Reference no: EM132792626

Lab: Intro to Physical Geology Lab Worksheet

Introduction to Lab 1

Density is an important concept in explaining why Earth is divided into compositional layers, why magma rises to the surface, and how tectonic plates interact to give us oceans and contiinents. The knowledge you gain in today's lab serves as the foundation for the rest of the course. In this lab, we will use the scientific method to explore the role that density has upon shaping our world.

Objects of lower density than their fluid medium tend to float in that fluid. Examples: Wood, being less dense than water, floats in water; a hot-air balloon has an overall lower density than the surrounding air and therefore floats in cold air.

Review the information for the three rocks below:
Basalt

1 Which of these three rocks should float highest in a fluid medium?
Andes.
Basalt
Peridotite

QUESTION 2

Rock	Mass	Volume
Basalt	15.00 g	5cm3
Peridotite	15.30 g	4.5 cm3
Andesite	12.72 g	5.3 cm3

Now it's time for you to use the Lab -1 Spreadsheet (you can also access it back on the Lab 1 page) If you have Microsoft Excel on your computer, download the attachment by clicking an this link: Lab 1 Spreadsheet(1).xlsx . When you prepare to submit/he file, you must rename it you MUST rename it using the template ',Insert First & Last Name Here, Lab 1 Spreadsheet" (for example, lane Doe's spreadsheet would he titled 'lane Doe Lab 1 Spreadsheet,.

If you cannot use Microsoft Excel, you can use the spreadsheet in Google Sheets by following these instructions:
1. Click here to access the Google Sheet.
2. To make a copy of the file for your personal use, click on the File drop-down menu, then select "make a copy..
3. Once you make your own copy,you MUST rename it using the template "(Insert First & Last Name Here) Lab I Spreadsheet" (for example, Jane Does spreadsheet would be titled 'Jane Doe Lab 1 Spreadsheet"). Ifyou do not make o copy, you will not be able to edit anything in the spreadsheet' And please rename it so that we know this is your work when we grade it!
4. Now that you have your own copy, you can use the spreadsheet to perform the calculations according to instructions in the Lab I worksheet.
5. When you are done with your work in this spreadsheet you will be asked to submit it as an Excel file at the end of the Lab 1 worksheet. In order to do this, you must click on the Ale drop-down menu, then select "Download" and then "Microsoft Excel (.xlsx)." Once you have this file downloaded to your computer, you will be able to upload it to the worksheet on HuskyCT and then submit it with the rest of your assignment

Once you have your own copy of the spreadsheet renamed and ready to use, do the following in the "Data. sheet:
1. Use the values in the table above to fill in the mass and volume of the provided rocks.
2. Construct functions to calculate the density of each sample {density = mass/volume).
3. For this lab, since we have data for one of each rock type, the calculated densities will also serve as the average densities.

Finally, you can answer the question below,

1.2 If you had hand samples of each of the rocks available, how would you go about measuring their masses and volumes? Keep in mind that hand samples of rocks are often irregular in shape so rneasuring length, width, and height would be insufficient to calculate an accurate volume.

QUESTION 3

To "do science'', we need observations, a testable hypothesis, and one or more predictions based on the hypothesis.

• Hypothesis- a testable explanation that can be verified or falsified

• Observations -facts, measurements, information, data collected using the senses

• Prediction - a statement of what will happen in a given situation or set of circumstances

1.3 Propose a hypothesis that explains why much of the Earth's surface has elevations within only two ranges (0 to 1 km and 4 to -5 km relative to sea level). To help you develop this hypothesis, understand that there are two types of crust: continental crust and oceanic crust (Note the elevation contrast between oceans and continents). What might be a potential difference between continental and oceanic crust that could explain their differences in elevation?

For the toolbar. press ALT-,10 (PC) or ALT+FN.F10 (Mack

QUESTION 4
Interlude: The scale of Earth's topography
The highest point on Earth, the summit of Mount Everest, sits at 79,029 feet (8,848 meters) above sea level. Seems impressive, right? Well, the deepest point on Earth, the Marianas Trench, sits at 36,070 feet (10,994 meters) below sea level and would swallow up the entirety of Mount Everest with a lot of room to spare!
You may be familiar with globes that have textured surfaces so that if you run your fingers along places where there are mountains, you can 'feel' these mountains because the surface of the globe is raised in these areas. Is this accurate? Let, find out!
First, let's start with Earth diameter, which is 7,917.5 miles. Convert this value to meters below (Hint: there are 1.61 kilometers in a mile, and 1000 meters in a kilometer).
Earth's Diameter: ___________

