Geology 105 Earth History Name: Group # Paleogeography and Biodiversity The objectives of this lab are to: o o o o o Become familiar with the relationship between plate tectonics, sea level, and climate. Observe the movements of the Earth s tectonic plates through deep time. Link changes in climate to changes in sedimentary rocks and structures. Link changes in climate and plate tectonics to major changes to life on Earth Create a generalized time line of major evolutionary events/tectonic changes from the Precambrian to today Materials: o Pencil o Fossil stations o Computer stations o Paleogeo.mov video, downloaded from OAKS Exercise 1: Plate Tectonics and Sea Level Changes 1. Watch the following video on the mid-ocean ridge (only watch from 0:30-2:00!). https://www.youtube.com/watch?v=bgye6vlopby a. Briefly, what is the mid-ocean ridge? b. The South Atlantic Ocean is formed as Africa and South America split apart. What kind of plate boundary is this? c. Think of the Earth s oceans as a giant bathtub. A volcanic mountain chain erupts in the middle. What is going to happen to the water level in the bath - will it rise or fall? d. Throughout Earth s history, there have been times with increased periods of tectonic activity, with the number of mid-ocean ridges increasing as well. What do you think happened to the global sea level at these times? 2. Watch the following videos on the formation of sea ice versus land ice (aka, glaciers), and how they affect sea level: http://oceandrilling.coe.tamu.edu/curriculum/sea_level/ice_volume/activity.html a. How do you predict having a continent move towards the north OR south pole will affect sea level on Earth? Remember, this will cause glaciers to form on LAND. b. What will the sea level do if that continent then moves away from the poles?
2 3. Mountain-building on land increases exposed surface area of the Earth, which increases erosion, which reduces the amount of carbon dioxide (a greenhouse gas) in the air. a. What effect does mountain building have on the climate? b. What effect will this have on global sea level? Exercise 2: Scotese s Paleogeographic Reconstruction Scotese is a paleogeographer who made a computer model of the movements of Earth s tectonic plates using many different techniques, including radiometric dating, paleomagnetism measurements, fossil distributions, past movements of glaciers, and formation of ancient mountain chains. The video plays from the present (0 MYA) to the past (700 MYA), but it s more helpful to look at in it reverse. Play the video once from start to finish, and then use the cursor to move from the end of the video back towards the present when you are answering the questions. With your group you will examine the continental configurations at different times in the Earth s history, and draw conclusions about the climate and conditions of life at those periods. By the end of the lab, you should have a simplified timeline of the history of life on Earth, and be able to understand how plate tectonics influenced evolution. Though the video moves from the present (0 million years ago) to the past (750 million years ago), in order to best understand the history of Earth, it is easier to start at the end of the video, and move the cursor from the past towards the present. USE YOUR PRE-LAB TO HELP ANSWER THESE QUESTIONS. Part 1: THE PROTEROZOIC 1. Use your cursor to move the video back to the continental configuration 750 million years ago, during the PROTEROZOIC. This is a time when Earth was populated by single-celled organisms (protists, archaens, and bacteria). Use this to fill in your answer on the Earth s timeline worksheet (last page of this lab exercise). a. What you re looking at is the supercontinent Rodinia (imagine that the reconstruction on the computer screen was a 3D globe though the land looks spread apart in 2D, it s actually all one big land mass). Give a very general compare/contrast of the Earth s continents today vs during the Proterozoic. b. Is Rodinia closer to the equator, or to the poles? How might this affect climate? c. Geologists have found 750 million year old striations in rocks from modern day Africa. What is the depositional environment for striations? Does this data make sense given our paleogeographic reconstruction for Rodinia?
