Historical Geology Understanding Our Planet\'s Past
cian. Originally, fossil evidence was scant and fragmentary. Little was known of their appearance or about their evolutionary hi ...
chains of islands and altering the shorelines of the continents. Reef-building corals created the foundations for spectacular un ...
tified by the complex structure of their skeletons, which aids in delineating specific geologic periods. Bryozoans have been ver ...
those that went extinct were many trilobite species. Before the extinction, trilobites accounted for about two-thirds of all spe ...
bacteria helped resist erosion by binding the sediment grains together and soak- ing up rainwater. Bacteria also provided nutrie ...
Lichens, which are a symbiotic relationship between algae and fungi whereby the two mutually live off each other, probably took ...
variations preceded changes in the extent of the more recent ice ages, suggest- ing that earlier glacial epochs might have been ...
middle Paleozoic fern Glossopteris(Fig. 68),named from the Greek word meaning “featherlike,” and whose fossil leaf impressions a ...
between about 570 and 480 million years ago suggests that this ancient sea- coast faced a wide, deep ocean. The Iapetus stretche ...
The foreland basins filled with thick sediments eroded from nearby moun- tains. Erosion from the mountains might have pumped nut ...
continent and deposited the formerly submerged rocks onto the present west coast of Norway. Slices of land called terranes resid ...
(Note: Do not confuse the term terranewith the word terrain,which means landform.) Terranes are usually bounded by faults and ar ...
ated on an oceanic plate retain their shapes until they collide and accrete to a continent. They are then subjected to crustal m ...
ophiolite belts, consisting of marine sedimentary rocks, pillow basalts, sheeted dike complexes, gabbros, and peridotites. Terra ...
a distinct trilobite species typical of North America but not of South Amer- ica. The fossil evidence suggests that the two cont ...
An inland sea flooded the continent in the middle Ordovician and reached a maximum in the late Ordovician. It partially withdrew ...
T his chapter examines the plant life and geology of the Silurian period. The Silurian, from 440 to 400 million years ago, was n ...
THE AGE OF SEAWEED Like animals, plants did not appear in the fossil record as complex organisms until the late Precambrian or e ...
as the Ordovician, plant fossils appeared to be composed almost entirely of algae, which probably formed stromatolite mounds and ...
microbes also aided in the weathering of rock into soil, helped to prevent soil erosion, and provided the nutrients more advance ...
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