An inland sea flooded the continent in the middle Ordovician and
reached a maximum in the late Ordovician. It partially withdrew in response
to a flood of sediments eroded from the Taconian mountain belts. One of
these sedimentary deposits is the widespread Ordovician St. Peter Sandstone
of the central United States. It is composed of well-sorted, nearly pure quartz
beach sands that are ideal for manufacturing glass.
After covering life and geology in the Ordovician,the next chapter
explores the first life-forms to leave the sea and settle on dry land during the
Silurian period.
Figure 75The
Caledonian orogeny in
Great Britain,
Scandinavia, Greenland,
and North America shown
in the shaded area.ORDOVICIAN VERTEBRATESAtlantic
OceanNorwegian
SeaNORTH
AMERICANewfoundlandGreenlandEUROPELabrador
Sea