QUESTION 5
Now, let's figure out how the height of Mt. Everest and the depth of the Marianas trench compare to this diameter. Divide the height of Everest by Earth, diameter (be sure to use meters for both!). Then do the same for the depth of the Marianas trench. What are the ratios that you get?
The height of Mt Everest is _______ of Earth% dia meter. (Provide a decimal ratio)

QUESTION 6
The depth of the Marianas trench is __________ of Earth's diameter. (Provide a decimal value, not a percentage)

QUESTION 7

Now, assume we're using a standard globe with a diameter of 1 foot, or 0.3048 meters. You can multiply your ratios from above by 0.3048 meters (or better yet, by 304.8 millimeters) to find out how high Mt. Everest would be and how deep the Marianas trench would be on the globe. Submit your answers below.
Height of Mt. Everest on a 1-ft diameter globe:____

QUESTION 8

Depth of the Marianas trench on a 1-Ft diameter globe: ____

QUESTION 9
So, now that you've made the calculations, do you think textured globes are accurate (For reference, the Himalayas on a textured globe often raise 12-3 mm from the surface)? Why or why not?

QUESTION 10

Part II: Wood as an analogy for Earth's crust

If you were given rectagular blocks of wood, and needed to determine their densities, how would you go about that? First describe how you would take measurements from the wood blocks and then describe any calculations you would need to do to determine density.

QUESTION 11

you are provided with the masses and volumes of three different types of wood blocks. Calculate the density of each block. Show your calculations below and enter these values in the correct location in the spreadsheet.

Type of Wood	Mass	Volume
Pine	73.50 g	175 cm3
Mahogany	113.75 g	175 cm3
Balsa	28.00 g	175 cm3

QUESTION 12

Review the images below. You MI see three different types of wood floating in water (pine. Mahogany. and Balsa). Look at the image for each type of wood and visually estimate (eyeball) what percentage of the wood is above the surface of the water and what percentage is below the surface of the  water.

QUESTION 13
Compare your densities of the wood blocks from part 2.2. the percentage of each block sitting below the water surface. Do you notice a pattern?

QUESTION 14

Look at the images of stacked wooden blocks below. Imagining that these stacks of blocks each represent a single larger block, does this change the % of the total thickness that is above or below the water for any specific type of wood?

QUESTION 15

How much of a wood block lies above or below the water is determined by isostasy, which is the state of equilibrium in which objectsfloat at levels determined by their thickness and density. Thicker blocks of wood will rise higher above the water but also extend farther below the surface. More dense blocks will float lower in the water than less dense blocks of similar size. (Assume the density of water =1 g/cm3).
We can use the equations below to calculate the thickness of the wood block found below and above the water, surface.

Thickness_below = Total Thickness x (D_wood / D_water) (Eq
Thickness_above = Total thickness -{ Total Thickness x (D_wood/Dwater) (Eq 2)
where D is density.
For example, we can determine the thickness below the water line for a pine block that is 5 cm in thickness with a density of 0.5 erm3.
Thickness_below = 5 cm x (0.5/1.0) = 2.5 centimeters

Using the density you calculated for the block of mahogany woad, determine the thickness of the block that should fie below the water, surface (Tbelow) and then express this as a percentage of the block's total thickness.

Show your work below.

QUESTION 16

Is the percentage you calculated in the previous question the same as your visual estimation from section 2.3? Why might it not be the same?

QUESTION 17

We will now model the isostatic response of beech/pine and mahogany wood M vf0e0 We will me the density and thickness you calculated for the beech/pine woad and the mahogany wood.
lsostasy Model procedures
• Return to the spreadsheet program on the computer. Open the "Isostasy_Model" tab.
• Set M1 to 'beech/pine wood", M2 to "mahogany wood", and MR to water.
• Enter in thicknesses of wood blocks in Millimeters (mm).
• Determine the average thickness of the block that should lie above the water's surface. Do this by constructing fit ndons, based upon Equation 2 above, for the two woods in the .Thickness above M3 surface column". Entering a function now, instead of just the values, is necessary for later steps in the lab. Your TA can help if you get stuck.

Either sketch or take a screenshot of the Isostasy Model that was produced with your data. If you make a sketch, photograph or scan you image and upload its file here. Label accordingly.

