Ch 21
Useful reference: Earth Science Reference Table:
http://www.p12.nysed.gov/assessment/reftable/earthscience-rt/esrt2011-engr.pdf
Relative age dating
What are three main ideas of geoscience?
- the rock record provides evidence of geologic events and life forms of the past
- processes observed on Earth in the present also acted in the past
- Earth is very old and has changed over time
What are the key principles of relative dating?
- law of superposition- in undisturbed layers of sedimentary rock, the older layers are below more recent layers.
- principle of original horizontality – layers of sediments are deposited in horizontal layers
- principle of cross-cutting relationships – a rock layer is older than a fault or igneous intrusion that cuts through it.
How do geologists interpret the rock record?
- The study of inclusions and unconformities
- Correlation of rock layers in different locations
3 Types of Unconformities
1. Disconformities
Click here for an animation of a disconformity
http://www.wwnorton.com/college/geo/egeo2/content/animations/10_4.htm
2. Nonconformities
Click here for another nonconformity
http://www.wwnorton.com/college/geo/egeo2/content/animations/10_4.htm
3. Angular Unconformities
Click here for animation of an angular unconformity
Click here for another angular unconformity
Click here for an animation of an angular nonconformity
http://www.wwnorton.com/college/geo/egeo2/content/animations/10_4.htm
Questions:
1. Describe how a disconformity forms.
2. Describe how an angular unconformity forms.
3. Describe how a nonconformity occurs? (Hint: what type(s) of rock)
4. How do a nonconformtiy and a disconformity differ?
5. Complete the table
Type of unconformity | Nonconformity | Disconformity | Angular Unconformity |
Sketch | |||
Notes |
21.3 Absolute Dating
Vocabulary
- radioactivity
- half-life
- radiometric dating
- radiocarbon dating
Objectives
What happens during radioactive decay?
- unstable atomic nuclei spontaneously decay, releasing energy
How are isotopes used in radiometric dating?
- Scientists measure the ratio between radioactive parent element and daughter products in the sample to be dated. The older the sample, the more daughter product it contains.
How can radiometric dating be used to date organic material?
- When an organisms dies, the amount of carbon-14 gradually decreases as it decays. By comparing C-14 to C-12 ratios, radiocarbon dates can be determined
How can radiometric dating be used to date sedimentary rock?
- Geologists must relate sedimentary rock to datable masses of igneous rock.
Review Videos:
Radioactive Dating 7:09
https://www.youtube.com/watch?v=1920gi3swe4
Carbon Dating: How Does it Work? 10:59
https://www.youtube.com/watch?v=udkQwW6aLik&index=3&list=PL9CE5DF26BD7E30F2
Carbon-14 dating 1 :15
mhttps://www.youtube.com/watch?v=81dWTeregEA&list=PL9CE5DF26BD7E30F2&index=2
Bill Nye: Explains half life 1:05
mhttps://www.youtube.com/watch?v=zzJF31Y2-rc
Link to Radioactive dating site
http://phet.colorado.edu/en/simulation/radioactive-dating-game
Radioactive dating practice problems:
Link for half life graph
mhttp://geology.wwu.edu/dept/faculty/hirschd/courses/2008/fall/101/homework/geoltime/Fig813.gif
http://geology.wwu.edu/dept/faculty/hirschd/courses/2008/fall/101/homework/geoltime/Fig813.gif
Ch 21.4
Fossil Review:
Bill Nye 34:35
mhttps://www.youtube.com/watch?v=hOX8_wqqRPs
The Rock Cycle
http://scienceviews.com/geology/images/rockcycle.jpg
The Rock Cycle video
MIT
http://video.mit.edu/watch/the-rock-cycle-13527/
“Formed this way” parody
Structure of the Earth:
Review Videos:
mhttps://www.youtube.com/watch?v=7NJQKs9-NM0
Theory of Plate Tectonics
Vocabulary
- plate
- plate tectonics
- divergent boundary
- convergent boundary
- transform fault boundary
- continental volcanic arc
- volcanic island arc
Objectives
What is the theory of plate tectonics?
Earth’s lithospheric plates move slowly relative to each other, driven by convection currents in the mantle.
What are 3 types of plate boundaries? Be able to identify each and describe what geologic feature is formed by each.
1. Converging –> <–
- continental-continental
- oceanic-oceanic
- continental-oceanic
2. Diverging <– –>
- continental-continental
- oceanic-oceanic
3. Transform <==>
- continental-continental
- oceanic-oceanic
Questions:
Using pages 262-263, locate the following.
1. A major plate that includes both an entire continent plus a large area of sea floor
2. Two example of a divergent boundary
3. One example of a convergent boundary
4. One example of a transform boundary
Complete the blanks.
According to the theory of plate tectonics, large pieces of the Earth’s _________________ called plates move slowly over Earth’s surface driven by _________________ ________________ in the mantle. Plates can include _________________ and or ________________ lithosphere. Plate interactions help cause earthquakes, __________________, and ____________________.
Types of plate boundaries
I. Convergent Boundaries = –> <–
Three types of convergent boundaries
1. Continental/Continental
Click here for animation. Watch the animation and label final diagram
What geologic feature forms at this types of boundary?
