How many times have the continents been joined in a supercontinent since the end of the Archean eon? Use this number to estimate the typical duration of a Wilson cycle and the speed at which plate tectonic processes move the continents.

500 million years duration

Explanation:

From the reconstruction of palaeomagnetic, it appears that the cycle of supercontinent assembly - break-up and subsequent reassembly - takes about 500 million years to complete and with increasing uncertainty, back to 750Ma and possibly earlier, therefore it became apparent that the continental masses have been assembled previously into supercontinents that have broken apart, and then later reassembled in a different configuration to form another supercontinent. This observation was noted by Wilson

However, the concept of periodicity in tectonic processes predates the acceptance of the plate tectonic paradigm Not until Wilson (1966) asked whether the Atlantic Ocean closed before it opened did such episodicity merged into a plate tectonic framework. Developed and defined as the ‘Wilson cycle’. The idea that oceans close and later reopen along former sutures has since become a fundamental concept in plate tectonics.

There is, however, a widespread misconception that the Wilson cycle is synonymous with the supercontinent cycle. The Wilson cycle refers to the history of a single ocean basin and includes the

stages of continental rifting (rift valley stage); early oceanization (Red Sea stage); divergence in a mature ocean (Atlantic stage); ocean basin convergence and closure (Pacific stage); and continent–continent collision. The Wilson cycle is not, however, a cycle sensustricto as not all the steps are required; it may abort after the first or second stages and it may span a few million or hundreds of millions of years. Additionally, a Wilson cycle is very

specific: it starts when rifting and seafloor spreading begin during the separation of two continents, and ends when the last of that seafloor is consumed in collison.

In contrast, the supercontinent cycle is conceived as a geodynamic mechanism that may explain the Long-term behaviour of the entire Earth and involves all of the Earth plates, both continental and oceanic. The process of amalgamation and breakup of supercontinents is thought to happen in a quasi-cyclical manner (sensu stricto) with time intervals of c. 500 myr.

In addition, whereas there is no hierarchical relationship with the Wilson cycle, a particular supercontinent cycle may involve multiple Wilson cycles, both partial and complete.

question 1

the reasons for the global discontent in the early 1900s were the following:

question 2

the reasons for the great depression were the following, and these led to wall street crash in october 1929 and caused the subsequent great recession period.

question 3

2.