Midterm Flashcards
What is paleontology, and what fields does it incorporate?
the study of the remains of ancient life, including body, chemical, and trace fossils
- involves biology, chemistry, physics, geology
- not archaeology-they study the remains of human civilization
What is a dinosaur? Give two different definitions
- dinosaurs were terrestrial diapsids that lived in the Mesozoic
- better definition: all the descendents of the common ancestor of the pigeon and Triceratops
How has the view of dinosaurs changed in the last 200 years or so?
- bones often thought to be monsters and often influenced artwork and mythology
- thought were giant lizards at first
- very primitive knowledge-but some developments made, factored into evidence for evolution, evolution helped get info about dinos
- then dinosaur craze hit the US in the early 1900s-2 competing museums on east coast-many dino species identified-Both found the large collections of bones in the American West-Both did much to promote dinosaur research in the late 1800’s
- the view of dinos shaped by way portrayed in media-in 20th century-esp 40s,50s, 60s-like the Flinstones
- portrayed dinos as slow, sluggish, largely inactive-but still violent
- looked like giant lizards
- things change in the late 60s and into the 70s-mostly due to John Ostrom
- dinos ancestors of birds-dinos somewhat birdlike
- child care and behavior of dinos similar to modern birds
- dino endothermy (dino warm-bloodedness)
- moving away from lumbering, lazy view of dinos
- feathered dinos
- why went extinct
- many new species named
What is science and why is it important? How does science get done?
- science is a process for finding things out in the natural world
- scientific method we’re familiar with-come up w question, background research, hypothesis, experiment, etc., start it again if disproved
- but this method isn’t a great way of thinking about it-too simplified-better scientific method involves a lot of things
- Science is self-correcting and progressive
- build on research of others
- an open debate of theories weeds out the weaker ones until a strong consensus is reached
- results must be repeatable
- scientists police the quality of research through peer review in journals-research that does not use quality data and methods is not published
- important cuz 2/3 americans don’t understand what science is, how it is conducted, and what one can expect from it-widespread belief in pseudoscience-other nations are advancing in science so it’s bad if we’re not-belief in evolution not as high as other rich countries-people in Congress denying climate change
What are the different ways of doing science?
- Inductive and Deductive
- -all scientists do a little of both, and there is a constant feedback between observation and experiment
inductive reasoning/science
- Observational
- Hypotheses made to explain a group of observations
- The search for ‘regularities’ in ‘Deep Time’
- Further observations are made to confirm or deny that hypothesis
- “Present is the key to the past”
- e.g. astronomy, paleontology, geology
deductive reasoning/science
- Experimental (and epidemiological)
- Test is designed to confirm/deny a hypothesis
- Further tests can be done
- e.g. chemistry, psychology, medicine
What are the steps in the practice of paleontology?
- Exploration
- Funding & permitting
- Collection & Transport
- Preparation & Replication
- Measurement & Data Collection
- Research & Publication
empirical evidence
Empirical – phenomena independent of perceptions and pre-conceived notions
Mean =
average
Standard Deviation =
a measure of variation
Paleontological Research: exploration-How do we know where to look?
- Geologic Maps
- Previous work-other people who have collected there, clues they look for to find fossils
- Preliminary Exploration-decide good spots to come back to
- Artistry-everyone has their superstitions and methods-some based on science, some on superstition
Why do we do most of our work in deserts?
- preservation-very little erosion there
- not a lot of trees or grass-easy to see sediment-would need to get through lots of grass and soil and vegetation if tried to find fossils in a forest or field
- less geologic activity (in some places)
Paleontological Research: funding and permitting-Funding Expeditions
- Federal Agencies
- National Science Foundation (NSF)
- Private Foundations
- National Geographic
- Professional Societies
- Society of Vertebrate Paleontology (SVP)
- Geological Society of America (GSA)
- Corporations
- Petroleum Industry
- Universities
Paleontological Research: funding and permitting-Where does that money go?
-Overhead (if prof gets a big grant, university takes a big chunk of it-pays for staff, maintenance, research assistants, etc-goes straight back to school-creates jobs-puts money back into the economy through paying people’s salaries)
-Salaries
-Students
-Equipment
-Travel
The money doesn’t go in a hole!!
