Man's physical universe

xanabras

UNIT III

SECTION 5

DIASTROPHISM AND VULCANISM TEND TO REVERSE

THE RESULTS OF DEGRADATION

That part of the surface of any heavy body will become more distant from

the center of its gravity which becomes of greater lightness. The earth therefore,

the element by which the rivers carry away the slopes of mountains and

bear them to the sea, is the place from which such gravity is removed; it will

make itself lighter and in consequence will make itself more' remote from the

center of gravity of the earth, that is from the center of gravity of the universe

which is always concentric with the center of gravity of the earth. . . . The

summits of the mountains in course of time rise continually. — Leonardo Da

Vinci.

Introduction.

It is reasonable to conclude that the agents of gradation are capable

of destroying all of the earth's land areas if given time. Furthermore,

there is every reason to believe that more than enough time has elapsed

to have brought about complete gradation of the lithosphere. The fact

that land areas exist today indicates that there are forces which tend

to balance the forces of gradation.

Diastrophism and vulcanism are the forces which lift up land areas,

and they are produced by the same changes that bring about gradation.

There is no reason to think that these balancing forces will not continue

as long as the earth has an atmosphere, and therefore as long as erosion

continues, because it is erosion itself that disturbs a condition of

equilibrium that exists and thus brings these compensating forces into

action. It is fascinating to study how erosion thus seems to defeat its

own ends.

Diastrophism refers to all movements of the outer shell of the earth.

Vulcanism refers to all phenomena that are connected with molten

rock ma,terial and its movements; the term is derived from Vulcanus,

the Roman god of fire, who was supposed to dwell in a volcano.

Earthquakes Are the Result of Tremendous Changes in the Earth's

Surface.

During the past fifty years,- the world has known many disastrous

earthquakes. Japan has experienced three such earthquakes — in

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