This black, square-​shaped plat­form is be­ing vi­brat­ed by an am­pli­fied wave gen­er­a­tor whose fre­quen­cy is be­ing grad­u­al­ly in­creased while some­one pours salt on it to re­veal the stand­ing waves gen­er­at­ed at the res­o­nant fre­quen­cy (the first pat­tern) or a har­mon­ic of the res­o­nant fre­quen­cy (all the oth­er pat­terns) of the black square. Each time the vis­i­ble pat­tern changes, the wave gen­er­a­tor "finds" an­oth­er har­mon­ic of the square's res­o­nant fre­quen­cy.

The salt makes these stand­ing waves vis­i­ble sine the salt is vi­brat­ed away from the ar­eas of the plat­form which are mov­ing, and sub­se­quent­ly rest in the ar­eas which not mov­ing. These ar­eas in the plat­form which are not mov­ing are where the stand­ing wave nodes re­side ( http://en.wikipedia.org/wi­ki/Stand­ing_waves ).

While the study of these waves is called cy­mat­ics ( http://en.wikipedia.org/wi­ki/Cy­mat­ics ), the pat­terns them­selves are caused by the stand­ing waves. These pat­terns ex­ist ev­ery­where, we just nor­mal­ly don't get to wit­ness them.

Some peo­ple in the com­ments have sug­gest­ed that this is how crop cir­cles form. My opin­ion on the mat­ter is that this is not like­ly since:

1) The am­pli­tude (the strength) of a stand­ing wave re­sid­ing in a ma­te­ri­al de­creas­es ex­po­nen­tial­ly with ma­te­ri­al thick­ness. Hence, the strength nec­es­sary to cause a stand­ing wave large enough to ef­fect corn stalks would cre­ate an earth­quake.

2) Ig­nor­ing the above, the chance that any stand­ing wave pat­terns which would some­how arise in earth that is as amor­phous as some ran­dom farmer's field would be would ac­tu­al­ly turn out to be well de­fined ar­range­ments of ge­o­met­ric shapes is high­ly, high­ly, high­ly un­like­ly.

2) If the salt sit in the ar­eas of the plat­form which are not mov­ing (stand­ing wave nodes), and it is the salt pat­terns which re­sem­ble crop cir­cles, then this would im­ply that the ar­eas where the crop cir­cle sym­bols ex­ist (the crushed/downed corn stalks) are al­so po­si­tioned at node points, mean­ing they do not move. If the area with the crushed corn stalks is not mov­ing, but the area of the field sur­round­ing the sym­bols are (as would have to be for there to be stand­ing waves), then why would the stalks that aren't mov­ing fall down but the corn stalks that are mov­ing stay stand­ing? It sim­ply makes no sense.