Paleontological Research: funding and permitting-permitting
- US Federal Lands require a permit
- Bureau of Land Management
- US Forest Service
- National Park Service
- Fish and Wildlife Service
- if find something on public land, can’t keep it-work on it, study it-but fossils must go to museum when done so other people can study them-this is called an Accession agreement
- Private land requires permission from the owner-fossils don’t necessarily need to go to a museum/institution-if you own private land, the fossils in it are yours
- Foreign expeditions will have varying rules and regulations-many foreign countries won’t let you take the fossils out of the country-they want them in a museum there
What does the story of Sue and what does it illustrate?
-Largest and most complete Tyrannosaurus rex skeleton ever found
-Discovered by workers from the Black Hills Institute (a private organization) on the Cheyenne
River Indian Reservation in South Dakota in 1990
-Found on “private” land
-The owner was part of the Sioux tribe
-But the land was a trust held by the US DOI
-so there was a fight about who owned it
-FBI seized the fossil in 1992, and a legal bamble ensued over its ownership
-Courts found in favor of the land owner, who put it up for auction
-The Field Museum in Chicago bought it, with help from Disney and McDonald’s for $7.6 million dollars-museums don’t like to buy fossils, don’t have a lot of money, don’t like to set precedent for buying fossils-would rather just get from public land-that’s the way it should be
-illustrates that dino fossils and information should be more the general public but that this gets complicated when fossils on private land
Paleontological Research: Collecting and Transport
- Prospecting: lots of walking around, looking at the ground
- Surface-collection: oftentimes can just pick up fossils right off the ground-this is called surface collection
- Quarrying: dig to particular area-not as common as you might think
- Plastering:if find something particularly big, can plaster it
- Screen-washing: take a bunch of sediment, and dig it up, tear up sediment in water-falls apart easily there-put sediment in screen boxes, then hopefully fossil comes out of it once water washes sediment out
- Identification
- Cataloguing
Paleontological Research: Preparation & Replication
- Preservative
- Matrix removal
- Physical
- Chemical
- Assembly
- Molding
- Casting
Paleontological Research: Research
- Museum work
- Measurement & Comparison
- New technologies
- GIS (Geographic Information Systems)
- CT Scanning
- Computer Modeling-build 3D models of bones, then put flesh on to see how mass and everything distributed on dinosaurs
What are the 3 different rock types and how are they made?
igneous, sedimentary, metamorphic
- igneous: lava that solidifies
- sedimentary: pieces of other rocks join together, deposited by water, air, or glaciers
- metamorphic: starts with protolith (unaltered rock), then changes occur under pressure and temperature
igneous rock
- solidified molten rocks
- intrusive (plutonic-solidify under earth’s crust) vs. Extrusive (magmatic-solidify in air)
- many crystals of various sizes inside of them-one of the big determinants of how big crystals are is how long rock takes to solidify-longer it takes, bigger the crystals are
sedimentary rock
-made up of eroded “clasts” (pieces of rocks) from other rocks
-deposited by water, air (aeolian), glaciers
-classified mainly on grain size
Conglomerate/breccia→ sandstone → mudstone/shale
(coarser————————————-> finer)
-chemical sediments-evaporates, get salt
-biogenic sedimentary rocks-limestones-things made up of chemicals that are deposited by living things-things like calcium carbonate, used to make shells
metamorphic rock
-solid state changes in texture of other rocks
-starts with protolith (unaltered rock)
-changes occur under pressure and temperature
-examples:
limestone → marble
shale → slate/schist/gneiss
-as heated up, changes in form/type of rock
-eventually it melts
aeolian deposition
deposition by air
strata
- aeolian deposition
- enough pressure that sand will solidify into sandstone after a long time
- like Zion?
Fluvial Deposition
deposition due to water
mudstone
- fluvial deposition
- Badlands National Park, south Dakota
- Uinta Basin, Utah
- huge piles of sediment over time
protolith
unaltered rock
Marble (metamorphosed limestone) in Death Valley
rocks formerly under a lot of heat and pressure, now on surface and starting to erode away
only _____ rock will conserve fossils
sedimentary
____rocks important for talking about dating rocks
igneous
Relative Dating
-just saying “this rock is older than this one”-how old rock is relative to another rock
James Huvon
- prior to Huvon, people thought world was shaped by giant biblical flood
- Father of modern geology
- to Huvon, the world was very old-has been here forever, will be here forever
- not completely true but idea of a very old earth was right
- one of the observations that led to this hypothesis was seeing layers of rocks over layers of rocks that were at 90 degrees-was trying to explain how you could get this formation over time
- said rocks formed-some geologic event titled rocks up-top part eroded away-new sediments laid on top
- Concepts of “Deep Time” and“Uniformitarianism”
- Opposed to “Catastrophism”
- Ideas popularized by Charles Lyell
- “We find no vestige of a beginning – no prospect of an end.” The Theory of the Earth
Uniformitarianism
- Concept of “Deep Time” – large amounts of time and recurring processes can account for the observations we make today
- “Present is the key to the past”–(only) events that occur today also happened in the past
- Opposed to Catastrophism/Neptunism–One large event (a flood) account for the geologic features we see
- our view is between the 2-yes, the things happening/here today were happening/here millions of years ago, but there are some catastrophies that changed the world-like the asteroid killing the dinosaurs
Determining relative ages (What are the rules of relative dating?)
