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IGNEOUS ROCKS
Lesson 1 - Page 3

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Early humans could not imagine where rocks came from. They could describe the physical features of a rock but it was difficult to determine where rocks came from. Rocks that formed through the action of water were observed early on. Since sedimentary rocks are the most common on the surface of the Earth, it was easy for people to make this connection.

Geologists even up to the early 1800's believed that all rocks crystallized from oceanic water. Even volcanic eruptions were thought to be burning of coal seams beneath a volcanic vent. Eventually the "Neptunists" or people who believed that all rocks came from water, were replaced by geologists who witnessed volcanic activity. An expedition around 1730's to Iceland, watched lava flows from fissures in the Earth, was the evidence that Plutonists (scientists who believed that volcanic rocks were from within the Earth) needed to dispel the theories of the Neptunists. 


Lava flow from Hawaii


Kenya, Africa

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