Merry student units engaged in a pyramid quiz in an introductory physical geology course, spring 2020.

Tentative Syllabus, Modified for Distance Learning:
Professor Vince Cronin's Section of
Geology 1405 The Dynamic Earth

The course syllabus prior to the extended Spring Break, 2020, is accessible via http://croninprojects.org/Vince/Course/PhysGeol/1405SyllabusSpring20-2covid.html .
That document is superceded by this document, which will change as the semester progresses.

We all wonder, "How can we proceed under these circumstances?" I think my friend Fr. Greg Boyle, S.J., has the best answer. To paraphrase, the response to all important problems is kindness . If needed, add mercy . All in a context of boundless hope and love .

Contact information for Vince Cronin

I prefer that you continue to contact me via email, using your Baylor email address.
My email address is Vince_Cronin@baylor.edu

If (and only if) you need to speak with me directly, call me on my personal cell phone. Check the course announcements on Canvas for that mobile phone number. Please be respectful and congnizant of the fact that I have 110 students, limited time and energy, and my own family to care for during this health crisis.

If you have concerns or face challenges in completing the work in this course, please let me know. My role is to facilitate your learning, and we are all called to help each other through this difficult experience.

Online Etext Availability from Pearson

To access the etext of the lecture textbook (Tarbuck and others, 2020, "Earth")

Sign-in to Canvas and then go to Mastering Geology from within Canvas. There should be a link to the etext that will give you free access to the textbook for the "lecture" part of the course, written by Tarbuck and others (2020) and titled Earth -- An Introduction to Physical Geology [13th edition]

To access the etext of the laboratory manual (Cronin, 2017)

You need to access the Pearson resources from outside of the Canvas learning management system . This free access to the etext requires you to register, following the instructions provided on the PDF document you can access via http://croninprojects.org/Vince/Course/PhysGeol/CroninLab_StudentRegistration.pdf .

Once successfully registered, you can access the etext of the lab manual via http://www.pearson.com/mastering

Tentative Due Dates (Revised March 27)

• All of the MasteringGeology homework assignments and dynamic study modules must be completed by 11:59 PM on Friday, May 1 .
• The lab answers, end-of-lab quiz, and "lecture" quiz associated with geologic time (Tarbuck and others chapter 9 & Cronin lab 8) must be completed/submitted by 11:59 PM on Friday, April 3 .
• The lab answers, end-of-lab quiz, and "lecture" quiz associated with earthquakes (Tarbuck and others chapter 11 & Cronin lab 16) must be completed/submitted by 11:59 PM on Thursday, April 9 .
• The lab answers, end-of-lab quiz, and "lecture" quiz associated with streams (Tarbuck and others chapter 16 & Cronin lab 11) must be completed/submitted by 11:59 PM on Friday, April 17 .
• The lab answers, end-of-lab quiz, and "lecture" quiz associated with groundwater (Tarbuck and others chapter 17 & Cronin lab 12) must be completed/submitted by 11:59 PM on Friday, April 24 .
• The "lecture" quiz associated with climate change (Tarbuck and others chapter 21) must be completed by 11:59 PM on Monday, May 4 .

The logic and role of this document ( et cetera )

• The purpose of this document is to organize the content of the remainder of Geology 1405 The Dynamic Earth for the spring semester of 2020.
• This web page will serve as the primary portal to the rest of the course.
• Confidential or proprietary information such as grades and quizzes will be handled through Canvas.
• Content that I develop or adapt for distance learning and make available either through this website or through the course Canvas site is my intellectual property, with the sole exception of copyright images and videos that are owned by Pearson Higher Education.
• I intend to add to this web page below in what a geologist would call "superposed order," meaning that new items will be added to the top of this web page (below these lines), and you will encounter older items as you scroll down toward the end of the page.
• The "lecture textbook" is "Earth, An Introduction to Physical Geology" 13th edition by Tarbuck, Lutgens, and Linneman, with illustrations by Tasa, published by Pearson (2020).
• The "lab manual" is "Laboratory Manual in Physical Gelogy" 11th edition by Cronin, illustrations by Tasa, published by Pearson (2017).

Contact Information for Teaching Assistants

——— New Material Will Be Deposited Below Here ———

Climate Change (April 26 — May 4)

Step 1 Review the video and audio files associated with Chapter 21 (Global Climate Change) from Tarbuck and others Earth (pages 592-618 in the paper textbook), so that you have a feel for the information it contains. They are listed below:

• Video "A tour of the cryosphere" at https://goo.gl/CQdAKP
• Concept Checker 21.1 at https://goo.gl/y2yz7a
• Tutorial "The climate record in glacial ice" at https://goo.gl/GjwGPz
• Concept Checker 21.2 at https://goo.gl/Y8Xu3w
• Tutorial "Gases in the atmosphere" at https://goo.gl/vUW9ht
• Video "Observing the Earth's aerosols and solar irradiance" at https://goo.gl/HUzK2m
• Concept Checker 21.3 at https://goo.gl/k8CH1F
• Video "An introduction to the electromagnetic spectrum" at https://goo.gl/aBy7Yu
• Tutorial "Solar radiation paths" at https://goo.gl/VngXxB
• Tutorial "3 planets, 3 climates" at https://goo.gl/KjVfh8
• Concept Checker 21.4 at https://goo.gl/3Y5kP6
• Video "Sunspot of October 18, 2014" at https://goo.gl/6HuYuu
• Concept Checker 21.5 at https://goo.gl/sL6s9P
• Tutorial "The Mauna Loa CO ₂ record" at https://goo.gl/fXDPZL
• Video "Global Temperature Trend 1880-2013" at https://goo.gl/FgFafg
• Concept Checker 21.6 at https://goo.gl/fY6CtZ
• Video "Melting Ice, Rising Seas" at https://goo.gl/EBZJfX
• Animation "Surface Air Temperature Anomalies" at https://goo.gl/vD3ePS
• Concept Checker 21.7 at https://goo.gl/c7yPh3
• Animation showing variations in arctic sea ice from March to September 2017 at https://goo.gl/UsCgWk

