Rocks Lab 1 - Tim Trostel
docx
keyboard_arrow_up
School
Colorado State University, Fort Collins *
*We aren’t endorsed by this school
Course
121
Subject
Geology
Date
Dec 6, 2023
Type
docx
Pages
9
Uploaded by CoachHedgehogPerson992
GEOL 121
Tim Trostel
Section L18
Rocks 1: Introduction to Rocks and Rock Processes
Scientists like to classify things - organisms, planets, stars, clouds, rocks, pretty much anything!
Classification is useful because it allows scientists to identify patterns and organize information. In this lab, you will investigate rocks by developing your own classification scheme. You will then learn how scientists classify rocks, and what can be interpreted about a rock’s history based on its classification.
Learning Objectives for this Lab:
1.
Identifying types of observations that are useful in identifying rocks
2.
Categorize rocks based on observable physical characteristics, and explain why classification is an important aspect of science
3.
Classify rocks as sedimentary, igneous, or metamorphic, and justify why each rock is included in its classification group
4.
Reflect on how their classification schemes compared to the one used by geologists
Part 1: Rock Exploration and Differentiation
1. In your groups, observe the samples given to you by your instructor (Sample Group A). Below, brainstorm a list of the observable properties of the rocks that you might use to differentiate them. The properties could be anything that you might see and note about the rock; there is no right or wrong answer here! ●
Color
●
Size
●
Luster
GEOL 121
2. Come up with a classification scheme for your rocks; organize your rocks into 3-6 groups. In
the table below, list the sample numbers in each group and write a description of the characteristics that define that group. Sample Numbers
Description
2, 4, 7, 8, 9, 10
All of these rocks are dark in color.
1, 3, 10, 11
All of these rocks contain obvious crystals inside of them.
5, 6, 12
All of these rocks are lighter in color.
3. Discuss your classification scheme with another table group. How are your classmates’ classification schemes similar to and different from the one you came up with? Describe below.
2
GEOL 121
The other group did smooth, shiny, matte, unsmooth, dark and light. We did have a few of the same classifications but they had a few more groups to divide their rocks into. 4. Your instructor will give you a new set of samples (Sample Group B). Consider how effective each of the classification schemes your group and your neighbor group \ came up with were in classifying these samples. Then, develop and describe a revised classification scheme based on your discussion and the introduction of the new data (samples). Our last scheme was fairly effective but we could have come up with a couple more ideas to classify them even better. ●
Color
●
Luster
●
Matte
●
Rough
●
Smooth
●
Hardness
5. Instead of rocks, imagine that your instructor had asked you to classify fruit- apples, pears, cherries, blueberries, oranges, limes, blackberries, bananas, in order to determine how they are related to each other.
a.
Would classifying the fruit by color or size help scientists identify and distinguish between different fruit groups? What issues could arise if these characteristics alone were used? E.g., how would this impact the classification of new fruits (pineapple, melons, tomatoes, avocados, etc….)
The scientists should classify the fruits by color as that will narrow down each group to only one or two fruits per group. Though if only color was used to classify the fruits a big issue would arise. This issue is that many fruits are the same color. More than just one characteristic must be used to classify the fruits. With new fruits the same problem would
occur as it introduces many more fruits that have the same color as each other and some of the existing fruits.
b.
Identify classification schemes that could help you divide these fruits into groups that illustrate how they are related to each other. Are there any observable characteristics could you use?
I would classify the fruits based on what types of seeds they have, interior or exterior. This is an observable characteristic.
3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
GEOL 121
*wait for instructor guidance before beginning Part 2
Part 2: Scientific Classification of Rocks
1) At this point, your instructor will lead you in a discussion of the accepted scientific classifications for the three primary rock types, and subcategories within each, which is based on how the rocks form. As part of this discussion, fill out the “identifying characteristics” column of the table below.
ROCK TYPE
SUB-TYPE FORMATION MECHANISM IDENTIFYING CHARACTERISTICS
EXAMPLES
Igneous
Extrusive
Forms from the cooling
and crystallization of
molten rock on the
Earth's surface. Extrusive igneous rocks do not
have visible crystals very often
as they cool quickly and are
fine grain. They sometimes
have a perforated look to them
from bubbles being trapped
when they cool. Basalt
Intrusive
Forms from the cooling
and crystallization of
molten rock underneath
the Earth's surface. Intrusive igneous rocks have
large visible crystals because
they cool slower under the
surface of the earth.
Granite
Sedimentary
Detrital
Forms from the
accumulation and
cementation of small
particles (sediments)
on/near the Earth's
surface.
Detrital rocks are clastic
meaning that they are made
from compaction and
cementation. If the grain size is
large you can see some of the
rocks that make it up.
Sandstone
Chemical
Forms from the
precipitation of materials
from water on/near the
Earth's surface.
Chemical rocks are formed
from silt and dissolved ions
from evaporation. It can be
classified by the types of
minerals that make it up.