QUESTION 18

Now let's explore isostasy of the wood block. We will change one variable at a time.
• Change Ml, M2, and M3 to "Manual entry".

Enter the thicknesses and densities into the model and submit an image of what this would look like relative to the water surface in the image below. If you complete the sketch on your computer, submit a screenshot image. If you sketch it out using a pen or pencil, submit a photo of what you draw. Be sure to include a scale bar or add a note of the thickness of the blocks above and below the water surface!

QUESTION 19

How does the density of an object control how it floats? Who role does thickness play in determining the total volume (NOTE: in this second part of the question we're not talking a bout percentage above or below the water) of the block that is above or below water?

QUESTION 20

Part III: Plate Tectonics Started Over 4 Billion years ago, geochemists report'

Read the article below ond answer the related questions that follow Consider the difference between observations, hypotheses, and predictions.

A new picture of the early Earth is emerging, including the surprising finding that plate tectonics may have started more than 4 billion years ago - much earlier than scientists had believed, according to new research by UCLA geochemists reported in the journal Nature. ''We are proposing that there was plate-tectonic activity in the first 500 million years of Earth's history,. said geochemistry professor Mark Harrison, co-author of the Nature paper. "We're revealing a new picture of what the early Earth might have looked like,. said lead author Michelle Hopkins, a UC. graduate student in Earth and space sciences. "In high school, we are taught to see the Earth as a red, hellish, onolten-lava Earth. Now we're seeing a new picture, more like today, with continents, water, blue sky, ocean, much earlier than we thought." The Earth 3 4.5 billion years old. Some scientists th in k plate tectonics -322 geological phenomenon involving the movement of huge crustal plates that make up the Earth's surface over the planet's molten interior - started 3.5 billion years ago, others that it began even more recently than that.

The research by Harrison, Hopkins and Craig Manning, is based on their analysis of ancient mineral grains known as zircons found inside once molten rocks from Western Australia. Hopkins analyzed the zircons with a microprobe instrurnent that enables scientists to date and learn the exact composition of samples. The analysis determined that some of the zircons were more than 4 billion years old. They were also found to have been formed in a region with heat flow far lower than the global average at that time.
Evidence for water on Earth during the planet's first 500 million years is now overwhelming, according to Harrison. "The inclusions we found tell us the zircons grew in water-saturated magmas. We now observe a surprisingly low geothermal gradient, a low rate at which temperature increases in the Earth. The chemistry of the inclusions in the zircons is characteristic of the two kinds of magrnas today that we see at plate-tectonic boundaries." There is only one place where you have heat flow that low in which magmas are forming: convergent plate-tectonic boundaries."

''You can't make a rnagma at any lower temperature than what we're seeing in these zircons. You look at artiste conceptions of the early Earth, with flying objectt from outer space making large craters; that should make zircons hundreds of degrees hotter than the ones we see. The only way you can make zircons at the low temperature we see is if the melt is water-saturated. There had to be abundant water. That's a big surprise because our longstanding conception of the early Earth is that it was dry."

Questions
3.1. What was the key hypothesis from the article?
 Scientists can use a microprobe to prove that Earth is older than was originally thought. 0 Magma is produced by plate tectonic processes that are associated with water.
 Zircon is formed in magmas and can be analyzed to determine the age of Australia.
 Plate tectonics has been going on for half-a-billion years longer than previously thought.

QUESTION 21

3.2 What was the observation that motivated the development of the hypothesis?

 Zircon was found in rocks that used to be magmas
 Zircons were shown to have formed in a region with low heat flow
 The geochemistry of ancient magmas was analyzed to show they formed in oceans. 0 There was water on the early Earth.

QUESTION 22
3 What was an example of a prediction that could have been tested to prove the hypothesis?
0 The chemistry of the zircons should be similar to that found at present-day convergent plate boundaries.
0 The zircons should contain water.
0 Zircons in craters formed by asteroids should be shown to have formed in higher temperature conditions.
0 Rocks of similar ages should contain fossils of organisms that lived in the early oceans.

QUESTION 23

Part IV: Density and Elevations of Ocean floor and Continents

Earth's surface is characterized by two major elevation levels:

• The average elewtion of the continents = 0.84 krn
• The average elevation of the floor of the oceans is approximately -4.0 km (or we could say the oceans have an average depth of 4.0 km).

