Earth Science –Bennett HS—Q3 –Notebook

The following notes should be entered into your notebooks (a spiral notebook or loose leaf paper in a 3-ring binder), in chronological order and will be collected and graded on April 15th.  Blank lines and any information that appears in brackets “[xxxx]” is information that should have been entered by each student and will vary for each student.

--Ms. Milligan



Geologic Time

Relative Time


“Who’s Older Than Who?

15 organisms throughout geologic time are listed below.  Predict the order from oldest to the youngest that these organisms appeared in Earth’s history. 


Grass         Humans                  Earliest Fish          Forest


Large Carnivores    Trilobites  Stromatolites  Sharks


Flowering Plants     Dinosaurs         Reptiles     Birds   


Insects                  Algal Reefs            Placental mammals


Record you prediction below:  (Remember the oldest is always at the bottom.)




































































Earth’s History

  • Scientists have good evidence that the earth is very old
  • approximately four and one-half billion years old.
  • radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age.
  • direct evidence from observations of the rock layers help determine the relative age of rock layers
  • Specific rock formations are indicative of a particular type of environment existing when the rock was being formed
  • For example, most limestones represent marine environments, whereas, sandstones with ripple marks might indicate a shoreline habitat or a riverbed



  • Fossils are remains of evidence of former living things
  • Examples: bones; shells; footprints; organic compounds
  • The majority of fossils are found in sedimentary rocks. 

    Why?  ___________________________________



[You do not have to copy the chart of fossils below, but look it over and read the descriptions.]

Figure 2-A. Sketches of Marine Fossil Organisms (Not to Scale)


NAME: Brachiopod
PHYLUM: Brachiopoda
DESCRIPTION: "Lampshells"; exclusively marine organisms with soft bodies and bivalve shells; many living species

NAME: Trilobite
PHYLUM: Arthropoda
DESCRIPTION: Three-lobed body; burrowing, crawling, and swimming forms; extinct

NAME: Eurypterid
PHYLUM: Arthropoda
DESCRIPTION: Many were large (a few rare species were 5 feet in length); crawling and swimming forms; extinct


NAME: Graptolite
PHYLUM: Chordata
DESCRIPTION: Primitive form of chordate; floating form with branched stalks; extinct

NAME: Horn coral
PHYLUM: Coelenterata (Cnidaria)
DESCRIPTION: Jellyfish relative with stony (Cnidaria)(calcareous) exoskeleton found in reef environments; extinct

NAME: Crinoid
PHYLUM: Echinodermata
DESCRIPTION: Multibranched relative of starfish; lives attached to the ocean bottom; some living species ("sea lilies")


NAME: Placoderm
PHYLUM: Vertebrata
DESCRIPTION: Primitive armored fish; extinct

NAME: Foraminifera (microscopic type)
PHYLUM: Protozoa (Sarcodina)
DESCRIPTION: Shelled, amoeba-like organism

NAME: Gastropod
PHYLUM: Mollusca
DESCRIPTION: Snails and relatives; many living species


NAME: Pelecypod
PHYLUM: Mollusca
DESCRIPTION: Clams and oysters; many living species

NAME: Ammonite
PHYLUM: Mollusca
DESCRIPTION: Squid-like animal with coiled, chambered shell; related to modern-day Nautilus

NAME: Icthyosaur
PHYLUM: Vertebrata
DESCRIPTION: Carnivore; air-breathing aquatic animal; extinct





NAME: Shark's tooth
PHYLUM: Vertebrata
DESCRIPTION: Cartilage fish; many living species



Index Fossils

  • Index fossils are used to find the age of the rock in which it is found
  • The best index fossils are organisms that were:

1.    around for a short time geologically

2.but were found over a large area of the earth


See pages 8 & 9 of the Earth Science Reference Tables (ESRT) for the index fossils used to identify geologic time in New York State.


Name two index fossils that are used to identify the time during which mammoths lived:

__________________ & ___________________


Name two index fossils that are used to identify the Permian period: 


__________________ & ________________









  • Process of correlation makes it possible rocks from different places are similar in age
  • Bedrock is an area’s local rock
  • bedrock layers can be matched up (correlated) with other similar layers
  • Similarities between appearance, color, mineral composition and rock sequence can be evidence of correlation
  • The most important property to show correlation is rock sequence – the order of the rock layers


Law of Superposition

  • rock layer on the bottom is the oldest
  • the layers get younger as you move up the profile
  • this is true for any undisturbed rock exposure

    Igneous Intrusions
  • formed when magma is injected into older rock layers in the crust
  • younger than rock they are found in
  • look for contact metamorphic rock in layer above and below the intrusion

  Igneous Extrusions

·      rocks that formed from lava on the surface of the earth

·      younger than rock layers below

·      look for contact metamorphic rock on the bottom only


·      bends in the rock layers

·      occur after the rock layers formed


·      cracks in rock layers where some movement has taken place

·      Faults produce offset layers.


·      buried erosion surface

·      formed when an area of the crust was uplifted above sea level and then eroded.

