INSTRUCTOR GUIDE Antarctica and Neogene Global Climate Change

Transcription

1 INSTRUCTOR GUIDE Chapter 11 Antarctica and Neogene Global Climate Change Summary This investigation introduces you to the status and role of Antarctica in Cenozoic (specifically Neogene) climate change and sets the stage for evaluating the two sediment cores retrieved from the floor of McMurdo Sound by the Antarctic Geologic Drilling Project (ANDRILL) in 2006 and 2007 (Figure 11.1). The cores are introduced in Chapter 12 (Interpreting Antarctic Sediment Cores). In this chapter you will build basic geographic and geologic knowledge of Antarctica and use geologic reasoning. In Part 11.1, you will review your understanding of the oygen isotope curve, interpret global climate conditions from this curve, and assess the validity of your global interpretations based on the global distribution of sediment cores. In Part 11.2, you will become familiar with the geography and geologic units of the Ross Sea region of Antarctica and review or build your knowledge of southern hemisphere seasons, sea-ice, ice-shelves, and the challenges associated with obtaining a sediment core from the floor of McMurdo Sound. You will also build and use your understanding of simple geologic maps, cross sections, and the geologic time scale, so you can eplain the reasons for selecting drill sites in McMurdo Sound. In Part 11.3, you will review the eisting data from sediment cores in the Ross Sea region of Antarctica and use the knowledge gained in Parts 11.1 and 11.2 to identify a target stratigraphic interval and select two drill sites. Evaluation of the ANDRILL core is undertaken in Chapter 12 Interpreting Antarctic Sediment Cores. Figure The ANDRILL drill site on the McMurdo Ice Shelf during the field season. Photo from Photo provided by the ANDRILL Program. Page 1 of 33

2 Goal: to investigate the status and role of Antarctica in Neogene climate change. This eercise also sets the stage for evaluating recent Antarctica coring results presented in Chapter 12. Objectives: After completing this eercise your students should be able to: 1. Describe general global climate conditions during the Cenozoic. 2. Assess the quality and quantity of data on Cenozoic climate history from the Antarctic region; for eample, describe the stratigraphic completeness and spatial distribution of sampling sites for the Neogene in and around Antarctica. 3. Interpret simple geologic maps and cross sections, and describe the geology, glaciology, and geography of the Ross Sea region of Antarctica. 4. Integrate data to propose selected drill sites to meet scientific objectives and logistical and cost constraints. I. How Can I Use All or Parts of this Eercise in my Class? (based on Project 2061 instructional materials design) Title (of each part) How much class time will I need? (per part) Can this be done independently (i.e., as homework)? Part 11.1 Part 11.2 Part 11.3 What do we think we know about the History of Antarctica Climate? mins (depends on how much review is needed) Yes. Would need follow-up presentation and discussion in class What is Antarctica s Geographic and Geologic Contet? mins (depends on amount of discussion and etra material used, or mini-lectures given) Yes. May need in-class preparation. Would need follow-up discussion in class What content will students be introduced to in this eercise? Science as human endeavor Judgement, decision-making, prob- lem-solving Science as an evolving process / Nature of Science New Research builds on previous research Unepected discoveries Eploratory research vs. focused questions Research enabled by technology (technology change through time) Selecting The Best Drillsites for the Science Objectives mins (depends on student level and amount of discussion) Yes. Would need follow-up discussion in class Page 2 of 33

3 Earth History Archives (nature of the sedimentary record) How do you know about earth history? Types of archives outcrops vs. cores Where do you go to learn about earth history? Land vs. sea vs. ice Geographic awareness Awareness of deep time Marine sediments (distribution & controls on distribution) Stratigraphic Principles Relative dating Correlation Stable isotopes Subdivisions of geologic time Unconformities, hiatuses, missing records Climate Change Glacial-interglacial cycles Climate change can be gradual Greenhouse - Icehouse Climate change can be abrupt Present day rates of change Regional to global scales of change Ocean-atmosphere-bio sphere-cryosphere system interactions/feedbacks High latitude climate change sensitivity What types of transportable skills will students practice in this eercise? Make observations (describe what you see) Recognize trends (abrupt vs. gradual vs. patterns) Plot data map, graph, pictoral form Interpret graphs, diagrams, photos, tables Make hypotheses or predictions Test a hypothesis Page 3 of 33

4 Critical reading & analysis Synthesize/integrate & draw broad conclusions Perform calculations (rates, averages, unit conversions) & develop quantitative skills Written communication Oral communication Making persuasive, well supported arguments Identifying assumptions & ambiguity Levels & types of uncertainty (quantitative vs. qualitative) Significance/evaluation of uncertainties & ambiguity What general prerequisite knowledge & skills are required? What Anchor Eercises (or Parts of Eercises) should be done prior to this to guide student interpretation & reasoning? None required, but prior eposure to the following topics would be helpful: 1.Use of oygen isotopes 2. Nature of sediment cores 3. General stratigraphic principles 4.General geologic time scale 5. Simple map and graph reading 1.Intro to Cores eercises; 2.Cenozoic Overview eercises; 3.Seafloor Sediments eercises 1.Basic map- reading skills (incl. geologic maps) 2. Basic knowledge of rock types 3. Basic understanding of geologic time scale 4. Basic math skills 1.None required, but helpful to do Part 1 of this eercise 2.Could provide additional background by doing Intro to cores eercise, Sea floor sediments eercise, & Cenozoic Overview eercise 1.Basic mapreading skills 2. Basic understanding of geologic time scale 3. Basic knowledge of what a sed core is 4.Basic math skills 1. Parts 1 and 2 of this eercise 2. Could provide additional background by doing Intro to cores eercise, Sea floor sediments eercise, & Cenozoic Overview eercise Page 4 of 33