Step 2 For each of the following questions, go back into the text of Chapter 21, find the answer, and then study the surrounding material (text and illustrations) so that you understand the answer.
The quiz this week will involve these questions.

1. Are most mountain glaciers (a.k.a. alpine glaciers) growing or shrinking?
2. Given that arctic sea ice expands every winter and contracts every summer, is the overall extent of arctic sea ice growing or shrinking over recent decades?
3. Is Greenland's ice sheet growing or shrinking? ...thickening or thinning?
4. How does weather differ from climate, in terms of the time interval associated with each term?
5. Where do we extract ice cores for climate studies that extend over tens or hundreds of thousands of years?
6. The fossil record indicates that humans like us ( Homo sapiens ) have existed on Earth for the past ~200,000 to ~300,000 years. Does the climate record preserved in ice cores indicate that the atmospheric concentration of carbon dioxide (CO ₂ ) has varied over the past 800,000 years, both with and without Homo sapiens ? Hint: examine Figure 21.4.
7. About what concentration (in parts per million or ppm) was the greatest concentration of carbon dioxide (CO ₂ ) in Earth's atmosphere for the 800,000 years prior to about the year 1700 AD? Hint: examine Figure 21.4.
8. Does the climate record preserved in ice cores indicate that the atmospheric concentration of carbon dioxide (CO ₂ ) today is smaller, about the same, or greater than it has been in the past 800,000 years?
9. What is the most abundant gas in clean, dry air in Earth's atmosphere?
10. What is the second-most abundant gas in clean, dry air in Earth's atmosphere?
11. Why is carbon dioxide an important gas in Earth's atmosphere?
12. What do we call a very small solid particle that is suspended in the atmosphere?
13. How do small solid particles suspended in the atmosphere contribute to cooling of the atmosphere?
14. How do small solid particles suspended in the atmosphere contribute to heating of the atmosphere?
15. How might the injection of volcanic ash and sulfur dioxide into the stratosphere during a major volcanic eruption affect the amount of solar radiation that reaches Earth's surface? Does it increase, decrease, or have no effect on radiation hitting the surface?
16. How might a major volcanic eruption affect the temperature of Earth's surface due to increasing the greenhouse gas concentration in the atmopshere? Would such a volcanically induced increase in greenhouse gases tend to increase, decrease, or have no effect on the average global temperature?
17. If Earth's atmosphere had a larger concentration of greenhouse gases, would its surface temperature likely be cooler, about the same, or hotter than it is now?
18. Has Earth's temperature decreased, stayed about the same, or increased between about 1880 and the present?
19. What is a primary reason for the increased concentration in carbon dioxide (CO ₂ ) in Earth's atmosphere during the past ~200 years?
20. Does raising the temperature of sea water cause sea level to decrease, stay the same, or increase? Hint: watch the video available at https://qrgo.page.link/Hd51t
21. Does melting of floating sea ice cause sea level to decrease, stay the same, or increase? Hint: watch the video available at https://qrgo.page.link/Mr42z
22. Does melting of glaciers and ice caps on continental crust cause sea level to decrease, stay the same, or increase? Hint: watch the video available at https://qrgo.page.link/bhXHa
23. What are the most important greenhouse gases — important either because of their prevalence (this gas forms a larger portion of the atmosphere) or potency (the same volume of this gas has a larger temperature effect than other gases)?
24. Approximately what is the atmospheric concentration of carbon dioxide (CO ₂ ) now? Hint: look for an answer at https://www.esrl.noaa.gov/gmd/ccgg/trends/weekly.html
25. How does the atmospheric concentration of carbon dioxide (CO ₂ ) relate (if at all) to the acidity of the world's oceans? Does an increased concentration of CO ₂ in the atmosphere result in less, about the same, or greater acidity in the world's oceans?

MasteringGeology and assessment of your knowledge

Step 1 Work on (and complete this week if possible) the MasteringGeology material related toclimate change. These online assignments are due by 11:59 PM May 1 — the last class day of the semester — but it is much better if you complete them before taking the lecture quiz.

Step 2 Review the chapter contents by studying the "Concepts In Review" (pages 618-623 in the paper textbook). Then, without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lecture Quiz through Canvas by 11:59 PM Monday May 4. The quiz should be accessible through Canvas by the end of the day April 29.

Optional information about this topic

Items relevant to this topic that would have been used in the face-to-face version of this course can be accessed via http://croninprojects.org/Vince/Course/PhysGeol/Climate-Change.html .
Note that any references to homework, extra credit, or other assignments on this optional page should be ignored as irrelevant to this distance-learning experiment that we are engaged in.

