LAB 1
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Trevan Powell GS150L ESSENTIALS OF GEOLOGY LAB Professor Dr. Coulson October 29, 2023 Lab 1 – Plate Tectonics and Scien3fic Observa3ons Introductory Materials Have you ever noIced that South America and Africa look like they fit together (Figure 1.1)? Figure 1.1
– A map of the world. Note how the eastern edge of South America (red arrow) matches the western edge of Africa (yellow arrow). Public Domain. You are not the first person to make such an observaIon. For instance, in 1858, Antonio Snider-Pelligrini included an image of South America and Africa fiXng together (Figure 1.2) in his book La Créa’on et ses mystères dévoilés
(“The CreaIon and its mysteries unveiled”). Snider-Pelligrini was a creaIonist who believed that the conInents were united in the past as one conInent before they split apart. We usually hear the ideas of “conInental dri\” and “Pangaea” connected to an ancient earth and evoluIonary narraIve. How should ChrisIans think about these issues? Is there evidence that the conInents have moved, and if so, what does that mean for the earth’s history, present, and future? In this lab, you’re going to go on a process of discovery, giving you a taste of what it’s like to be a scienIst. You’ll be making observaIons about various pieces of data and trying to determine what they might mean. At the end, we’ll connect these observaIons together to see what we can learn about conInental dri\.
Figure 1.2
– A figure from La Créa’on et ses mystères dévoilés by Antonio-Snider Pelligrini (1858). The le\ image shows the conInents before separaIng, and they’re shown in present posiIons on the right. Public Domain.
Fossil Observa3ons
1.
Observe Figure 1.3
. The two fossils (
Figure 1.3A,B
) are from an exInct creature called Lystrosaurus
(life reconstrucIon in Figure 1.3C
). Lystrosaurus
is a member of the group DicynodonIa, exInct relaIves of mammals with rotund bodies, toothless beaks, and noIceable tusks. The skull (
Figure 1.3A
) is from South Africa, whereas the fossil of the front half of the body (
Figure 1.3B
) is from AntarcIca. Why is this remarkable? __This is remarkable because it shows how this animal was created to be able to survive in both hot and cold weathers . 2.
A hypothesis (plural: hypotheses) is a possible explanaIon for some scienIfic observaIons. Develop two hypotheses for why there might be fossils of the same animal (
Lystrosaurus
) on both South Africa and AntarcIca. a. _The connecIon of the conInents before separaIng allowed the Lystrosaurus
to move from AntarcIca to Africa. b. _The Lystrosaurus
were created to be able to live in very hot and cold environments. 3.
Consider the following hypotheses for how it is that Lystrosaurus can be found on two conInents with an ocean separaIng them. Our first step is rejecIng any hypotheses that are completely unreasonable. Consider the hypotheses below. Can we throw any out at this stage? a.
God separately created Lystrosaurus
on mulIple conInents. b.
Lystrosaurus
could swim the distance from South Africa to AntarcIca. c.
South Africa and AntarcIca used to be next to each other but have since dri\ed apart. d.
There used to be a land bridge connecIng South Africa and AntarcIca that has since sunk into the ocean. Reject/Unreasonable
e.
Aliens abducted South African Lystrosaurus
and dropped them off in AntarcIca. Reject/
Unreasonable f.
Lystrosaurus
built boats and sailed between the two conInents. Reject/Unreasonable
4.
How could we test between the different hypotheses listed in quesIon 3?
_We would have to research and study the Bible and other historical arIfacts to be able to test these hypotheses.
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Figure 1.3
– Fossils and a life reconstrucIon of the dicynodont Lystrosaurus
. A)
UC 1516, a skull of Lystrosaurus from South Africa, photographed by the author at the AntarcIc Dinosaurs temporary exhibit at the Los Angeles County Museum of Natural History. B)
Cast of UW Burke Museum 95525, an arIculated anterior half of a skeleton of Lystrosaurus
from AntarcIca, photographed by the author at the AntarcIc Dinosaurs temporary exhibit at the Los Angeles County Museum of Natural History. C)
A life reconstrucIon of Lystrosaurus murrayi
by Dmitry Bogdanov. CC BY-SA 3.0
. Obtained via Wikipedia. A
B
C
5.