Principle of Superposition
Principle of Original Horizontality
Principle of Cross-cutting relations
Principle of Included Fragments
Determining relative ages: Principle of Superposition
older rocks under younger rocks
Determining relative ages: Principle of Original Horizontality
- rock layers (strata or “Beds”) are originally deposited horizontally
- folded layers near Lulworth Cove, England, indicate that originally horizontal sedimentary beds were deformed after formation
- Grand Canyon shows how rocks usually are deposited horizontally
Determining relative ages: Principle of Cross-cutting relations
older rocks may be cut by younger rocks or other geological features-typical of igneous intrusions
Determining relative ages: Principle of Included Fragments
- if fragments of one material are included in another-then the included material must be older
- all clasts in a sedimentary rock must be older than the rock in which they are found-be careful in dating, not to just date those older pieces-will get inaccurate date
Unconformities
- gap in time in the sedimentary record
- sometimes we’re missing time periods-erosion takes rock away, move rocks away, will be missing some layers or pieces
- even if missing rock in one area can usually find it in another though?
- an unconformity occurs when no beds are deposited or when part of the rock record is removed by erosion
What is an index fossil and what makes a good one?
- Index fossils are fossils used to define and identify geologic periods a
- although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil.
- what makes a good index fossil?
- be widely distributed-Pollen makes a good index fossil, being wind-borne
- be readily preserved in the fossil record-Birds, for example, would make bad index fossils, because although there are many species which have wide ranges, they fossilize very poorly: their skeletons come apart easily
- have a short time of deposition as a proportion of the fossil record, since we want to use it to identify a particular chapter in the history of deposition: it should represent a geographically broad but temporally narrow slice of the record
- Easily distinguishable
- Widespread
- Short periods of geologic time
- Abundant
- Called “Fossil Correlation” & Biostratigraphy
- These principles allowed for the creation of the “Geologic Time Scale”
- The various Eras, Periods, and Epochs were defined by assemblages of fossils
- But how did we put dates on them?
What might cause problems with index fossils?
- maybe they lived in diff environments-will affect types of rocks found
- or in one area didn’t have type of rock-area missing
- animals move and migrate-that will screw it up
Absolute Dating
- actually getting age in numbers-putting a time/year on something
- best way to do this is through radiometric dating
What do we use to tell time?
- So far we’ve only been talking about relative dating–age of things relative to one another
- We need a method of absolute dating–how far in the past did something occur
- Things with regular periodicity:
- Earth’s rotation
- Earth’s revolution
- Pendulums
- Vibrations of crystals and atoms
- Radioactive decay occurs at a constant rate – provides the basis for a clock
Radiometric Dating
The decay activity of an isotope is proportional to the number of radioactive parent atoms ΔΝ/Δτ= -λΝ Parent (P) decays to Daughter (D) The age equation: t = 1/λ × ln(1 + D/P)
Some assumptions of radiometric dating
- Crystallization of the rock resets the clock-so igneous rocks are used for dating, NOT sedimentary rocks or the actual fossils
- There is no daughter isotope at the time of crystallization
- No parent or daughter has entered or left the sample since crystallization
- Under most contexts these are completely reasonable assumptions, but there are methods to correct for violations of them (e.g., taking multiple measures)
Combining Relative and Absolute Dating: Problem
It’s not possible to date all rocks by radioactive isotopes
- e.g., can’t directly determine the age of deposition of most sedimentary rocks
- but, the record of life on this planet is preserved in sedimentary rocks as fossils!
