GC1MJ0D Which Way is Up?
Type: Earth | Size: Other | Difficulty: | Terrain:
By: ernie66 @ | Hide Date: 02/09/2009 | Status: Available
Country: United States | State: Colorado
Coordinates: N39° 22.748 W104° 51.386 | Last updated: 08/30/2019 | Fav points: 0
                   

---

This earthcache is located on a ring trail around the base of the rock outcrop on top of Castle Rock. Walk 6/10 mile up the John Emerson Summit Trail. Elevation gain is approximately 300 feet.

---

Begin at the Rock Park parking lot at N39 22.900 W104 51.466. Please stay on the trails and note that the park is open from 5AM to 11PM.

Castle Rock is an example of Inverted Topography. The rock on top of this mountain was the bottom of a river millions of years ago. Surrounding areas have all been eroded by more than 300 feet while the erosion-resistant top layer of Castle Rock has remained largely unchanged. What used to be the lowest place around is now the highest! At the listed coordinates, look toward the east. You can see several distinct layers of sedimentary rock with different characteristics. The topmost layer is relatively hard while the layer at trail level is very soft. The soft layer is eroding out from under the top layer, leaving an overhang. The large chunks embedded in the sandstones are rhyolite. A volcano near Mt. Princeton erupted about 36.7 million years ago and spread very hot ash over a large area downwind. The ash was so hot that it melted together upon landing and formed a glassy rock called welded tuff. Castle Rock Rhyolite, also called Wall Mountain Tuff, has been found throughout Douglas County, up to 20 feet thick in places. The chunks of rhyolite embedded in the sandstone were not formed there. Rather, they broke loose from outcrops and ended up in the river that deposited the layers that now form Castle Rock.

To log this earthcache, send email with answers to the following questions: 1. Estimate the size of the largest chunk of rhyolite you can see from the listed coordinates. 2. Was the sandstone on top of Castle Rock formed before or after the eruption near Mt. Princeton? 3. Based on the size of the grains in the visible layers, can you conclude anything about the size and speed of the river over the time period it took to lay down these layers? In your log for this cache, include a photo of you and your GPS with the rock in the background. This serves as proof that you actually visited the earthcache location.

Logs without supporting documentation will be deleted!

References http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_127720.htm Park Map http://en.wikipedia.org/wiki/Inverted_topography

Additional Waypoints

PK1MJ0D - Parking Area
N 39° 22.900 W 104° 51.466

05/03/2019 By FORK
We, too, have driven past here many times, but never stopped. Today was the day, and we enjoyed the exercise, and this earth cache once we got to GZ!

03/28/2019 By oz8118
What a nice view and workout to get here. Although I've driven by the rock numerous times, I've never took the time to hike to it until today. It was nice to be outside geocaching on such a beautiful spring day. Thanks for creating this great EarthCache!
Cheers.

03/27/2019 By estes01
Wow! 44 favorites on an earthcache and I can see why. Left the answers up to WingsAndTales (of course) and I'm sure she got an A+ Permission received to qualify for the smiley even though I don't even know what the questions were. I DID take the photo she posted, even though that's not the cache. Thanks for an earthcache I actually didn't mind doing.

03/27/2019 By WingsAndTales
I have been wanting to get up here for years. It was fun to see it up close after seeing it from I-25 so many times. We had a perfect spring day for the hike. Email sent with the answers. TFTC

09/28/2018 By vorlon40
This was a nice hike with a nice geology lesson to boot. Answers emailed. I’m glad the rescue squad folks were there in case I needed any assistance. Thanks for the cache.

07/26/2018 By wcsexton
We stopped and made a decent climb up to the top. There's a lot of interesting stratigraphy in the section that's visible through here

07/20/2018 By LostinDenver
This was a challenge and a combined effort. @intrepiidexplorer sent the answers. I'll attach two is my screenshots showing our location.

07/20/2018 By WindAtMyBack
Found with@LostinDenver and @intrepiidexplorer make sure you turn up the brightness to see Castle Rock in the background

07/20/2018 By intrepiidexplorer
Tftc!! I hope our answers were sufficient :)

05/19/2018 By fearthefish
I had the good fortune to be out caching today with the5millers, MagicCacher and herndonrd on an overcast day in Castle Rock. We decided to go all the way up to the top of the rock since none of us had ever done it before. Along the way we could not resist stopping for your Earthcache. Herndonrd had already done this one so he watched as the rest of us read the description and looked over the area. Travis of the5millers sent in the answers on behalf of all of us and has included a beautiful photo of the two of us at the cache location. Thanks for the fun Earthcache and for your contribution to a great day of caching with good people and herndonrd.