Observe Figure 1.4
. The two fossils (
Figure 1.4A,B
) are from an exInct creature called Thrinaxodon
(life reconstrucIon in Figure 1.4C
). Thrinaxodon
is a member of the group CynodonIa, exInct close relaIves of mammals. The Thrinaxodon
skull fossil (
Figure 1.4A
) is from South Africa, whereas the fossil of nearly the whole skeleton (
Figure 1.4B
) is from AntarcIca. Why is it useful as a scienIst to see that another fossil animal is found on both Africa and AntarcIca? _It is useful for a scienIst to see another fossil animal found in two different conInents because it releases more informaIon on the stability of the animal in different weather climates. Since the fossil was found in two completely different climates it can reveal the elements of the animal that allowed it to live. 6.
Does the addiIon of Thrinaxodon
make any of the remaining hypotheses in quesIon 3 less likely or more likely? Explain. _The addiIon of Thrinaxodon
makes the second hypothesis in quesIon 3 less likely because it is said to be an ‘exInct close relaIve of mammals’, which brings me to believe that it was not as likely that they would be capable of swimming such long distances. B
C
Figure 1.4
– Fossils and a life reconstrucIon of the cynodont Thrinaxodon. A)
UR 156, a skull of Thrinaxodon from South Africa, photographed by the author at the AntarcIc Dinosaurs temporary exhibit at the Los Angeles County Museum of Natural History. B)
Cast of SAM-PK-K10434, the majority of the skeleton of a Thrinaxodon
, photographed by the author at the AntarcIc Dinosaurs temporary exhibit at the Los Angeles County Museum of Natural History. C)
Life reconstrucIon of Thrinaxodon
by Nobu Tamura. CC BY 2.5
. Obtained via Wikipedia.
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7.
Consider Figure 1.5
. The exInct plant Glossopteris
has a very widespread geographic range. Fossils of Glossopteris
have been found in the geographic areas indicated with yellow stars. Indicate which of the landmasses below contain Glossopteris
fossils. a.
North America b.
Greenland c.
South America d.
Europe e.
Arabia f.
Asia (excluding India) g.
India h.
Africa i.
Madagascar j.
Antarc3ca k.
Australia 8.
Provide at least one hypothesis as to why fossils of Glossopteris
would be found on some conInents, but not others that is consistent with your observaIons on Lystrosaurus and Thrinaxodon
. _When the conInents were connected, the Glossopteris
would have been on the lower/Southern region of the Pangea. A
B
Figure 1.5
– DistribuIon of Glossopteris
across the world. A)
Fossil of a leaf of Glossopteris
cropped from a photograph of a larger slab of Glossopteris
leaves in the Houston Museum of Natural Science by Daderot. Public Domain. B)
World map with locaIons of Glossopteris
discoveries indicated by yellow stars. Public Domain. Rock Observa3ons
9.
The world map in Figure 1.6
has Lower Permian basins with supposed glacial deposits marked with yellow stars. As these units are all from nearly the same secIon of the geologic rock column, it is inferred that they are all part of the same event. The rock units, called diamicItes, are typically interpreted to be from glacial Ill (although they could also be from large mass movements, such as debris flows). How is this map similar to the map in Figure 1.5
? _The rock units, diamicItes, are also found in the lower/Southern region of the Pangea. 10.
