Hi Lowell. I thought that since the Rocky Mountains were in your back yard, you could have at least gave a description of them and how they came to be the way they are, and how they are in a consistent state of change. This was taken from the Rocky Mountain National Park page. Take Care…Don in creepy town

Most of the rocks in Rocky Mountain National Park—excluding the newer rocks of the Never Summer Mountains—originally were shale, siltstone, and sandstone, along with some volcanic rocks deposited about 1.8 to 2 billion years ago in an ancient sea. Between 1.7 and 1.6 billion years ago, these sedimentary rocks were caught in a collision zone between sections of the Earth's crust called tectonic plates.

These rocks, then in the core of an ancient Proterozoic mountain range, were recrystallized into metamorphic rocks by enormous heat and pressure resulting from the collision. The shale, which contained mostly clay minerals and some very fine sand and silt, was converted into biotite schist. The layers with more sandstone were converted into biotite gneiss.

Granites found in the park probably resulted from the melting of pre-existing sedimentary or metamorphic rocks 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. We do not know what caused this igneous episode.

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. Little else is known about the geologic events in this area during this time span because no rocks of that age are present in the region.

About 500 million years ago, this relatively flat area became covered with shallow seas. Over the next 200 million years, several hundreds of thousands of feet of Paleozoic sedimentary rocks were deposited on the old Proterozoic surface. During the middle Pennsylvanian Period, yet another mountain range was uplifted in this area. From it the Paleozoic Period sediments were eroded.

Sediments shed from these "ancestral Rocky Mountains" were deposited along the mountain flanks. Today, these make up the Fountain Formation, which comprises the

"Flatirons" west of Boulder, Colorado;
the spectacular walls of Red Rocks Park west of Denver; and
the red rocks in the Garden of the Gods near Colorado Springs.
The Fountain Formation appears as a fairly continuous outcrop along the east edge of the present mountain front.
The area that is now Rocky Mountain National Park was eroded again and intermittently covered by seas from the middle of the Permian Period to the end of the Cretaceous Period about 65 million years ago. Abundant bones and tracks found in sedimentary rocks in the Rocky Mountain region date back to Jurassic and Cretaceous times, indicating that dinosaurs lived here during those periods.

Major tectonic plates of the Earth's crust began to collide along what was then the western edge of North America about 130 million years ago. Uplift caused by this collision began to affect the area of the present Colorado Rockies about 70 million years ago. As the region began to rise, the Cretaceous sea withdrew and the thick layer of sedimentary rocks that had accumulated began to erode. Within a few million years, the sedimentary rocks of the Front Range had eroded away, and the Proterozoic igneous and metamorphic rocks again were exposed to erosion.

As uplift proceeded, deep fault zones formed as enormous stresses pulled the Earth's crust apart at what is now the west side of the park. This allowed granitic magmas to rise into the present area of the Never Summer Mountains. 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.

From the plate collision to the present, rivers and streams have eroded the mountains and transported enormous amounts of sediment to the oceans. By the end of the Tertiary Period, the mountains of Rocky National Park were still fairly high but rounded. The area also was characterized by wide, V-shaped stream valleys.

Then, the Rocky Mountain National Park area saw more drama. About 2 million years ago, Earth's climate cooled and the Ice Age began. Large ice sheets ebbed and flowed across much of the Northern Hemisphere. During several major periods of glaciation—as well as several minor episodes—ice covered much of North America and Europe. The high mountain valleys filled with glaciers.

Rocky Mountain National Park felt the effects of the Ice Age. Glaciation in the park probably started about 1.6 million years ago. Specific evidence of the earliest glaciations doesn't exist because moraines formed by the early glaciers were destroyed by glaciers that followed later. Each time glaciers flowed down the mountain valleys they eroded the valley sides and bottoms, helping to straighten and deepen them, removing evidence of earlier glaciations.

Evidence of the last two major periods of ice accumulation is quite clear, however. The first of these two glacial periods is called the Bull Lake Glaciation. The Bull Lake advance began about 300,000 years ago and ended about 130,000 years ago. A few isolated remnants of moraines from the Bull Lake glaciers can be identified at various places in the park. They indicate that the amount of ice in the valleys then was equal to or greater than ice volume during the most recent period of glaciation.

After the Bull Lake glaciation came a warmer period that lasted about 100,000 years. The last major glacial episode, called the Pinedale Glaciation, began about 30,000 years ago when Earth's climate once again cooled. The Pinedale glaciers reached their maximum extent between 23,500 and 21,000 years ago. Most of the major valleys in the park were filled with glaciers during this time. One of the largest of the park glaciers, with a length of 13 miles (21 km), was in Forest Canyon just south of the high point of today's Trail Ridge Road. The largest glacier, about 20 miles (52 km) long, was the ice flow that occupied the Colorado River Valley on the west side of the park. The ice in many of these glaciers reached thicknesses of 1,000 to 1,500 feet (305 to 457 m).

Between 15,000 and 12,000 years ago, the climate warmed and the glaciers rapidly disappeared. The only glaciers found in the park today occupy locations that receive a large amount of snow blown across the mountain ridges into northeast-facing, shaded cirques where snow melts slowly during summer. None of these glaciers are remnants of Ice Age glaciers.

Some scientists believe that we are living today in a warming interglacial period. But they speculate that climates might cool again, and the glaciers could return.