Groundwater (April 17 — April 24)

17.1 The Importance of Groundwater, and
17.2 Groundwater and the Water Table

Step 1 Read chapter 17 from Tarbuck and others Earth , sections 17.1 and 17.2 and all of their subsections, (pages 474-479 in the paper textbook).

• View the Tutorial Video "Groundwater" at https://goo.gl/iakFai
• Work through Concept Checks 17.1 (p. 476 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/q4wkXe
• Do the same for Concept Checks 17.2 (p. 479 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/3hcNSQ

Related activities in the Lab Manual

Step 2 Read laboratory 12 in the AGI/NAGT Laboratory Manual , "Introduction" (pages 326-328 in the paper lab manual).
To prepare for Activities 12.2 and 12.3, read the material in Lab 9 Topographic Maps, specifically the section titled "What Are Topographic Maps?" on pages 244-250, studying the content in Figures 9.11-9.14, to familiarize yourself with contours and the process of making a contour map. To help with Activity 12.2, take a look at the map in question 5 on page 500 from the "Give It Some Thought" section near the end of Tarbuck and others Earth , chapter 17.

Step 3 Complete Activities 12.1 and 12.2 in your lab manual, and transcribe your answers onto the lab 12 answer sheet (accessible via http://croninprojects.org/Vince/PhysGeoLab/First-Last-Lab12Answers.docx ) that you will transmit to your TA via email when it is entirely completed. Note that there are videos of Experiment 2 in Activity 12.1B that you will need to watch via http://CroninProjects.org/Vince/GW/index.htm

17.3 Storage and Movement of Groundwater

Step 1 Read chapter 17 from Tarbuck and others Earth , section 17.3 and all of its subsections, (pages 479-481 in the paper textbook).

• View the Tutorial Video "Groundwater Flow" at https://goo.gl/SdSHVb
• Work through Concept Checks 17.3 (p. 481 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/taeBVv

Related activities in the Lab Manual

Step 2 Read laboratory 12 in the AGI/NAGT Laboratory Manual , Introduction and its subsection "Mapping Groundwater Below the Water Table" (page 330 in the paper lab manual).

Step 3 Complete Activity 12.3 in your lab manual, and transcribe your answers onto the lab 12 answer sheet (accessible via http://croninprojects.org/Vince/PhysGeoLab/First-Last-Lab12Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

17.4 Wells and Artesian Systems, and
17.5 Springs, Hot Springs, and Geysers

Step 1 Read chapter 17 from Tarbuck and others Earth , sections 17.4 and 17.5 and all of their subsections, (pages 482-487 in the paper textbook).

• View the Animation "Cones of Depression" at https://goo.gl/EgC3Do
• View the Tutorial Video "Artesian Systems" at https://goo.gl/UHnjQR
• View the Tutorial Video "Geysers" at https://goo.gl/jYoqfU
• Work through Concept Checks 17.4 (p. 484 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/jeczmJ
• Do the same for Concept Checks 17.5 (p. 487 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/X

17.6 Environmental Problems

Step 1 Read chapter 17 from Tarbuck and others Earth , section 17.6 and all of its subsections, (pages 487-493 in the paper textbook).

• View the Tutorial Video "Cone of Depression" at https://goo.gl/8bZhjD
• Work through Concept Checks 17.6 (p. 493 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/RfCHig

Related activities in the Lab Manual

Step 2 Read laboratory 12 in the AGI/NAGT Laboratory Manual , Land Subsidence Hazards Caused by Groundwater Withdrawal and all of its subsections (pages 335-336) in the paper lab manual).

Step 3 Complete Activity 12.6 in your lab manual, and transcribe your answers onto the lab 12 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab12Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

17.7 The Geologic Work of Groundwater

Step 1 Read chapter 17 from Tarbuck and others Earth , sections 17.7 and all of its subsections, (pages 493-496 in the paper textbook).

• View the Mobile Field Trip Video "A Mammoth Cave" at https://goo.gl/Wb1Zhu
• Work through Concept Checks 17.7 (p. 496 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/ZvS3MW

MasteringGeology and assessment of your knowledge

Step 1 Work on (and complete this week if possible) the MasteringGeology material related to geologic time. These online assignments are due by 11:59 PM May 1 — the last class day of the semester — but it is much better if you complete them before taking the lecture quiz.

Step 2 After you have finished working on the lab and without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lab Quiz through Canvas by 11:59 PM Friday April 24. The quiz should be accessible through Canvas by the end of the day April 22.

Step 3 Review the chapter contents by studying the "Concepts In Review" (pages 497-499 in the paper textbook). Then, without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lecture Quiz through Canvas by 11:59 PM Friday April 24. The quiz should be accessible through Canvas by the end of the day April 22.

Optional information about this topic

Items relevant to this topic that would have been used in the face-to-face version of this course can be accessed via http://croninprojects.org/Vince/Course/PhysGeol/Groundwater.html .
Note that any references to homework, extra credit, or other assignments on this optional page should be ignored as irrelevant to this distance-learning experiment that we are engaged in.

Streams (April 5 — April 17)

16.1 Earth as a System: The Hydrologic Cycle
16.2 River Systems

Step 1 Read chapter 16 from Tarbuck and others Earth , sections 16.1 and 16.2 and all of their subsections, (pages 440-445 in the paper textbook).

