This layer of rock is referred to as the "basement" since all other rocks formed since this time period lay on top of it. Eventually this layer of rock split and caused rifts to be filled with lava and sediment, causing new rocks to form. Down below is a Precambrian map of the continents and tectonic structure of the world.
|Late Precambrian continental structure. (From http://www2.humboldt.edu/natmus/lifeThroughTime/PlateMaps/Precambrian/PreCamPlates.htm)|
Believe it or not, Ohio used to be on the the eastern shore of our continent, until another continent collided with ours and caused mountains to form in modern day Ohio. Now the granite and rhyolite rocks are crystalline, extremely hard and resistant to weathering, ( from http://www.galleries.com/rocks/rhyolite.htm) but the mountains that formed eventually eroded which led to the sedimentary rocks of later periods.
|Map of the Grenville Tectonic Front Zone today.|