5 What other resources or materials do I need? (e.g., internet access to show on-line video; access to maps, colored pencils) What student misconception does this eercise address? What forms of data are used in this? (e.g., graphs, tables, photos, maps) What geographic locations are these datasets from? 1.World map or globe 2.Geologic time scale 3.Document camera or over head projector for discussions 4.Online connection for access to additional drillcore information and videos 1.Antarctica is just ice 2.There have always been ice sheets in Antarctica 3.Volcanic rocks are only found in warm areas 4.Because it is far away Antarctica is not relevant 5.Generalized data (i.e. global data) tell one about eact conditions at a specific locality 6.Sediment cores only tell one about what happened in their immediate vicinity Graph, map Global distribution of data 1.World map or globe 2. Geologic time scale 3.Internet/projector to show/watch NASA & ANDRILL videos 4. Maps / materials for reviewing reasons for the seasons and east vs. west in Antarctica 5.Calculators 1.Variability within the cryosphere 2.Hemispheric control on seasons 3.Antarctica has always been cold 4. Polar deserts 5. No rocks in Antarctica 6.We can infer events when we don t have a direct record of them 7. Good datasets are not usually pure luck the research is carefully planned Videos, maps, tables, cross-sections Antarctica (Ross Sea Region) 1.World map or globe 2.Map of Antarctica & Ross Sea region 3.Internet & projector to show maps/cross sections 4. Maps / materials for reviewing reasons for the seasons and east vs. west in Antarctica 5.Calculators 1.There is nothing on the seafloor 2.The sedimentary record is discontinuous 3.Antarctica s climate has changed 4.Scientists can always figure out the right answer straight away 5.Scientists may get lucky with results sometimes, but most science requires careful planning Map, stratigraphic summary chart, table, cross section Antarctica (Ross Sea region) Page 5 of 33

6 How can I use this eercise to identify my students prior knowledge (i.e., student misconceptions, commonly held beliefs)? How can I encourage students to reflect on what they have learned in this eercise? [Formative Assessment] How can I assess student learning after they complete all or part of the eercise? [Summative Assessment] Where can I go to for more information on the science in this eercise? What is the Contet for use of these eercises? Instructor grading of eercises checks on student understanding of: 1.Oygen isotope curve 2.Role Antarctica plays in controlling global climate (global conveyor belt) 3.How sediment core data is used to interpret past climate Instructor grading of eercises checks on student understanding of: 1.Reasons for the seasons & seasonality in the southern hemisphere 2.Latitude & Longitude 3.Reading time scales, geologic maps and cross- sections Instructor grading of eercises checks on student understanding of: 1.Map reading skills 2.Unconformities 3.Stratigraphic summary charts 4.What data are needed to support a hypothesis 5.Ability to think geologically 6. Ability to place detailed study in global contet 1.Ask students: what they found interesting/useful? 2.Ask students: what was new? 3.Ask students: what questions it makes them want to ask? See suggestions in Summative Assessment section below. See the supplemental materials and reference sections below. This could be used as a final review & capstone activity in an introductory geoscience course, or as an introductory review in an upper-level geoscience course. Part 2 could simply be used to introduce students to the cryosphere. Part 1 assumes some awareness of oygen isotopes Use the Cenozoic Overview eercises. Part 1 could be a stand-alone eercise. Part 1 could be done after Part 2. Part 3 could be a stand-alone eercise IF students are adequately prepared. II. Annotated Student Worksheets (i.e., the ANSWER KEY) This section includes the annotated copy of the student worksheets with answers for each Part of a chapter. This instructor guide contains the same sections as in the student book chapter, but also includes additional information such as: useful tips, discussion points, notes on places where students might get stuck, what specific points students should come away with from an eercise so as to be prepared for further work, as well as ideas and/or material for mini-lectures. Page 6 of 33

