Friday, April 27, 2012

Week of 4/30/12

Monday- Chapter 2 Napoleon's Button
Tuesday- Boyle's Law Worksheet
Wednesday- Boyle's Law Virtual Lab, 'genre' project due at end of class
Thursday- Gas Laws
Friday- Virtual Gas Law

Physical Science
Monday- strata lab, Grand Canyon
Tuesday- review questions
Wednesday- computer lab
Thursday- review questions
Friday- Historical Geology Test

Remember, the Topo Map Quiz closes at end of week.

Friday, April 20, 2012

Week of 4/23/12

Monday- read Chapter 2 "Napoleon's Buttons"
Tuesday- Review Ch 13
Wednesday- computer lab, 'genre activity'
Thursday- Quiz Ch 13, review on 'moodle'
Friday- computer lab, 'genre activity'

Physical Science
Monday- 1/2 life
Tuesday- 1/2 life
Wednesday- computer lab, 'Dino Dig'
Thursday- 1/2 life activity
Friday- computer lab,"Radioactive Dating Game"

You will have 2 weeks to complete the Topographic Maps Quiz, in the Topographic Maps Section.

Tuesday, April 17, 2012

Index Fossils

One tool that helps geologists to place geologic events in proper order, relative dating, is the use of index fossils. Index fossils allow geologists match rocks of the same age in different regions. An index fossil must be widespread geographically, easily identified and have a short geologic time period.
Also, different types of fossils organisms succeed one another in a definite order-fossil succession

Historical Geology

The Scottish geologist, James Hutton, in the mid 1700's put forth the ides of "uniformitarianism". Hutton put forth that the processes that shape the Earth today are also the processes that shaped the Earth in the past. many of these past geologic events are recorded in sedimentary rocks. Sedimentary rocks record events such as volcanic eruptions and also contain fossils.

Fossils are the remains of prehistoric life preserved in sedimentary rocks. Igneous and metamorphic rocks do not contain fossils as the heat and pressure would destroy any evidence of past life. Below are listed some characteristics of fossils:
  • the type of fossil depends on the conditions where the organism died and how it was buried
  • organisms need hard parts and rapid burial
  • the faster the burial, the greater the chance of a fossil being formed.
  • animals with hard parts, see fossilized horse above right, stand better chance of becoming a fossil.
  • petrified wood, above left, is a fossil whose remains have been altered.
  • dinosaur footprints and other types of tracks are referred to as molds.

Mountain Types

Credits: top left-USA Today, top right-NASA, bottom left-Westfield State College.

Folded Mountains- Appalachians, bottom left, compressional stress.
Fault Block- Tetons, top left, compressional stress.
Convergence- Andes, top right, colliding plates.

The fourth type of mountains are domes from a large batholith which upwarps the crust. The Black Hills of South Dakota are an example of this type these types of mountains.


Faults in the Earth surface are of three basic types:
  • strike/slip- top picture, also known as a transform plate boundary, the slabs of the crust slide past one another in the horizontal plane.
  • reverse/thrust - top right picture, the hanging wall is forced up and over the footwall. In a reverse fault the dip angle is > 45 degrees, a thrust fault dip angle < 45 degrees, compressional stress.
  • normal- bottom left picture, hanging wall drops below footwall, dip angle about 60 degrees, tensional stress.

Folds in the Earth's Crust

Folds can be of three types:
  • anticline- the upfolding of the crust, think crest of a wave.
  • syncline- down folding of the crust, think trough of a wave.
  • monocline- usually associated with a fault with only one limb present. Limbs are the "arms" extending from either side of a fold.

Deformation of the Earth's Surface

Image: Tasa Arts

There are three basic types of stress that we covered in class:
  • Tensional- this happens when the crust is pulled apart.
  • Compressional- the crust is compacted/ pushed together.
  • Shear- a piece of the crust has opposing movement acting on it.
Deformation of a body of rock will cause a change in the rock and/or change in volume.