Rock layers, as we’ll learn later, originate from giant blankets of sediment that stretch out laterally. Thus, it makes sense to think of a giant layer that connects all of the stars. If this layer of sediment was deposited with the conInents in their current posiIons, then what would we expect to find in the South AtlanIc Ocean, Indian Ocean, and AntarcIc Ocean basins? _We would expect to find sediment all throughout the bonom of the South AtlanIc Ocean, Indian Ocean, and AntarcIc Ocean basins. Figure 1.6
– World map with Lower Permian basins containing glacial deposits marked by yellow stars. World map image is public domain. Data obtained from Figure 1 of Wopfner and Jin, 2009, Pangea megasequences of Tethyan Gondwana-margin reflect global changes of climate and tectonism in Late Palaeozoic and Early Triassic Imes – A review, Palaeoworld 18(2):169-192. Con3nental DriS, Seafloor Spreading, and Plate Tectonics
German scienIst Alfred Wegener used these kinds of observaIons and others to develop his theory of Con3nental DriS
, which he first presented in 1912. Wegener pieced together many separate observaIons to develop his model, but his theory was not widely accepted in his lifeIme. This was, in large part, because Wegener did not have a convincing mechanism for how the enormous conInents could be moved through the solid rock of the ocean basins. In the 1950s, scienIsts using SONAR to study the ocean floor were surprised to discover a giant, underwater mountain chain in the middle of the AtlanIc Ocean: The Mid-Atlan3c Ridge (
Figure 1.7
). Figure 1.7
– World map showing physical relief. Note the dark mountain chain that runs through the AtlanIc Ocean. Photograph by the author. 11.
Is the AtlanIc Ocean the only spot where you see the dark-colored mountain chain in Figure 1.7
? If not, where else do you see it? _No, we also see dark-colored mountain chains in the Pacific Ocean and Indian Ocean. 12. What island naIon in the North AtlanIc lies directly on top of the Mid-AtlanIc Ridge? _The island naIon that lies directly on top of the Mid-AtlanIc Ridge is Iceland. The Mid-AtlanIc Ridge is just one local expression of the largest mountain chain in the world. It runs all around the world like the seam on a baseball. Lava erupts from this Mid-Ocean Ridge
underwater, and at certain spots above water, such as Iceland. On both sides of the Mid-Ocean Ridge, scienIsts discovered idenIcal magneIc bands. AddiIonally, when the rocks surrounding Mid-Ocean Ridges were radiometrically dated, scienIsts discovered that the youngest rocks in the ocean were at the ridges, and the rocks got older on either side of the ridge in essenIally equal porIons (
Figure 1.8
).
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Figure 1.8
– Ages of ocean crust on either side of Mid-Ocean Ridges off the coast of California, Oregon, Washington, and BriIsh Columbia. Image from USGS. Why would these panerns be idenIcal on either side of the Mid-Ocean Ridges? In 1960, Henry Hess proposed a model called seafloor spreading
that makes sense of Mid-Ocean Ridges. Hess proposed that Mid-Ocean Ridges are locaIons where new seafloor is being made. As magma pushes up from below at the Mid-Ocean Ridge, it reaches the surface as lava and cools to form igneous rock. That igneous rock pushes away the igneous rock previously found at the Mid-Ocean Ridge in direcIons perpendicular to the ridge. Thus, the whole seafloor is pushed away in either direcIon perpendicular from the Mid-Ocean Ridges like a conveyor belt.
12.
How can Hess’s hypothesis of seafloor spreading help Wegener’s idea of conInental dri\? _Hess’s hypothesis of seafloor spreading helps Wegener’s idea of conInental dri\ because it creates a more likely reason for land to spread much like the ocean floor. But you can’t just keep making new ocean crust. One soluIon is that the earth has expanded over Ime. This would allow for new crust to keep appearing. Another possibility is that ocean crust is being destroyed just as quickly as it’s being made. One other surprise about the seafloor was the discovery of incredibly deep trenches. Such a trench is visible on the map in Figure 1.7
, just south of Alaska’s AleuIan Islands. It has been hypothesized that these trenches are where ocean crust is sinking back into the earth’s mantle to be recycled. A visual depicIon of this model, called Plate Tectonics
, can be seen in Figure 1.9
. In plate tectonics, the earth’s surface is made up of rigid pieces of the crust called plates. These plates can be made up of just oceanic crust, just conInental crust, or both. These plates can interact with each other in three basic ways: divergent boundaries
, convergent boundaries
, and transform boundaries
. Divergent boundaries are where new ocean crust is made, like at Mid-Ocean Ridges. Convergent boundaries are where two crusts meet. Usually, one crust is forced beneath the other at an oceanic trench, although when two conInents meet, neither is forced under and they both buckle and li\ up forming mountains. A transform boundary is where plates slip past each other without colliding. Transform boundaries can be recognized where they offset divergent boundaries. In the theory of plate tectonics, these three boundary types mark the divisions between the plates.
