Alejandro HW 4 Geology
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Rowan University *
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Geology
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Apr 3, 2024
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GEOL 01.101 | Physical Geology | Rowan University Let’s take a virtual field trip! Our home state of New Jersey has a fascinating geologic history and some really cool rocks and landforms. Rich Volkert and Ron Witte of the NJGS will guide us on a journey through more than 1 billion years of tectonic activity, deformation, weathering, erosion and deposition, and economic exploitation. https://www.njgeology.org/enviroed/freedwn/HighlandsVFT.pdf
The document above is 100 pages long. Please save a tree and DO NOT print the whole thing out, but feel
free to download it and save to your computer, flashdrive, or cloud file system of choice. Answer the following questions based on your understanding from class, your textbook, labs, and your “field” experience. There is no need to consult outside sources for this assignment. The questions will point you to both the explanatory text and to the field locations that exemplify each topic. Enjoy your trip! 1. First thing’s first. Take a look at the Index Maps and read the Introduction and Highlands Origin sections on pages 2-9. A) Where are the Highlands in relation to Rowan? B) What physiographic province are we in here in Glassboro? C) Why do you think the Highlands are called that? D) What makes the Highlands region of NJ unique? E) Where else in North America do we find rocks that are similar to the ones we find in the NJ Highlands?
a)
In New Jersey, the highlands are north and in Pennsylvania lie west of Rowan.
b)
Coastal Plain
c)
Because it is mountainous.
d)
It is the oldest part of New Jersey.
e)
In Virginia and Vermont
2. Next, go to the last page and take a look at the chart that illustrates geologic time. What are the four Eras geologists use to describe the periods of Earth’s past? List them below, along with their
time spans, in order from youngest to oldest. In the third column, list 1-2 life forms that appeared during each era. Finally, in column 4, write down 1 geologic process or event that occurred during each era that affected the rocks we see in the Highlands today.
Era Years ago (Ma) Evolution of Life Geologic Events
Proterozoic era (precambrian)
1,000 Ma
First soft-bodied invertebrates and colonial algae.
Collision between north and south American plates formed mountains and
produces supercontinent Rodinia.
Paleozoic Era
550-365 Ma
All phyla exist today Large erosional gap
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are developed - great mass extinction
forming limestone and dolomite deposits.
Further collisions make more mountains,
Mesozoic Era
230-67 Ma
Dinosaurs - meteor extinction leading to flowering plants.
Pangea breakup has begun.
Developed Atlantic Ocean basin.
Cenozoic Era
67-2 Ma
Mammals and birds -
humans
Lots of weathering and erosion.
Glaciation wears down hills and slopes from highlands.
3. What is the age of the oldest rocks in the Highlands? What is the age of the youngest rocks? Why are there no rocks of Mesozoic age that appear in the Highlands? The oldest rocks are 1,300 Ma years old and the youngest rocks are 960 Ma years old.Existential stresses from rifting resulted in the down-dropping of crustal blocks in the highland faults.
4. Look at the picture on p. 40. Diabase is an igneous rock texturally between gabbro and basalt. How do we know that the lighter rocks around the dike are older? What would the dark-colored
feature be called if it were horizontal rather than vertical? Because when a dike cuts through rock that is an indication that magma has crept up and solidified forming the dike.If the intrusion was horizontal it would be called a sill.
5. The picture on p. 43 shows two different rock types. Explain what the contact between them is called and what it means. The contact between these rocks is known as an unconformity. It represents an erosional gap of more than 500Ma. The sandstone dips down a little to the right, indicative of it being older than
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the gneiss.
6. Based on your reading on pp. 10-11, what are the four main types of rocks found in the Highlands? Which are the two most common types, and what are their approximate ages? The four main types of rocks in the highland are quartzite, marble, granite, and gneiss.One of
the most common types is granite that makes up 50% of the highlands with Byram granite being an ample amount of the granite. Another common rock is Gneiss making up 45% of the highlands.
7. What minerals make up the igneous rocks in question 6? [see pp. 54-56] The minerals that make up the Igneous rock in the previous question are as stated: Pyroxene, feldspar, quartz, biotite, and hornblende.
8. What is the banding called in the metamorphic rocks in question 6? What causes this? [see pp. 53,57-61] The banding is called foliation.
9. Based on your reading on pp. 12-13, what is the most seismically active fault in NJ? When did this fault first form? [see pp. 62-65] The Ramapo fault is the most seisemically active fault in the region. This fault first formed during the late Proterozoic and Mesozoic eras.
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10. During which two time periods did folding occur in the Highlands rocks? What, besides their ages, is the difference between these two episodes of folding? [see pp. 66-68] Most folds occurred about 1,000 Ma years ago in the Precambrian era and commonly featured in the paleozoic era as well. As opposed to the precambrian era, Paleozoic folds formed at a much lower temperature.
11. Pp. 14-17 discuss the role of mining in the NJ Highlands. What are two minerals that have historically been sourced from this area? When were the mines for these minerals active? [see
pp.68-89]
Iron and Zinc have been sourced from the highlands historically. These mines were active as early as 1665 for iron and stopped around 1996 while the mining for zinc lasted from 1770 to 1954.
12. Franklinite is a zinc ore that is named after the town in NJ where it was first described. What else is unusual about some of the zinc-containing minerals found in NJ? [see pp. 74-78] The zinc found in these deposits are like no other in the entire world. These mines are unusual because they have produced 360 mineral species with 33 being indigenous to New Jersey.
13. Head to pp. 18-19. Stromatolites are some of the oldest known fossils in the world, and they were discovered in the NJ Highlands in 1999. What do they tell us? What other signs of life exist in these 1.3 billion-year-old rocks? [see pp. 46,90] The presence of stromatolites are indicative of microbial organisms living on these rocks and tell us there was life 1,300 Ma years ago in the ancient precambrian sea.
14. The modern landscape of the Highlands is very much influenced by glaciation, as discussed on pp. 20-24. Three separate ice sheets left their marks on the area – what were these periods called,
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and when did they happen? Pleistocene Glaciation (1.8 to 0.8 Ma), Pliocene Glaciation (2.5 to 1.8 Ma), Wisconsinan Glaciation (0.021 Ma).
15. Glaciers have extraordinary power to change the landscape. They scour and shape underlying rocks, move huge amounts of sediment and loose material vast distances, and deposit those materials as the ice melts and retreats. What can striations tell us about the movement of a glacier? [see pp. 92,95] Striations tell us the direction that the glacier flowed.
16. Look at the pictures on pp. 93-94. What are these boulders called, and how did they get there? These boulders are called tripod rocks and form when a larger erratic settles on top of small boulders making a base to support the larger rock.
17. What is the difference between the till pictured on p. 96 and the more layered sediments on p. 97? They are both glacial deposits – why do you think they look so different? They have vastly different textures. Although they are both glacial deposits they are different because
the one on page 96 had its weathered rocks and soil removed making it look like unsorted boulders and clay.
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BONUS Many of the pictures from the field contain an object like a hammer, backpack, car key, or pencil.
Why do you think they are included in the photographs? Is it sloppy picture taking, or is there a reason?
I’d assume since rocks and landscaped come in such varying sizes having a scale reference would
be a large reason for containing common items in these photographs. Another reason for having a bunch of items with varying sizes and uses in this picture could also help document field work because it provides a visual record of the tools or equipment (like a hammer or chisel) used when studying the geological environment. Finally, a reason to have objects like a pencil or hammer is to tell you which way the striations or folds are in comparison to the item. This could be useful as
some geological structures aren’t the most clear especially when you are looking at a picture as opposed to being there in person and it is good to have a reference point.
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