• View the Tutorial Video "The Water Cycle" at https://goo.gl/k3gvnd
• View the Tutorial Video "Drainage Basins" at https://goo.gl/vTqboN
• View the Tutorial Video "Headward Erosion" at https://goo.gl/WnUUbt
• View the Mobile Field Trip Video "The Water Gap at Sheep Mountain" at https://goo.gl/cSXAGm
• Work through Concept Checks 16.1 (p. 441 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/sQnDkj
• Do the same for Concept Checks 16.2 (p. 445 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/wjPqb2

Related activities in the Lab Manual

Step 2 View the introductory video for Laboratory 11 at https://goo.gl/225WpT

Read laboratory 11 in the AGI/NAGT Laboratory Manual , Introduction and What are the Components of Stream Systems? (pages 294-295 in the paper lab manual).

Step 3 Complete Activity 11.1 in your lab manual, and transcribe your answers onto the lab 11 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab11Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

16.3 Streamflow Characteristics, and
16.4 The Work of Running Water

Step 1 Read chapter 16 from Tarbuck and others Earth , sections 16.3 and 16.4, and all of their subsections, (pages 446-452 in the paper textbook).

• View the Mobile Field Trip Video "The Mississippi River" at https://goo.gl/kvBCZv
• View the Tutorial Video "Head to Mouth" at https://goo.gl/Kcmmnd
• View the Animation "Sediment Transport by Streams" at https://goo.gl/SS3Kj1
• Work through Concept Checks 16.3 (p. 449 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/ANxZcm
• Do the same for Concept Checks 16.4 (p. 452 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/X7VrvF

Related activities in the Lab Manual

Step 2 Read laboratory 11 in the AGI/NAGT Laboratory Manual , How Does Water Flow Across a Surface? and all of its subsections (pages 295-301) in the paper lab manual).

16.5 Stream Channels

Step 1 Read chapter 16 from Tarbuck and others Earth , section 16.5 and all of its subsections, (pages 453-454 in the paper textbook).

• View the Tutorial Video "Incised Meanders" at https://goo.gl/htpmDS
• View the Animation "Formation of an Oxbow Lake" at https://goo.gl/ytN4qX
• Work through Concept Checks 16.5 (p. 454 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/https://goo.gl/ZJm5yr

Related activities in the Lab Manual

Step 2 Read laboratory 11 in the AGI/NAGT Laboratory Manual , Stream Channels and Floodplains and all of its subsections (pages 301-303) in the paper lab manual).

Step 3 Complete Activity 11.5 in your lab manual, and transcribe your answers onto the lab 11 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab11Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

16.6 Shaping Stream Valleys

Step 1 Read chapter 16 from Tarbuck and others Earth , sections 16.6 and all of its subsections, (pages 455-462 in the paper textbook).

• View the Condor Video "Meandering Rivers" at https://goo.gl/hKofCs
• View the Tutorial Video "Incised Meanders" at https://goo.gl/dv1tYs
• View the Condor Video "River Terraces and Base Level" at https://goo.gl/7soXyf
• Work through Concept Checks 16.6 (p. 459 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/UmRZSa

Related activities in the Lab Manual

Step 2 Read laboratory 11 in the AGI/NAGT Laboratory Manual , Stream Profile (pages 304-305 in the paper lab manual).

Step 3 Complete Activity 11.6 in your lab manual, and transcribe your answers onto the lab 11 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab11Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

16.7 Depositional Landforms

Step 1 Read chapter 16 from Tarbuck and others Earth , section 16.7, and all of its subsections, (pages 459-462 in the paper textbook).

• View the Mobile Field Trip Video "Mississippi River Delta" at https://goo.gl/tC8x5s
• View the Animation "Natural Levee Development with Flooding" at https://goo.gl/cNnWb3
• View the Condor Video "Characteristics of Alluvial Fans" at https://goo.gl/Jun3Nd
• Work through Concept Checks 16.7 (p. 462 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/MvXqGW

Related activities in the Lab Manual

Step 2 Read laboratory 11 in the AGI/NAGT Laboratory Manual , How Does Water Flow Across a Surface? and all of its subsections(pages 295-301 in the paper lab manual).

Step 3 Complete Activity 11.3 in your lab manual, and transcribe your answers onto the lab 11 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab11Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

16.8 Floods and Flood Control

Step 1 Read chapter 16 from Tarbuck and others Earth , section 16.8 and all of its subsections, (pages 462-466 in the paper textbook).

Related activities in the Lab Manual

Step 2 Read laboratory 11 in the AGI/NAGT Laboratory Manual , Flood Hazards and Risks and all of its subsections (pages 305-306 in the paper lab manual).

Optional Step 3 Complete Activity 11.7 in your lab manual, which compliments the reading in both the lecture text and laboratory manual. You need not hand-in this completed activity.

MasteringGeology and assessment of your knowledge

Step 1 Work on (and complete this week if possible) the MasteringGeology material related to geologic time. These online assignmens are due by 11:59 PM May 1 — the last class day of the semester — but it is much better if you complete them before taking the lecture quiz.

Step 2 After you have finished working on the lab and without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lab Quiz through Canvas by 11:59 PM Friday April 17. The quiz should be accessible through Canvas by the end of the day April 15.

