Partly Plain

The National Park Service charges a fee to enter the park:

Automobile - $20 and valid for seven consecutive days, including the date of purchase
Pedestrians, bicycles, motorcycles and mopeds - $10 per person, not to exceed $20 per vehicle. Valid for seven days including the date of purchase

A Rocky Mountain National Park Annual Pass or America the Beautiful Pass will cover the entrance fees.
You can find out more about entrance fees for Rocky Mountain National Park here.

Remember that this is a national park. The natural and historic features of the park are protected by law. Please do not alter or remove any natural or historical feature. Also be sure to not travel off the trail. Step on rocks without plant life to minimize tundra impact.

“Take only pictures (and smilies ), leave only footprints.”

The easiest route to this earthcache starts from Bear Lake and is 5.2 miles (10.4 miles roundtrip) with an elevation gain of 3230 feet. The average grade to Hallett Peak is 14.1%. The trail is maintained, well defined hardpack up to Flattop Mountain. An 0.6 mi unmaintained trail continues to Hallett Peak. The unmaintained trail is very rocky and unstable. Minor scrambling may be required.

Depending on your fitness, the climb should take you about 6 to 7 hours. Bring lots of water and be prepared for thin air. The climb should not be attempted for those who are out of shape. Lightning strikes are also common so check the weather before you climb and turn back at any signs of danger. Learn more about safety here.

Parking is located at Bear Lake but is usually filled by morning during peak season. You can also park at a shuttle bus parking lot and ride a shuttle bus to Bear Lake. Public restrooms are located at Bear Lake.

Many cycles take place and have taken place in Rocky Mountain National Park. This earthcache describes many but not all of the cycles that occur in the park.

Peneplain
Along the crest of the highest peaks in Rocky Mountain National Park, there are numerous flat or gently rolling surfaces that seem to be the remnants of an ancient peneplain. In theory, a peneplain occurs when a land is shaped by fluvial erosion until it reaches a point in which it cannot be flattened anymore.

Late Cretaceous Uplift
The Rocky Mountains began to form during the late Cretaceous Period. During a slow but extensive period of uplift, the Rockies rose from the Western Interior Seaway to an elevation of nearly 30,000 ft. The range took the form of a great fold or arch which had a core of Pre-Cambrian schists and granites. In addition, thousands of feet of sedimentary beds (deposited at the bottom of the sea) blanketed the arch.

Flattop Cycle
In the period that followed the uplift, nearly 2 miles of sedimentary layers were eroded away from the top of the fold by streams. In the upper sections of the range, the sedimentary layer had been worn to the core. The exposed schists and granites were bordered by the remaining sedimentary layers which were left dipping away from the axis of erosion.

All of the erosion resulted in the formation of a rolling plain with low rounded mountains. The disintegrated sedimentary beds of clay and sand that had been eroded from the great fold was carried by streams and deposited east of the range. The layer of deposited sediments forms part of the rocks which compose the Great Plains today.

The large expanse of gently rolling land has become known as the Flattop Peneplain. The isolated low rounded mountains that rise a few hundred feet above the peneplain such as Hallett Peak represent some of the higher peaks of the range today. These peaks are known as monadnocks which means- isolated hill or mountain. Although the summits of the low rounded mountains are at about the same elevation above the peneplain as millions of years ago, it is possible that some of these peaks may have been altered in height after the formation of the peneplain due to frequent faulting and uplift up to the present. For example, Long’s Peak is nearly 2,000 ft above the average elevation of the Flattop Peneplain. Longs Peak’s large flat summit is considered by some to be part of the Flattop Peneplain. Assuming it’s part of the Flattop Peneplain, Longs Peak could have been a rather tall monadnock on the peneplain but it is more likely that Longs Peak was raised from its original elevation by an uplift. It is also possible that Longs Peak is not part of the Flattop Peneplain. Its unusually high elevation may hint that it is from peneplain older than the Flattop Peneplain.

Angular biotite schist fragments line the tundra environment of Flattop Mountain and Hallett Peak. Courtesy of USGS

Canyon Cycle
In the early part of the canyon cutting cycle, streams on the peneplain reacted to another stage of uplift by carving into the peneplain. Canyons were formed and took the V-shaped characteristics of a gorge carved by a stream. Later in the cycle, glaciers replaced the streams during two periods of glaciation. Many of the canyons replaced the V-shape with the U-shaped characteristic of glacial erosion. The widespread glaciers during the periods of glaciation dramatically shaped the peneplain. Wide valleys and canyons caused by glaciation have dissected the peneplain. The canyon cutting cycle continues to the present. Today, agents of erosion such as creeks still erode the valleys and canyons.

Freeze Thaw Cycle
Freeze thaw cycles over thousands of years have pushed up the angular fragments of rock on Flattop Mountain and Hallett Peak

LOGGING REQUIREMENT
On order to log a find, send me an email with the required answers to the following questions via my profile link. Use the information in the listing and your onsite observations to answer the questions to your best ability. Happy caching!

Flattop Mountain Waypoint: Name one agent of erosion you see in Tyndall Gorge. (Wind, water, etc.)
Do you think Longs Peak is part of the Flattop Peneplain? Why or why not?
Hallett Peak Waypoint: Based on the shape of Tyndall Gorge, was the gorge carved by an ancestor of Tyndall Glacier or Tyndall Creek? Was Chaos canyon carved by ice or by water?
Hallett Peak Waypoint: What is the width of Tyndall Gorge? Use the Flattop Mountain Waypoint as a reference point. (The width is your distance from Flattop Mountain)
Pictures are most welcome!

Congratulations Denali41 for FTF!

Credit:

Lee, Willis. "Cycles of Erosion in The Rocky Mountain National Park." Peneplains of the Front Range and Rocky Mountain National Park, Colorado GEOLOGICAL SURVEY BULLETIN 730—A: 1-17. Print.

Thanks to Rocky Mountain National Park for allowing the placement of this Earthcache. I have earned GSA's highest level:

Additional Waypoints

BL56Y4M - Bear Lake Trailhead
N 40° 18.717 W 105° 38.739

FM56Y4M - Flattop Mountain
N 40° 18.534 W 105° 41.412

HP56Y4M - Hallett Peak
N 40° 18.161 W 105° 41.151