7 Part 11.1 What Do We Think We Know About the History of Antarctic Climate? Suggestion: The documentary produced by WGBH and Nova is centred around the ANDRILL Core, and includes ecellent field and lab shots, as well as good diagrams and eplanations. It is available at: This would be a good video for the instructor to watch as background before doing Ch 11 and 12. It is also well-worth showing in class or assigning for students to watch after completing Ch 11 and Ch 12. Introduction Over the last 40 years, numerous studies have used sediment cores recovered from the ocean floor to eamine the history of the Earth s climate during the Cenozoic (the last 65 million years). Many of these studies have identified changes in the Earth s climate during the Cenozoic and have invoked conditions in Antarctica as a major influence on climate and environments elsewhere around the world. In particular, the steps in the Antarctic climate that have been interpreted from these studies include those shown in Table This is an important point. Some students think only of the impact that global climate has on Antarctica. Antarctic Ice can be both influenced by climate and influence climate around the globe because of Earth System feedbacks. 1 The oygen isotope curve (Figure 11.2) was constructed using data from multiple ocean drilling sites and is used to interpret Antarctic ice volume. Eplain how and why this curve supports the three major steps listed in Table Approimately 34 million years ago Approimately 15 million years ago Approimately 15 million years ago to present time The first major cooling in Antarctica and the first development of large ice sheets in Antarctica A second additional cooling step and development of major ice sheets in Antarctica Persistence of a cold polar climate and large stable ice sheets in Antarctica Table General Interpretation of Oligocene-Holocene Antarctic Climate, as of the late 1970s (Kennett & Shackleton, 1976 a, b; Shackleton & Kennett, 1975; Kennett, 1978). Student answers will vary depending on the level at which they understand/have been introduced to the oygen isotope curve. It also depends on students understanding that geologic time is measured backwards from now; they need to be broadly familiar with the time scale. The Biostratigraphy and Paleomagnetism eercises could be completed prior to this eercise. No introduction is given to oygen isotopes in this Chapter. For an introduction to the use of oygen isotopes, see Chapter 6 The Benthic Oygen Isotope Record of Cenozoic Climate Change. The Instructor could also get the students to annotate the figure so left = colder (greater ice volume), and right = warmer (less ice volume). Page 7 of 33

8 At the more basic level, students need to be able to eplain that when water evaporates from the ocean surface it preferentially incorporates 16 O, and the water left behind in the ocean is richer in 18 O. If the water that has evaporated falls as snow and gets locked up in ice, the oceans will have therefore a higher 18 O concentration during periods of higher ice volume; this increased 18 O value will be recorded in the shells of marine organisms (such as single-celled deep-sea benthic foraminifers) growing in the ocean at the time. Students will note that the oygen isotope curve supports the overall interpretation in Table 11.1, because it shows a marked kick (a positive ecursion) at ~34 Ma, and a smaller kick at ~15 Ma, with an overall shift to the left (cooling; greater ice volume) thereafter. The sudden temperature increase indicated by the data in the graph at 25 Ma DOES NOT match any changes specifically postulated in Table If this is a higher-level class, the trickier part is getting them to pay close attention to the scale at the top and to find out whether they understand the use of δ 18 O (the mathematical basis for using δ 18 O, what VPDB is, and why/how it is used. See The Cenozoic Overview eercise module for a review of these details. In a lower-level class, these details can be glossed over as they get in the way of big picture understanding although one can define and use terms such as positive ecursion or negative ecursion in δ 18 O. Students will probably note that the overall the trend from 50 Ma to present is a cooling one, but that this is NOT a smooth trend and includes some abrupt warming events (the PETM at 55 Ma, and a late Oligocene warming at 26 Ma) as well as cooling events (~34 Ma, ~24 Ma, 15 Ma, and after 3 Ma). During the discussion of their evaluation of the curve it is a good time to review use of the terms greenhouse and icehouse. Greenhouse is the term used for times when no ice sheets are present on Earth, and Icehouse is the term used for times when ice sheets are present on Earth. Colder Warmer Figure Composite marine record for δ 18 O from benthic foraminiferal calcite (modified from Zachos et al., 2008). Page 8 of 33

9 An annotated oygen isotope curve such as that shown in Zachos et al.(2001) shown below could be introduced, and the correlation with documented and postulated global events could be discussed. 2 What do you notice about the distribution of deep sea drilling sites (Figure 11.3), some of which were used to build the composite oygen isotope curve in Figure 11.2? Students will note that most of the cores are not from polar regions. Many students will not be familiar with the casual use of the terms high-latitude, mid-latitude, and low-latitude, so as you use these terms they should be defined. For geographically challenged students, or students who need practice working with latitude and longitude, they could be assigned specific cores to plot on the map-such as ODP and IODP cores that have been collected proimal to Antarctica. Information and Data on these cores can be obtained at: Some students may be not see that relatively few cores have been taken proimal to Antarctica because there are cores taken from the Antarctic Peninsula region, as well as the southern Indian ocean and the South Atlantic. The overall point is that the number of cores from localities proimal to the Antarctic margin (or the Arctic for that matter) is proportionally very low. The Arctic eercise module uses cores obtained in the Arctic, and complements this eercise module well. Page 9 of 33

10 Figure Map showing distribution of DSDP, ODP, and IODP core locations. Map courtesy of IODP. From 3 Does the distribution of sites in Figure 11.3 provide a relatively direct indicator of climatic conditions near the Antarctic continent? Eplain your answer. General answer is NO The core distribution samples mostly mid- and low-latitudes. Because of the efficiency/time scale at which ocean water is mied (~1000 years), these cores provide an indicator of the overall global ice volume through the proy (indirect) data (oygen isotope data from deep-sea benthic foraminifers). Only sediment cores that directly sample sediment deposited on the Antarctic margin will provide direct evidence for the history of Antarctic ice volume. Student understanding of the global nature of the oceans, and of the thermohaline circulation varies, and they may be confused as to whether the oygen isotope curve has any validity [yes, it does]; conversely, students (like scientists) often struggle to see that while the curve may be valid, it does not provide adequate information about specifically how Antarctic ice may have been behaving. 4 Based on the distribution of drill site locations, where would you go to test the interpretations in Table 11.1 further? Put three X s on the map to indicate your selection of future drill sites. Eplain the reasoning for your site selections. Page 10 of 33

