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      The Vredefort Structure.

                       Misconceptions and Facts.   Joe Mayer

                                                                                                                     

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Frequently asked questions and their answers

 

 

          Question:  How many impact sites are known in the world?

 

      Answer:   At present about  122 impact sites have been identified for the world.

 

      Question:  How many impact sites are known for Africa?

 

      Answer:  Nineteen  impact  sites have been  identified in Africa .

 

      Question: How many impact sites are known in South Africa?

 

      Answer:  In South Africa  4 impact sites  have been identified to date  i.e.

                   1.  Kalkkop  with a diameter of 640 m and age ± 250 my.

                   2.  Morokweng with a diameter of  70 km and age ± 145my.

                   3. Tswaing (formerly Pretoria Salt Pan) with a diameter of 1.13 km and age ± 220 my.

                   4. Vredefort with a diameter of about 300 km and age ±  2023 my.

 

     Question:  Is the Vredefort Dome the oldest meteorite impact site?

 

      Answer:  No,  in Russia Suavjärvi is an impact site supposed to be the oldest with 

                   age ~400 my.

 

     Question: Why do all impact craters appear round as if they all come from strikes that are

                    perpendicular to the impacted surface?   Shouldn't there be a mix of a few round

                   and many different  oval shapes to account for all of  the strikes that are glancing

                   blows instead of direct hits?  It seems there should be many more indirect hits

                   that produce oval impact craters rather than perfect perpendicular hits which

                  which make perfect impact circles.

 

     Answer:  The short answer is that the energy involved in an impact is so huge that when  

                   the impactor hits the ground, it explodes like a bomb, rather than just denting

                  the surface like a rock thrown into mud.  Explosions are generally symmetric,

                  so the resulting crater from most impacts is circular.  Only very shallow impacts

                  form elliptical craters, but they do exist!             

  

 

 

 

 

 

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