際際滷 show presentation of Precambrian tectonic history of the North American craton up to the end of the Cambrian Period. 際際滷 show the reconstruction of cratonic blocks being assembled to produce the continent, accompanied by audio text and soundtrack music. Part A is the first part of a four part series to include the Phanerozoic tectonic hisotyr (Part B), British Columbia (Part C), and Alaskan (Part D) tectonics.