Rock and Roll

NOTE: This Earth Cache may not be available during times of high water or flooding on the Poudre River. Always be smart around moving water!

Welcome to the Poudre Learning Center! The PLC is a nonprofit InStem education center, hosting more than 36,000 school children on field trips from more than 20 different school districts every year. The PLC is also open to the public for meetings or special events, or to simply take a detour from the adjacent Poudre Trail to enjoy the variety of natural habitats on the site.

Please stay on designated trails, walk and talk quietly, replace whatever you might pick up to investigate, and Be Safe, especially near the water. If children are present, dogs are not allowed. All other times, dogs must be on leash. Please respect these restrictions and help preserve this area for others to enjoy. Remember, take nothing but pictures, leave nothing but footprints.

With this Earth Cache we will be observing an area often used to teach field trip students lessons about rocks. How often do you stop to think about what is right there on the ground under your feet?

You are standing in our own ‘Poudre Canyon’ with the Cache la Poudre River to the north and the fishing lake to the south. The flood of fall 2013 cut out this area and river water flowed into the lake. All the rocks, gravel, and sand were deposited where they are now.

Deposition is the geological process in which sediments — soil and rocks — are added to a landform or land mass. Wind, ice, water, and gravity transport previously weathered surface material, which at the loss of the carrier’s kinetic energy is deposited, building up layers of sediment. Erosion is the geological process in which Earth materials are moved from one location to another.

Most of the rocks that you see in this area are granite, a type of igneous rocks, which are formed from the solidification of molten rock material. Granite is intrusive igneous — rocks that crystalize below Earth’s surface and cool slowly, which allows large crystals to form. These granite rocks you see around you are made of minerals: quartz (white or pink); feldspar (orangey-beige); biotite (brownish mica). The granite here was carried down from the mountains by the river.

The igneous rocks (granite) are broken down into smaller pieces including sand, silt, and clay - they can become sedimentary rocks like sandstone over time (because sand, silt, and clay are sediments). The stone ‘steps’ that lead from the ‘canyon’ to the river are sandstone (that were placed there by humans).

Both igneous and sedimentary rocks can be changed to metamorphic rocks through exposure to extreme heat and pressure, usually while buried below Earth’s surface.

Weathering is the breaking down of rocks to create new materials (sand, silt and clay) that can then be categorized by size:

cobble = rocks the size of a potato

pebble = rocks the size of a golf ball

gravel = rocks the size of a marble

sand = rocks the size of small seeds

silt = vey fine

clay = like dust

TO LOG THIS CACHE:

You must answer the questions below and email me your answers. Do NOT post answers in your log (even if encrypted) or it will be deleted. Logs without verification will also be deleted. Photos are not required, but are encouraged.

Send me a note titled “Rock & Roll EarthCache” and your answers to these questions:

Most of the rock here is what type of rock? Are these rocks jagged or smooth - why?
What 2 geological processes created this ‘canyon’?
Is the floor of the ‘canyon’ different material than the walls?
Consider the various sizes of deposited materials - which sizes do you see? Why does the deposited material in the 'canyon' includes so many sizes?

Additional Waypoints

P08KAXX - parking
N 40° 26.483 W 104° 48.783
free
R08KAXX - turn
N 40° 26.550 W 104° 48.983

R18KAXX - turn
N 40° 26.750 W 104° 48.983

T08KAXX - trailhead
N 40° 26.483 W 104° 48.783
you will follow paths for a walk of a little more than .5 mi one way