Step 3 Review the chapter contents by studying the "Concepts In Review" (pages 467-469 in the paper textbook). Then, without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lecture Quiz through Canvas by 11:59 PM Friday April 17. The quiz should be accessible through Canvas by the end of the day April 15.

Optional information about this topic

Items relevant to this topic that would have been used in the face-to-face version of this course can be accessed via http://croninprojects.org/Vince/Course/PhysGeol/Streams.html .
Note that any references to homework, extra credit, or other assignments on this optional page should be ignored as irrelevant to this distance-learning experiment that we are engaged in.

Earthquakes (March 30 — April 9)

11.1 What Is An Earthquake?

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.1 and all of its subsections, (pages 312-316 in the paper textbook).

• View the Tutorial Video "Smart Figures: Faults cause earthquakes" at https://goo.gl/7Bx2jN
• Work through Concept Checks 9.1 (p. 316 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/2Qnz28

Related IRIS resources (optional but recommended)

• IRIS animation , Take 2: Epicenter vs Hypocenter (1 min 59 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_Take2_Epicenter_vs_Hypocenter.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/take_2_epicenter_vs_hypocenter__
• IRIS animation , Earthquake: Foreshock -- Mainshock -- Aftershock (6 min 32 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_004_ForeshockAftershock.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/earthquake_foreshockmainshockaftershock
• IRIS Web ap : Seismic Monitor for seeing recent earthquakes plotted on global or regional maps https://www.iris.edu/hq/inclass/software-web-app/seismic_monitor
  Direct access to ap: http://ds.iris.edu/seismon/

Related activities in the Lab Manual

Step 2 View the introductory video for laboratory 16 at https://goo.gl/gMj34o
Read through the introductory text in laboratory 16 in the AGI/NAGT Laboratory Manual (pages 409-416 in the paper lab manual).

11.2 Seismology: The Study of Earthquake Waves

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.2 and all of its subsections, (pages 316-318 in the paper textbook).

• View the Tutorial Video "Smart Figures: Seismographs" at https://goo.gl/cgR39h
• View the Tutorial Video "Smart Figures: P and S waves" at https://goo.gl/1ZzWQK
• View the Tutorial Video "Smart Figures: Seismic Wave Motion" at https://goo.gl/cV7eTx
• Work through Concept Checks 9.2 (p. 318 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/P3YuNb

Related IRIS resources (optional but recommended)

• IRIS animation , Earthquake Wave Analogies: LIKE ripples on water (1 min 47 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_waterdropearthquake1.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/earthquake_wave_analogies_like_ripples_on_water
• IRIS animation , Earthquake Wave Analogies: UNLIKE ripples on/in water (1 min 48 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_waterdropearthquake2.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/earthquake_wave_analogies_unlike_ripples_onin_water
• IRIS animation , USArray Visualizations: Tutorial on Viewing (2 min 23 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_004B_usarraytutorial.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/usarray_visualizations_tutorial_on_viewing
• IRIS animation , Data Visualization of Wells, NV Magnitude 6 Earthquake (8 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_waterdropearthquake3.mp4
  The vertical-component Ground Motion Visualization for this earthquake is accessible via http://ds.iris.edu/spudservice/data/412108?nolog=y
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/data_visualization_of_wells_nv_magnitude_6_earthquake
  An explanation of IRIS Ground Motion Visualizations of data from selected past earthquakes is accessible via http://ds.iris.edu/ds/products/gmv/
  Ground Motion Visualizations for other earthquakes can be accessed via http://ds.iris.edu/spud/gmv#
• IRIS animation , Body Waves: P-wave Motion (9 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006A_seismicP-Wave_braile.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_wave_motions4_waves_animated
• IRIS animation , Body Waves: S-wave Motion (9 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006B_seismicS-Wave_braile.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_wave_motions4_waves_animated
• IRIS animation , Surface Waves: Rayleigh-wave Motion (9 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006C_RaleighWave_braile.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_wave_motions4_waves_animated
• IRIS animation , Surface Waves: Love-wave Motion (9 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006D_LoveWave_braile.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_wave_motions4_waves_animated
• IRIS animation , 1-Component Seismogram: Building response to P, S, surface waves (48 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_seismicbuilding_1station1seismogram.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/1component_seismogram_building_responds_to_p_s_surface_waves
• IRIS animation , 10 Different Earthquakes of Equal Magnitude Recorded by One Station (1 min 22 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_seismictraveltime_sphere10stn.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/earthquakes_scattered_across_the_globe_recorded_by_one_station
• IRIS animation , 3-Component Seismogram Records Seismic -Wave Motion (2 min 53 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_6_seismicbuilding_3component.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/3component_seismogram_records_seismicwave_motion
• IRIS animation , Seismic Wave Behavior: Curving Paths Through the Earth (1 min X sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_010_refract5_WhyCurvingpath.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_wave_behavior_curving_paths_through_the_earth
• IRIS animation , Layers of the Earth: The Moho (9 min 21 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_001_WhatIsTheMoho.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/layers_of_the_earthwhat_is_the_moho
• IRIS animation , Seismic Shadow Zones: Basic Introduction (2 min) https://www.iris.edu/hq/inclass/uploads/videos/A_6_shadowzone1_basic.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_shadow_zone_basic_introduction
• IRIS animation , Seismic Shadow Zones: P Wave (3 min 25 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_6_shadowzone3_pwave.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/seismic_shadow_zones_p_wave
• IRIS Web ap : Seismic Waves Viewer for seeing how P, S, and surface waves from actual recorded earthquakes moved across the surface of Earth as well as through Earth's interior https://www.iris.edu/hq/inclass/software-web-app/seismic_waves_viewer
  Video introducing the Seismic Waves Viewer https://youtu.be/tF7D3ZYIC2s
  Direct access to web ap: http://ds.iris.edu/seismon/swaves/
• IRIS Web ap : Station Monitor for looking at the current seismic signal being recorded by a particular seismograph station https://www.iris.edu/hq/inclass/software-web-app/station_monitor
  The seismic station I oversee on behalf of Baylor University and the US Array is located at Lake Whitney, and has the station name WHTX
  Direct access to web ap: https://www.iris.edu/app/station_monitor/