Combining Relative and Absolute Dating: Solution
- date absolute (formation) age of igneous intrusions that cross-cut sedimentary layers
- date minerals in volcanic ash and lava flows (which are deposited “instantaneously”) and use principle of superposition to bracket ages of adjoining sedimentary strata
ma/mya=
Ga/bya=
Ma/mya – Mega-annum/millions of years ago
Ga/bya – Giga-annum/billions of years ago
Oldest minerals on Earth
4.5Ga
Oldest rocks on Earth
4Ga
Oldest record of Life
3.5Ga
Beginning of Phanerozoic Eon/Paleozoic Era
550Ma
Beginning of Mesozoic Era/Triassic Period (when dinosaurs coming into their own)
245mya
Beginning of Jurassic Period
210mya
Beginning of Cretaceous Period
150mya
Beginning of Cenozoic Era/Tertiary Period (last dinos to die out)
65mya
dinos around for
150 million years
…while humans only around for
1 million years
P/T Extinction
245 mya-end of Paleozoic/Permian period-beginning of Mesozoic Era/Triassic Period
Cambrian explosion
first hard parts-500mya
K/T extinction
65mya
Earth’s layers
- center -solid iron core
- outer core-molten iron
- layer in between-the mantle-gooey rock-rocks under enough pressure and hear that they’ll actually flow, the way lava does, the way a lava lamp does
- crust-outside coating
earth’s crust
- outside coating-very thin relative to the rest of the layers
- we know this because of earthquakes
- pressure of earthquake refracted as travel through layers
- the crust is relatively rigid-doesn’t flow like the mantle beneath it-it breaks (faults) instead of flowing
- 2 types of crust: continental crust and oceanic crust
.What are the differences between continental and oceanic crust?
- continental crust a little less dense than oceanic crust-so continental coast floats a little bit higher-but continental thicker (like in km)
- Continental crust is thicker, less dense, and a lot older than oceanic crust
what are faults and what are the different fault types?
- where crust has broken
- faults are fractures in the crystal rocks
- rocks can handle a lot of stress, but eventually they break or fracture, forming faults
- depending on the direction of stress, rocks form different kinds of faults
- 3 types: normal fault, reverse or thrust fault, and strike-slip or transform fault
normal faults
take crust and pull it apart-eventually so much that starts to break and fall down
reverse or thrust faults
push up crust over other crust-Sunset Blvd.
strike-slip or transform faults
move side to side relative to each other-one area slides past another area-San Andreas
does size matter when it comes to dinos?
-size doesn’t matter-just cuz it’s big doesn’t mean it’s a dino
dinos’ legs are…
underneath their body, like mammals-upright posture-w lizards and crocodiles, legs on sides (but recently found crocodiles that existed before dinos with upright posture)
could any dinosaurs swim?
no-dinos weren’t aquatic
dinos’ defining feature
skull holes
did dinos fly?
dinos didn’t fly-that’s a closely related group but not dinos-but some dinos eventually evolved flight
what are examples of modern day dinos?
- modern day birds-all dinos-hummingbirds to ostrichs
- birds (dinos) and crocodiles (closest living group to dinos) are only dino-like things still alive
Dinosaur Hips-Ornithischia vs. Saurischia
-pubism oriented diff-1 forwards 1 backwards (will talk about better later)
Dinosaur Diversity
-number of known dino genera=600
-number of known dino species=720
over time dinos became much more diverse
-probably number of dino genera=1800
-Probable number of dinosaur species≈2200
number of living species
Fish-31,000 Amphibians=6,500 Reptiles=9,000 Birds=10,000 Mammals=5,500 Insects=1,000,000 Plants=320,000
we keep finding more dinos
Gideon and Mary Ann Mantell
- he was a physician
- published a monograph of dino discoveries in 1822-first publication about dinos-in England-named the first dino-named Iguanadon (an ornithopod) and other taxa
William Buckland (1784-1856)
- Oxford University, England
- First to name a dino-Megalasaurus (a theropod)
- thought it was a giant lizard
- coined the term “palaeontology”
- taught Charles Lyell (father of modern geology)
Sir Richard Owen (1804-1892)
- head of the British Museum of Natural History
- Brilliant Anatomist
- Coined the term “Dinosauria”
- actually thought dinos might be endothermic (warm-blooded)
- believed in evolution (although not of the evolution of man) and worked on some of Darwin’s specimens
Crystal Palace Dinosaurs-1851
- fake dino park-restaurant inside one dino
- didn’t think anything that big would be active-sluggish, giant lizards
Archaeopteryx
- discovered in 1861
- Lake Jurassic
- Solnhofen Limestone, Germany
- Recognized as a transitional form between dinos and birds
- added to later editions of Darwin’s Origin of Species as an example of evolution
Bone wars!