Limestone
Metamorphic
Foliated
Forms when rocks are
subjected to some
combination of high heat,
high pressure, and hot
mineral-rich fluids.
Foliated rocks have visible
layers from all the different
rocks and minerals being
squeezed on top of one
another during high heat and
pressure.
Gneiss
4
GEOL 121
Non-
Foliated
Forms when rocks are
subjected to some
combination of high heat,
high pressure, and hot
mineral-rich fluids.
Non-foliated rocks are formed
from extreme heat and
pressure but do no have rocks
in them that form visible layers.
Marble
2. Fill out the
first three columns of the chart below, classifying each sample from Sample Group A according to the sub-type described on the previous page. Include a description of your
reasoning; what observations support your hypothesis?
Rock
Sample #
Hypothesized
Classification &
Formation
Mechanism
Supporting Observations
& Reasoning
Corrected
Classification
& Formation
Mechanism
Supporting
Observations &
Reasoning
1
Intrusive Igneous
There are visible crystals in the rock meaning that it cooled slowly underground.
All are correct
2
Detrital Sedimentary
The rock is formed in a low energy area as the grain size is very small. 3
Extrusive Igneous
This rock has very small visible crystals and has a perforated texture implying that it cooled quickly with bubbles trapped inside it.
4
Foliated Metamorphic
The rock is layered and does not have large crystals in it but still has some crystals. It could have gone through a textural chemical change Implying it is foliated metamorphic.
5
Non-foliated Metamorphic
This rock looks almost as if it is a whole crystal but is mixed with other rock. This could have gone under a textural chemical change.
6
Detrital Sedimentary
There are visible smaller rocks which make up the 5
GEOL 121
entire rock meaning it is a large grain detrital.
7
Intrusive Igneous
There are large crystals in
the rock suggesting it cooled slowly and crystalized underground.
8
Chemical Sedimentary
The rock looks very silty and has a few crystals in it. It could have formed as a result of evaporation.
9
Foliated Metamorphic
The rock is layered and does not have large crystals in it. It could have gone through a textural chemical change Implying
it is foliated metamorphic.
10
Extrusive Igneous
This rock has a few small crystals inside of it meaning that it did not cool very slowly.
11
Intrusive Igneous
This rock is full of crystals all around it meaning it cooled slowly since there are so many. 12
Detrital Sedimentary
This rock was formed in a low energy area as the grain size is very small and there are no crystals.
Check your answers from question 2 with your instructor before moving on in the lab. Fill out the last two columns on the table based on instructor feedback.
3. Repeat this process with Sample Group B. Rock
Sample #
Hypothesized Classification &
Formation Mechanism
Supporting Observations & Reasoning
13
6
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
GEOL 121
14
15
16
17
Part 3: Reflection
1. Reflect on the ease of implementation of the classifications your groups developed in Part 1 of the lab, versus the geologist-defined classifications. a.
Which system of classification is easiest to use? Why?
In my own opinion, the easiest classification to use depends on your goal and how deep you want to classify them. So the easiest classification would be by color as it takes the least amount of observing skills. b.
Which system of classification is the most useful? Justify your answer, including a discussion of what you are defining as “useful”
The most useful classification would most likely be the the color as well as the color of a mineral can tell you what it is made of, where it comes from, and how it was formed too. 7
GEOL 121
c.
Explain why classification systems are common across all branches of science, and how
scientists may decide what types of observations would be useful to use in classifying rocks, objects, organisms, etc.
Classification systems are common because they allow scientists to separate objects into different groups that are made differently or act differently to things. Scientists decide what types of observations are useful based off how unique it can make each group.
2. Imagine you’re on a trip with a friend and they do not have a background in geology. You both see a rock outcrop and your friend wonders what type of rock the outcrop is made of. a.
In a few sentences, how would you describe to your friend what to look for to determine the rock type? You can tell a friend to look at the rock and see if they can notice any defining features such as layers, other smaller rocks inside of it, or if they notice any crystals.
b.
Give a brief description (a few words) of what observations you would expect your friend to make if the rock is:
i.
Igneous intrusive: there are crystals stuck inside the rock
ii.
Igneous extrusive: the rock is full of holes in it, there were bubbles trapped in it
iii.
Foliated metamorphic: there are distinct layers in the rock
iv.
Non-foliated metamorphic: the rock has a interesting composure
v.
Detrital sedimentary: the rock may have other smaller rocks inside of it that make
up the entire rock
vi.
Chemical sedimentary: the rock might made of organic matter
3. What aspects of making observations, rock classification, and/or the six rock categories defined in this lab do you feel most confident about?
I feel most confident in being able to determine if a rock is igneous intrusive and extrusive as both have a very distinct look.
8
GEOL 121
4. What aspects of making observations, rock classification, and/or the six rock categories defined in this lab do you still have questions about? I still have questions about how chemical sedimentary rocks are made but other than that I have
a good understanding of what was taught today. 9
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help