NTRODUCTION
At least five times in Earth’s past, the vast majority of plant and animal species have been annihilated in a geologic instant. What triggered these dramatic events, and what might they tell us about the fate of our world? What do we know about Earth’s past history, and what does science tell us about the coevolution of Earth’s systems and life?
Assignment 1
In this part of the assignment your will use the web application EarthViewerLinks to an external site.. Watch the 1:40 minute tutorial on how to use EarthViewer (if it doesn’t automatically pop up when opening the webpage, you can access the tutorial by clicking on the Info button at the bottom right of the page and then click on Tutorial).
1. Charts in EarthViewer
Click on the Charts button at the bottom of the page and then select the Oxygen. Click, hold, and drag down the horizontal silver slider on the timeline down to 300 MYA, the time when oxygen levels were highest in the atmosphere.
a. What percent oxygen was there in the atmosphere at 300 MYA? _________________________
b. What is the name of this geological period during the Paleozoic Era? ________________
c. What is the percent oxygen in the atmosphere today (move the silver slider to today, 0 Ma). ____________________
d. Sedimentary rocks of this time, 300 million years ago, have vast coal deposits and indicate a humid, vast swamp environment of deposition. Give a hypothesis as to why the oxygen levels were so high during this geological time period. _______________________________________________________________________________________
Close the oxygen chart by clicking the “X” in the upper right-hand corner and move the horizontal silver slider on the timeline back to today, 0 Ma.
2. Mass extinctions
Click on “View” at the bottom of the screen; turn on “Mass Extinctions.” Click “View” again to minimize the menu. Note the five yellow triangles that appear on the right side of the timeline. These correspond to mass extinctions.
a. Drag the horizontal silver slider to the Ordovician extinction, 440 MYA. Click on the Charts at the button of the page and select Biodiversity. For Biodiversity, you will need to move the slider carefully and record the number of marine genera present just before and just after the extinction event. For example, the number of general just before the Ordovician mass extinction is about 1361 genera and it’s about 838 genera after the mass extinction. Place these numbers in the chart below in Biodiversity before and after columns.
Mass Extinction MYA Temperature Oxygen % CO2% Day length Luminosity % Biodiversity before Biodiversity after % Genera lost
Ordovician
Devonian
Permian
Triassic
Cretaceous
Present
b. Gather data in the same manner for the remaining four mass extinctions. Leave the biodiversity for the present blank.
c. To obtain data for Temperature, Oxygen, CO2, Day Length, and Luminosity percent, click on the Charts button and select the appropriate chart. Then move the horizontal silver slider to each mass extinction event to collect the data. Fill in the chart above.
d. Calculate the biodiversity loss in each extinction and report in terms of percent and add it to the last column on the chart. For example, we noted that the Ordovician mass extinction went from 1361 genera to 838 genera during this extinction event. Take 1361 – 838 = 523. This means that 523 genera went extinct during this event. Now, to determine percent, take 523/1361 = 0.38 and then multiply by 100 to get 38%. Thus, 38% of genera went extinct during the Ordovician mass extinction. Put this percent in the chart and do the same for the other mass extinction events and calculate the % genera lost for the other extinctions.
e. What patterns or correlations emerge from your chart?
Assignment 2
In this part of the assignment you will watch the Smithsonian video presentation on mass extinctionsLinks to an external site..
a. Scientists now know the cause of the K-T or Cretaceous – Paleogene mass extinction that occurred 65.5 MYA. What was the cause of this mass extinction?
b. There were several lines of evidence used by the scientists to come to a conclusion as to the cause of the K-T mass extinction.
What did Walter Alvarez note about the limestones in Gubbio Italy that led him to pursue more study of the K-T mass extinction event?
Back at UC Berkeley, the Alvarez’s found compelling chemical evidence for the cause of the K-T mass extinction. What chemical evidence did they find?
What was the explanation for the occurrence of large boulders in the fine mudstone deposits along the Brazos River in Texas?
Scientists working in badlands of Montana and the Dakotas noted a rich biodiversity of dinosaurs (22 species) in rocks of the Hell Creek Formation. The top of the Hell Creek Formation marks the end of the Cretaceous. An important observation made here by the paleontologists is that dinosaur fossils occur only in __________________________________________________.
c. Sam Bowering and other scientists used numerical age dating of zircons to investigate the cause of the end-Permian mass extinction. The scientists went to southern China along the Red River to find the location of the end-Permian mass extinction. Here black shales lie over fossiliferous limestones and document the great dying. Because numerically dating sedimentary rock will only give you the age of the source material and not the age of the rock, Sam Bowering had to find another rock near the end-Permian marker to radiometrically date. What rock did they find near the end-Permian marker bed?
d. Sam Bowering and his crew then went up to Siberia to radiometrically date the large igneous province of basalt lava outpouring called the Siberian Traps. They found a contact where the basalt lava directly overlies the Permian sedimentary rocks. What radiometric date did they obtain for these basalt lavas of the Siberian Traps?
e. Did the age of the Siberian Traps lavas correspond to the age of the unit that Sam Bowering dated form the Red River in China?
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