The major extinction event marking the end of the Ordovician Period reduced the diversity of all trilobite orders with most asaphid families disappearing.
42.
Evidence suggests that an algal scum formed on the land, but it was not until the Ordovician period, around, that land plants appeared.
43.
Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician Period.
44.
Green Side is composed of andesite rock, part of the Borrowdale Volcanic Group, formed during the Ordovician Period, roughly 450 million years ago.
45.
A well known locality for graptolite fossils in Britain is Abereiddy Bay, Dyfed, Wales, where they occur in rocks from the Ordovician period.
46.
During the Ordovician Period, the collision of the North American and African tectonic plates initiated the Alleghenian orogeny that created the Appalachian range.
47.
It dates from the late Proterozoic through the early Ordovician periods, though the marine transgression did not begin in earnest until the middle Cambrian.
48.
This topography was shaped by folding and faulting that occurred during the middle Ordovician period of the Paleozoic Era by the collision of plates.
49.
The earliest hints come from the finding of tiny spores in 475-million-year-old rocks, placing them in the Ordovician period, a part of the Paleozoic.
50.
During the Ordovician Period, tectonic subduction responsible for forming the Appalachians left a number of seismically active fault lines stretching from northern Alabama to eastern Tennessee.
