1. On earth, thedistribution of elements consists of iron, oxygen, silicon, and magnesium.
Planets such as Jupiter and Saturn consist of mainly volatile gases. Some ofthese volatile gases are water, methane, and ammonia. 2. It is believedthat during the first five hundred million years of the earth’s accelerationfrom smaller bodies, a giant impact took place which resulted in the earthtilting on its axis.
The time between the acceleration of the earth and theformation of the oldest existing rocks may be accounted for by thestratification or differentiation of the earth. The original rocks may havebeen melted and their components redistributed into the core, mantle, and crustduring this interval. 3. In the 1960s and1970s, a new view of the earth’s internal structure began to emerge. This viewallowed geologists to integrate data and observations from many diverse fieldsinto a unifying theory of the earth’s behavior, called plate tectonics.
Thistheory now forms the basis of our understanding of the earth’s large-scaleinternal behavior and also has many implications about the geological processthat we can observe at the surface as well. The new model considers the earth’smolten outer core to be a very active zone of circulation.4. The earth’smagnetic field originated because of the circulation of molten metal in theouter core.
This occurred because metals conduct electricity. Magnetism of thelithosphere support the model of plate tectonics by providing strong evidencethat new oceanic crust formed volcanism at the ridge crest in the prevailingpolarity of the earth’s magnetic field.5. Gravity varies dueto the rotation of the earth, topography, and variations in density. Isostaticequilibrium is implied in the theory of isostasy is the idea that crustalmasses establish a state of dynamic equilibrium with the mantle.
Thus, thedense basalts of the ocean basins lie at a low elevation in comparison withlighter granitic mountain ranges, which float higher in the mantle.6. The first piece ofevidence for plate tectonics is the theory of continental drift which proposedall the continents were once assembled into large continental mass and then drifted apart to their presentposition. The next piece of evidence for plate tectonics is the theory ofsea-floor spreading. The symmetrical bands of alternately magnetized volcaniccrustal rock provided important evidence for the sea-floor spreading theory,which proposed that new crustal material was formed by volcanic eruptions atthe crests of the midoceanic ridges and that slow lateral movement of the crustaway from the ridges was occurring. 7. Divergent plate margins: Occur where risingconvection currents in the asthenosphere nearly reach the earth’s surface.
Divergent plate boundary can be recognized at the earth’s surface as cracksapart parallel to the boundary, large linear blocks subside downward alongfaults to form rift valleys or grabens along the crest of the rift zone, oneexample is the mid-atlantic ridge. Convergentplate boundaries:Mark the zone ofcontact or collision where plates move toward each other. Convergent platesboundaries can be recognized at the earth’s surface as a line of volcanoes,examples includes the Cascade volcanoes and the Andes in South America. Transform boundaries:Lithosphericplates are sliding past each other along vertical fractures, known as transformfaults, at these boundaries. 8. Solar energyarriving at the earth is not equally distributed. Rays that arrive at and nearthe equator strike the planet directly, which concentrates the heat containedwithin a small area.
In contrast, rays that arrive at the surface near thepoles strike the earth in an oblique fashion, which distributes the same amountof energy over a larger area. Whenever there is a temperature difference, heatwill flow from areas of higher to lower temperature. Atmospheric circulation isbroken into a series of cells limited to specific latitude due to divergenceand convergence zones. As the air masses rises from the surface, air movesalong the surface from the north and south to replace the rising air masses,this creates a convergence zone. At about 30º north and south, the air massesbegin to sink back toward the surface, producing a zone of high pressure.
Whenthey descend to near the surface, the flow splits apart, creating a divergencezone.9. Atmosphericcirculation is circulation of the air due to a heat imbalance on the earth’ssurface caused by rays hitting the earth at different angles.
On the otherhand, oceanic circulation is circulation of the water on our planet that isintricately linked to the biosphere, atmosphere, and lithosphere.