4.1. What is the difference in elevation of continental and ocean rocks? km

QUESTION 24

Earth is composed of compositional layers (i.e. crust, mantle, core) of different densities. Early in Earth's formation, our planet was completely rnolten. Denser materials, like hop, sank down to the core, while less dense silicates rnigrated toward the crust, resulting in density stratification. The outer core is so hot that the metals present are always molten, while the higher pressures at the inner core are enough to keep it a solid, despite the 5000-6000°C temperature, The movement of the liquid outer core generates Earth's magnetic field, which shields us from harrnful cosmic radiation, keeps our atmosphere in place and allows life to flourish.

Earth Layer	Average Density Ig/cm3]	Layer Thickness [km]
Continental Crust	2.8	30-40
Oceanic Crust	3.0	5-10
Mantle	3.4-5.4	2850
Outer Core	10-12.3	2260
Inner Core	15	1220

What state of matter is continental crust?

 Solid
 Liquid
 Gas

QUESTION 25

What state of matter is oceanic crust?

 Solid
 Liquid
 Gas

QUESTION 26

What state of matter is the mantle?

 Solid
 Liquid
 Gas

QUESTION 27

What state of matter is the outer core?

 Solid
 Liquid
 Gas

QUESTION 28

What state of matter is the inner core?

 Solid
 Liquid
 Gas

QUESTION 29

In the following questions, label the cross sector through the Earth below.

Layer A

QUESTION 30

Layer B

QUESTION 31

Layer C

QUESTION 32

Layer D

QUESTION 33

The continent and oceanic crust float in the mantle like wood blocks float in water. The continental crust is thicker and composed of less dense rocks than the oceanic en'slust as we calculated how much of the block would float above the water level, we can do the same for the continental and oceanic crust. We can modify Equation 2 accordingly.

Thickness of crust_above = Total thickness - {Total Thickness x (D_crust/D_mantle)} (Eq 3)

3. Use Equation 3 (and values from the table in question 24) to determine the following. Use the average densities far the Mantle: a. How much of the continental crust would float above the lead of the top of the mantle?

QUESTION 34

How much of the oceanic crust would float above the level of the top of the mantle?

QUESTION 35

On the bases of these calculations, what is the calculated elevation difference between the continental and oceanic crust?

QUESTION 36

Geologists refer to the portion of the crust that is "sunk" Into the mantle (I.e., Thickness_below) as the crustal root. Thinking about how Thickness_below scales with Thicknes_above, where's somewhere on Earth where you'd expect to find an especially deep {thick) crustal root?

QUESTION 37

Explain why your values were not the same as the 4.84 km difference above. How could you change the values you used to arrive at a number closer to 4.64 km?

QUESTION 38

Part V: Experimental modeling of Earth's layers

5.1. In the space below, revise or expand upon your hypothesis in Part I. Assuming that each of the three igneous rocks we examined earlier represents either the continental crust, oceanic crust, or mantle, how does the isostatic equilibrium' between them (the relationship between their thicknesses and densities) control the variation in elevations across Earth's surface?

QUESTION 39

5.2 Now test your hypothesis with the Isostasy Model on the computer. List your inputs below (i.e., which rock sample represents oceanic crust, continental crust, or mantle?), including the associated density values.

QUESTION 40

5.3 Examine the computer !sesta, Model produced by your inputs. Draw a labeled sketch showing the relative thicknesses and distribution of the two types of crust and upper mantle. Before you begin sketching consider necessary adjustments you will need to make to make this model more realistic and include these adjustments in your sketch. Hint: the mantle is not exposed at Earth's surface! Include the image as a photo if you hand-draw this sketch, or submit it as a screenshot if you complete this sketch on your computer.

QUESTION 41

Please upload your Lab 1 spreadsheet here with the data filled in from questions in the lab.
Please make sure that your submission is in the format of an Excel spreadsheet (if you worked with it as a google sheet just save it and convert it). IMPORTANT:
Forthis file submission please be sore to change the name of the file so that we can differentiate between submissions easily. EXAMPLE: 'Jane Doe Lab_1_Spreadsheet.xlsx. (Remember xlsx is the file type, the name you give it is all before that)

QUESTION 42

5.4 Extra Credit: "Break the Model". Enter values into the hostas,/ Model that produce results that are out of the ordinary for plate tectonics on Earth. Indicate the values you used and describe why the results are not realistic.

Attachment:- Assignment worksheet.rar