11 The aim of this question is to get students to recognize that sediment cores collected adjacent to the Antarctic margin will provide the most direct record of Antarctic climate (in the absence of an on-land sedimentary record). Hence any X that is located adjacent to Antarctica is valid. Depending on their prior knowledge, students may reason that the locations should be spread around the continent to get the big picture or should be a series of localities closer together (e.g. Ross Sea, Weddell Sea etc.) in order to capture adequate detail from one region close to Antarctica. 5 Based on what you have learned from other eercises in this book that you have done thus far, what observations and data from sediment cores can be used to help interpret past climates? This is designed as a review question, or as a question that would allow you to segue into a discussion or mini-lecture of specific features indicative of ice and cold climates (e.g. tills, ice-rafted debris, clay composition or geochemistry, microfossil types and abundance). This could also elicit a mini-lecture/discussion that addresses the fact that the best-preserved records of glaciation are in marine deposits as opposed to terrestrial deposits students tend to epect the best record to be terrestrial, forgetting that subsequent ice advances or erosional events will remove the record of previous glaciations. 6 Thinking back to Chapter 2, what type(s) of sediment would you epect to be deposited (a) adjacent to a glaciated Antarctica and (b) to an unglaciated Antarctica? (a) Tills/diamictites, together with Ice-rafted debris in more ice-distal settings (b) NOT tills or diamictites; possibly diatomites or other sediment that does NOT record the large influ of sediment associated with glacial erosion and transport. This is designed to prompt either a discussion (or mini-lecture) regarding the likely sedimentary sequences and their characteristics, or a review of prior knowledge that students may have about sedimentation in marine and marginal marine glacial and sub-glacial settings, as well as evidence that would not support deposition in or adjacent to a glaciated continent. Chapter 2 Seafloor Sediments builds student knowledge of the composition and distribution of common seafloor sediments. Part 12.1 of Interpreting Antarctic Sediment Cores deals with recognizing glacially-influenced marine depositional environments. One can use this point to introduce clay geochemistry and the way in which it can be used to interpret climate during weathering. 7 How might changes in global climate, such as an increase in global average temperature or a change in global precipitation patterns, have an impact on Antarctica? (answer with question 8 below). 8 Not only can changes in global climate affect regional climate (Question 7), but changes in regional climate can in turn affect global climate. Use your understanding of the Earth s Page 11 of 33

12 system feedbacks (Chapter 5), of thermohaline circulation (Chapter 10), and sea level to eplain how melting of the Antarctic ice sheets might affect global climate? These two questions address the fundamental issue: Not only can global climate change (changes in CO 2 for eample) influence regional climate, and regional changes (in places such as Antarctica), but that changes in Antarctica can influence global climate change. This is designed to prompt discussions of: Oceanic thermohaline circulation, as well as the role that break-up and melting of ice shelves would have on global sea level. It is also possible that students might bring up the role of plate tectonics in opening up circum-antarctic circulation, and the subsequent impact on Antarctic climate. Students could watch the 2006 ANDRILL video Sedimentology Team focus especially on the last 1½ minutes, when deepwater formation and the ocean conveyor is discussed.go to Melting ice shelves do not contribute directly to sea level rise, because the ice that forms the ice shelves is already in the ocean. Losing the ice shelves, however, can remove the buttress that holds glacial ice that is presently on land, increasing the rate at which that ice flows into the ocean. Feedbacks in the climate system (especially positive feedbacks such as sea-level, albedo, and marine primary productivity) The role of meridional temperature gradients and winds Part What is Antarctica s Geographic and Geologic Contet? 1 Antarctica has been described as the coldest, windiest, driest, and harshest place on earth. Find out what the current weather is at McMurdo Station, Antarctica. When you enter Antarctica you will pull up a list of all the weather-reporting stations in Antarctica. Select McMurdo by clicking on it. You can also click on Select Weather History or Seasonal Averages. This question could be turned into an entire investigation in its own right. Eample responses for weather at McMurdo Station on July Windspeed and Direction: 4 mph Precipitation: Light snow Temperature ( o F) : -16 o F Humidity: 48% 2 What is the temperature (from question 1) in C? Conversion F to C = ([F] 32)х ) Show your calculations below. [-16 o F]- 32 = * = -26. Both Question 1 and Question 2 are designed to help bring more immediacy and connection to Page 12 of 33

13 the Antarctic Continent, as well as provide or encourage thinking in the metric system and provide eperience in simple mathematical calculations. The results will obviously vary. For a large class with online access one could get students to determine the temperature at a variety of locations in Antarctica. Watch the videos and peruse the websites introduced in Questions 3 5 to learn about the Antarctic geography as well as logistical, technological, and scientific challenges associated with scientific research in Antarctica, then answer Questions 3 to 8. Watch A Tour of the Cryosphere: Earth s Frozen Assets produced by NASA at: (select the version with narration). What are the main types of ice body that make up the cryosphere in the Antarctic region? Ice Sheets (the West Antarctic Ice Sheet or WAIS, and the East Antarctic Ice Sheet or EAIS) Outlet Glaciers Ice Streams (fast moving portions of the Ice Sheets and associated outlet glaciers) Ice Shelves Icebergs Sea Ice Some additional discussion of the differences between these entities may be needed. The National Snow and Ice Data Center ( provides an ecellent glossary and eplanatory material, including a photo gallery. 4 Learn about Antarctic sea ice and its seasonal variability at: (a) On each of the maps below (Figure 11.4) indicate which specific month is represented. (b) Eplain how you used the reasons for seasonal variability in sea-ice etent to select your answer to 4(a). (see net page) Page 13 of 33

