Dunn's Mountain- Igneous Intrusion EarthCache
Dunn's Mountain- Igneous Intrusion
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Dunn's Mountain offers many geological features. First being the large exposed boulders are the uppermost evidence of the Salisbury Pluton, the largest igneous intrusion in Rowan County NC. Second is the mountain's manmade quarries that has become home to some of natures creatures. The park itself will show off its splendor and beauty made by nature and human hand.
Please see related web page for park hours. An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly cools into a solid, the different parts of the magma crystallize into minerals. Many mountain ranges, such as the Sierra Nevada in California, are formed mostly by intrusive rock, large granite (or related rock) formations. Intrusions are one of the two ways igneous rock can form; the other is extrusive, that is, a volcanic eruption or similar event. Technically speaking, an intrusion is any formation of intrusive igneous rock; rock formed from magma that cools and solidifies within the crust of the planet. In contrast, an extrusion consists of extrusive rock; rock formed above the surface of the crust. Intrusions vary widely, from mountain-range-sized batholiths to thin veinlike fracture fillings of aplite or pegmatite. When exposed by erosion, these cores called batholiths may occupy huge areas of Earth's surface. Large bodies of magma that solidify underground before they reach the surface of the crust are called plutons. Coarse-grained intrusive igneous rocks that form at depth within the earth are called abyssal while those that form near the surface are called hypabyssal. Intrusive structures are often classified according to whether or not they are parallel to the bedding planes or foliation of the country rock: if the intrusion is parallel the body is concordant, otherwise it is discordant. A well-known example of an intrusion is Devils Tower. -------------------------------------------------------------------------------------------------------------------------------------------------- At the posted coordinates is the trailhead. Take your time and take in the many sights that the trail offers. As you proceed up to the top, reference points are provided for areas you need to stop at to collect information for the below questions. To receive credit for the cache. Please send e-mail to me via my profile the answers to the following. 1- Take an elevation reading at the top of the mountain. The viewing center elevation reading is not correct anymore. 2-At reference point 1--You are standing in front of some evidence of the intrusion. a. Describe the sizes and shapes of the rocks. b. From what you observe and read about intrusions, would you say the spaces that the magma moved through was small or large? WHY? ------------------------------------------------------------------------------------------------------------------------------------------------- This is strictly optional and hope all of you enjoy the spectacular view from the top of the mountain. Posting pictures of you and the mountain would be a great way to show others in the geocaching community what they need to come and experience for themselves. SEE UPDATE BELOW!!!! The staff is very friendly and will talk richly in detail of the mountains history and features. I have purchased a number of EARTHCACHE lapel pins.****( NONE LEFT AS IF 4/15/21)**** Each Geocacher that provides the 3 keywords to staff member Bob Peeler will be rewarded one of the pins. Will try to keep them stocked up. Staff will have a logsheet for you to sign to validate that you have already received your pin. The 3 keywords are the answers to the following questions. 1-At reference point 1--The information sign teaches you about the intrusion itself. What Roman god is mentioned for the name for an igneous intrusion? 2-At reference point 2--This information sign speaks of the mountains quarrying. Fill in the blank from the last sentence. These pictures are from circa _____ postcards. 3-At reference point 3--This information sign at the quarry overlook teaches about a type of rock's outcrop and the plant communities that exist on the rock. What type of rock is the outcrop? Update 3/10/2018 ****Note info sign for Reference point 3 is missing but the view shows the old quarry. Clue to answer, rhymes with tan it. ****UPDATE****4/15/2021 RANGER BOB no longer works for the park. He will be deeply missed. Due to this and there not being anymore pins. The bonus is for INFORMATIONAL ONLY!!! Rowan County Parks Permit #16
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