Related activities in the Lab Manual

Step 2 Read laboratory 16 in the AGI/NAGT Laboratory Manual , Earthquake and Seismic Waves and Interpreting Seismograms (pages 411-412 in the paper lab manual).

Step 3 Complete Activity 16.2 in your lab manual, and transcribe your answers onto the lab 16 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab16Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

11.3 Locating the Source of an Earthquake

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.3 (pages 318-319 in the paper textbook).

• Work through Concept Checks 9.3 (p. 319 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/qj3FLa

Related IRIS resources (optional but recommended)

• IRIS animation , 4-station Seismograph Network Records a Single Earthquake (1 min 30 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_seismic4stations_4seismogram.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/4station_seismograph_network_records_a_single_earthquake
• IRIS animation , 5 Different Earthquakes Equidistant from One Seismograph Station (1 min 10 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_006_seismictraveltime_sphere1dist.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/five_earthquakes_equidistant_from_one_seismograph_station
• IRIS Web ap : Earthquake Triangulation for using data from three seismograph stations to locate the epicenter of an earthquake https://www.iris.edu/hq/inclass/software-web-app/earthquake_triangulation
  Direct access to ap: https://www.iris.edu/app/triangulation/
• IRIS Web ap : Global Seismogram Viewer for comparing multiple seismograms for a single earthquake https://www.iris.edu/hq/inclass/software-web-app/global_seismogram_viewer
  Direct access to web ap: http://ds.iris.edu/gsv/

Related activities in the Lab Manual

Step 2 Read laboratory 16 in the AGI/NAGT Laboratory Manual , Interpreting Seismograms (pages 412-413 in the paper lab manual).

Step 3 Complete Activity 16.3 in your lab manual, and transcribe your answers onto the lab 16 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab16Answers.docx ).
You might choose to complete this exercise with the assistance of the following IRIS Web ap:
Earthquake Triangulation : https://www.iris.edu/app/triangulation/
More information about this Web ap is available via https://www.iris.edu/hq/inclass/software-web-app/earthquake_triangulation
Direct access to ap: https://www.iris.edu/app/triangulation/
Then transmit to your TA via email when it is entirely completed.

11.4 Determining the Size of an Earthquake

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.4 and all of its subsections (pages 320-322 in the paper textbook).

• View the Tutorial Video "Smart Figures: Intensity vs. Magnitude" at https://goo.gl/2JvUvh
• Work through Concept Checks 9.4 (p. 322 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/v9LgRz

Related IRIS resources (optional but recommended)

• IRIS animation , Magnitude Explained: Moment Magnitude vs. Richter Scale (5 min 39 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_004A_momentmagnitude.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/magnitudes_moment_magnitude_explained
• IRIS animation , Magnitude Perspective: Graphical Comparison of Earthquake Energy Release (NOAA) (1 min 52 sec.) https://www.iris.edu/hq/inclass/animation/magnitude_graphical_comparison_of_earthquake_energy_release#videoPlayer2
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/magnitude_graphical_comparison_of_earthquake_energy_release
• IRIS animation , Take 2: Magnitude vs. Intensity (1 min 55 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_Take2_Magnitude_vs_Intensity.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/take_2_magnitude_vs_intensity

11.5 Earthquake Destruction

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.5 and all of its subsections, (pages 323-328 in the paper textbook).

• View the Tutorial Video "Smart Figures: Tsunamis" at https://goo.gl/T4ApaZ
• View the Tutorial Video "Smart Figures: Tsunami" at https://goo.gl/x4nV2d
• Work through Concept Checks 9.5 (p. 328 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/uiQ58p

Related IRIS resources (optional but recommended)

1. IRIS animation , Alaska: The Great Alaska Earthquake of 1964 (6 min 42 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_007__alaska_1964.mp4
   More information about this video is available at https://www.iris.edu/hq/inclass/animation/alaska_the_great_alaska_earthquake_of_1964
2. IRIS animation , Alaska: Tectonics and Earthquakes (8 min 39 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_007_alaskatectonics.mp4
   More information about this video is available at https://www.iris.edu/hq/inclass/animation/alaska_tectonics_and_earthquakes
3. IRIS animation , Building Resonance: Structural Stability During Earthquakes (5 min 31 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_005_buildingresonance.mp4
   More information about this video is available at https://www.iris.edu/hq/inclass/animation/building_resonance_the_resonant_frequency_of_different_seismic_waves
4. IRIS animation , Buildings & Bedrock: Effects of Amplification & Liquifaction (1 min 12 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_4D_amplificliquefaction.mp4
   More information about this video is available at https://www.iris.edu/hq/inclass/animation/buildings__bedrock_effects_of_amplification__liquefaction
5. IRIS animation , Subduction Zone: Tsunamis Generated by Megathrust Earthquakes (5 min 43 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_2_megathrustearthquakes.mp4
   More information about this video is available at https://www.iris.edu/hq/inclass/animation/subduction_zone_tsunamis_generated_by_megathrust_earthquakes

Related activities in the Lab Manual

Step 2 Read laboratory 16 in the AGI/NAGT Laboratory Manual , Effects of Earthquakes on Structures (pages 411-412 in the paper lab manual).