- dino craze hit US
- mostly led by Othniel Charles Marsh and Edward Drinker Cope-worked for competing museums on east coast
- Both found the large collections of bones in the American West-Both did much to promote dinosaur research in the late 1800’s
Bone wars-Othniel Charles Marsh
- 1831-1899
- Helped found the Yale Peabody Museum
- Worked at the US Geological Survey and was president of the National Academy of Sciences
- Named 26 genera of dinosaurs, including Apatosaurus, Allosaurus, Diplodocus, Stegosaurus, and Triceratops
Bone wars-Edward Drinker Cope
- 1840-1897
- Worked at the Academy of Natural Sciences in Philadelphia
- Published over 1,400 papers
- Named more than 1,000 vertebrate species
Dinosaur Discoveries in the Early 1900s
- gastroliths (“stomach stones”)
- dinosaur eggs
- dinosaur national monument
- cleveland-Lloyd Dinosaur Quarry
- Mongolia expeditions by Roy Chapman Andrews
- Coelophysis mass burial in New Mexico
John Ostrom and Deinonychus-1969
- Solidified dinosaur ancestry of birds
- reinvestigated the idea of dino ancestry of birds
- his reconstructions of deinonychus were much more accurate and bird-like
- knew their wrists could fold back like birds do
Dinosaur Renaissance
- Jack Homer-Dino mamas-child care and behavior of dines, similar to modern birds
- Bob Bakker-popularized idea of dino endothermy-dino warm-bloodedness
- moving away from lumbering, lazy view of dinos
Modern Achievements
- these guys were the start of paleobiology
- more new species found in the last 25 years that in all the years previous
- much new exploration in Africa, South America, and Asia
- First Antarctic dinosaurs
- explosion of feathered dinosaurs-many dinosaurs had some sort of feather covering
- use of new technologies-computer monitoring
- asteroid impact theory of dinosaur extinction-prior to that, many ideas as to why they went extinct, now we know there was a meteor that was the nail in the coffin for dinos
New questions about dinosaurs
- What are the origins of dinos?
- What are the details of bird origins?
- How “warm-blooded” were they?
- How smart were they
- Did they care for their young?
- How fast did they move?
- Why did large size evolve multiple times?
Modern Portrayals of Dinosaurs
- were in media before this, but after the 60s, became much bigger part of the media
- toys, movies, cartoons-The Land Before Time, Barney
- Jurassic Park is probably the most famous
theory or law
- something that has been tested time and time again and continues to be tested
- we are taught these as if they are the truth, but in actuality they are well-supposed theories, paradigms, or laws-ex: gravitation, evolution, atomic, plate tectonics etc.-they all make predictions and explanations
- but they are always at risk of being replaced by more inclusive, more sophisticated description of nature
- all scientific ideas are subject to challenge and modification. This is the strength of science!
- an open debate of theories weeds out the weaker ones until a strong consensus is reached
- results must be repeatable
- scientists police the quality of research through peer review in journals-research that does not use quality data and methods is not published
- science builds on itself-doesn’t work in a vacuum-research builds on previous work and confirms, explains, or disputes it
- science asks more questions than it answers-we’ll never know everything in science
Science is not a ____!
- Science is not a democracy!
- not everyone’s voice gets to be heard
- science is a rigid meritocracy, where only the hypotheses that can explain the most evidence are accepted
- there are no “centrist” views in science
- There is little room for ‘debate’ around the big issues
- There are disagreements, but usually only on the periphery of the well-established laws and theories
Science is a part of _____
- culture
- Science can be influenced by culture, and in turn influences culture
- Religion is a part of culture too, as are any other man-made institutions (government, universities, etc.)
- Nevertheless, there are empirical facts that science/culture is based on – e.g., the Earth goes around the sun
- “You don’t get to have your own facts.”
science can be applied to ___
-non-scientific pursuits
-reasoning that is evidence-based-making decisions, evaluating news stories and their sources, Evaluating news stories and their sources, voting
-The key is the evidence
-Empirical – phenomena independent of
perceptions and pre-conceived notions
-You don’t get to make up your own facts!
A bit about measurement
- Everything in the natural world varies
- As scientists, we quantify that variation, and minimize it in our measurements
- Statistics is the mathematics specific to describing variation and accounting for it
Pre-Plate Tectonics Ideas-What were some lines of evidence for plate tectonics?