·      after that the area subsided below sea level and new sediments were deposited on top of the eroded surface



Cross-sectional view of a portion of the Earth’s Crust:


[Click here to view the diagram.  Sketch the diagram in your notebook, then write and answer the questions below.]



Which section is an igneous intrusion? ____


Which sections may contain fossils? ___________


What is evidence of igneous intrusion?


_____________   ________________________


Which section is the youngest? ____


Where is the fault? _________


Is there evidence of folds? ______


Is there evidence of an unconformity? _______




Absolute Dating of Rocks


Using Radioactive Decay

·      Some elements exist as isotopes

·      Isotopes have a different mass than other isotopes of the same element

·      Some isotopes are unstable or radioactive and they decay (lose mass) at a steady rate



·      Half-life is the amount of time it takes for radioactive material to decay to half of its original mass


[see page 1 of the ESRT for the half-life data of several isotopes]


A sample of rock contains 100 grams of C-14.


After one half-life

(5,700 years)

mass C-14  =  50 g à (1/2 of 100 g)


After two half-lives

(11,400 yrs. = 5,700 yrs. + 5,700 yrs.)

mass C-14  =  25 g  à (1/2 of 50 g)


After three half-lives

(17,100 yrs. = 5,700 years + 5,700 years + 5,700 years)

mass C-14  =  12.5 g à (1/2 of 25 g)



A sample of granite has 10 grams of U-238.  After 9 billion years, how much U-238 would be left?




·      The ratio of the mass of radioactive isotope to the mass of its decay product is measured.  This is called the decay-product ratio.



A sample of granite is found to contain a 1 gram Uranium-238 to every 3 grams of Lead-206.


So the ratio is :      


=              relative mass of isotope                  .

     rel. mass isotope + rel. mass decay product


=                           1 g U-238           .

                    1 g U-238 + 3 g Pb-206


=              1 g   .   =   0.25  left

               4 g


=         25% of the U-238 remains

or 75% decayed


How many half-lives does it take for ¼ or 0.25 of a sample to remain?

1 half life  à ½ of original material remains

2 half lives à ¼ of original material (½ of ½ = ¼)


Therefore, 2 half lives have passed.  For Uranium-238, each half-life is 4.5 billion years.


So, it took 9 billion years for 4 grams of U-238 to decay by 75%.


How many grams of the 4 gram U-238 sample would remain after 4.5 billion years? 








Continental Drift

Around 1912, a German scientist named  Alfred Wegener theorized that:

àEarth's continents were once joined in a single, large landmass, called Pangea.

à the continents separated and collided as  they moved around over the last few million years,  called continental drift.




                                  [Click here to view the diagram.]




Using page 9 of ESRT,  give the name of the name of the period when Pangea was formed:   ________________________         


Evidence he used to support his theory:

1) Continent Shapes- continents appear to be shaped in such a way that they would fit together nicely, like a jigsaw puzzle.

2) Rock Formations- rock formations on different continents that match up beautifully when the continents are put back together.

3) Fossils- fossils found on different continents that would also match up nicely if the continents were all once together.


People of the time mostly thought Wegener was crazy!


New Evidence
In the 1950's, scientists discovered some surprising evidence in support of Wegener's theory.

àWhile mapping the ocean floor, scientists discovered two important, and unexpected things:

First, the age of the rocks that make up the ocean floor gets older as you move away from the ridges at the center. This meant that the youngest rocks were found near the ridges, and the oldest rocks near the continents.


                                  [Click here to view the diagram.]



Second, there are stripes of alternating magnetic polarity on each side of the ridge.


                                  [Click here to view the diagram.]



These discoveries gave rise to the now respectable science of Plate Tectonics:

àthis is the theory that the Earth's seemingly solid crust is actually made up of several pieces, or plates, that move around independently.


Answer the following questions using page 5 of the ESRT:


How many plates are there? _________

List the names of all of the plates:
















Types of Plate Boundaries
The places where the different plates meet, called plate boundaries, are where the tectonic action really is. There are three basic types: convergent, divergent, and transform boundaries.


All of the different boundaries and their locations are found on  page 5 of the Earth Science Reference Tables.  Notice the key that shows the different boundaries and their symbols.




Convergent Boundaries: This a when two plates are moving toward each other, as shown below.


                                  [Click here to view the diagram and sketch into your notebook.]



Using ESRT pg. 5, give the names of two plates that form a convergent boundary between them:


___________________ and __________________



If the two plates are of relatively low, and similar densities, the plates will form a Collision Boundary.


                                  [Click here to view the diagram.]



In this scenario, the crust is forced upward by the collision, resulting in mountain building. The diagram above shows how this type of collision between India and China forced the formation of the Himalayan Mountains.




If one of the plates is more dense than the other, as happens when oceanic and continental crust meet, then the more dense plate will be forced under the less dense plate. This forms a trench, or deep valley, where the plates meet. This is called subduction, and is shown in the diagram above. This often results in a chain of volcanoes running parallel to the trench.


                                  [Click here to view the diagram.]



Divergent Boundaries: As you might expect, this is essentially the opposite of a convergent boundary. This occurs when two plates are moving away from one another, as shown below. This is seen at mid-ocean ridges and rifts.


