America's Volcanic Past
|"Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994|
Volcanic Highlights and Features:
|[NOTE: This list is just a sample of various Rocky Mountains features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of the Rocky Mountains.]|
The Late Cretaceous and Early Tertiary
periods were geologically eventful in the West.
The Rocky Mountains, which were uplifted
about 50 to 100 million years ago, extend
from southern Colorado northwest to the
Canadian border. Their rocks and topography
are diverse and highly complex. Many of the
individual ranges that make up the Rocky
Mountains appear on maps as variously
shaped bull's-eyes surrounding a
center. Each crudely ringed pattern was
created by the Tertiary erosion of Paleozoic
and Mesozoic sedimentary rocks that once
overlay and now surround a core of uplifted
USGS, A Tapestry of Time and Terrain Website, 2001
Granites found in the park probably resulted from the
melting of pre-existing sedimentary or
in the primordial crust shortly
after the formation of the Earth. The
Silver Plume granite
that occurs in much of
the east side of the park intruded upward into the metamorphic rocks about 300 million
years after the formation of the Proterozoic mountains.
The high mountains that
formed here during Proterozoic time were slowly eroded and reduced to a fairly flat
surface, exposing the core of metamorphic rocks and granite.
This erosion occurred over
a long period, from approximately 1,300 million to 500 million years ago.
|Never Summer Mountains|
Never Summer Mountains:2
Between 29 and 24 million years ago, the magmas reached the surface and erupted as volcanoes. The tops of the volcanoes stood several thousand feet above the present granitic masses of the Never Summers, which since have been eroded to their present size. Lava flows and extensive ash beds from the volcanoes are preserved in several areas within the park.
|Silver Plume Granite|
Silver Plume Granite:2
The Silver Plume granite that occurs in much of the east side of the park intruded upward into the metamorphic rocks about 300 million years after the formation of the Proterozoic mountains.
1) USGS/NPS Geology in the Parks Website, 2001
2) U. S. National Park Service Website - Geology Fieldnotes; Rocky Mountain National Park, Colorado, 2000
3) USGS A Tapestry of Time and Terrain Website, 2001
America's Volcanic Past - States and Regions]
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