- Deluvian Flood
- Uniformitarianism
- Lyell & Chuck D
- Land bridges
- Upheaval Theory
- Continental Drift
Continental Drift
- Alfred Wegener 1915
- looked at maps-south america fits pretty well into Africa
- first line of evidence: continents fit together like a puzzla
- first to come up w name Pangea (“all the earth”)
- people came up w Laurasia (top half of earth) and Gondwana (bottom half) concepts/words later
Continental Drift: Biogeographic Evidence
- another line of evidence
- looked at distribution of animals that can’t swim across oceans
- found them on many different continents/countries/islands
- matched up ranges of animals when put together pangea
Continental Drift: Glacial and Rock Evidence
- evidence for large scale glaciation in the past-can see direction they moved by looking at rocks-scratches on the rocks they plow over
- saw these glacial striations and rocks all over the world-looked fairly random-didn’t really make sense-but when put together pangea made sense, pattern-central point of glaciation and glaciers moving different directions from that spot
Continental Drift No More-why rejected
- Rejected because of a lack of a mechanism
- Continents can’t move through the dense basalt of the ocean floor-duh!
- Evidence explained away as coincidence and with land bridges
Paleomagnetism-magnetic reversals
- Magnetic rocks (e.g. magnetite and basalts) record the record of both the inclination and reversals
- So… if you have a record of magnetic rocks you tell when and where (latitude) they are from, or, conversely, where the pole was at that time
Harry H. Hess
- Naval sonar operator and geologist
- Mapped the topography and magnetism of the ocean floor
- What did he find:
- World’s longest mountain range
- Volcanoes and heat output at the crest of the mountains
- Gradation of sediment thickness outward
- Magnetic “stripes” the same on both sides
- Hess even had a mechanism-convection!
- “Continents” are just pieces of continental crust rafting along on ocean basalts, and together they make up plates
Convection in the Mantle
-It took scientists many years to accept it, but the forces generated by thousands of degrees of heating actually overcome the high viscosity of rocks. In other words, the mantle convects.
Where does the old sea floor go?
- Down deep sea trenches, of course!
- Spreading and sinking are happening all over the world!
What is the life cycle of a plate?
Plate Life Cycle (Part 1)-rift opening (divergent margin) and spreading (pulled apart) to make passive margins-eventually if get pulled apart enough get a new oceanic basin-because it’s a pulling motion get lots of normal faults as the crust gets pulled apart
Plate Life Cycle (Part 2)- subduction (convergent boundaries) and mountain building
-2 plates come together, mountains and volcanos form
Terrestrial divergent margin & nascent ocean, e.g. Ria Valley
-starting to get new oceans
-Lots of normal faulting. Can lead to new oceanic plates
The new East African Ocean!
Passive (intraplate) margin, e.g. Atlantic coast
-Inactive continental shelf, with lots of deposition over old normal faults
Old Passive Margin-where?/example
Grand Canyon National Park
What’s going on in the middle of the continental plates?
Not much-ex: Canadian Shield
Craton
stable center of continental plates
What happens at subduction zones?
- Earthquakes at subduction zones
- note that the epicenters get deeper inward from the trench
Convergent Boundaries
- oceanic -oceanic (o-o)
- e.g. Japan
- oceanic - continental (o-c)
- e.g. Andes and Pacific Northwest
- continental - continental (c-c)
- e.g. Himalayas
- Subduction determined by density
Oceanic-oceanic (O-O)
- Mountain building
- e.g. Japan, Caribbean
- oceanic convergent boundary
- denser oceanic crust goes under other oceanic crust
- creates trench
- crust that goes over-rumpled a little, creates mountains and volcanos?