14 March September Figure Maps of Antarctica and the Southern Ocean; Etent of sea ice shown in dark blue. Ross Sea region indicated with arrow, and McMurdo Station with a black square in a white bo. Maps courtesy of the Australian Antarctic Division ( A = March, B = September Sea ice forms when the surface waters of the ocean freeze. In the Southern Hemisphere it is dark (=cooler) April to September, and light (=warmer) October to March. Hence the sea-ice buildup is at a maimum in September, and sea ice has melted to least coverage in March. This question begs for students to have an understanding of the reasons for the seasons. Most introductory Earth Science tets have a section on the seasons. 5 Watch: Southbound (ANDRILL, 2006) at: and Antarctica Today (ANDRILL, 2007) Antarctic Geology (ANDRILL, 2007) Historical Journey (ANDRILL, 2007) at: Make sure you download these ahead of time it can take some time to download them. NOTE: These videos largely portray old white men. Whilst the Antarctic community has in the past been dominated by men, it is very important to stress to students that the Antarctic Research Community is now much more diverse, and includes many international partners - go to for more information. Use the information from these online videos to summarize the technical, logistical, and scientific challenges of doing research in Antarctica: Page 14 of 33

15 Logistics of people travelling to Antarctica and of getting equipment there Having equipment/machines that work in cold conditions 6 months light/dark Cold temperature Communication / isolation Lack of instant technical and other support that we are now accustomed to in research settings Limited baseline data because of access to rocks (ice cover), and complications associated with retrieving cores Financial support (very epensive) 6 Based on the information conveyed in the videos above (Questions 3 5), outline the climatic history of Antarctica for the past 350 million years. Record your responses in the table below. (For more information on icehouse vs. greenhouse conditions see Chapter 5.) The information presented in the ANDRILL Video Antarctic Geology is summarized in the table below, oldest at bottom, and youngest at top. You may want your students to use additional resources, such as Students will need to know that the term Greenhouse refers to a time when no ice sheets are present, and Icehouse refers to a time when Ice sheets are present. Name and age (in millions of years) of time block The past 42 million years ago (Cenozoic) NOTE: 42 Ma is the # used in the video for the initiation of icehouse conditions. This # does not match eactly the # of 34 Ma used elsewhere in this eercise. 70 million years ago (Cretaceous) ~200 Million years ago (Jurassic) ~250 million years ago (Triassic) ~300 million years ago (Late Paleozoic = Permian) ~ Ma Climate Condition: Icehouse or Greenhouse? Icehouse Greenhouse Greenhouse Greenhouse Icehouse Greenhouse Proy Evidence for the Climatic Condition At ~42 Ma there were conifer forests in Antarctica, similar to those currently seen in southern Chile. This marked the start of the transition to Icehouse conditions Lush vegetation (trees, forests, plants, animals) Ginkgos, Cycads, Dinosaurs Glossopteris plants, swampy areas, coal deposits in the rocks now eposed in the Transantarctic Mountains Glacial deposits (not directly specified in video); Small multiple ice sheets covered southern continent of Gondwana Page 15 of 33

16 7 In Questions 1 and 2 you eamined data on current weather at McMurdo Station. In Question 6 you summarized data on Antarctic paleoclimates. Use your knowledge and resources to: (a) Eplain the difference between weather and climate at a given location (e.g. Antarctica): Good Links for information: Weather is what happens on essentially a day-to-day basis at a certain location. Climate is the summary of the weather patterns over a long-term period (30 years plus). (b) Eplain the difference between local climate and global climate : Local Climate is the climate in or at one location; global climate is an overall global average. For eample, some local climates might show evidence for cooling (or warming) for a given time frame, whereas the overall global climate might show evidence for warming (or cooling). In the past 50 years much research has taken place near McMurdo Station, the largest US research base in Antarctica (Figure 11.5). McMurdo Station is located on Ross Island, an island in the western Ross Sea built from active and recently active volcanoes. The Ross Island volcanoes and other volcanic features in the region form the Erebus Volcanic Province, where volcanic activity has occurred throughout the past approimately 15 million years. The Trans Antarctic Mountains (TAM) mark the eastern margin of East Antarctica, and are well eposed approimately 60 km to the west of Ross Island. The TAM are composed of older rocks (Figures 11.6 & 11.7). Note that on average only 2% of the surface of Antarctica today is eposed rock; the rest is covered by ice. Page 16 of 33

17 Figure Map of Antarctica showing location of East Antarctic Ice Sheet (EAIS), West Antarctic Ice Sheet (WAIS), Transantarctic Mountains (TAM) & Ross Ice Shelf. Map also shows main ice divides. Arrow points to Ross Island. Map modified from Hambrey et al, Figure Simplified geologic map of McMurdo Sound region showing Ross Island and the Transantarctic Mountains, as well as location of selected drillsites (CRP, DVDP, CIROS & MSSTS). Rocks identified as Basement Comple and Beacon/Ferrar on this map constitute Bedrock and are detailed in Figure 11.7, as are the McMurdo Volcanics. The line of cross section for Figure 11.8 (A-A ) is also shown. The Ross Sea (ocean) is white in this image, and the Ross Ice Shelf is blue. Outlet glaciers shown in bright blue. Map drawn by Werner Ehrmann, Universitat Leipzig. Page 17 of 33

