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THE STORY OF A ROCK it was a late summer day and I was with my wife and older brother. We decided to drive up Farmington canyon and look around a bit at the geology of the canyon before we went home. We had just come from the dinosaur park at Ogden, Utah were we had spent the last four hours studying geology in the musuem and taking pictures of life size dinosaur models outside and touring the dinosaur exibits in the museum. Both the park and the museum are great places to learn about life and the earth’s history 200 million years ago. I have always been interested in rocks, gems, mineral, fossil collecting and geology. My parents used to take us on trips and even when I was five years old to collect rocks. I didn't know it then but I had a keen interest in geology even then.
As we drove up Farmington canyon the geology of the canyon was spectacular. we passed the old beach shore line of Lake Bonneville an ancient lake that filled most of north western Utah about 20,000 thousand years ago and more. The old beach shore line was a level broad line cut into the mountains by wave action. The water stayed at this level for thousands of years and made a line around all of the mountains surrounding the lake sorta like the bath tub ring you get when you take a bath. this is relatively speaking recent geology on the geologic time scale of earth. We soon came to the mouth of the canyon and began to see huge boulders and rock slides and the solid rock formations of the canyon. The stream was below us and still cutting down and into the canyon walls as it had been for millions of years. The rock was mostly grey with some white and black bands in it. The bands were swirled and contorted and very different. These rocks were some of the oldest rocks found in the state of Utah. The canyon and the geology are a geologists dream and every where you looked a thousand stories could be told concerning the earths history. I have a saying “only the rocks know the story” and I believe this to be true! There was gneiss and schist, migmatite and quartzite and all these rocks were metamorphic rocks that is to say rocks that have been changed by heat and pressure and have laid buried 10 miles beneath the earth’s surface for over 1.7 to 2.0 billion years. To get a perspective on time and how long that is. You would have to live 2,666,666 life times if you were to live to the ripe old age of 75 years.
Gneiss is a rock most commonly formed from the parent rock granite which is an igneous intrusive rock that has cooled and crystallized under ground. Schist are most of the time formed from the parent rock shale which is a sedimentary rock and which in turn is formed from clays and or mud’s schist can form from other types of rocks as well. Migmatite is the same as gneiss except it has been under even more heat and pressure to the point it has become partly melted warped and distorted into wavy bands both dark and light colored. Quartzite was originally sandstone a sedimentary rock that usually forms in beaches or sand dunes and was partly melted by heat and pressure. The heat and pressure occurs deep beneath the earth’s surface.
We drove up the canyon a little further and parked the car the geology got even better. here there were huge boulders larger than a house down towards the stream. These boulders were balanced so precarious that during a medium size earth quake they will probably roll down into the stream below and block the flow of the steam creating a small lake up stream and in the process flood the houses below the canyon.
I got out of the car to look around and crossed the road to view some interesting rock out crops. This was the migmatite discussed earlier. As I looked down I saw a very interesting rock laying on the ground it was angular on one side and rounded and worn on the other side which told me two things first it had weathered out of the canyon wall some where up stream, traveled down steam by being worn down by being caught up in a glacier or was worn as it traveled down stream tumbling as it went or both till it came to rest near were I picked it up it was then crushed and broken by falling down the canyon wall. The rock is composed of coursed grained metamorphosed quartzite and rock pebbles 1.5 inches in size down to course sand grains which makes it a metamorphosed conglomerate which now has its own stories to tell. (See sedimentary rocks below) Each rock is cycled through the rock cycle at least once and some times more. When hunting for rocks, gems, minerals or fossils its good to know the rock cycle and the geology and how rocks, gems, minerals, fossils are formed.
Three types of rock make up the crust of the earth they are metamorphic rocks the type discussed earlier , igneous rocks (fire formed) formed ether beneath the earths surface are igneous intrusive such as granite, and the like. Then there are the volcanic rocks igneous extrusive such As lava usually takes the form of basalt. like most of the rock found around the volcanoes in Hawaii. When you are searching for rock, gems, minerals, fossils it’s good to know the geology of the area and the environment that they will be found in. for example gems the more expensive gems are usually associated with ether igneous or metamorphic rock but can be formed in sedimentary rock as well.
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