Continental Oceanic (C-O)
- Mountain Building
- e.g. Andes
- ex: pacific northwest
- oceanic crust goes under continental crust
- continental convergent margin
- trench created, then mountains/volcanos created on continental part that’s rumpled
Batholiths
Evidence of old subduction
Continental Continental (C-C)
- Mountain Building
- e.g. Himalayas
- Continents collide with other continents or island arcs, usually with lots of thrust faults
- convergent plate boundary
- Main boundary thrust-Pakistan-thrust faulting near the Pakistan/Afghanistan border
Transform Boundaries
- Where plates slide past one another with strike-slip faults
- Either between continents or linking spreading ridges
- There can be mountain building here as well due to the shape of the transform boundary
- transform margin-e.g. CA’s San Andreas
Interplate volcanism-hot spots
- A volcanos island or seamount is built up by extrusions from a hot spot, or source of magma, in the mantle
- as the plate moves, the volcano is carried away from the source of magma and becomes extinct. The surface of the island can then be eroded to sea level, and reefs can grow to form an atoll. A new island is then formed over the hot spot
- continued plate movement produces a chain of islands
- the islands of the chain are progressively older away from the hot spot
- ex: Hawaii, Yellowstone
Hot spot/Subduction Interaction
- can cause there to be a lot of volcanic activity
- may contribute to how explosive Yellowstone eruptions can be
Overview of plate boundaries and tectonics-type: divergent: spreading center
earthquakes: yes, many small, some bid along the transform faults
volcanos: lots of oozing, slow
Overview of plate boundaries and tectonics
-type: divergent: passive margin
earthquakes: at normal faults early on, then nothing
volcanos: none
Overview of plate boundaries and tectonics-type: convergent: ocean-ocean
earthquakes: yes, of varying depths
volcanos: lots and violent
Overview of plate boundaries and tectonics-type: convergent: ocean-continent
earthquakes: yes, of varying depths
volcanos: yes, and violent
Overview of plate boundaries and tectonics-type: convergent: continent-continent
earthquakes: yes, along thrust faults
volcanos: none after suturing
Overview of plate boundaries and tectonics-type: Transform
earthquakes: lots, of varying magnitudes
volcanos: none
Overview of plate boundaries and tectonics-type: Hot Spots
earthquakes: some associated with magma movement
volcanos: lots of oozing making shield volcanos. Can be explosive if continental.
Geologic Movement: Permian-latest Paleozoic
- everything was crammed together in one supercontinent-pangea
- much of western US is underwater
Geologic Movement: Jurassic-middle Mesozoic
- Appalachian mountains were big and new-they’ve been eroding since then
- subduction going on in the west-volcanos that would become Sierra (mountains?)
- sea level higher
- eventually the Atlantic Ocean starts to form
Geologic Movement: Formation of the Atlantic
heat rose due to convection, pulled apart crust, created normal faults, started to form this new proto-ocean, eventually spread to the point where have big new ocean-just like is happening in Africa now
Western US Sedimentation-example
Zion
Aeolian Deposition and Strata-example
Great Sief Dune, Egypt, Zion National Park
Building Continents
- Continental lithosphere (crust) and oceanic lithosphere meet-but the 2 plates that are moving are both oceanic, just 1 turns into land-passive continental margin where content meets water-island arc in middle of water, where the 2 oceanic plates meet
- collision-cesation of subduction-island arc has moved closed to land now as the oceanic place moves over the other oceanic plate (which gets pushed down)
- arc material (island) added to continent-continued collision, with deformation (island wrinkled)-incipient rupture is where water meets land (now the island)-old oceanic crust thats been pushed under other oceanic crust/slab may break off and sink
- subduction commences with formation of new subduction zone. new arc forms on continental margin-where former island meets water is active continental margin
- ocean-ocean boundaries can change to ocean-continent boundaries
- the island arc gets sutured to the continent
a current passive margin example
Atlantic Coast
Western interior seaway
-there used to be a big relatively shallow seaway in middle of North America
Sierra and Sevier Orogenies - making the Sierras and the Wasatch Mtns.
- Subduction accompanied by inland thrust faulting
- oceanic crust moves under continental crust (subducting Pacific plate moves under contintental margin)-trench created where plates meet-volcanos and batholiths form on land
Sevier Thrust Mountains example
the Wasatch Mtns.
Plate Tectonics has an impact on ___!
- life
- Determines dispersal routes
- e.g. abelisaurids
- Isolates groups so they evolve independently
- e.g. ceratopsians are only found in Laurasia
- Affects climate
- e.g. dinosaurs in Antarctica
End of Late Heavy Meteor Bombardment
Moon formation
3,700mya or so, in the Archean Period
4,400mya or so, in the Archean PEriod
Origin of Life (When did life start?)
3.5-3.8bya
Early Atmosphere
- evolution doesn’t have much to say about the origin of life-about how life changes
- we don’t know exactly
- we have bits and pieces, theories
- we do know what the earth looked like at that time
- CH4(?), NH4(?), H20, N2, H2, H2S, CO2, maybe O2-all in atmosphere-a lot diff from today-mostly nitrogen, oxygen, and CO2 not
- life changed the atmosphere
- these compounds probably came from interstellar space!
