GCZJQC A Day at the Beach
Type: Earth | Size: Other | Difficulty: | Terrain:
By: Eagle1977 @ | Hide Date: 11/27/2006 | Status: Available
Country: United States | State: Colorado
Coordinates: N37° 41.614 W105° 32.876 | Last updated: 08/30/2019 | Fav points: 63

---

IMPORTANT NECESSARY LOGGING REQUIREMENTS ARE AT THE END OF THE DESCRIPTION!

During the Paleozoic Era, over 500 million years ago, shallow seas and river systems deposited sedimentary materials throughout the region. The Sangre de Cristo mountain range east of the dunes is composed of Paleozoic rocks as well as metamorphic rocks from the much older Precambrian period. Eons later, pressures from within the Earth pushed the landscape high above sea level, limiting sedimentary deposition and leaving a gap in the region's Mesozoic record.

Around 40 million years ago, an arid landscape dominated where rivers and intermittent lakes emerged and subsided upon the land. Evidence of this period are found in the silts, clays, sands, and gravels of the early-Tertiary Blanco Basin Formation. Recurring lava flows poured onto the landscape about 34 million years ago from volcanic vents in the San Juan mountains, creating a subsurface layer that geologists call the Conejos Formation.
After the San Juan Mountain lava flows subsided, volcanic activity continued and for four million years ash flows blanketed the earlier lavas of the Conejos Formation. These ash-flow tuffs are visible on the west side of the Sand Luis Valley. Rapid uplift of the Sangre de Cristo Mountains began about 19 million years ago. Rifting associated with the uplift widened the valley and caused its floor to drop significantly. (This process continues today.) Water-born and eolian sediments were deposited in the subsiding San Luis Valley, creating the Santa Fe Formation.

Around five million years ago, a new series of volcanic activity rocked the region, at times damming rivers that flowed out of the southern half of the San Luis basin. The Alamosa Formation formed during this time, made of lake, river, marsh sediments and wind-deposited layers of clay, sands and silts. Locally known as the "blue clay layer," the Alamosa Formation is a confining layer between aquifers found under the valley floor.

The Pleistocene began 1.8 million years ago as climate changed globally. Glaciers grew in mountain valleys, some pouring ice and rock far into the San Luis Valley. Many scientists consider the Pleistocene to be the period in which dune formation began in the San Luis Valley. Cooler temperatures also caused the Earth's oceans to contract, creating, land bridges that permitted a worldwide diaspora of animals between North America and Asia.

Only about 12,000 years ago, a warming climate melted many glaciers worldwide and signaled the end of the Pleistocene. Large quantities of silt, gravel and sand were carried by rivers and streams into the San Luis Valley. Although the dunes existed long before the Pleistocene ended, glacial outwash materials provided new sources of sand for winds to rework into even greater sand dunes. Today, the rivers and creeks continue to transport sediment into playa lake systems which are sources of sediment for dune-forming winds of the San Luis Valley.

TO LOG (2 Parts)
The cache coordinates will lead you to the entrance of the park. From there, you will have to explore to discover the answer to the cache validation question. Throughout the Dunes are patches of black sand.
1) Email me with the name of these sands and research what they are. Also describe it's consistency as compared to the "normal" sand of this location.
2) Please take a picture of you/your team with GPSr in hand with the location in the background.

NB: Often it is requested in situations like this to email the cache owner prior to logging the cache. If an email with the answer is not received within one week of the log, the find will be deleted. There have been several logs posted without answers so I must resort to this action against my best wishes. E77

10/13/2018 By Jazzeykat
Found with Wyochiver on my first trip to see and hike the sand dunes. TFTC

10/13/2018 By Wyochiver
Found with Jazzeykat on our way to the park to hike on the dunes. Answers sent via email.
Thanks for the fun earth cache.

10/08/2018 By wesser26
This was interesting. My picture is from another spot thanks for a interesting earthcache

09/19/2018 By rhodorooter
TFTC. My wife and I decided to check out Great Sand Dunes National Park on our way back to NC. Excellent Earthcache, have posted photo and sent CO answers to questions.

08/12/2018 By YankaBucs
Picking up this EC while visiting Great Sand Dunes National Park. Answers have been sent, Thanks for the EC.
GCZJQC

08/10/2018 By CyBen82
Decided to swing by this interesting National Park on our way home to Iowa from our family vacation. Very neat location! TFTC
Photo

08/10/2018 By Abby the Explorer
My answers have been sent. We did notice the black sand and now I know what it is! Thanks for the fun earthcache!
Photo

08/06/2018 By HarvestMoon2
Took a trip to the Sand Dunes to grab a few caches. Had a great day and great time! Thanks to all the COs for placing these for us to find! Signed log HM2 Answers and photos being sent by FWIA

08/05/2018 By Izzifix
Even if I have a bad cold, I wanted to visit the Sand Dunes during my stay in Colorado. We started very early in the morning to be at time at the National Park. Good decision, bc shortly after the Lunch break the rain and thunderstorms were hitting the area. It is always great to see such a interesting geological place! Thanks for this Earthcache! Favorite point! FWIA sent the answers for Harvestmoon2 and me. Best regards, Izzifix

08/05/2018 By FWIA
Ah yes, back in beautiful Colorado with Izzifix & Harvestmoon2 for family time.

Today was our day to visit The Great Sand Dunes National Park. We got a couple of Earthcaches and a Virtual but decided hiking to the High Dune was not for us today. We still enjoyed the beauty and geology here.

Stopped for a few more caches on the way back to Olney Springs, driving through wind, rain and hail. We were even lucky enough to grab an FTF on a cache published 3 months ago. Very exciting day indeed.

Thanks to all the CO’s for placing the caches we enjoyed hunting. Much
appreciated.

Email to follow shortly by FWIA.
Photo

Photo

08/01/2018 By jeremeh
We came in late at night on the way home from a backpacking trek near Creede. In the morning we came out to the dunes and looked around for a bit but had to get on the road. I had been here once before as a kid and it is still just as awesome as I remembered. If you happen to go into Alamosa you should have a burger at The Rubi Slipper. I had the “Mizer” and it was probably one of the best burgers I’d ever had. Thanks for the cache.
GCZJQC

07/24/2018 By jasperdakota
Thanks for the earthcache! We're camping in the Sand Dunes for a couple of days.
Norbert28 at the Sand Dunes

07/23/2018 By Blestmomof6
Took my grandson to see the Great Sand Dunes National Park and Preserve and wanted to grab some of the earthcaches while there. I sent answers to the CO. Sadly the stream was dry this visit, but we did climb some of the lower sand dunes, and he rolled down one while I video'd him at a distance. I certainly got my workout! TFTC
Photo

Photo

07/06/2018 By toolrep1
My family and I visited the Sand Dunes while on vacation in Colorado from Chicago. We have smaller dunes in Northwest Indiana, but nothing like this...Very impressive. Here's a picture and email sent-TFTEC!
Photo

Photo