Figure 1.9
– Visual depicIon of the major processes involved in Plate Tectonics. New ocean crust is made at the oceanic spreading ridge. Old crust is forced down into the earth at an oceanic trench. Image from USGS. So how do we determine whether plate tectonics or an expanding earth is more reasonable? Well, plate tectonics would predict that we should have about equal percentages of divergent and convergent boundaries. This would make the amount of ocean crust being made nearly equal to the amount being destroyed, so that the planet is near equilibrium. If, instead, the earth were growing in size, then we could expect significantly more crust being made than being destroyed. 13.
Fill in the chart below: 1
15.
By comparing the percentages, do you think that the earth is expanding (increasing in size)? Why or why not? _I believe the earth is expanding because there are more divergent boundaries than any other, which corresponds with earth expansion. Effects of Plate Tectonics 16. Consider Figure 1.10
, which shows the distribuIon, depth, and magnitude of various earthquakes. Are earthquakes randomly and evenly distributed across the whole earth? _In Figure 1.10, it seems as though earthquakes are not randomly and evenly distributed across the whole earth. 17.
Categorize each of the following geographic areas as either having abundant
or rare
earthquakes. Lithospheric Plate Boundary Type
Total Length (km)
Total Length of the 3 Main Boundary Types
Percentage of the Whole
Convergent
Ocean-ocean
17,449
91,762km
23%
Ocean-conInent
51,310
ConInent-conInent
23,003
Divergent
ConInental ri\
27,472
94,810km
58.5%
Mid-ocean ridge
67,338
Transform
Oceanic
47,783
73,915km
18.5%
ConInental
26,132
Chart adapted from a similar one in Laboratory Manual in Physical Geology
, 10
th
EdiIon edited by Richard M. 1
Busch, illustrated by Dennis Tasa, and published by the American Geoscience InsItute and NaIonal AssociaIon of Geoscience Teachers.
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a.
Eastern Asia _
rare
b.
Western North America _abundant
c.
Eastern North America _
rare
d.
Northern Europe _
rare
e.
Western South America _abundant f.
Australia _
rare
g.
The Middle East _
abundant
h.
AntarcIca _
rare
Figure 1.10
– DistribuIon, depth, and magnitude of earthquakes across the world. Image by USGS. 18. Consider Figure 1.11
, which shows the locaIons of volcanoes across the world. Are volcanoes randomly distributed across the earth’s surface, or are they more common in certain areas? _Volcanoes are more common in certain areas across the earth’s surface. 19.
Compare the maps of earthquakes (
Figure 1.10
) and volcanoes (
Figures 1.11
). Do you noIce any areas where earthquake and volcanic acIvity overlap? If so, which areas are similar? _Yes, Western North America and the area above Australia.
