A hydrological divide is a boundary between two drainage basins or watersheds. The Continental Divide runs along the crest of the Rocky Mountains. These mountains are lower than those to the south, reaching heights of around meters 12, feet.
These ranges formed as a result of the uplift and erosion of the Idaho Batholith, a mass of granitic plutons that formed during the Cretaceous when the oceanic Farallon plate subducted beneath the west coast of North America.
The batholith , which underlies about 39, square kilometers 15, square miles of central Idaho Figure 4. These mountains are formed of granite from the Idaho Batholith. The Northern Rocky Mountains of Montana are also home to the Cordilleran fold-and-thrust belt, an area of deformed rock created by crustal compression during the collision of the oceanic Farallon plate with the North American plate.
Blocks of older rock were thrust forward on top of younger strata, resulting in the Lewis Overthrust, a kilometer-long mile-long overthrust fault that extends from central Montana into southern Alberta, Canada.
Glacier National Park in northern Montana contains many outcrops related to this fault belt, including the meter-high foot-high Chief Mountain Figure 4. The surrounding thrust sheet has been eroded, leaving behind the mountain as an isolated block. The Wasatch and Teton mountains were uplifted during the Cenozoic as a result of faulting, possibly due to processes related to extension in the Basin and Range region.
Both ranges stretch in a north-south direction, and both border the Basin and Range: the Tetons stretch along the border of Wyoming and Idaho, and the Wasatch Range extends from the southeastern edge of Idaho down through Utah. The Wasatch Mountains called the Bear River Mountains where they enter Idaho formed from Cretaceous thrust faulting and the erosion of granitic batholiths followed by more recent uplift.
The Teton Mountains are the youngest range in the Rockies, formed as the rocks along one side of a normal fault were uplifted due to crustal extension between nine and six million years ago. Rocks along the other side of the fault were downdropped, creating a valley that is today known as Jackson Hole. Thanks to the fault at the base of the range, the Tetons lack foothills on their eastern side, and rise sharply up to meters feet above the valley floor.
See Region 5: Basin and Range later in this chapter to learn more about the unique processes that formed its topography.
The Bighorn and Wind River mountains both have Precambrian rocks at their cores, with overlying Paleozoic and Mesozoic sedimentary rocks that were uplifted and exposed during the Cretaceous. The Wind River Mountains, formed by Mesozoic-Cenozoic thrust faulting, are the highest mountains in Wyoming with 40 peaks standing over meters 13, feet high.
The creation of Rocky Mountain National Park has been over a billion years in the making! Shortly after that, relatively speaking, at 1. This caused regional metamorphism and created the basement igneous and metamorphic rocks found within the park. During the Paleozoic era Ma , inland seas covered much of present-day North, depositing thick layers of marine sediments that would later turn into sandstone and limestone. At about million years ago, a mountain building processes raised the ancient Rocky Mountains.
This ancient mountain range was much smaller than the modern Rockies, only reaching up to 2, feet high and stretching from Boulder to Steamboat Springs, Colorado. Over the next couple hundred million years the ancient Rockies eroded away, leaving behind sediment and a much less rugged landscape. This flooding left behind large amounts of sedimentary deposits, like the Pierre Shale and Fox Hills Formation sandstone.
Starting 75 million years ago and continuing through the Cenozoic era This process uplifted the modern Rocky Mountains, and was soon followed by extensive volcanism ash falls, and mudflows, which left behind igneous rocks in the Never Summer Range.
Another period of uplift and erosion during the Tertiary period raised the Rockies to their present height and removed significant amounts of sedimentary deposits and revealing the much older basement rocks. Over the last , years there were two major periods of glaciation: The Bull Lake Glaciation period occurred from ,, and the Pinedale Glaciation Period occurred from 30,, years ago.
Glaciation is one of the strongest erosional forces on the planet and is responsible for shaping Rocky Mountain National Park as it is today. In the last , years, there have been at least 6 major glaciation events, with the two most recent Bull Lake and Pinedale causing the most easily noticeable alterations to the landscape.
Glaciers are massive amounts of ice and snow over land that form in places where more snow accumulates the accumulation zone in an area during winter than is lost during the summer the ablation zone. Glacial erosion is very strong because the massive ice blocks apply a formidable downward force on the rocks beneath them - enough to carve, crack, and push rocks of any size down the mountain collectively known as till.
Ripped up rocks can be picked up and incorporated into the ice and can travel along for the ride within the glacier, scraping lines striations into the bedrock as the glaciers travel across the land and leaving behind evidence of the direction the glaciers dragged them along.
Rocky Mountain National Park is defined by its many broad U-shaped valleys instead of steep V-shaped valleys which come from rivers and streams carving out steep canyons. At the edges and end of these valleys are depositional features called moraines lateral moraines along the sides of the glacier and terminal at the end of the glacier which are the dumping grounds of glaciers, composed of rocks of various sizes and glacial flour that were once trapped in the ice.
Each summer month typically has the most precipitation in the form of rain, recieving around 50mm of rainfall in each month. Many find that the hot temperatures are made more bearable by the dry climate.
Plants and Animals: The Rocky Mountains can be a difficult region to inhabit, with the climate and the elevation, but regardless there are lots of animals—large or small, mammals or birds, herbivores or carnivores.
On a hike it is common to see some smaller animals like squirrels and chipmunks. However, on a quieter routes or during specific times of year there is also a good chance you might come across a black bear. Spotting a grizzly bear is less likely, but still possible especially if you're roaming a less densely forested area.
Cougars also known as Mountain Lions are very rare predators to see and probably one of the most dangerous in the Rockies. In the spring and early summer seasons the Rockies are full of wonderful wildflowers.
The wild rose also Alberta's provincial flower is abundant in the mountain ranges. The crimson paintbrush has brilliant red petals filled with a sweet nectar, that even humans can get to. Bluebells, Canadian goldenrods, oregon grapes, and western wood lilies also add splashes of color to the trails of the Rocky Mountains.
At the southern point of the rockies the tree line is at it's highest elevation of 3, meters. However, due to the presence of more basins and plateaus in the mountain ranges of the USA Rockies, there tend to be less trees except around streams. Human Presence: Human establishment in the Rockies has exhisted far back into history. Indigenous groups of the Rockies have managed to inhabit the harsh climate and steep elevation of the Rockies for years.
The Stoney or Nakoda tribe in the Canadian Rockies is a very well known tribe with rich culture. The Nakoda tribe even helped to establish outdoor camps so that children could experience the Rockies in a natural sense.
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