folded rocks, formed when two plates came together into the continent of
Antarctica. Prior to the end of the Permian, the younger parts of West Antarc-
tica had not yet formed, and only East Antarctica was present.
LATE PALEOZOIC GLACIATION
The continents of Africa, South America, Australia, India, and Antarctica were
glaciated in the late Paleozoic, around 270 million years ago, as evidenced by
glacial deposits and striations in ancient rocks. The continents were joined in
such a manner that ice sheets moved across a single landmass, radiating out-
ward from a glacial center over the South Pole.
The late Paleozoic was a period of extensive mountain building. Massive
chunks of crust were raised to higher elevations, where glaciers are nurtured
in the cold, thin air. Glaciers might have also formed at lower latitudes when
lands were elevated during continental collisions. When Gondwana and
Laurasia combined into Pangaea, the continental collisions crumpled the crust
and pushed up huge blocks into several mountain chains throughout many
parts of the world. With land at high elevations, temperature decreases and
precipitation increases, maintaining glaciers in the high altitudes. Evidence for
widespread glaciation include beds of Permian tillites found on nearly every
continent (Fig.126).
Besides folded mountain belts, volcanoes were prevalent. Unusually long
periods of volcanic activity block out the Sun with clouds of volcanic dust and
Figure 126Permian
tillite in Roxbury
conglomerate,Hyde Park,
Suffolk County,
Massachusetts.
(Photo by W. C.Alden,
courtesy USGS)PERMIAN REPTILES