GEO-151 Assignment 1

8/9/2019 GEO-151 Assignment 1

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Valo S. Gonzalez

GEO-151

Assignment 1

1. What are the relationships among Earths mantle, crust, asthenosphere, and lithosphere?

The theory of Plate Tectonics been demonstrated to reliably indicate that the surface of the Earth,

the crust, and its immediate sublayer the uppermost portion of the mantle (the lithosphere) are fractal

portions of one whole. Though the sum of these pieces (plates) are the constituents of a unified layer on the

surface (Earths crust), their behavior is far from harmonious. The plates that form the lithosphere are in a

constant state of motion which is measured from the perspective of geologic time that is spans of time that

are contextually appropriate for the pace at which geological events occur. Underneath the lithosphere lies a

deeper layer of mantle known as the asthenosphere where weaker mantle rocks in a partially melted, crystal

and-liquid state are transferred through the region easily by ductile flow. An important concept relative to all

geological events is the process of earths internal and external heat engines, devices that convert heat

energy into mechanical energy. These engines are governed by a process known as convection, movement

due to density differences caused by heating and cooling. Internal forces are classified as convection that

occurs within the asthenosphere forcing areas of higher heat, and less density upward toward the lithosphere.

This upward exertion of mass from the asthenosphere generates a force known as tectonic force, which

causes the deformation of rock by bending and breaking it as well as vertical and horizontal movement of

portions of the Earths crust evidenced by the raising of mountain ranges an example of mechanical energy

which comprise the majority of tectonic forces. Mechanical movement of Earths crust may be continuous and

gradual, or else stored and suddenly released as when an earthquake occurs. Otherwise tectonic forces are

converted to heat energy at which time such events as volcanic activity is the result. Surficial processes the

Earths external heat engine which is driven by solar power, pertain to portions of the Earths surface that are

exposed to the atmosphere. Convection at the surface occurs when the sun heats the ground and creates

areas of lower atmospheric pressure which causes cooler adjacent areas of greater atmospheric pressure to

move toward the area of displaced atmosphere. The movement of cooler, denser, surface based

atmospheric mass converging on an area of displaced upward moving warmer air, illustrated how winds are

generated. The upward moving warm parcel of air begins to cool and condense forming clouds, which when

saturated with moisture from evaporated bodies of water, will produce precipitation. Wind and precipitation

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Valo S. Gonzalez

GEO-151

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cause erosion to occur at exposed portions of the Earths crust above sea level. As weather driven by Earths

external heat engine forces the breakdown of rock, what is left is known as sediment loose material.

Sediment may be transported by an agent of erosion, such as running water in a stream or river into the sea.

When such an agent slows down as it meets the sea, the sediment being transported as, for example sand, is

deposited as a layer of sediment on the ocean floor. Over time the layer of sediment becomes cemented or

otherwise consolidated (lithified) into a sedimentary layer of rock. Sedimentary rock that becomes deeply

buried in the Earth may later be transformed by heat and pressure into metamorphic rock.

Since the theory of plate tectonics regards the lithosphere as broken into plates that are in motion up the

underlying asthenosphere, much of what is observed and recorded is explained by the type of motion that

occurs along the plate boundaries. These boundaries are classified into three types based on the type of

motion they exert upon each other. They are Convergent, Divergent, or Transform boundaries. Convergent

boundaries involve two plates that are moving toward each other which are the sites of the largest

earthquakes. Divergent boundaries involve plates that are moving away from each other, the majority of

which coincide with the crests of submarine mountain ranges, called mid-oceanic ridges. Transform

boundaries are areas where two plates slide horizontally past each other. Although most transform faults are

found along mid oceanic ridges, occasionally a transform fault cuts through a continental plate. Transform

boundaries between plates (transform faults) are the segments of the fractures between offset ridge crests.

Earthquakes resulting from motion along transform faults vary in intensity depending on whether the fault cuts

through oceanic or continental crust and on the length of the fault.

2. By what processes did the planets form from the clouds of gas and dust? What are some of the main

differences between the Earth-like planets and the giant outer planets such as Jupiter and Saturn?

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Valo S. Gonzalez

GEO-151

Assignment 1

The planets formed from the clouds of gas and dust through a process known as the Nebular Hypothesis.

This hypothesis was first postulated in the 18th

century by German philosopher Immanuel Kant, and also

by the French mathematician Pierre Simon Laplace. The original framework of this hypothesis has

remained largely intact and is well supported by evidence available today. The Nebular Hypothesis

proposes that our solar system was born about 4.6 billion years ago from an interstellar cloud which

consisted of gas and dust which was probably a few light-years across and was made mostly of

hydrogen, and helium gas, with tiny traces of other chemical elements. The dust particles were a mixture

of silicates, iron compounds, carbon compounds, and water frozen into ice. Gravitational forces caused

the elements of the interstellar cloud to collapse inward while rotating. Dust particles in the disk began to

stick together and grow in size and eventually become small planet like bodies (planetesimals). The

central mass of the cloud eventually became the sun while the planetesimals formed into the respective

planets of our solar system.

The main differences between the Earth-like planets and the gas giant outer planets has to do with the

composition of the of the particles that formed them, which was dependant upon where in the disk they

formed. In the inner part of the disk, it was too warm for water-ice to condense. Solid particles there

were thus composed almost entirely of silicate and iron-rich material. At about Jupiters distance from the

Sun was the disk cold enough for water-ice to condense on the particles. Thus, particles in those outer

regions consisted of silicate and iron-rich material in addition to frozen water. For this reason the disk

became divided into two regions that contained either silicate and iron planetesimals near the sun, and an

outer zone of silicate and iron particles onto which ice also condensed. Atmosphere formation was the

last part of the planet-forming process. The outer planets captured most of their atmospheres directly

from the solar nebula as it was rich in hydrogen and helium, just as the atmospheres of the outer planets

are today. The inner planets were not massive enough and were too hot to capture gas directly from the

solar nebula and are therefore deficient in hydrogen and helium. The atmospheres of the inner, rocky

planets formed from a combination of processes such as volcanic eruptions releasing gases from their

interiors, vaporization of comets and icy panetesimals that have struck them.

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GEO-151 Assignment 1