Geological History of Rocky Mountain National Park

Ouzel Lake and Mahana Peak, Rocky Mountain Nat...
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The Rocky Mountain National Park . . . for centuries people have marveled at their rugged beauty, they’ve photographed ’em, climbed’em, hiked ’em, camped in ’em, sung songs about ’em, but how did they get there? What’s the story? Well, to be honest, not one but many geological events have been involved in creating the splendid recipe which became the Rocky Mountain National Park.

  • take hundreds and millions of years of rock formations
  • mix with the repeated uplift of these mountains by the most gigantic of tectonic forces and . . .
  • add millions of years of erosion by ice and water, carving out and sculpting the mountains into how they are today

That’s the recipe which was used to form the Rocky Mountain National Park.

Geological History of the Rocky Mountain National Park

The rocks in the Rocky Mountain National Park started out life as shale, sandstone and siltstone, as well as some volcanic rocks which were deposited around 2 billion years ago (yes, billion, how many noughts is that . . . no, I’m not sure either). Anyway, the rocks in the Never Summer Mountains are a bit newer, but I mean the rest of the rocks in the Rocky Mountain National Park. Anyway, these rocks were all caught up in the collision zone between tectonic plates and huge sections of the Earth’s crust . . . wham, bam, the rocky mountains were born, well, the core of the ancient mountain range anyway . . . they were crystallized by the enormous heat and pressure from the collision. Anyway, over time (millions of years actually) these mountains were eroded and ended up being a pretty flat surface, which (approximately 500 million years ago) was covered with shallow seas. During the next 200 million years or so hundreds of thousands of feet of sedimentary rocks were deposited and then . . . another mountain range was uplifted in the area.  Wow, there’s sure been a lot of eroding and forming, eroding and forming going on . . .

You see, the top of the mountains were the bottom of the sea . . . the landscape is flat / high / flat / high etc. etc.

Rocky Mountain National Park

The area which is now the Rocky Mountain National Park was intermittently eroded and covered by seas around 65 million years ago (you see, it’s getting closer). There have been tons of bones found within the sedimentary rocks dating right back to the Jurassic and Cretaceous times . . . you’ve got it . . . Jurassic . . . dinosaurs lived in the Rocky Mountain National Park during this period.

Rocky Mountain NP - Alluvial Fan

Rocky Mountain NP - Alluvial Fan

Let’s go back in time just a little, to 130 million years ago when the major tectonic plates of the Earth’s crust began colliding again, along what was to become the west side of North America. The uplift which was caused by this began to affect the area which we now know as Colorado Rockies around 70 million years ago. The area began to rise, and the Cretaceous sea withdrew, so that the thick layer of sedimentary rocks which had been accumulated beneath the sea began to erode. All this took just a few million years, by which time the sedimentary rocks had completely eroded away once again exposing the igneous and metamorphic rocks of the region.

Simplification, that’s a great buzz word and just what we needed, an idiots guide to mountain building!

Glaciers in the Rocky Mountain National Park

Okay, let’s skip forward a few million years (it doesn’t sound like a long time if you say it quick) to two million years ago, when the climate of the Earth cooled and the Ice Age arrived (not the animated movie, the real Ice Age). During this time large sheets of ice floated around large areas of the Northern Hemisphere, and much of North America and Europe was covered by ice. The valleys between the high mountains became glaciers, probably around 1.6 million years ago, and each time a glacier flowed down between the valleys the valley sides and bottom were eroded, each glacier removing evidence of the one which moved before it.

The climate started to warm (where have I heard that before) around 12,000 to 15,000 years ago and the glaciers melted and disappeared. The glaciers which are still present in the Rocky Mountain National Park are nothing to do with the Ice Age, they’re only found in locations which receive large amounts of snow blowing across the mountain faces which melts only very slowly throughout the summer.

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