3 d. Refer back to your pre-lab for help answering this question: Will diversity of life on Earth be high or low for this time period? Why or why not? PART 2: THE EDIACARAN 2. Move your cursor from 750 to 600 million years ago, the start of the EDIACARAN PERIOD. a. Describe sea level at this time (remember: compare shallow light blue to deep dark blue, and remember shallow blue = FLOODED CONTINENTAL SHELVES). b. Which direction did the continents begin moving? c. How/why did this effect sea level? d. Keep in mind that as glaciers melt, they move across the landscape, eroding continental rocks and dumping nutrients in the water! Because of this, it is during this time period we see the first multicellular animals evolve. Mark this on your Earth timeline worksheet. e. Visit Fossil Station A. The 600 million year old fossil Charnia there is one of the first known multicellular animal fossils, and has been found from areas as widespread as Newfoundland, Canada as well as Flinders, Australia. Watch the video on the Ediacaran fauna at the laptop provided at this station. (https://www.youtube.com/watch?v=v361iqh6dpe) f. Name three other species listed in the video. i. ii. iii. g. Give a very general description of the shape and mobility of these Ediacaran animals. h. These animals aren t just weird-looking. Many were preserved in a strange way, too in coarse-grained sandstone. What sedimentary rocks do we usually find fossils in (aka, which rocks are FOSSILIFEROUS)? i. Find the location of Australia and Canada during the Ediacaran (do this by returning to the start of the video, and tracing the continents as they move back). Are they close together, or far apart? j. Given that we find Charnia in rocks from Australia and Newfoundland, do you think the diversity for Charnia and the other Ediacaran animals is high or low? (remember, low = one broad ecological province, high = many small provinces)
4 PART 3: THE CAMBRIAN PERIOD 3. Move your cursor to 540 million years ago, during the start of the CAMBRIAN PERIOD. a. What is the sea level like at this time? b. Do you predict biodiversity will be high or low? Why? c. Visit Fossil Station B, and watch at least the first 2 minutes of video there on the Burgess Shale, taken from the Royal Ontario Museum and set to delightful music.) (https://www.youtube.com/watch?v=u5qv7tck470) Describe the animals found in this rock formation, and give at least four ways they are different from the previous animals of the Ediacaran. d. Mark the origin of modern of modern animal groups (aka phylums) on your Earth timeline worksheet. e. The Burgess Shale is found today in the Canadian Rockies. Find North America on the globe (it may help to zoom back to the beginning and follow North America until it reaches the Cambrian, 550 MYA. What latitude is it at? f. Based on its location, what is the climate probably like at the Burgess Shale 550 million years ago? g. What is a modern environment that is climatically similar to the Burgess Shale? PART 4: THE ORDOVICIAN-DEVONIAN PERIODS 4. Move your cursor from 540 to 400 million years ago. During this time you should see two continents colliding in the center of the map, near the equator. This is ancient North America (known as Laurentia at this time) and ancient Europe (known as Baltica). a. What mountain chain currently running along the East Coast of North America began to form as a result of this collision? b. Is the sea level high or low at this time? c. Do you see more convergent or divergent plates during this time period? What do you think will BEGIN to happen to sea level as a result? d. 400 million years ago, we are in the THE DEVONIAN PERIOD. During this time period, we see the origin of the first true forests, or rather, the first true swamps. Mark this event on your Earth timeline worksheet. e. What kind of sedimentary rocks should we expect to find from 400 million year old swampy coastal environments?
5 PART 5: THE CARBONIFEROUS PERIOD 5. Move your cursor to 350 million years ago, the CARBONIFEROUS PERIOD. The first four-legged animals, the tetrapods, evolved from fish shortly afterwards, during. a. Mark the evolution of tetrapods on your Earth timeline worksheet. b. Visit Fossil Station C Acanthostega, an early amphibian. Describe two characteristics it has that link it with fish, and then two characteristics it has that make it different from fish. Fish traits: Tetrapod traits: - c. Swamps were so common at this time, the entire terrestrial planet was basically a giant Amazon rainforest/delta. The name Carboniferous refers to the carbon-rich sedimentary rock which is very common from this time period, and today is mined for energy. d. How do you think the evolution of the first swamps influenced the evolution of tetrapods from fish ancestors? Think about why this happened in the Carboniferous instead of the Cambrian. No wrong answers here this will be discussed/or has been discussed in further detail in lecture. e. What is sea level doing from 380-320 mya (hint: take note of whether shallow seas are increasing or decreasing)? Hypothesize why this is happening. PART 6: THE PERMIAN PERIOD 6. Move your cursor to 240 million years ago, during the middle of the PERMIAN PERIOD. The supercontinent Pangaea has begun forming. a. Are there more convergent or divergent plates on Earth? b. Describe the sea level compared to the Carboniferous period. c. What do you predict will happen to the diversity of life during this period? Remember what you learned about provinces and supercontinents in the pre-lab. d. The farther away land is from ocean moisture, the more extreme the temperature changes become between seasons, and the dryer it becomes, leading to the formation of vast deserts. What sedimentary rock/sedimentary structures would you expect to find in the center of Pangaea? Give at least 3 examples. e. As a result of the reduction of swamp environments, the first amniote (egg-laying) reptiles began to evolve. Mark the evolution of reptiles on your Earth history timeline.