18 McMurdo Sound is a southward etension of the seasonally open-water portion of the Ross Sea; it lies between Ross Island and the East Antarctic mainland (Figure 11.6), and is covered during the southern hemisphere winter by sea ice approimately 2 6 m thick. During the southern hemisphere summer, most of this sea ice melts and open-water conditions are present. The McMurdo Ice Shelf lies to the south of Ross Island and connects to the east and south with the larger Ross Ice Shelf. Both of these ice shelves are fed by glacial ice flowing from the large West Antarctic Ice Sheet and the much larger East Antarctic Ice Sheet and cover the remainder of the Ross Sea. Water depths beneath the ice shelves are as much as approimately 1000 m. 8 Based on the geologic map and related key for the western Ross Sea area near Ross Island (Figure 11.7), estimate the percentage of land area eposed in the western Ross Sea area. Consider only areas above sea level %. In this estimation students should only consider the areas above sea level (i.e. rocks that are eposed, not covered by glacial ice or below ice-shelf or seawater); this can be a difficult concept for some students to grasp. This is significantly more eposure than the 2% average when the entire Antarctic continent is considered. Page 18 of 33

19 Figure (a) Portion of geologic map and (b) legend from Geologic Map of Antarctica, Sheet 14, Terra Nova Bay McMurdo Sound Area, Victoria Land. Note that south is towards the top of the map, and that white regions on the map indicate ice (and therefore no eposed bedrock). From Warren, Page 19 of 33

20 Figure Continued Page 20 of 33

21 9 Is this more or less than is eposed in Antarctica in general? (Note: In Figure 11.5 areas of white are covered by ice and gray is ice shelf.) This is significantly more eposure than the 2% average when the entire Antarctic continent is considered. 10 Based on the summary information provided and that presented in Figures 11.6 & 11.7, what are the general rock types and ages eposed in the Trans Antarctic Mountains? This question can segue into a mini-lecture on the finer points of reading and using geologic map legends. Trans Antarctic Mountain Rock Types Trans Antarctic Mountain Rock Ages Volcanic Rocks (McMurdo Volcanics) Igneous Rocks (Kirkpatrick Basalt, Ferrar Dolerite) Sedimentary Rocks (Beacon Group) Igneous Rocks Metamorphic Rocks Quaternary & Tertiary Upper Triassic - Jurassic Devonian Lower Jurassic Cambrian and Ordovician PreCambrian and Cambrian 11 Based on information given above and on the maps (Figures 11.6 & 11.7) what is the general rock types and ages on Ross Island (the location of McMurdo Station & Scott Base)? Note that the main point here is that they are volcanic rocks. The table only really needs to have one line filled in. There are three volcanic lithologies described in the key, students can separate them out if they so choose. There is an etra unneeded bo in this table. Ross Island Rock Types Ross Island Rock Ages Volcanic (Olivine basalt) Quaternary (+/- Tertiary?) Volcanic (Trachyte) Pyroclastic Deposits Quaternary (+/- Tertiary?) Quaternary (+/- Tertiary?) Page 21 of 33

22 12 How much information does the type of rock you identified in Question 11 give you about climate at the time the rocks formed? Eplain. Volcanic rocks provide no information on climate (although the teture of a volcanic rock might provide information as to whether it interacted with water during the eruptive process). Note: It is a common student misconception that volcanic activity is associated with warmer climates and equatorial regions. This question is designed to help the students realize that the more-easily accessible rocks on land provide no significant data on Climate Change for the Tertiary / Quarternary. Sedimentary layers are somewhat like wall posts on your facebook wall. Each wall post tells another step or part of a story. The oldest wall posts are at the bottom and the youngest (newest, most recent) wall posts are at the top. Presumably, the more wall posts there are, the more complete the story (or record) is. This general analogy also applies to a book or journal; the more pages there are, the more complete, or more detailed, the story is. 13 Using the wall post or journal analogy, consider a complete sequence of sediments (i.e. a lifetime of wall posts!). Broadly speaking, does a thicker or thinner sedimentary sequence provide a more complete record of geologic events affecting the area adjacent to the basin in which the sediments are accumulating? Eplain your reasoning. Thicker sequence. Note that some layers could be unusually thick (i.e. very lengthy wallposts), and significant time periods could be absent (i.e. there could be long periods with no wallposts, providing no indication as to what is happening). Additional analogies could be introduced the language of the wallpost might not be familiar to us, and require translating; the ability of the writer to record appropriate details might be lacking. 14 Based on the maps (Figures ) and the cross section (Figure 11.8), where in general are you most likely to find a complete Cenozoic sedimentary sequence? In the Ross Sea / McMurdo Sound (= the Victoria Land Basin) Page 22 of 33