- Lots of energy around-Lightning, Volcanoes and Vents, UV light - no ozone! hits surface of earth now, but not as much, cuz now have ozone layer-didn’t have ozone layer back then, cuz didn’t have a lot of oxygen
Miller-Urey Experiment (What is some of the evidience of the earliest life)
- asked themselves can we simulate what this early earth looked like and see what happens-can we create life?
- put it through this system
- what they found wasn’t life but very complex molecules that we associate with life-so could get building blocks of life by those primitive chemicals in atmosphere
Earliest Life (What is some of the evidience of the earliest life cont.)
- some of the earliest fossils
- microscopic, innocuous
- found in very old sedimentary rock
- to find the fossils: get rocks, cut in very thin slices, put under microscope, put light under it, look for fossils
- there are some modern analogs of these today (still exist or similar creatures now)
Stromatolites
- 3.5 Ga
- there are a few big fossils (macrofossils) found around this time
- don’t look like much
- thought were just weird rocks, no fossils
- but then actually found modern version of this-still alive today-get same structures in fossils
- this was the final proof that these were evidence of past life
- life is pretty simple-single cells that might have grouped together but nothing else really
Banded Iron Formations
- 3-1.5 Ga
- these gave off oxygen, so oxygen started to build up in atmosphere-became more like today
- sediment, has iron in it-and iron when exposed to oxygen rusts-so as these sediments was settling out of ocean-any oxygen rusted with sediment-got these really stripe-y rocks-big build up of oxygen in atmosphere rusting with rocks-this was evidence of oxygen in atmosphere-eventually reach kind of an equilibrium though-so don’t see these sorts of things today-but this was evidence that life was starting to change the world
- Evidence of increased oxygen in the atmosphere
Origin of Eukaryotes
- before this, just prokaryotes-single cell organisms
- symbiosis of bacteria-like organisms
- forms the mitochondria, chloroplasts and possibly also the nucleus
Ediacaran Fauna-first multicellular life
- what’s challenging about looking at this fauna is none of it looks like anything we have today
- this makes sense-part of evolution is that as we go farther and farther back in time, fossils should look more and more different
- don’t really know what these creatures are-no comparison
- multicellular
- some of them were the first animal-like creatures
Ediacaran Fauna-first multicellular life-burrows
- primitive invertebrate animals need front and back end to make burrows
- so burrow tells us animals like this existed
- tells us life getting more complex at this time
Edicaran Life
- simple creatures
- looks vaguely like things today but don’t look quite right
Burgess shale
- preservation is phenomenal-see soft and hard parts of animals, tracks
- The Burgess Shale Formation, located in the Canadian Rockies of British Columbia, is one of the world’s most celebrated fossil fields. It is famous for the exceptional preservation of the soft parts of its fossils. At 505 million years (Middle Cambrian) old, it is one of the earliest fossil beds containing soft-part imprints.
Reconstruction
- things starting to look like today
- crustaceans like shrimp existed, copepods
- aquatic worms
- terrestrial worms
- trilobites
- vertebrates!!! first ones: pikaia, amphioxus
- predators like the opabinia, anomalocaris (2 meters!!), scary sea creatures, Amiskwia, Wiwaxia
- HUGE diversity of species-Cambrian explosion
Why is there such a huge diversity? (What is the Cambrian Explosion and what were some possible causes of it?)
-The “Cambrian Explosion”-refers to the appearance in the fossil record of most major animal body plans about 543 million years ago. The new fossils appear in an interval of 20 million years or less.
-huge diversity of species
-possible causes:
Evolution of the asshole
Remnants of a Mass Extinction?
Increasing complexity
Predators
Snowball earth?
possible causes of Cambrian Explosion-evolution of the asshole
- more primitive mammals have 1 hole-take in, digest, goes out same hole
- more complex animals eat things through 1 end and expel out other
- big deal-allows you to do more things, like burrow, more complex body plan
possible causes of Cambrian Explosion-Remnants of a Mass Extinction?
- or maybe they all died out, new ecosystem to be filled
- after dinos, mammals take over and fill same niches
- so maybe here happens too-1 cell things die off, then more complex animals created
possible causes of Cambrian Explosion-Increasing complexity
-as animals get more and more complex start creating new environments, other animals can explore these environments, use then, evolve, become more complex