Step 3 Complete Activity 16.1 sections C, D, and E (only) in your lab manual, and transcribe your answers onto the lab 16 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab16Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

11.6 Where Do Most Destructive Earthquakes Occur?

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.6 and all of its subsections, (pages 328-330 in the paper textbook).

• Work through Concept Checks 9.6 (p. 330 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/FmN1vN

Related IRIS resources (optional but recommended)

• IRIS animation , Mexico: Earthquakes & Tectonics (7 min 46 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_007_Mexico1984.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/mexico_earthquakes__tectonics
• IRIS animation , Central America--Earthquakes and Tectonics (9 min 28 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_007_centralAmerica.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/central_americaearthquakes_and_tectonjics
• IRIS animation , Japan's Earthquakes & Tectonic Setting (10 min 03 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_007_Japan_regional.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/japans_earthquakes__tectonic_setting
• IRIS Web ap : Seismic Monitor for seeing recent earthquakes plotted on global or regional maps https://www.iris.edu/hq/inclass/software-web-app/seismic_monitor
  Direct access to ap: http://ds.iris.edu/seismon/
• IRIS Web ap : IRIS Earthquake Browser, an interactive map for viewing many earthquake epicenters (or hypocenters in the 3D mode) simultaneously https://www.iris.edu/hq/inclass/software-web-app/iris_earthquake_browser
  Video introduction https://youtu.be/jlOMdHN_jVA
  Direct access to web ap: https://www.iris.edu/ieb/

11.7 Earthquakes: Predictions, Forecasts, and Mitigation

Step 1 Read chapter 11 from Tarbuck and others Earth , section 11.7 and all of its subsections, (pages 330-336 in the paper textbook).

• Work through Concept Checks 9.7 (p. 336 in the paper textbook) and then listen to the Concept Checker at https://goo.gl/s1KeE1

Related IRIS resources (optional but recommended)

• IRIS animation , Take 2: Can Earthquakes Be Predicted (Part 1) (1 min 41 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_Take2_Prediction1_FortuneTeller.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/take_2__can_earthquakes_be_predicted_part_1
• IRIS animation , Take 2: Can Earthquakes be predicted? (Part 2) (1 min 38 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_Take2_Prediction2_HeartAttack.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/take_2_can_earthquakes_be_predicted_part_2
• IRIS animation , Take 2: Seismic Hazard vs. Seismic Risk (1 min 57 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_Take2_Hazard_vs_Risk.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/take_2_hazard_vs_risk
• IRIS animation , Pacific Northwest vs. Japan: Mirror-Image Subduction Settings? (4 min 12 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_007_gpspacificnwvsjapan.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/pacific_northwest_vs_japan_similar_tectonic_settings
• IRIS animation , GPS as an Essential Component of Cascadia Earthquake Early Warning (6 min 55 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_004_eewpacificnw.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/earthquake_early_warning_pacific_northwest_subduction_zone

Related activities in the Lab Manual

Step 2 Read laboratory 10 in the AGI/NAGT Laboratory Manual , Brittle Deformation and Types of Faults (pages 273-277 in the paper lab manual). Then look at the following two short videos from IRIS:

• IRIS animation , Fault: Strike-slip (18 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_003strike-slipfault.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/fault_strikeslip
• IRIS animation , Fault: Strike-slip direction (left lateral and right lateral) (21 sec.) https://www.iris.edu/hq/inclass/uploads/videos/A_003_Strike-Slip_Left-Right.mp4
  More information about this video is available at https://www.iris.edu/hq/inclass/animation/fault_strike_slip_direction_left_lateral_and_right_lateral

Step 3 Complete Activity 16.4 in your lab manual. You can download and print a copy of Figure A16.4.1 for use in Activity 16.4 at http://croninprojects.org/Vince/PhysGeoLab/FigureForActivity16-4.pdf

Transcribe your answers onto the lab 16 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab16Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

MasteringGeology and assessment of your knowledge

Step 1 Work on (and complete this week if possible) the MasteringGeology material related to geologic time. These online assignmens are due by 11:59 PM May 1 — the last class day of the semester — but it is much better if you complete them before taking the lecture quiz.

Step 2 After you have finished working on the lab Without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lab Quiz through Canvas by 11:59 PM Thursday April 9. The quiz should be accessible through Canvas by the end of the day April 7.

Step 3 Review the chapter contents by studying the "Concepts In Review" (pages 284-285 in the paper textbook). Then, without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lecture Quiz through Canvas by 11:59 PM Thursday April 9. The quiz should be accessible through Canvas by the end of the day April 7.