Two basic types of deformation:
  • brittle- near surface rocks, low pressure/low temperature, typically granite and basalt, process takes a long time and fracturing of the rock will occur
  • ductile- greater depth in the surface, high pressure/high temperature, sedimentary rock, process takes a long time, bending of the rock occurs.


Picture credit: (Trilobite), right- (Dinosaur)

Two major extinctions occurred in the Earth's history. The extinction at the end of the Paleozoic era wiped out 50% of all marine invertebrate families and 90% of all marine invertebrate species became extinct. There are several theories what caused these extinctions but climatic changes (cooling) is one of the leading explanations.

The Mesozoic extinction which killed off the dinosaurs has been blamed on the impact of a meteorite. This impact put so much dust in the air it blocked out sunlight which halted photosynthesis and global temperatures also diminished. Proof of this meteorite collision lies in the discovery of the Cretaceous-Tertiary boundary. This is a worldwide layer of iridium. Iridium is found in high concentrations of some meteorites.


Radioactivity is produced when the nucleus of an atom breaks apart or decays.

This radioactivity can be used to date rocks/fossils - absolute dating. Many radioactive materials, such as Uranium-235, decay at a constant rate.
This specific rate is half-life - the time it takes for 1/2 (50%) of the material to decay into a stable substance/isotope. Remember an isotope is the same element but with a different number of neutrons. This change in the number of neutrons will change the mass of the atom

Let's look at an example using the graph above. If we assume we have 20 grams of the parent material, half-life of 5 years, how many grams will be left of the parent after one half-life and how much time has passed? After one half-life 50% or 1/2 (10 grams) of the parent material will be left and 5 years will have passed. After 2 half-lives have passed 25% or 1/4 (5 grams) of the parent material is left and 10 years have passed. Remember the time remains constant!

Uranium is great for dating real old stuff- millions of years but for recent geologic events (up to 75,000 years ago) radiocarbon is used, Carbon-14.

Geologic Time

The geologic time scale has divided the Earth's history into units that are based upon rock units and changes in fossil forms. Scientists have determined the Earth to be approximately 4.6 billion years old. The vast majority of the Earth's history (88%) lies in the Precambrian time span. In this early part of Earth's history life was sparse and much of this rock is buried deep within the ground. Therefore not much information is known about this time period.

Some other time periods that are relevant to our study is the Paleozoic era "ancient life". During this era life became abundant around the globe. The current geologic period is the "Quaternary". This is the time period in which we reside- the current time period.


Unconformities-very long times of nondeposition and/or erosion, of which there are three basic types.
  • disconformity- surface(erosion) seperating younger from older rocks. These rock layers are horizontal (parallel) to each other.
  • nonconformity- erosion surface that separates old metamorphic rocks from younger sedimentary rocks.
  • angular unconformity- tilted sedimentary rocks that are overlain by younger flat-lying sedimentary rocks.
Cross-cutting principle- the intrusive rock body is younger than the rocks it cuts. You cannot cross-cut rock layers if they are not already present.

Principle of inclusions- inclusions or fragments in a rock are older than the rock itself.

Sunday, April 15, 2012

Week of 4/16/12

Monday- review sections 13.1 & 13.2
Tuesday- "Napoleon's Buttons"
Wednesday- computer lab
Thursday- phase change graphs
Friday-computer lab

Physical Science
Monday- historical geology/ relative dating
Tuesday- relative dating
Wednesday- computer lab "Virtual Stream"
Thursday- Michigan geology
Friday- computer lab

Physical Science- you should be working on your stream projects.

Sunday, April 8, 2012

Week of 4/9/12

Monday-  review MSE, start Ch 13
Tuesday- Ch 13
Wednesday-computer lab
Thursday- Ch 13
Friday- computer lab

Physical Science
Monday- review MSE, review Water Project, watch lecture Historical Geology
Tuesday- fault block mountains
Wednesday- computer lab, sinuosity lab
Thursday- principles of stratigraphy
Friday- computer lab, pretest ESE, glogster