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[SenadR]

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[nona]

Moj favorit
(Usput, Seno, kakva je tamo podloga, granit ili nesto a-la-krecnjak)

[SenadR]

Nona , dobro pitanje :) , nadam se da ovo moze pomoci:
GEOLOGIC ACTIVITY OF THE INDIAN PEAKS

Resting due south of Rocky Mountain National Park, the Indian Peaks Wilderness shares a rich geologic history with its more famous and federally protected neighbor. The formation of the Indian Peaks Wilderness is the product of a complex geologic epoch spanning almost 2 billion years.

The area occupied by both the Indian Peaks and Rocky Mountain National Park has been repeatedly uplifted and eroded. Although many of its mountaintops have been flattened by ancient erosion, recent glaciation has left steep scars, U-shaped valleys, lakes, and moraine deposits. The area's oldest rocks were produced when plate movements subjected sea sediments to intense pressure and heat. The resulting metamorphic rocks (schist and gneiss) are estimated to be 1.8 billion years old. Later, large intrusions of hot magma finally cooled about 1.4 million years ago to form a core of crystalline igneous rock (mostly granite).

During the long Paleozoic Era, the greater Indian Peaks and Rocky Mountain areas were variously submerged, lifted up, and eroded. Early in the Mesozoic Era, approximately 100 million years ago, dinosaurs roamed the shoreline of a shallow sea which extended from the Gulf of Mexico to the Arctic Ocean. Animal remains were deposited in layers of sand, silt and mud. The resulting sedimentary rock layers (including fossils) are now exposed in the foothills to the east of the the high peaks.

Almost 70 million years ago, the Rocky Mountain Uplift began. Giant blocks of ancient crystalline rock, overlain by younger sedimentary rock, broke and were thrust upward. Even as the uplift occurred, streams started eroding away the sedimentary rocks washing new sediments to the east and west. When the sedimentary rocks were mostly gone, erosion continued leveling the ancient Precambrian rocks until only a few isolated remnants projected above the gently rolling landscape. The gentle slopes atop Pawnee Pass are remnants of this erosion surface.

During the Cenozoic Era, some faulting and regional up warping lifted the Rocky Mountain Front Range as much as 5,000 feet to its present height. Some volcanic activity left young volcanic rock in contact with Precambrian rocks.

Differential movement along faults disrupted drainage patterns, resulting in higher mountains, waterfalls and large valley areas, such as Estes Park Valley. Streams had established drainage patterns with V-shaped valleys cut into hard rock before the climate became cooler, perhaps 2 million years ago. In the higher valleys, snow changed to glacial ice which flowed down the valleys. Glacial erosion changed V-shaped valleys into U-shaped valleys. The converging rivers of ice flowed down into lower valleys where the ice warmed, melted, and dropped the debris it had scraped from the mountainsides above. Loose rock material carried by the ice was deposited along the sides, forming lateral moraines. At the ends of the glaciers, ice carried rocks were dumped to form terminal moraines.

[nona]

Hvala Seno.

[SenadR]