23 Figure Simplified geologic cross-section of the western Ross Sea region. Adapted from Naish et. al., 2005, ANDRILL Contribution 4 ( The Line of cross-section is shown on Figure The colored lines in the Miocene-Pleistocene sediments are marker horizons (or reflectors ) based on seismic surveys. Hut Point Peninsula is the south-southwest projection of Ross Island. The gray area at sea level is the Ross Ice Shelf; the pale blue line at sea level represents region covered by varying amounts of sea-ice. MSL = Mean Sea Level. Note that this is essentially the same as Fig (which has additional information), however, thery are used for different purposes. From Harwood et al., On Figure 11.8 draw a distinct vertical line where the Cenozoic sedimentary sequence is thickest and is undisrupted by faults. (a) What was the probable source of the terrigenous Cenozoic sediments? Rocks in the Transantarctic Mountains (removed by erosion, transported to and deposited on the floor of Ross Sea / McMurdo Sound). The big question is how were they eroded, transported & deposited? Ice? Surface water? Wind? Note that the question specifies terrigenous sediments this is to focus student attention to the fact that sedimentary basins act as archives of Earth history. It also draws attention away from biogenic sediment (diatomites or limestones), and forces students to connect sediment infilling a basin to the adjacent landmass. (b) Considering that Southern McMurdo Sound and the McMurdo-Ross Ice Shelf are covered with sea ice or ice shelves, how might you obtain a drill core in the location you have selected? With Difficulty - It is an area of sea ice (or ice shelf if they try to locate a drillsite between Hut Point Peninsula and White Island) From a drillship that can somehow stay above a spot in sea ice (not possible with current technology / ice strength ) Put a drill rig on the sea ice Invent some submersible drilling contraption Time the drilling seasonally (some students may argue for drilling in summer when there is less sea ice, while others could argue for drilling in winter when the ice shelf/sea ice is more stable). Page 23 of 33

24 Part Selecting The Best Drill Sites for the Science Objectives In the past 35 years, several drilling projects have taken place in the McMurdo Sound region. The sites drilled by these projects are shown in Figure 11.9 and the ages of the sediments recovered are shown in Figure For most of these projects, a drilling rig was placed on the sea ice or the ice shelf at the drilling location during the southern hemisphere spring and early summer, in other words, the ice (rather than a ship) acted as the drilling platform. Note that the eceptions are DSDP sites 270, 272 & 272 in the Central Ross Sea (not shown on this map) which were drilled by the Glomar Challenger, and DVDP 10 and 11 which were drilled on land in Taylor Valley. Figure Geography of McMurdo Sound Region, showing geographic and tectonic features & location of drill cores. Red dotted line outlines etent of the Erebus Volcanic Province (Kyle and Cole, 1974). Volcanic centers of Erebus (E), Terror (T), Bird (B), Discovery (D) and Morning (M) are marked. Also shown are locations of previous stratigraphic drill holes (DVDP, CIROS, MSSTS, and CRP) in McMurdo Sound. Completed and Potential ANDRILL sites shown with red squares. From Harwood et al., Page 24 of 33

25 Figure Age of sediments retrieved from drilling projects in the Ross Sea region. Figure adapted from Harwood et al., The location of the Deep Sea Drilling Project (DSDP) cores is not shown in Figure Discussion of this diagram could segue into a mini-lecture on unconformities. The important information is that the disconformities indicate times for which there is no sedimentary record; this could mean that no sediment was ever deposited or any sediment that was deposited has been eroded. 1 Do the datasets from the Ross Sea region (Figure 11.10) provide adequate data to evaluate the history of environmental and climatic conditions postulated (Table 11.1) for Antarctica throughout the past 34 million years? Eplain your answer. This question is distinct from the net question because this question is just about whether there is data available for one to eamine for the time period in question; it does not ask whether the data supports /refutes the postulated Antarctic climate history. Note: Technically the core data is not direct information, but proy information we are using evidence in the sedimentary record to infer/interpret climate changes BUT it is the most direct data that we have in Antarctica. Overall the answer would be only to a very limited etent. Firstly, this is because there is no sedimentary record of the time period between 15 million years ago and ~5 million years ago. Thus we do not even have the indirect evidence that a sedimentary record provides for this window of time. For the time period between ~34 million years ago and 15 million years ago (i.e. late Eocene to middle Miocene) there is a discontinuous record. 2 How does the drill core data summarized in Figure support or refute the hypotheses about Antarctic Ice volume and climate that have been proposed (see Table 11.1)? Eplain your answers. Page 25 of 33