Optional information about this topic

Items relevant to this topic that would have been used in the face-to-face version of this course can be accessed via http://croninprojects.org/Vince/Course/PhysGeol/Earthquakes.html .
Note that any references to homework, extra credit, or other assignments on this optional page should be ignored as irrelevant to this distance-learning experiment that we are engaged in.

Geologic Time (March 22 — April 3)

Dating geological objects and events relative to each other

Step 1 Read chapter 9 from Tarbuck and others Earth , section 9.1 Creating a Time Scale: Relative Dating Principles and all of its subsections, (pages 264-270 in the paper textbook).
View the Condor Video "Principles of Relative Dating" at https://goo.gl/CgDBtv
View the Tutorial Video "Smart Figures: Relative Dating" at https://goo.gl/D4gFk9
View the Tutorial Video "Smart Figures: Unconformities" at https://goo.gl/GaMXhn
View the Tutorial Video "Smart Figures: Geologic Histories" at https://goo.gl/RpFf54
Work through Concept Checks 9.1 (p. 270) and then listen to the Concept Checker at https://goo.gl/w9iosG

Step 2 View the introductory video for laboratory 8 at https://goo.gl/k3LPxG
Read laboratory 8 from the AGI/NAGT Laboratory Manual , Introduction , Principles for Determining Relative Age , and Contact Relations and all of their subsections (pages 207-213 in the paper lab manual).

Step 3 Complete Activities 8.1 and 8.2 in your lab manual, and transcribe your answers onto the lab 8 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab8Answers.docx ) that you will transmit to your TA via email when it is entirely completed.

Fossils and correlation of rock layers

Step 1 Read chapter 9 from Tarbuck and others Earth , section 9.2 Fossils: Evidence of Past Life and section 9.3 Correlation of Rock Layers and all of their subsections (pages 270-275 in the paper textbook).
Work through Concept Checks 9.2 (p. 273) and then listen to the Concept Checker at https://goo.gl/LJnUSC
Work through Concept Checks 9.3 (p. 275) and then listen to the Concept Checker at https://goo.gl/PNCXC8

Step 2 Read laboratory 8 from the AGI/NAGT Laboratory Manual , The Geologic Time Scale and all of its subsections (pages 214-217 in the paper lab manual).

Step 3 Complete Activity 8.3 in your lab manual, using the revised version of Figure 8.13 that is available to you via Canvas, and transcribe your answers onto the lab 8 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab8Answers.docx ).

Numerical dating of geologic materials

Step 1 Read chapter 9 from Tarbuck and others Earth , section 9.4 Numerical Dating with Nuclear Decay and section 9.5 Determining Numerical Dates for Sedimentary Strata and all of their subsections (pages 277-282 in the paper textbook).
View the Tutorial Video "Smart Figures: Half Life" at https://goo.gl/hkbqK2
Work through Concept Checks 9.4 (p. 281) and then listen to the Concept Checker at https://goo.gl/nNqhDB
Work through Concept Checks 9.5 (p. 282) and then listen to the Concept Checker at https://goo.gl/FGtFDr

Step 2 Read laboratory 8 from the AGI/NAGT Laboratory Manual , Determining Numerical Ages by Radiometric Dating and all of its subsections (pages 218-220 in the paper lab manual).

Step 3 Complete Activities 8.4 and 8.5 in your lab manual, and transcribe your answers onto the lab 8 answer sheet (accessible via http://croninprojects.org/Vince/Course/PhysGeol/First-Last-Lab8Answers.docx ).

Geologic time scale

Step 1 Read chapter 9 from Tarbuck and others Earth , section 9.6 The Geologic Time Scale and all of its subsections (pages 282-284 in the paper textbook).
Work through Concept Checks 9.6 (p. 284) and then listen to the Concept Checker at https://goo.gl/RnF4hb

MasteringGeology and assessment of your knowledge

Step 1 Work on (and complete this week if possible) the MasteringGeology material related to geologic time. These online assignmens are due by 11:59 PM May 1 — the last class day of the semester — but it is much better if you complete them before taking the lecture quiz.

Step 2 After you have finished working on the lab Without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lab Quiz through Canvas by 11:59 PM Friday April 3. The quiz should be accessible through Canvas by the end of the day April 1.

Step 3 Review the chapter contents by studying the "Concepts In Review" (pages 284-285 in the paper textbook). Then, without referring to (or help from) any other people or resources (books, notes, internet sources, people), complete the Lecture Quiz through Canvas by 11:59 PM Friday April 3. The quiz should be accessible through Canvas by the end of the day April 1.

Optional information about this topic

Items relevant to this topic that would have been used in the face-to-face version of this course can be accessed via http://croninprojects.org/Vince/Course/PhysGeol/Geologic-Time.html . Note that any references to homework, extra credit, or other assignments on this optional page should be ignored as irrelevant to this distance-learning experiment that we are engaged in.

MasteringGeology

Assignments in MasteringGeology will become available to you to work on in the general order in which the content is presented, but the due dates will all be set for the last day of class this semester. This is to provide you with the flexibility you might need to complete them. You are STRONGLY ENCOURAGED to complete MasteringGeology assignment as we are passing through the corresponding material (i.e., do the MG assignments associated with geologic time while I am providing you with online material about geologic time).

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