Historical Geology Understanding Our Planet\'s Past

teria might have arisen in the earliest stages of biologic evolution, probably about 3.5 billion years ago. Iron-metabolizing ba ...

30 feet. The evidence suggests that at an early age, the Moon orbited much closer to Earth, and its strong gravitational attract ...

ever, the development of the eukaryotic cell possibly took as long as 1 billion years before it resembled anything living today. ...

Figure 18The contact between Manitou limestone and Precambrian gneiss and schist, Priest Canyon, Fremont County, Colorado. (Phot ...

Free ebooks ==> http://www.Ebook777.com gluelike substance secreted from their bodies.The organisms ranged from the Precambri ...

shells of remarkably intricate designs, including a needlelike, rounded, or open-network structure of delicate beauty (Fig. 20). ...

Sulfur combined easily with metals such as iron to form sulfates. Since the atmosphere and ocean lacked oxygen, the bacteria obt ...

energy of sunlight to extract from water molecules the hydrogen they needed for self-construction, leaving oxygen as a by-produc ...

led to the evolution of the eukaryotes.Therefore, oxygen was largely respon- sible for the evolution of higher forms of life (Ta ...

Free ebooks ==> http://www.Ebook777.com which covers much of Scandinavia in Europe. More than a third of Aus- tralia is Preca ...

the oldest known rocks of North America are the 2.5-billion-year-old gran- ites of the Canadian Shield. The shields are associat ...

which are the metamorphic equivalents of granites and the predominant Archean rock types (Fig. 25).Their color derives from chlo ...

plate tectonics operated early in the Archean. Indeed,plate tectonics appears to have been working throughout most of Earth’s hi ...

meteorite impacts characterized the unusual geology of the Archean. Since greenstone belts are geologically unique to the Archea ...

contain chemical fingerprints of complex cells as much as 3.9 billion years old.Around this time, a swarm of debris left over fr ...

Ophiolites are the best evidence for ancient plate motions. They are sec- tions of oceanic crust that peeled off during plate co ...

The average rate of continental growth since then was perhaps as much as a one cubic mile a year. The constant rifting and patch ...

T his chapter examines the more complex life-forms and the develop- ment of the continents during the Proterozoic eon from 2.5 b ...

of their primitive asexual reproduction. They used simple fission, whereby species essentially cloned themselves,which offered l ...

Free ebooks ==> http://www.Ebook777.com of oxygen by the Proterozoic. About 2 billion years ago, when the oxygen- absorbing b ...