f. Go to Fossil Station D, where you will find two of the earliest reptiles Dimetrodon and Euparkeria. How are these animals generally different from Acanthostega and other early amphibians? g. Remembering the lab exercise on natural selection, briefly explain how tectonic-driven climate changes influenced reptile evolution. AKA, which individuals were more likely to survive and reproduce? h. We find Permian fossils from continents that are currently widely separated. Looking at the fossil distribution on the map below, how does this support the theory of plate tectonics and the idea that a supercontinent like Pangaea once existed? (Also, be sure to look for some of these fossils in our museum!) 6
7 PART 7: THE MESOZIOC ERA (the Triassic, Jurassic, and Cretaceous periods) 7. Move your cursor way ahead to 140 million years ago, during the JURASSIC PERIOD. a. Find North America on the globe. What new ocean is being born between North America and Europe? b. Are South America and Africa still connected? Now move forward to 80 million years ago, during the CRETACEOUS PERIOD, observing the changes to the continents and sea level as you go. The continents during the Cretaceous in similar but still slightly different locations from the modern ones. c. What has happened to Pangaea? d. Are there more convergent or divergent plates? e. Describe the sea level. How does this relate to the above question? f. The South Atlantic has now formed. Are the oceanic crusts on the coast of South America and Africa the same age as the center of the South Atlantic? Why or why not? (REMEMBER WHAT YOU LEARNED ABOUT THE MID-OCEAN RIDGE IN PART 1 of this lab.) g. Find India it is currently an island continent. What direction is it moving? h. Describe the currents between the Atlantic and Pacific during this time. Are they connected? i. Compare the climate of the continents during the Cretaceous compare to the climate during the Permian. Think about access to ocean moisture. j. As you will see in the tetrapod lab, the dinosaurs that evolved during the Mesozoic (the Triassic, Jurassic, and Cretaceous) were some of the most diverse land animals to ever live. How does that relate to plate tectonics and biodiversity? k. Mark domination of diverse dinosaur species for the Cretaceous on your Earth History worksheet. l. Based on the fact that we find dinosaur and palm tree fossils in the Arctic as well as in Antarctica during this time period, how does the global climate compare to the climate on Earth today? m. If we could invent a time machine and create a modern day Cretaceous park, do you think North Pole dinosaurs and South Pole dinosaurs could interbreed? Why or why not?
8 PART 8: THE EOCENE EPOCH 8. Move your cursor ahead to 50 million years ago, during the EOCENE PERIOD. a. How have the continents changed since the Cretaceous? Be very general. b. Has India hit Asia yet? c. This is one of the warmest periods of Earth s history, due to a release of methane from frozen tundra in Siberia. There is NO ice on Earth during the start of the Eocene. How has the sea level changed as a result? d. What kind of Eocene sedimentary rocks would you expect to find in modern day Egypt? e. The earliest whales evolved from four-legged mammals in the Tethys Sea in between Africa and Eurasia during this time. What kind of climate/environment were these ancient whales adapted to? f. Mark evolution of ancient whales (and other modern mammal groups like primates and horses) on your Earth History worksheet. PART 9: THE OLIGOCENE EPOCH 9. Move your cursor from 50 million years ago towards 25 Million years ago and answer the following questions. a. During this period, India finally collides with Asia. What enormous mountain range does this form? b. How will this affect the climate? (Return to part one of this lab for help on this) c. Do you think the mammals that evolved in India will be able to interbreed with the Eurasian mammals? d. Antarctica separates from Australia during the OLIGOCENE PERIOD. How is this going to change the currents around the South Pole, and what do you predict this will do to the climate on Earth? e. How does the sea level on Earth change after the circumpolar current forms (the current surrounding Antarctica)? f. What has happened to the Tethys Sea (the shallow tropical sea between Asia and Africa) during this period? What does this do to the climate of the Middle East as a result?
9 g. Modern whales, with thick blubber and echolocation, don t evolve until after Antarctica separates from Australia, which caused an upwelling of deep sea nutrients to reach the seas surface. The resulting phytoplankton bloom increased the richness of the food web. If this is true, how do you think polar conditions lead to the evolution of modern whales? (Think climate and light levels). h. Mark the evolution of modern whales in the appropriate place on your Earth History worksheet. PART 10: THE PLIOCENE EPOCH 10. Move your cursor from 25 million years ago forward to approximately 3 MYA during the Pliocene Epoch. a. North America and South America formed a land bridge. How will this change the Earth s currents? (Return to fig.1 of your pre-lab for help on this). b. This is the beginning of the modern Ice Ages and evolution of the genus Homo. Mark this on your Earth History worksheet. (We will return to how ice ages influenced human evolution later in lab/lecture!) c. The Ice Ages caused a constant cycle of changes between savannahs and forests to deserts in Africa, and from forests to glaciers in Eurasia. How might this fluctuating climate have influenced human evolution? No right/wrong answer just use your brain and be creative! d. South America used to be primarily populated by marsupials (mammals that give birth to young in a pouch), but these were outcompeted by placentals (mammals that give live birth to well-developed young) after the formation of the land bridge. Now that you know that, explain why plate tectonics have caused marsupials to be the most common kind of mammal found in Australia, while to the rest of the continents on Earth have very few remaining marsupial mammals.
10 PART 11: THE FUTURE 11. If the continents continue moving in the predicted paths, in the next 250 million years a new supercontinent, Pangaea Ultima, will form. What do you predict will happen to the climate on Earth, and why? 12. What do you predict will happen to biodiversity, and why? Exercise 3: Complete Your Earth History Timeline You should have filled in all the major life history events now go back through your lab exercise using the answers to the questions, and the Scotese video, describe what was happening on the Earth at this time. BE VERY BRIEF. Use the provided examples to guide you. BE SURE TO GET THE CORRECT ANSWERS FROM YOUR PROFESSOR OR TA WHEN YOU FINISH. This timeline will be used as a quiz in future labs.
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