26 This question is asking about how and whether the data that are presented in the summary stratigraphic chart (i.e. the core data) provide enough evidence (i.e. are robust enough) to support or refute the hypotheses summarized in Table Once again, the overall answer is essentially No, the data are not adequate. The lack of a sedimentary record for the interval ~15 Ma to ~5 Ma is a problem. Other observations would include: There is only one record (CIROS 1) for the proposed time (34 Ma) that reaches the age of the proposed onset of Antarctic glaciations The sedimentary record for the time period between ~34 Ma and ~15 Ma does include sediments that are influenced by ice, which are interbedded with sediments that are only somewhat influenced by ice. Note that the records for this interval do show some sediments not influenced by ice in DSDP Hole 270; details for this interval are not clear-cut. Cape Roberts 2 (CRP 2)includes some late early Oligocene sediments not influenced by ice. This summary record shows us that the role of ice was variable in the Ma interval. There is a record for the period 2.5 Ma to current time; it does provide evidence for glacially influenced sediments. You may want to point out that even though there are records (DVDP & CIROS) that span the Pliocene, they are very thin sequences that do not necessarily provide a complete record of events. Using the Facebook wallpost analogy, they might be considered equivalent to 7 or 8 long wallposts over a year-long period, compared to daily, short wallposts over the same time period. Imagine that you have been assigned the job of developing the net drilling program for the Ross Sea region. Consider the following logistical and financial constraints: The project is funded for two drill sites. Funding is US$20 million. The drill rig is limited to a maimum 1500 m of penetration below the seafloor at any site drilled. 3 Eamine Figure and identify the age interval within the Cenozoic that should be your primary drilling target. In other words, what age interval has been least sampled by previous drilling programs, so that you would obtain the most scientific bang for the buck by sampling it? Eplain your choice of an age interval. The middle and late Miocene, i.e. the time block between ~15 Ma and ~5 Ma. This is because there is currently NO sedimentary record for this time block 4 Assuming that your project is enormously successful and recovers 3000 m of core, how much does 1 m of core cost? Show your calculations. Total cost = $20,000,000 Core length = 3000 m $ 20,000,000 / 3000 m = $6, for 1m of core Page 26 of 33

27 The sediments younger than approimately 5 Ma that have been sampled previously in the Ross Sea region form relatively thin layers and are poorly dated. As a result, the environmental and climatic history of Antarctica for the last 5 million years is poorly known. 5 Why might you be particularly interested in developing a detailed history of Antarctica for the past 5 million years? Eplain. The past 5 million years represents the time period during which the current cold polar regime developed in Antarctica. If we can develop an understanding of eactly how the ice has behaved in Antarctica during this time period, we will be able to correlate that information with records in low and mid latitudes for the past 5 Ma, and we will be able to better understand what the global implications are for Antarctic ice melting during a period of future warming. Figure is a generalized geologic cross section of the western Ross Sea region. The colored lines beneath the seafloor of the Victoria Land Basin indicate the positions of distinctive seismic reflectors (or distinctive sediment layers). Where known, the interpreted ages of these reflectors are listed at the bottom of Figure Figure Cross-section of the Victoria Land Basin of western Ross Sea region (adapted from Naish et al., 2005); line of cross-section shown on Figure 11.8; Hut Point Peninsula is part of Ross Island; MSL = mean sea level; gray area to right of Hut Point Peninsula is the Ross Ice Shelf. This figure is similar to Fig. 11.8, but it contains more information on the seismic reflectors. From Harwood et al., Use Figure to pick locations for two drill sites one to sample the age range you identified as your primary drilling target in Question 3 above and the second to sample sediments younger than approimately 5 Ma. In each case, you want to core through the target interval, but are limited to total penetration into the seafloor of 1500 m or less; you also need to make sure the core does not intersect any faults. Clearly show your drill sites on Figure Page 27 of 33

28 and eplain/justify your choice of drill sites in the space below. Four possible drillsites are identified for each interval on the diagram above. The RED location in each instance represents the site that was actually selected by ANDRILL to obtain a core. Core from the Pliocene sequence was retrieved in Oct-Dec 2006, and is Hole ANDRILL 1-B, referred to as ANDRILL MIS (McMurdo Ice Shelf). Core from the Miocene sequence was retrieved in Oct-Dec 2007, and is ANDRILL 2-A, referred to as ANDRILL SMS (Southern McMurdo Sound). The ANDRILL core is introduced in the Case Study on Interpreting Antarctic Sediment Cores, which includes an introductory portion on facies and interpretation of sediments deposited in ice-proimal environments. Page 28 of 33

29 III. Summative Assessment 1. Eplain how the oygen isotope curve is used to interpret past global climates. 2. Describe the geology, glaciology, and geography of the Ross Sea region of Antarctica. 3. How is the geology, geography and climate different in Antartica than where you live? 4. In general, would a thinner or thicker sedimentary sequence provide a more complete record of geologic history of a region? Why? 5. Summarize the pros and cons of using the eisting drillcore databases for global climate interpretations/antarctic ice volume. 6. Summarize what we think we know (i.e., the paradigm of thought) about the history of ice in Antarctica, and how we know it. 7. What is the rationale for obtaining a new core that captures the Neogene Antarctica sedimentary sequences? 8. Where would you recommend scientists obtain this new core and why? IV. Supplemental Materials Supplemental materials on Antarctica: Information about ongoing research in Antarctica, especially that related to the sedimentary record and climate change can be found at: The documentary produced by WGBH and Nova is centred around the ANDRILL Core, and includes ecellent field and lab shots, as well as good diagrams and eplanations. It is available at: ( The ANDRILL (Antarctic Geologic Drilling Program) web page ( The Scientific Committee on Antarctic Research web page ( The National Snow and Ice Data Center ( The National Science Foundation Office of Polar Programs summary of Recent Antarctic Research Discoveries ( Information on the 2009 IODP Epedition 318 to the Wilkes Land margin: ( The Antarctic Marine Geology Research Facility this is the national repository for geological materials collected in and around Antarctica: ( Two suites of short (3-8 minutes each) videos relating to the research being conducted by ANDRILL can be viewed or downloaded at the Andrill Education Materials web page ( The most appropriate videos to accompany this eercise are: Page 29 of 33