This article is about the bacterium. For the disease, see Salmonellosis. Salmonella /ËsÃ¦lmÉËnÉlÉ/ is a genus of rod-shaped (bacillus) gram-negative bacteria of the Enterobacteriaceae family. The two species of Salmonella are Salmonella enterica and Salmonella bongori. Salmonella enterica is the type species and is further divided into six subspecies that include over 2,500 serotypes. S. enterica subspecies are found worldwide in all warm-blooded animals, and in the environment.
The Four Geologic Eras. Geology is a complex and difficult subject, especially for the novice. I recommend that beginners first concentrate on the four major divisions of geologic history: the Geologic Eras.he Precambrian Era (4.6 billion years ago to 600 million years ago) encompasses the great majority of Earth's geologic history, stretching from the formation of our planet to the appearance of shelled marine life.
The term geological processes describes the natural forces that shape the physical makeup of a planet. Plate tectonics, erosion, chemical weathering and sedimentation are all examples of forces that significantly affect the Earthâs surface and account for its major features.hen rock is worn away by water, ice or even wind, this is known as erosion. It is one of the most important geological processes, and, over time, can transform landscapes. Particles of grit and sand carried by water or wind have an abrasive effect and can sculpt rock into new shapes on a large scale.