Geology Reference
In-Depth Information
When early geologists looked at the mountains, valleys, and seas around them, they
realized that something dramatic must have occurred to create what they saw. Because
people believed that the earth was only a few thousand years old, the only way to ex-
plain what they saw was by assuming the occurrence of occasional catastrophic events,
such as massive floods, volcanic eruptions, and earthquakes.
This early belief that earth's features were created by a series of catastrophic
events is called
catastrophism.
Geologic explanations involving dramatic, worldwide, catastrophic events were in sync
with stories from the Bible, such as the great flood. In this way, catastrophism recon-
ciled strong biblical beliefs with explanations of geologic processes that scientists now
know occur over many hundreds of thousands (or even millions) of years.
Early Thoughts on the Origin of Rocks
While catastrophism attempted to explain the creation of earth's features, questions
about the origin of earth's rocks remained. Where did the rocks on the crust of the earth
come from before they were subjected to the catastrophes that shaped and shifted
them?
Two theories dominated early thoughts on the origin of rocks: Neptunism and
Plutonism.
Neptunists proposed oceanic origins.
The Neptunist theory of rock origins pro-
posed that all the rocks on earth were created from sea water, having crystallized
from the earth's first oceans. (The theory is named after the Roman god of the sea,
Neptune.)
Plutonists proposed volcanic origins.
The Plutonists believed that all earth's rocks
originated from volcanoes and were then changed by pressure and heat into other
rocks. (The theory is named after the Roman god of the underworld, Pluto.)
