Goal
Build community with peers
Learn with your peers
Initial Post (13pnts)
In your initial post, share with us your answers to the following questions:
What is the main difference between igneous rocks, metamorphic rocks, and sedimentary rocks? (2pnts)
Go to the website Alltrails (Links to an external site.) and explore your favorite trail(s) across the country, Share with us the trail location you choose: ________(1pnt)
You must have been curious about the various rocks encountered along the trail – what are they? Let’s look them up on geologic maps (Links to an external site.), which represent the distribution of different types of rock and surficial deposits, as well as locations of geologic structures such as faults and folds. We can find their ages and listen to their stories!
USGS (US Geologic Survey) has a comprehensive data base of geologic maps (i.e. USGS Geologic Map Database (https://ngmdb.usgs.gov/ngmdb/ngmdb_home.html)). It also provides a map view (https://ngmdb.usgs.gov/mapview/?center=-97,39.6&zoom=4) to find the specific map of your trails. So go to the map view website (https://ngmdb.usgs.gov/mapview/?center=-97,39.6&zoom=4) (https://ngmdb.usgs.gov/mapview/?center=-97,39.6&zoom=4 (https://ngmdb.usgs.gov/mapview/?center=-97,39.6&zoom=4) and zoom in to your trail area. For example, the screenshot picture below shows you my hiking trail Switzer Falls in Angeles National Forest (https://www.alltrails.com/trail/us/california/switzer-falls-via-gabrielino-trail?u=i).
Click on More Info on the left panel, scroll down a little and click on the image of “Map Preview” (see the screenshot below) to enlarge the image. (Note to writer: for all picture example images look in files they will all be there for very picture example I mentioned in the instructions).
Pan around the map, compare the map with google map of your trail on AllTrails.com to locate your trail on map. For example, my trail is just a little offset of Hwy 2 and I found it located in the section 16 on the geologic map (see below).
The letter labels you see on the map are the labels of rocks, which should be called “Geologic Unit Labels”. Please go to this website (https://www.maine.gov/dacf/mgs/pubs/mapuse/bedrock/bed-read.htm#:~:text=What%20do%20the%20geologic%20unit,%22%20or%20%22member%22%20name.) to learn how to read them. Record the Geologic Unit Labels in your hiking area: ________________(2 pnts).
On the right of the map, you can find your labels on the geologic time scale, and more detailed information about the rocks. See the screenshot below:
Share with us:
What are the TYPES of rocks in your hiking area? Are they igneous, metamorphic, or igneous (or, all of them are found in your area)? (2pnts)
Sort the ages of the rocks in your hiking area from older ones to younger ones; and when were they formed? (2pnts)
Write up the rock formation processes in your hiking area with your own words (DO NOT GOOGLE IT). You will need to refer to the three basic rock formation processes (i.e. igneous, metamorphic and sedimentary) you have learn in this module. (4pnts)
for example, the geologic units in Switzer Falls hiking area are “grd” and “hdg”. I located them on the right geologic time scale and learned that “grd” is granite (a type of igneous rock) and “hdg” is grabro (a type of igneous rock). I also learned that “hdg” is older and “grd” is younger since “grd” is found on top of “hdg”. They were both formed in the Mesozoic Era when dinosaurs were governing the Earth (251-65 millions of years ago)! Amazing!!!
Reply to Peers
Browse the posts of ONE of your GROUPMATES and read his/her observations and explanation. Reply by reflecting:
Do you agree or disagree his/her interpretation of the rock formation processes in the initial post? Why or why not? Point out other mistakes you have spotted in the initial post, if any. (2pnts)
***** NOTE TO WRITER: I WILL YOU ONE OF MY CLASSMATES INTITAL POST FOR YOU RESPOND TOO*****
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