. As the Farallon Plate made contact with the North American Plate and began subducting beneath it, it fragmented into
1080-480: The chosen reference frame. This is called the Oberth effect . But the total energy of the system, including kinetic energy, fuel chemical energy, heat, etc., is conserved over time, regardless of the choice of reference frame. Different observers moving with different reference frames would however disagree on the value of this conserved energy. The kinetic energy of such systems depends on the choice of reference frame:
1125-418: The current spreading center, will be older and deeper... (from thermal contraction and subsidence ). It is at mid-ocean ridges that one of the key pieces of evidence forcing acceptance of the seafloor spreading hypothesis was found. Airborne geomagnetic surveys showed a strange pattern of symmetrical magnetic reversals on opposite sides of ridge centers. The pattern was far too regular to be coincidental as
1170-458: The energy of motion, but the process is not completely efficient and produces heat within the cyclist. The kinetic energy in the moving cyclist and the bicycle can be converted to other forms. For example, the cyclist could encounter a hill just high enough to coast up, so that the bicycle comes to a complete halt at the top. The kinetic energy has now largely been converted to gravitational potential energy that can be released by freewheeling down
1215-432: The formula 1 / 2 mv given by classical mechanics is suitable. However, if the speed of the object is comparable to the speed of light, relativistic effects become significant and the relativistic formula is used. If the object is on the atomic or sub-atomic scale , quantum mechanical effects are significant, and a quantum mechanical model must be employed. Treatments of kinetic energy depend upon
1260-399: The game of billiards , the player imposes kinetic energy on the cue ball by striking it with the cue stick. If the cue ball collides with another ball, it slows down dramatically, and the ball it hit accelerates as the kinetic energy is passed on to it. Collisions in billiards are effectively elastic collisions , in which kinetic energy is preserved. In inelastic collisions , kinetic energy
1305-439: The hill than without the generator because some of the energy has been diverted into electrical energy. Another possibility would be for the cyclist to apply the brakes, in which case the kinetic energy would be dissipated through friction as heat . Like any physical quantity that is a function of velocity, the kinetic energy of an object depends on the relationship between the object and the observer's frame of reference . Thus,
1350-515: The implications of the experiment and published an explanation. The terms kinetic energy and work in their present scientific meanings date back to the mid-19th century. Early understandings of these ideas can be attributed to Thomas Young , who in his 1802 lecture to the Royal Society, was the first to use the term energy to refer to kinetic energy in its modern sense, instead of vis viva . Gaspard-Gustave Coriolis published in 1829
1395-428: The kinetic energy of an 80 kg mass (about 180 lbs) traveling at 18 metres per second (about 40 mph, or 65 km/h) as When a person throws a ball, the person does work on it to give it speed as it leaves the hand. The moving ball can then hit something and push it, doing work on what it hits. The kinetic energy of a moving object is equal to the work required to bring it from rest to that speed, or
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1440-445: The kinetic energy of an object is not invariant . Spacecraft use chemical energy to launch and gain considerable kinetic energy to reach orbital velocity . In an entirely circular orbit, this kinetic energy remains constant because there is almost no friction in near-earth space. However, it becomes apparent at re-entry when some of the kinetic energy is converted to heat. If the orbit is elliptical or hyperbolic , then throughout
1485-453: The molecular or atomic level, which may be regarded as kinetic energy, due to molecular translation, rotation, and vibration, electron translation and spin, and nuclear spin. These all contribute to the body's mass, as provided by the special theory of relativity. When discussing movements of a macroscopic body, the kinetic energy referred to is usually that of the macroscopic movement only. However, all internal energies of all types contribute to
1530-538: The opening gap as the two opposing plates move away from each other. Over millions of years, tectonic plates may move many hundreds of kilometers away from both sides of a divergent plate boundary. Because of this, rocks closest to a boundary are younger than rocks further away on the same plate. At divergent boundaries, two plates move away from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below. The origin of new divergent boundaries at triple junctions
