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A mountain range is growing
A mountain range is forming, arises.
The formation of the Rocky Mountains ended about 40 million years ago. In the
period up to about 170 million years before that, intense plate tectonic
activity began. Within 130 million years, there were three major
mountain-building phases that fundamentally reshaped western North America. All
of this took place during the Middle Jurassic and Middle Eocene. Responsible for
the uplift of the Rocky Mountains is the Laramian mountain building over a
period of 70 to 40 million years. There exists a plexus of earth crustal clasts
(terranes), each of which underwent a distinct geologic evolution.
Much older are the Ancestral Rocky Mountains, a Paleozoic mountain range in
western North America.
About the same time as the Variscan orogeny in Europe, Eurasia and western North
Africa, this mountain range was formed during the Upper Carboniferous about 300
million years ago. At that time, a shallow sea covered most of the then uplift
area. There, a sedimentary cover of mainly calcareous sediments was formed.
At the time of Mesozoic to Laramian mountain
building, tectonic movements began. Floes of more differentiated crust
on a significant scale, were attached to what was then the western
margin of the North American continent. These extrinsic terranes were
thereby brought to the continental margin. Subduction processes
occurred, where plates of too low density were not subducted, but
sheared off the oceanic plate and attached to the continental margin.
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Magma generated in the upper mantle penetrated the continental crust
of the North American continent at a distance of 300 to 500 kilometers inland.
Huge amounts of molten rock were intruded into deeper areas, where it slowly
cooled and solidified into large magmatic bodies (plutons). Magma generated in
the upper mantle, which penetrated the continental crust of the North American
continent, could have an influencing effect.
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The sediments deposited during the course of the Mesozoic
sediments were marine, transitional and continental in nature. On 15
geological formations, different types and layers of sediments were deposited.
of sediments were deposited, some of which measured 3000 - 4500 meters. Depending
they changed their character depending on the crustal conditions. |
Geologists are puzzled by the formation of the Rocky Mountains. Some
peculiarities have occurred that differ from a typical formation history. The
mountain range formed much farther inland than the usual 200 to 400 kilometers
behind a subduction zone. Possibly due to shallower dipping angle and magma
formation, at the subducting plate the frictional forces and other interactions,
can increase with the overlying continental crustal mass.
Sheared crustal layers are stacked on top of each other by overthrusts of huge
magnitude.
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Further rock and sediment layers were pushed through
the remnants of the former Upper Carboniferous and Permian sedimentary
cover as they rose. However, spectacular deformation of the younger
overburden layers also took place.
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With this graphic and the preceding ones how the
layers of the earth were pushed, folded and arranged
on top of each other by subduction and arranged. |
In the Front Range, a mountain range of the Rocky Mountains, Mount Blue Sky is the
highest and best known mountain. With its 14,264 feet (4350 meters) height, it
is one of the 54 so-called Fourteeners in Colorado.
The first ascent was in 1863 by Albert Bierstadt, who named the rock massif
Mount Rosalie after his wife-to-be.
In 1895, the mountain was officially named "Mount Evans" after John Evans, the
second territorial governor of Colorado.
Mount Blue Sky is the name to which the summit monument was currently renamed in
2023.
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During the Precambrian era, in the Mesoproterozoic,
Mount Blue Sky formed from batholith. This was formed by intrusion of magma
into the earth's crust and consists mostly of granodiorite. This
batholith was deeply cut by glacial cirques and canyons. Around Mount
Blue Sky, several lakes are located in glacial canyons, which helped to
shape the appearance of Mount Blue Sky during its formation. Due to their
peculiarity, these lakes are also called tarns. |
On the summit of Mount Blue Sky, the elevation and the
different stages of erosion provide special insights into the
sedimentary layers. Different types of sedimentary layers can be seen,
and their boundaries can be seen very clearly on the rocks. Brownish,
reddish seams, about the width of a hand, separate the lighter layers
from each other. It is easy to see how this "line" runs through the
rocks.
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Comparable to a carpet being pushed together over a hard surface is the
uplift of the rock masses of the Rocky Mountains. Within the thrust surfaces,
the mass bundles and forms folds. In combination of subduction with shallower
dipping angles, the formation of magmas and the influence of terranes, the
typical appearance of the Rocky Mountains was formed.
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In a typical subduction zone, an oceanic plate typically sinks at a fairly
steep angle and a volcanic arc grows above the subduction plate. The angle of
the subduction plate may have been flattened considerably during the growth of
the Rocky Mountains. As a result, the center line of the mountain buildup is
much farther inland than normally expected. It is believed that the
extraordinary width and height of the Rocky Mountain range was formed by an
enormous amount of crustal sheets stacked on top of each other. This would be
due to the shallow angle of the subduction plate, friction and other
interactions, with the thick continental mass that was greatly elevated above
it.
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Attention: On the summit and in other places, there
are unique plants everywhere between the rocks. In order to protect and not damage this and the
special tundra, it is important not to leave the designated paths. In order to
complete the tasks, only the specified places and paths must and may be entered.
Thanks for your understanding.
Log condition:
- Explain in your own words subduction and dip angle.
- When in the Earth's history is the Mesoproterozoic to be considered?
- How is batholith defined?
- What is granodiorite?
- Tarns, how are they created and what is their peculiarity?
- Name at least two of the tarns at Mount Blue Sky, other than Summit Lake.
- Look at the outcrop at the summit. What can be noted, recognized there?
- How does the seam line relate to the summit ridge?
The log includes a picture of you, your GPS or mascot in the area at the summit.
Sorces:
https://en.wikipedia.org/wiki/Mount_Blue_Sky
https://www.nps.gov/romo/learn/education/upload/Geology-Rocky-Teacher-Guide-Final.pdf
https://www.14ers.com/php14ers/historyview.php?peakid1=10014&peakid2=10038
https://de.wikibrief.org/wiki/Mount_Evans
https://de.wikipedia.org/wiki/Geologie_der_Rocky_Mountains
https://earthathome.org/hoe/sw/rocks-rm/ |