The division is based on differences in mechanical properties and in the method for the transfer of heat. The lithosphere is cooler and more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conductionwhereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient.
The Earth's Interior Just as a child may shake an unopened present in an attempt to discover the contents of a gift, so man must listen to the ring and vibration of our Earth in an attempt to discover its content.
This is accomplished through seismology, which has become the principle method used in studying Earth's interior. Seismos is a Greek word meaning shock; akin to earthquake, shake, or violently moved. Seismology on Earth deals with the study of vibrations that are produced by earthquakes, the impact of meteoritesor artificial means such as an explosion.
On these occasions, a seismograph is used to measure and record the actual movements and vibrations within the Earth and of the ground. Scientists categorize seismic movements into four types of diagnostic waves that travel at speeds ranging from 3 to 15 kilometers 1.
Two of the waves travel around the surface of the Earth in rolling swells. The other two, Primary P or compression waves and Secondary S or shear waves, penetrate the interior of the Earth. Primary waves compress and dilate the matter they travel through either rock or liquid similar to sound waves.
They also have the ability to move twice as fast as S waves. Secondary waves propagate through rock but are not able to travel through liquid. Both P and S waves refract or reflect at points where layers of differing physical properties meet.
They also reduce speed when moving through hotter material. These changes in direction and velocity are the means of locating discontinuities. Seismic discontinuities aid in distinguishing divisions of the Earth into inner core, outer core, D", lower mantle, transition region, upper mantle, and crust oceanic and continental.
Lateral discontinuities also have been distinguished and mapped through seismic tomography but shall not be discussed here. It is believed to have solidified as a result of pressure-freezing which occurs to most liquids when temperature decreases or pressure increases.
This conductive layer combines with Earth's rotation to create a dynamo effect that maintains a system of electrical currents known as the Earth's magnetic field.
It is also responsible for the subtle jerking of Earth's rotation.
This layer is not as dense as pure molten iron, which indicates the presence of lighter elements. Although it is often identified as part of the lower mantle, seismic discontinuities suggest the D" layer might differ chemically from the lower mantle lying above it.
Scientists theorize that the material either dissolved in the core, or was able to sink through the mantle but not into the core because of its density.
It probably also contains some iron, calcium, and aluminum.Compare explanatory power: Plate Tectonics - Globally random; each location has its own peculiar alphabetnyc.comg forces are speculative and inadequate.
How the Earth's crust is split into large sections called tectonic plates is described. Their movement and effects at plate boundries are explained e.g. earthquakes, volcanoes, mountain building, ocean ridges/trenches, subduction (part of the rock cycle).
Evidence to support the theory plate tectonic movement is also described e.g. fossil similarities, . You must be a current Student, Staff or Faculty member of OSU in order to purchase all Apple products.
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Plate Tectonics -- Evidence of plate movement. Let's think a little bit about the different clues that have led us to conclude that we have these lithospheric plates moving relative to each other.
A large collection of astronomy articles, photos, information and research from NASA and major universities. This series shows the physical processes and human activities that shape our planet. From earthquakes and volcanoes to the creation of sea-floor crusts and shifting river courses, Earth Revealed offers stunning visuals that explain plate tectonics and other geologic concepts and principles.
Follow geologists in the field as they explore the primal forces of the Earth.