Fossils
Relative Age
Aboslute Age
Geologic Time
Review
100
What is a fossil?
The remains, imprints, or traces of prehistoric organisms.
100
What is relative age?
The age of a rocker layer in relation to those around it.
100
What is absolute age?
The age in years of a rock or other object.
100
What is the geologic time scale?
Division of Earth's history into time units based largely on the types of life-forms that lived only during certain periods.
100
How old is the Earth?
4.6 Billion years old
200
What do fossils help scientists determine?
When life first appeared, when plants and animals first lived on land, and when organisms became extinct.
200
What is the law of superposition?
Law that states in undisturbed rock layers the oldest rocks are on the bottom and the rocks become progressively younger toward the top.
200
What is half-life?
The time it takes for half the atoms in the isotope to decay.
200
How might plate tectonics affect speicies of organisms?
Changes in Earth's surface that altered habitats could have caused organisms with traits most suited to the new habitat to evolve
200
What are the 2 types of dating?
Relative Dating and Absolute Dating
300
What are the characteristics of an index fossil?
1. Geographically widespread
2. Abundant
3. Lived for a relatively short period of time
300
What is an unconformity?
Gaps in rock sequence.
300
If you were a geologist trying to determine the absolute age of a rock layer, what method would you use?
Radiometric dating
300
What is an era?
Absolute dating of rocks and fossils differs from relative dating in that it helps scientists
300
Name the three subatomic particles
Protons, neutrons and electrons
400
How is an index fossil useful to a geologist?
A geologist can use it to determine the age of a rock layer.
400
What is disconformity?
Younger sedimentary layers are deposited on older layers that have been eroded.
400
What is uniformitarianism?
The principle that states that Earth processes occuring today are similar to those that occured in the past.
400
What is a period?
Absolute dating of rocks and fossils differs from relative dating in that it helps scientists
400
List the following in order from oldest to youngest?
First Birds
First Bacteria
First Fish
First Humans
Bacteria, Fish, Birds, Humans
500
Why can't any type of fossil be used to determine the age of a rock layer?
If we do not know when that fossil lived or died, we would not know when the rock layer it is in was formed. You would need an index fossil to do this.
500
What are the three ways to correlate similar rock layers in two different areas?
Match rock types
Look for presence of matching fossils
Compare relative positions in the geologic column
500
Would we use Carbon-14 or Uranium 238 to date something 18,000 years old
Carbon-14
500
Fossils from the Precambrian Period are:
A simplest forms of life
B studied by carbon dating
C some of the largest animals
D only land animals
Simplest forms of life
500
Which conclusion about the geologic history of the rock can be made from the picture?
Layer G is the youngest
Layer B intruded into A
Layer C is an unconformity