Figure 1.11
– World map showing the locaIons of volcanoes around the world. Image from Museums Teaching Planet Earth. Data sources listed in the image. It’s amazing how much overlap there is between these two maps, especially in the ring of volcanoes and earthquakes that surrounds the Pacific Ocean (called the Ring of Fire
). Earthquakes are caused by the release of stress built up by rocks pushing up against one another or sliding along one another. Plate Tectonics theory proposes that the reason major earthquakes are concentrated along certain areas is due to those being boundaries between different crustal plates (
Figure 1.12
). Volcanoes are common along oceanic trenches because, according to Plate Tectonics theory, melIng occurs in the subducIng slab and the overlying mantle wedge, that leads to the accumulaIon of magma and the formaIon of volcanoes (see 9, 10, 12, and 13 on Figure 1.9
). Note how, in Figure 1.12
, the Pacific Ocean is surrounded by plate boundaries, which explains the Ring of Fire. Thus, Plate Tectonics is an incredibly useful theory in geology that makes sense of many different observaIons, from ancient fossil distribuIons to the presence of earthquakes and volcanoes. But if Plate Tectonics is true, then shouldn’t we be able to observe the conInents moving today?
Figure 1.12
– The major plates that make up the earth’s lithosphere (crust and upper mantle). Image by USGS. Plate Tectonics in the Present If the conInents are, in fact, moving, then we should be able to detect that movement. And that’s exactly what’s going on in our world today! Through the use of GPS satellites and over 1200 receivers on the ground in the United States alone, scienIsts are able to determine how fast a parIcular area is moving. Watch the following video before beginning QuesIon 20: hnps://www.youtube.com/watch?
Ime_conInue=48&v=S1m1tAGbfL4&feature=emb_logo
. Now it’s your job to figure out how quickly your home area is moving! Visit UNAVCO’s GPS Velocity Viewer
. Since some of you live outside the United States, the direcIons here are split up into internaIonal and naIonal secIons. Follow the direcIons for the secIon that makes the most sense for you. DirecIons for InternaIonal Students 1.
Make sure “
World, IGS08/NNR, GEM GSRM
” is selected under GNSS Data source
. 2.
Under vector color
, choose yellow
. 3.
Check Sta’on labels and data download
.
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4.
Under Sites displayed
, select show one in ten
. 5.
Click on “
Draw Map
”. 6.
Zoom out to view the whole world. 7.
Now zoom in to where you are from and try to locate the staIon nearest to your home. Depending on where you live, there may be many staIons near you or very few. When you find the staIon closest to your home, click on the blue tag and record the following informaIon: Sta3on:
_______________ Horizontal Speed:
_______________ Direc3on:
_______________ Home Town and Country: _________________________ DirecIons for Students Within the United States 1.
Make sure “
N. America, NAM14, UNAVCO
” is selected under GNSS Data source
. 2.
Under Data Source
, choose no net rota3on
. 3.
Under vector color
, choose yellow
. 4.
Check Sta’on labels and data download
. 5.
Under Sites displayed
, select show one in ten
. 6.
Click on “
Draw Map
”. 8.
Zoom in to where you are from and try to locate the staIon nearest to your home. Depending on where you live, there may be many staIons near you or very few. When you find the staIon closest to your home, click on the blue tag and record the following informaIon: Sta3on:
_USNA Horizontal Speed:
_0.92 mm/yr Direc3on:
_141.15 Home Town and State: _Cumberland, MD. Plate Tectonics in the Past Now that we know the plates are moving today, we can think about what this means for movement in the past. Today, the plates are moving—on average—at the speed at which your fingernails grow. Let’s extrapolate these numbers back into the past to understand how the conInents moved then. As discussed in the video, North America is moving away from Europe every year. This means that the AtlanIc Ocean is geXng wider every year. This makes sense as we know that the Mid-AtlanIc Ridge is a divergent boundary, where new ocean crust is made. The oceanic crust conveyor belts push
out from the Mid-AtlanIc Ridge both to the west and to the east, which explains why North America is geXng farther away from Europe. Consider Figure 1.13
. The colors represent the ages of the ocean crust at those locaIons. As young-earth creaIonists, we believe the absolute ages are wrong, but that the relaIve age relaIonships are correct. In other words, we agree that the pink rocks are younger than the yellow and green rocks, although we’re not sure by how much exactly. Figure 1.13
– Ages of the North AtlanIc seafloor. Image from AcIvity 2.5 (AtlanIc Seafloor Spreading) on page 63 of Laboratory Manual in Physical Geology
(10
th
EdiIon), edited by Richard M. Busch, illustrated by Dennis Tasa, and produced by the American Geoscience InsItute and the NaIonal AssociaIon of Geoscience Teachers, and published by Pearson. 21.
