To Jenkins' Spoiler-Laden Guide to Isaac Asimov Introduction Though perhaps best known throughout the world for his science fiction, Isaac Asimov was also regarded as one of the great explainers of science. His essays exemplified his skill at making complex subjects understandable, and were written in an unformal style, liberally sprinkled with personal anecdotes that endeared him to a legion of faithful readers.
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. This division should not be confused with the chemical subdivision of these same layers into the mantle comprising both the asthenosphere and the mantle portion of the lithosphere and the crust: The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plateswhich ride on the fluid-like visco-elastic solid asthenosphere.
Tectonic lithosphere plates consist of lithospheric mantle overlain by one or two types of crustal material: Because it is formed at mid-ocean ridges and spreads outwards, its thickness is therefore a function of its distance from the mid-ocean ridge where it was formed.
The location where two plates meet is called a plate boundary. Plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features such as mountainsvolcanoesmid-ocean ridgesand oceanic trenches.
These boundaries are discussed in further detail below. Some volcanoes occur in the interiors of plates, and these have been variously attributed to internal plate deformation  and to mantle plumes.
As explained above, tectonic plates may include continental crust or oceanic crust, and most plates contain both. For example, the African Plate includes the continent and parts of the floor of the Atlantic and Indian Oceans.
The distinction between oceanic crust and continental crust is based on their modes of formation. Oceanic crust is formed at sea-floor spreading centers, and continental crust is formed through arc volcanism and accretion of terranes through tectonic processes, though some of these terranes may contain ophiolite sequences, which are pieces of oceanic crust considered to be part of the continent when they exit the standard cycle of formation and spreading centers and subduction beneath continents.
Oceanic crust is also denser than continental crust owing to their different compositions. Oceanic crust is denser because it has less silicon and more heavier elements " mafic " than continental crust " felsic ". Types of plate boundaries Main article: List of tectonic plate interactions Three types of plate boundaries exist,  with a fourth, mixed type, characterized by the way the plates move relative to each other.
They are associated with different types of surface phenomena. The different types of plate boundaries are: The relative motion of the two plates is either sinistral left side toward the observer or dextral right side toward the observer.
Transform faults occur across a spreading center. Strong earthquakes can occur along a fault. The San Andreas Fault in California is an example of a transform boundary exhibiting dextral motion.
Divergent boundaries Constructive occur where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin. At zones of continent-to-continent rifting, divergent boundaries may cause new ocean basin to form as the continent splits, spreads, the central rift collapses, and ocean fills the basin.
Active zones of mid-ocean ridges e. Convergent boundaries Destructive or active margins occur where two plates slide toward each other to form either a subduction zone one plate moving underneath the other or a continental collision. At zones of ocean-to-continent subduction e.
Earthquakes trace the path of the downward-moving plate as it descends into asthenosphere, a trench forms, and as the subducted plate is heated it releases volatiles, mostly water from hydrous mineralsinto the surrounding mantle. The addition of water lowers the melting point of the mantle material above the subducting slab, causing it to melt.Read this Science Essay and over 88, other research documents.
The Plate Tectonics Theory. For millions of years, tectonic plates have been determinate of changes in the physical face of the earth, and they /5(1). The theory of plate tectonics offers a comprehensive explanation for several geological phenomena — continental drift, mountain building and volcanism, and, of course, earthquake.
Jun 21, · In the following, Team C will discuss the theory of plate tectonics and how the theory shaped the form and composition of the movement within Continue Reading Plate tectonics essay. The primary authority for Creation Ministries International is the infallible Word of God, the Bible (see Q&A Bible).
All theories of science are fallible, and new data often overturn previously held theories. Evolutionists continually revise their theories because of new data, so it should not be. In casual conversation, people often use the word theory to mean "hunch" or "guess": If you see the same man riding the northbound bus every morning, you might theorize that he has a job in the.
The table below presents an abbreviated geologic time scale, with times and events germane to this essay. Please refer to a complete geologic time scale when this one seems inadequate.