1575-411: The orbit kinetic and potential energy are exchanged; kinetic energy is greatest and potential energy lowest at closest approach to the earth or other massive body, while potential energy is greatest and kinetic energy the lowest at maximum distance. Disregarding loss or gain however, the sum of the kinetic and potential energy remains constant. Kinetic energy can be passed from one object to another. In
1620-412: The other side of the hill. Since the bicycle lost some of its energy to friction, it never regains all of its speed without additional pedaling. The energy is not destroyed; it has only been converted to another form by friction. Alternatively, the cyclist could connect a dynamo to one of the wheels and generate some electrical energy on the descent. The bicycle would be traveling slower at the bottom of
1665-739: The paper titled Du Calcul de l'Effet des Machines outlining the mathematics of kinetic energy. William Thomson , later Lord Kelvin, is given the credit for coining the term "kinetic energy" c. 1849–1851. William Rankine , who had introduced the term "potential energy" in 1853, and the phrase "actual energy" to complement it, later cites William Thomson and Peter Tait as substituting the word "kinetic" for "actual". Energy occurs in many forms, including chemical energy , thermal energy , electromagnetic radiation , gravitational energy , electric energy , elastic energy , nuclear energy , and rest energy . These can be categorized in two main classes: potential energy and kinetic energy. Kinetic energy
1710-409: The reference frame that gives the minimum value of that energy is the center of momentum frame, i.e. the reference frame in which the total momentum of the system is zero. This minimum kinetic energy contributes to the invariant mass of the system as a whole. The work W done by a force F on an object over a distance s parallel to F equals Using Newton's Second Law with m the mass and
1755-408: The relationship p = m v and the validity of Newton's Second Law . (However, also see the special relativistic derivation below .) Applying the product rule we see that: Therefore, (assuming constant mass so that dm = 0), we have, Since this is a total differential (that is, it only depends on the final state, not how the particle got there), we can integrate it and call
1800-575: The relative motion of the bodies in the system. For example, in the Solar System the planets and planetoids are orbiting the Sun. In a tank of gas, the molecules are moving in all directions. The kinetic energy of the system is the sum of the kinetic energies of the bodies it contains. A macroscopic body that is stationary (i.e. a reference frame has been chosen to correspond to the body's center of momentum ) may have various kinds of internal energy at
1845-434: The relative velocity of objects compared to the fixed speed of light . Speeds experienced directly by humans are non-relativisitic ; higher speeds require the theory of relativity . In classical mechanics , the kinetic energy of a point object (an object so small that its mass can be assumed to exist at one point), or a non-rotating rigid body depends on the mass of the body as well as its speed . The kinetic energy
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1890-523: The result kinetic energy: This equation states that the kinetic energy ( E k ) is equal to the integral of the dot product of the momentum ( p ) of a body and the infinitesimal change of the velocity ( v ) of the body. It is assumed that the body starts with no kinetic energy when it is at rest (motionless). If a rigid body Q is rotating about any line through the center of mass then it has rotational kinetic energy ( E r {\displaystyle E_{\text{r}}\,} ) which
1935-530: The widths of the opposing bands were too closely matched. Scientists had been studying polar reversals and the link was made by Lawrence W. Morley , Frederick John Vine and Drummond Hoyle Matthews in the Morley–Vine–Matthews hypothesis . The magnetic banding directly corresponds with the Earth's polar reversals. This was confirmed by measuring the ages of the rocks within each band. The banding furnishes
1980-434: The work the object can do while being brought to rest: net force × displacement = kinetic energy , i.e., Since the kinetic energy increases with the square of the speed, an object doubling its speed has four times as much kinetic energy. For example, a car traveling twice as fast as another requires four times as much distance to stop, assuming a constant braking force. As a consequence of this quadrupling, it takes four times
2025-435: The work to double the speed. The kinetic energy of an object is related to its momentum by the equation: where: For the translational kinetic energy, that is the kinetic energy associated with rectilinear motion , of a rigid body with constant mass m {\displaystyle m} , whose center of mass is moving in a straight line with speed v {\displaystyle v} , as seen above
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