——————————————————————————-
Continental/Oceanic
Click here for animation. Watch the animation and label final diagram
What geologic feature forms at this types of boundary?
——————————————————————————-
Oceanic/Oceanic
Click here for animation. Watch the animation and label final diagram
What geologic feature forms at this types of boundary?
………………………………………………………………………………………………………………………………………..
II. Divergent Boundaries = <– –>
Click here for links to diagrams
1. Oceanic/Oceanic
What geologic feature forms at this types of boundary?
——————————————————————————-
2. Continental/Continental
What geologic feature forms at this types of boundary?
………………………………………………………………………………………………………………………………………..
3. Transform Fault Boundary <==>
Click here for links to diagrams
Continental/Continental
What geologic feature forms at this types of boundary?
—————————————————————————
Vocabulary
continental drift
Pangaea
Objectives
Review plate tectonics (types of boundaries) and forces driving plate movement; examine evidence of plate movement
Examine the science process that progressed from continental drift to sea-floor spreading to plate tectonics
What is the Wegener’s hypothesis of continental drift?
The continents had once been joined to form a single super continent. It was called Pangaea meaning all land.
What evidence support continental drift?
1. Puzzle piece fit of continents
2. Matching fossils
Fossils of Mesosaurus have been found on both sides of the South Atlantic Ocean and no where else in the world. These, as well as the remains of other fossil organisms, appear to link these landmasses.
3. Matching rock types
The Appalacian Mtns in the USA are similar in age to the Caldonian Mtns found in the British Isles & Scandinavia.
4. Ancient climates
Ice sheets covered large areas of the Southern Hemisphere. At the same time, large tropical swamps existed in the Northern hemisphere
Why was Wegener’s hypothesis rejected?
Wegener could not describe a mechanism capable of moving the continents
Questions:
Click this link to answer the questions
or type http://www.dynamicscience.com.au/tester/solutions/space%20science/evdn.html
1) How did fossils provide evidence for continental drift?
2) Explain the term paleomagnetism. How is paleomagnetism used to support the theory of continental drift?
3) Is any one piece of evidence overwhelming support for continental drift?
4) What is the geological evidence for continental drift?
5) What are glacial till deposits? How are they used to support continental drift?
Click the links below for the handouts and reassemble Pangaea.
For each student group:
Student Map of the World Today
Key to Wegener’s Evidence sheet
Student Puzzle Pieces
———————————————————-
Vocabulary
- sonar
- deep-ocean trench
- mid-ocean ridge
- rift valley
- sea-floor spreading
- subduction
- paleomagnetism
Objectives
What are mid-ocean ridges and deep-ocean trenches?
Mid-ocean ridge- a long chain of mountains extending the length of the ocean. It is the longest feature on Earth’s surface.
Click here to see map of mid ocean ridges
Deep ocean trench – a long curved valley along the edges of some ocean basins.
What occurs during sea-floor spreading?
New ocean crust forms along mid-ocean ridges. Fractures along the central valley of the ridge fill with magma. Gradually, the magma cools forming new ocean crust.
As new ocean floor is added, the older ocean floor moves outward away from the ridge on both sides
Although new ocean floor is constantly being added, the planet remains the same size as older older ocean floor is subducted and returns to the mantle as it sinks into an ocean trench.
Click here to see image of a subduction zone
What is the evidence for sea-floor spreading?
1. Magnetic strips
Click link for image. Scroll down to “Magnetic reversals and sea-floor spreading”
2. Earthquake Patterns
Earthquake patterns indicate subduction zones
Click here for link to Wadati-Benioff zones
How are these patterns evidence of subduction?
3. Age of ocean Floor
Questions:
1. What do you notice about the pattern of magnetic reversals on either side of a mid-ocean ridge? Hint: Click this link. Scroll down to Magnetic reversals and sea floor spreading.
2. How are these Wadati-Beniof patterns evidence of subduction?
3. Where is the sea floor the youngest? Use this link
4. How old is the oldest ocean floor floor between So America and Africa?
5. What happens to the oceanic crust as it approached the continent?
6. Why does oceanic crust sink below continental crust? Hint: Read this link
————————————————————————————————–
———————————————————————————————————–
Ch 9.4 Mechanism of Plate Motion
Week 4 vocabulary
- convection current
- slab-pull
- ridge-push
- mantle plume
Week 4 Objectives
What causes plate motions?
Convection currents in the mantle provide the basic driving forces for plate motions.
What are the mechanism of plate motions?
The sinking of cold oceanic lithosphere directly drives the motion of mantle convection through slab pull and ridge push. Some scientists think mantle plumes are involved in the upward flow of rock in the mantle.
Questions.
Click here for an animation on convection currents
Scroll down to “3.1.1 Convection in a Little More Detail”
1. Describe how a convection cell works. You may wish to draw a sketch but you must label the sketch.
Click this link for a short animation.
2. What does the green represent?
3. What does the red represent?
4. What happens to the green over time?
5. How do convection currents cause the movement of plates? Click here
——————————————————————————————-