                                  [Click here to view the diagram and sketch into your notebook.]



Using ESRT pg. 5, give the names of two plates that form a divergent boundary between them:

__________________ and __________________


Transform Boundaries: This type of boundary forms when two plates are sliding past one another. The diagram below illustrates this motion. The most popular example of this is the San Andreas Fault in California.


                                  [Click here to view the diagram and sketch into your notebook.]



Using ESRT pg. 5, give the names of two other plates that form a transform boundary between them:


___________________ and __________________







Tectonic Forces
The movement of the plates is driven by convection currents in the mantle. These currents cause the solid plates to float along on top of the semi-molten mantle material.


                                  [Click here to view the diagram and sketch into your notebook.]



Sometimes, there is an opening in the middle of a plate that allows the molten material to flow through it. This is called a hot spot, and usually results in a chain of volcanic islands that form as the plate moves over the hot spot. The Hawaiian Islands are a great example of this.


                                  [Click here to view the diagram.]






                                3 TYPES OF

                          TECTONIC PLATE


Organization Chart


Organization Chart




Organization Chart





Earthquakes and Volcanoes


o     Earthquakes and Plate Tectonics are vitally connected.

o     The movement of the Earth's crustal plates is the major cause of earthquakes, and volcanoes also.

See page 5 of the Earth Science Reference Tables.

If you were to plot all of the earthquakes that occur on Earth, you would find that they follow a pattern.

This pattern follows fairly closely the plate boundaries indicated on the reference table.

                                  [Click here to view the diagram.]

You would see a similar pattern if you plotted the volcanoes of the world.


·       An earthquake is a movement or shaking of the Earth's crust.

·       Most earthquakes occur along a fault.

·       A fault is a crack or break in the Earth's crust along which there has been some movement.


                                  [Click here to view the diagram. Sketch this in your notebook.]



The picture above shows the effect on the surface after the movement along such a fault.


                                  [Click here to view the diagram. Sketch this in your notebook.]



·       The exact location of the crustal movement is called the focus.

·       Since we are usually concerned about effects on the surface,

    we often refer to the epicenter, which is the location on the surface directly above the focus.

·       When an earthquake occurs, several kinds of seismic waves are produced, and travel outward from the focus.


Measuring Earthquakes
There are two different scales that are commonly used to

measure the severity of an earthquake:

·       The Richter Scale measures the amount of energy released by the earthquake. It is a logarithmic scale, meaning that a 6 is 10 times more powerful than a 5.

·       The Mercalli Scale attempts to measure the severity of the earthquake by observing the damage that it causes.  A simplified Mercalli Scale is shown below:


                                  [Click here to view the table and copy it into your notebook, if you did not get the handout in class.]



Earthquake Waves
Although earthquakes produce several different types of waves, we will focus (no pun intended) on two: P Waves and S waves.

·       Both waves are produced at the moment an earthquake

   occurs, but they have several different characteristics.

   It is important to understand the differences between

   these two waves.


P waves

S waves

Primary waves

Secondary waves

Travel faster, and at seismic stations first.

Travel slower, and arrive at seismic stations second.

Push-pull, or compression waves.

Side-to-side, or shear waves.

Travel through solids, liquids, and gases.

Travel only through solids.













The two pictures below illustrate the difference between the motion in a P wave (the top), and an S wave (the bottom).



[Click here to view the diagram. Sketch this into your notebook.]



[Click here to view the diagram. Sketch this into your notebook.]





Locating the Epicenter  (handout)
Since P and S waves travel at different rates, we can use them to calculate our distance

to the epicenter.   P waves travel faster than S waves, and will always

arrive at a seismic station first. How far ahead of the S waves they arrive depends

on how far away the earthquake is. The further away the epicenter is, the wider

the gap will be between the P and S waves. This is similar to the effect during

a thunderstorm, when you can estimate how far away the lightning is by timing

how long you have to wait for the thunder.

See the chart on page 11 of the Earth Science Reference Tables to

help with this.


To use the chart on page 11, simply find the time delay between arrival of the

P wave and the arrival of the S wave. Let's say the P wave arrives at 1:32, and

the S wave arrives at 1:37.  There is a 5 minute gap between the P and S waves.

You would be able to see this gap on a seismograph like the one below.


                                  [Click here to view the diagram.]




So you need to find the place on the chart where the P and S waves are 5 minutes apart.


                                  [Click here to view the diagram.]




To do this, draw a line on a sheet of scrap paper that represents 5 minutes on the graph.

Then slide the paper up the curves until the 5 minute gap matches

the gap between the lines. When you find the spot where the curves are

5 minutes apart, simply drop vertically down to read the distance. In the

example above, the earthquake epicenter is 3,600 km away.



Locating the Epicenter of an Earthquake


[Click here to view the diagram.]

Once you determine the distance from the seismic station to the epicenter, you could draw a circle around that station to show the possible epicenter locations.



[Click here to view the diagram.]

To locate the epicenter exactly, you need 3 stations to all do the same thing. You will end up with 3 circles that only meet in 1 location: the epicenter.




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