University:
Arizona State University
Course:
ABS 370 | Ecology
Academic year:

2024
Views:

120

Pages:

2
Author:

Thuyoul US

CALEDONIAN OROGORI When Laurentia approached Baltica at the end of the Siluria about 400 million years ago, they closed the Sea of Iapetus about 200 million years before the modern Atlantic began to open up. When continents collide, they squeeze the crust and force the mountains up at the point of impact. The seams joining the mainland are preserved as an eroded ancient mountain core called an orogen. The collision of the Paleozoic continent lifted enormous masses of rock into several folded mountain belts around the world. An episode of major mountain buildings from the Cambrian to the central Ordovician deformed the area between all the continents comprising Gondwana, showing their collision during this interval. Suitable geological provinces exist between South America, Africa, Antarctica, Australia, and India. The Cape Mountains in South Africa have an counterpart to the Sierra Mountains south of Buenos Aires in Argentina. Games also exist between mountains in Canada, Scotland, and Norway. During this time, most of Gondwana was in the south polar region, where glaciers extended throughout the continent, leading to the Ordovician ice age. The closure of the Sea of Iapetus from the middle Ordovician to the Devonian as Lawrence approached Baltica produced the great Caledonian orogeny (Figure 75), or mountain-building episode. This orogenic activity formed a mountain belt extending from south Wales, spanning Scotland, and flowing through Scandinavia and Greenland, possibly including today's extreme northwest Africa as well. In North America, this orogeny built a mountain belt that stretched from Alabama through Newfoundland and reached as far west as Wisconsin and Iowa.Vermont still retains the roots of this ancient mountain range, which was pushed upward between about 470 and 400 million years ago but has since been planned by erosion. The central Ordovician Taconian Orogeny named after the Taconic Range in eastern New York State culminates in a folded mountain chain that runs from Newfoundland through the Canadian and New England Maritime Provinces, reaching as far south as Alabama. During the Taconian disturbance, extensive volcanic activity occurred in Quebec and Newfoundland and from Alabama to New York, stretching as far west as Wisconsin and Iowa. The inland sea flooded the continent in the middle Ordovician and reached its maximum in the late Ordovician. It partially withdrew in response to a flood of eroded sediments from the Taconian mountain belt. One of these sedimentary deposits is the Ordovician St. Peter's Sandstone which is widespread in the central United States. It consists of well-sorted and almost pure quartz beach sand ideal for glassmaking. After covering life and geology in the Ordovician, the next chapter explores the first life forms that left the sea and settled on dry land during the Silurian period.