Surrounding you is a lovely selection of rock specimens. Among them, you'll find:
Fossil Palm Leaves
Fifty million years ago, before the Cascades were formed, a giant swampy flood plain and river system covered most of the Pacific Northwest. As time progressed, layers of sediment collected in this expansive riverbank basin and formed the Chuckanut Formation. The Chuckanut Formation consists of 6,000 meters of sedimentary sandstone deposit, the largest formation of its kind in North America.
There is a high volume of fossils of ferns and palms in the Chuckanut Formation since swampy conditions are perfect for forming fossils. (Western Washington Universtiy)
Petrified Logs
When wood becomes petrified, silica gradually replaces the plant cells and ultimately turns them into stone. The Ginkgo Petrified Forest is located in Vantage, Washington where visitors can camp, hike, go boating, and see CCC-built interpretive spaces with unique Ginkgo specimens (Washington State Parks, 2015)
Sandstone
Very common in Washington State, sandstone is a sedimentary rock made of small rock grains or other sand-sized material being condensed with heat and pressure. Most sandstone is make of quartz or feldspar since those are two of the most common minerals on Earth.
Ropy Lava
Even though the volcanoes currently in Washington State are composite volcanoes, thousands of years ago pahoehoe lava flowed through Washington and there are lava beds people can still visit. If a lot of lava is flowing out of the volcano during the eruption (an eruption with a high effusion rate) `a`a flows tend to form. When the effusion rate is low, a pahoehoe lava flow is more likely. The smooth flowy surface of pahoehoe lava comes from the outer layer of lava cooling before the inner layer so the inside continues to flow while the outside slows. (USGS, 1999)
Glacial Erratic
Any place that had a glacier covering nearby will have glacial erratic, or rocks placed as a glacier receded. These rocks are often identified by scraping marks or groves on the surface, rocks unique to the area and usually dissimilar from other rocks in the area.
Gabbro
Gabbro is a course-grained igneous rock. It is the most common rock in deep oceanic crust. Gabbro can be polished to a brilliant black luster. Brightly polished gabbro is used to make cemetery markers, kitchen counter tops, floor tiles, and other dimension stone products. The most common use of gabbro is as a crushed stone or aggregate. Crushed gabbro is used as a base material in construction projects, as a crushed stone for road construction, as railroad ballast and other crushed-stone uses. (Gabbro, 2015)
Quartz
Quartz is the second-most abundant mineral on Earth after feldspar. Quartz comes in many varieties, some of which are semi-precious gemstones.
The Ancient Greeks referred to quartz as κρύσταλλος (krustallos) derived from the Ancient Greek κρύος (kruos) meaning "icy cold", because some philosophers believed the mineral to be a form of supercooled ice. (Tomeieff, 1941)
Breccia
Breccia forms where broken, large fragments of rock or mineral debris accumulate. There are many types of breccia, from flow breccia to igneous breccia to fault breccia to pryroclastic breccia. (Breccia, n.d.)
Actinolite
Actinolite is formed when volcanic rocks on the ocean floor are pushed deeper and changed by heat and pressure. The green color of acctiolite is from the iron in its chemical structure… the more iron, the darker the specimen. Though silky in luster (as opposed to shiny or dull), Actinolite is composed of fibers which it is in the amphibole group of minerals.(Minerals.net, n.d.)
Works Cited
Breccia. (n.d.). Retrieved from geology.com: http://geology.com/rocks/breccia.shtml
Gabbro. (2015). Retrieved from Geology.com: http://geology.com/rocks/gabbro.shtml
Minerals.net. (n.d.). The Mineral Actinolute. Retrieved from Minerals.net: http://www.minerals.net/mineral/actinolite.aspx
Tomeieff, S. M. (1941). On the origin of the name 'quartz'. Mineralogical Magazine, 172-178.
USGS. (1999, May 27). Pahoehoe and `a`a lava flows. Retrieved from Hawaiian Volcano Observatory: http://hvo.wr.usgs.gov/volcanowatch/archive/1999/99_05_27.html
Washington State Parks. (2015). Ginkgo Petrified Forest / Wanapum Recreational Area. Retrieved from http://parks.state.wa.us/288/Ginkgo-Petrified-Forest
Western Washington Universtiy. (n.d.). Geology: The Chuckanut Formation . Retrieved from Sehome Hill Arboretum: http://www.wwu.edu/share/geology.html
To Log this Earthcache:
Please email me the answers to the following questions. If I do not receive answers from you after you have logged your find, I will delete your log, as per EarthCache logging requirements.
(all answers can be found on-location)
1. Do you see any pyrite in the Vein Quartz sample?
2. What color is the Pegmatite dyke in the gabbro?
3. Is the ropey lava sample pahoehoe or 'a'a? Why?
4. How many palm fronds can you count in the sandstone sample?
5. Extra Credit bonus points (and therefore not required for logging): Post a picture of yourself with your favorite rock specimen in the courtyard area.