What color overlaps with the locaIon of the divergent plate boundary between the Americas on the west and Europe and Africa in the east? 2
_Yellow and pink. 22.
Explain how you can locate transform fault plate boundaries in Figure 1.13
. _You can locate transform fault plate boundaries in Figure 1.13 by the different colors that represent the ages of the ocean crust. 23.
How far away are points B and C today? _About 4,000 kilometers. 24.
Calculate the average rate, in kilometers per million years, that points B and C have moved apart, assuming it took 145 million years. _27.59km every million years 25.
Convert your answer from kilometers per million years to millimeters per year. QuesIons 21-27 are adapted from AcIvity 2.5 (AtlanIc Seafloor Spreading) on page 63 of Laboratory 2
Manual in Physical Geology
(10
th
EdiIon), edited by Richard M. Busch, illustrated by Dennis Tasa, and produced by the American Geoscience InsItute and the NaIonal AssociaIon of Geoscience Teachers, and published by Pearson.
_27.59mm/yr 26. Using Figure 1.13
and your answer to QuesIon 24, and assuming a uniformitarian perspecIve, how many million years ago and during which geologic period would Africa and North America be part of the same conInent? _About 2 million years apart. The Cenozioc Ime period. 27.
Based on your answer to QuesIon 25, how far in meters have Africa and North America moved apart since the United States was founded in 1776? _6704.37mm 28.
NoIce that there are no dark green bands between South America and Africa. What does this mean about the separaIon of South America and Africa? a.
South America and Africa separated aSer North America and Africa did. b.
South America and Africa separated before North America and Africa did. c.
South America and Africa separated at the same Ime that North America and Africa did. d.
This informaIon is irrelevant to the quesIon being asked. We have already pointed out that young earth creaIonists disagree with the convenIonal community on the absolute dates in millions of years that are presented here for tectonic plate movements. Nevertheless, the plates are clearly moving in the present, and there are good evidences (as you have seen) that the conInents used to be connected in a large superconInent (Pangaea) in the past. 29.
What assumpIon is made by scienIsts operaIng under the convenIonal paradigm about the speeds of plate movements in the past? _An assumpIon that is made by these scienIsts is that the plate movements are not as young as some believe them to be, which brings more thought to the idea of the “Old Earth”. 30.
In one of the introductory videos for this module (Catastrophic Plate Tectonics), Dr. McLain suggested that plate tectonics may have operated faster in the past, and that this plate movement may have been the driving force for the global Flood. This model, called Catastrophic Plate Tectonics (CPT)
, was first proposed in a paper presented at the InternaIonal Conference on CreaIonism in 1993. Since then, several creaIonist scienIsts have conInued to research CPT and incorporate it into geological and paleontological models related to the Flood and post-
Flood world. This is a good example of posiIve model building, which stands in contrast to much of what has been done in creaIonism in the past (poinIng out flaws in evoluIonary arguments). Based on what you have learned in this lab about observaIons and hypotheses, why do you think it is important for creaIonist scienIsts to engage in posiIve model building rather than just poking holes in evoluIonary models? Please answer in a complete, well-thought out, paragraph. _It is important for creaIonist scienIsts to do this because it gives them a more biblical foundaIon. If all they did was poking holes in evoluIonary models, then there would not be much evidence for their beliefs. As creaIonist scienIsts, they typically have a biblical viewpoint on these topics, so they should want to learn and study more biblical and truthful aspects of the earth, rather than only studying the evoluIonary side of things. This gives them more credibility
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and, again, foundaIon in their works and studies. It also brings more aspects of science as a whole since science is full of research and discovery.