University:
Arizona State University
Course:
ABS 370 | Ecology
Academic year:

2024
Views:

470

Pages:

2
Author:

Thuyoul US

OROGORI APPALACHIAN Perhaps the most impressive landforms on Earth are mountains, created by the forces of uplift and erosion. The collision of the Paleozoic continents squeezed the crust, pushing enormous masses of rock into several mountain chains in many parts of the world. Mountains have complex internal structures formed by folds, faults, volcanic activity, metamorphism, and frozen intrusion (Fig. 124). The Appalachian Mountains, stretching about 2,000 miles from central Alabama to Newfoundland, were uplifted during a continental collision between North America, Eurasia, and Africa.This occurred at the end of the Paleozoic from about 350 million to 250 million years ago during the construction of Pangaea. The Southern Appalachian is constituted with more than 10 miles of flat sedimentary and metamorphic rocks, while the surface rocks are severely deformed by collisions. This type of formation suggests that the mountain is the product of thrust faulting, which involves crustal material being carried horizontally for very long distances. Sedimentary strata rise west over Precambrian metamorphic rocks and fold, bending the crust into a series of mountains and valleys (Figure 125). The existence of sedimentary layers beneath the Appalachian core suggests that a push involving underground rocks was responsible for the formation of mountain belts, possibly since plate tectonic processes began. Pushing and stacking thrust sheets during continental collisions may also be a major mechanism in the continued growth of continents. The Mauritanide Mountains of West Africa are the counterpart (the other side) of the Appalachians. It is characterized by a series of east-to-west running belts that are similar in many ways to the Appalachian belt. The eastern part of the range consists of sedimentary strata partially covered with metamorphic rocks that have impinged sediments from the west along thrust faults. Older metamorpohic rocks resembling the southern Appalachian lie to the west of the region, while younger horizontal rock coastal plains cover the rest. Furthermore, a period of metamorphism and impetus similar to the formation of the Appalachians occurred before the opening of the Atlantic. In this case, the two mountains are practically mirror images of each other. This episode of mountain building also raised the Hercynian Mountains in Europe, which stretched from Britain to Ireland and continued through France and Germany.The folding and faulting were accompanied by large-scale frozen activity in Britain and on the European continent. The Ural Mountains were also formed by the collision between the Siberian and Russian shields. The Transantarctic Range, which consists of a large belt of folded rock, was formed when two plates united into the continent of Antarctica. Before the end of the Permian, the lower part of West Antarctica had not yet formed, and only East Antarctica was present.