Hidden Cool Rocks

It is very very  rare that I get excited about rocks which I blame on my horrible college geology professor who made the study of geology about as exciting as watching paint dry. However, there are a few rocks I can totally get behind and if you have a chance to see these rocks I would say they are going to be well worth the effort.

Rock #1- The Xenolyth

Back in 2008 I was tasked with teaching and "fun and engaging" program on geology to a group of local 4th grade students. Kill me now was my only thought, but with digital camera in hand I scoped the designated are this program would take place in hoping to find cool things to talk about.Hours later I came back to the office and with my coworker who has a degree in geology we flipped through the pictures to see if I had found anything good. After hearing 'nope" to just about every picture I showed her she grabbed the computer mouse from my hand and started zooming in. "This has potential, but I need to see it up close." After a short drive and a few minutes of walking we arrived at the rock. "Yep, that's what I thought ya found a xyenolyth." she said giving me a high five. She explained that as lava welled up from deep inside the earth pieces of rock that the lava came up through broke off and were carried to the surface in this river of lava. When the lava cooled down the rock chunk was forever sealed inside. The dark square rock being one type of rock while the lighter colored igneous rock is lava that surrounds it. A rock within a rock. For those wishing to view this rock it is along the trail in Rocky Mountain National Park, but sadly I cannot remember the name of the trail.

Rock #2 Stromatolites

If you hike all the way to the end of the Grinell Glacier tail in Glacier National Park you can see the famous stromatolites.  What makes these rocks interesting is they are over 1.5 billion years old and were originally made when Glacier National Park sat under either an ocean or a large lake, but right now scientists are not sure which it was because noone has been able to find any fossils. these circular rock formations that I'm sitting on was made by cyanobacteria (blue green algae) which trapped sediments on their sticky coatings. These sediments then reacted to the calcium carbonate in the water to form limestone.  Stomatolytes grow very slowly a three foot tall one could be over 2,000 years old. While these stomatolytes were forming they were living in a time with no other life forms, no plants, no animals in fact there was not enough oxygen to support either life forms.  As the cyanobacteria multiplied and photosynthesized they produced more and more oxygen and over thousands of years were able to start creating the environment that the first primitive plants enjoyed. 

Rock #3- Lewis Overthrust

Also in Glacier National Park you will find the Lewis overthrust an area where you are staring at the oldest rocks laying on top of the younger rocks on the bottom. During the time that the Rocky Mountain Range was forming as two tectonic plates were pushing against each other. Now at the risk of botching up an explanation as to how this structure came to be I will leave that to the experts. See the explanation by clicking here.  

Rock #4-Sedimentary Rocks

On both the Canadian and American sides of Glacier National Park you will find some stunning red rocks and green rocks along with rocks are swirled red and green. These sedimentary rocks were formed with sediments rich in iron oxide. When the water level receded and the sediments were exposed to air the iron oxidized or rusted producing these amazing red sedimentary rocks.  Other sedimentary rocks also rich in iron oxide which spent a greater time under water tend to have a greenish color to them. The iron oxide in these rocks combined with silica and then through pressure and heating were transformed into chlorite the green coloring of the rocks.  In certain areas of the park you can find rock with both read and green stripes which tell shows the water level in that area was constantly fluctuating.

Keep your eyes peeled the next time your outside on a trail or even walking around your neighborhood to see if there are any cool rocks near you.


Want to know more:
https://www.nationalgeographic.org/encyclopedia/xenolith/
https://blogs.agu.org/georneys/2011/05/18/geology-word-of-the-week-x-is-for-xenolith/
http://www.indiana.edu/~geol105b/images/gaia_chapter_10/stromatolites.htm
https://www.nps.gov/parkhistory/online_books/glac/3/sec5.htm