Sunday, May 24, 2015

South America: Part Once Under Water – Part II

Continuing from the previous post on explaining how South America was once partially under water. To best understand this, it is important to realize that the Earth is a dynamic, constantly changing planet, with moving parts forever in motion. As an example, the wind and pressure systems of the Pacific conform closely to the planetary system—the patterns of air pressure and the consequent wind patterns that develop in the atmosphere of the Earth as a result of its rotation (Coriolis force) and the inclination of its axis (ecliptic) toward the Sun. They are, in essence, a three-celled latitudinal arrangement of the atmospheric circulation, with the systems in the Northern and Southern hemispheres mirroring each other on opposite sides of the Equator.
The vast extent of open water in the Pacific influences wind and pressure patterns over it, and climatic conditions in the southern and eastern Pacific—where the steadiness of the trade winds and the westerlies is remarkable—are the most uniform on the globe. In the North Pacific, however, conditions are not so uniform, particularly the considerable climatic differences between the eastern and western regions in the same latitude. The rigor of the winters off the east coast of Russia, for instance, contrasts sharply with the relative mildness of winters in the region of British Columbia.  
    The trade winds of the Pacific represent the eastern and equatorial parts of the air circulation system; they originate in the subtropical high-pressure zones that are most pronounced over the northeast and southeast Pacific between latitudes 30° and 40° N and S, respectively. The obliquity of the ecliptic (an angle of 23.44° that is the difference between the planes of the Earth’s rotation on its axis and its revolution around the Sun) limits the seasonal shifting of the Pacific trade-wind belts to about 5° of latitude. The easterly winds between the two subtropical zones form the intertropical airflow and tend to be strongest in the eastern Pacific. The equatorial region, where the trade winds of the Northern and Southern hemispheres converge, is an area of calms or light variable breezes and is known as the doldrums.
    All of this is constant and has been going on for millennia in the same manner and under the same circumstances. The winds obviously move the oceans and create currents that are constant and never-ending, moving in the same direction over the history of the Earth.
    At the same time, continents move in their slow process as the tectonic plates move into (subduction) and around (slippage) one another. Islands, of course, are continental in nature—geologically, they consists partly of sedimentary rocks and their structures are similar to those of the coastal mountain ranges of the adjacent continent. All the islands, mountain ranges, and other features are the result of plate tectonics—the movement of continental plates. The western Pacific arcs of volcanic islands and deep trenches are convergent zones where two plates are colliding, one being subducted (forced under the other), with the East Pacific Rise an active spreading center where new crust is being created. The northeastern Pacific margin is the strike-slip zone where the American Plate and the Pacific Plate are gliding laterally past each other via the major San Andreas Fault system
As the (Blue) Nazca Oceanic Plate subducts, is forced beneath the (Red) Continental South American Plate, the entire plate is (White Arrow) lifted upward and at the convergence, the earth folds and buckles, causing (Red Arrow) Mountains to form and rise
    In the southeastern Pacific the Nazca Plate and the South American Plate are colliding to form the Andes Mountains along western South America and, a short distance offshore, the Peru-Chile Trench. The floor of the northeastern Pacific is remarkable for its several major fracture zones, which extend east and west and which, in some instances, are identifiable over distances of thousands of miles.
    With this in mind, then, we turn to South America, a very large continent, though very different from almost all the others. As an example, South America west of the Andes slopes gently toward the Pacific Ocean, honeycombed by criss-crossing mountain ranges creating numerous valleys; however, to the east of the Andes, the continent is relative flat with almost all of the Amazon Basin—an area 2.67 million square miles and about the size of the 48 contiguous United States—is barely above sea level as it slopes toward the Atlantic Ocean 4,000 miles to the east. Some 15,000 tributary rivers flow through this largest river basin in the world, and into the Amazon River. The entire Basin is contained by two large stable masses of ancient rock, the Guiana Shield or Highlands to the north and the Central Brazilian Shield or Plateau to the south, with the Andes Mountains to the west.
    The movement of water from the Andes to the Atlantic is about eight trillion gallons a day, 60 times that of the Nile and eleven times that of the Mississippi, with an average discharge of 6,350,000 cubic feet per second, which rises to more than 7,000,000 during a flood. All of this empties into the Atlantic through a mouth that is 250 miles wide.
Top: The Amazon River. Yellow Arrow points to the Andes Mountains in the far distance and out of sight; White Arrow points to the direction of flow of the Amazon. Note the extreme flatness of the entire Basin area; Bottom: Mouth of the Amazon River on a NASA satellite photo showing it 250 miles wide
While the Amazon River is 150 feet deep, it increases to 300 feet at the mouth, and its width varies from one mile to 35 miles along its course; however, during flood time, which is more than half of the year, the flood waters render nearly the entire Basin under water.
Anciently, this continent sat mostly beneath the surface, with the area in the west, called the Proto-Andean rift, a comparatively flat lowland of hills and an occasional mountain visible above the surface, and in the east two large mountainous plateau areas—Guayana Shield to the northeast, and the Brazilian Shield to the central and southeast. In between were the Pebesian Sea to the north and the Paranense Sea to the south with the Amazon Through Seaway to the east that flowed past and between the Guayana and Brazilian Shields.
    During this time the Nazca Plate collided with the South American Plate, creating a rise all along the proto-Andean rift, and uplifting the Andes Mountains. As these mountains lifted, the land to the east making up the two seabeds, rose with them, bringing them up to sea level or a little above. Waters trapped within the spaces of the uplifting mountains rose to several thousands of feet, creating the Lauricocha (Lawriqucha) and Titicaca lakes, along with several other small water areas, and forming numerous rivers, such as the Marañòn and Apurímac, that flowed eastward into the newly formed Amazon Basin.
    Thus, when oceanic and continental plates come together, geologists claim the continental crust buckles. On the surface, the buckling manifests itself as a rising mountain range, but beneath the crust, the buckling creates a heavy, high-density "root" that holds the crust down like an anchor as tectonic convection of the fluid mantle deep in the Earth erodes this heavy root, allowing mountains to rise as the crust shortens and thickens.
    Of course, while this usually takes time to occur, Samuel the Lamanite saw it happen immediately, so when the Lord is involved, the root heats up quickly and oozes downward, breaking free and sinking into the hot fluid mantle, causing the mountains above, suddenly free of the weight of the blob, to rush upward and, in the case of the Andes, suddenly lift from the valley floor upward to a “height which is great” (Helaman 14:23).
    In fact, Samuel said, “many shall see greater things than these, to the intent that they might believe that these signs and these wonders should come to pass upon all the face of this land, to the intent that there should be no cause for unbelief among the children of men” (Helaman 14:28).
    Obviously, this was done in a unique manner by the Lord, as a sign of his involvement and the fulfillment of Samuel’s prophesy, that the ancient Nephites as well as we today can see the hand of the Lord in all things.

No comments:

Post a Comment