Formation of the Earth
What principle states that geological processes happening today also happened in the past?
Uniformitarianism
True or False: Relative dating can provide an exact age in years for a rock or fossil.
False; it can only tell us if something is younger or older relative to something else
What is the study of fossils called?
paleontology
True or False: The amount of daughter isotope can provide the relative date of when a rock formed.
False; the absolute date
True or False: Uniformitarianism suggests that the Earth's surface was shaped by sudden, catastrophic events.
False; it suggests that the same gradual geologic process we see today shaped the Earth's surface
The principle of superposition states that _____
In undisturbed rock layers, the oldest rocks are found at the bottom and the youngest are at the top
True or False: Paleontologists use fossils as a data source.
True
What is an isotope and what makes it radioactive?
An atom with a different number of neutrons; it is radioactive if it is unstable
How does uniformitarianism explain the formation of canyons and mountains?
Rocks were weathered and erosion processes moved the sediment, which was then deposited elsewhere.
Identify the four disturbances to rock layers.
Folding, tilting, faults, and intrusions
What can fossils tell us about extinct species?
Define half-life and determine the percentage of parent isotope left after 3 half-lives.
Half-life is the amount of time for one-half of the parent isotope to decay; 12.5%
Who is the geologist often credited with developing the concept of uniformitarianism?
James Hutton
What is an unconformity and how does it form?
An unconformity is a gap in the rock layer, formed by erosion or lack of deposition
What can fossils tell us about how the environment has changed?
It can tell us about the climate and landforms during the time the fossil formed
How old is the Earth and how was this determined?
4.6 billion years old; radiometric dating on moon rocks and meteorites
What do geologists today believe about how the Earth formed?
A mixture of uniformitarianism and catastrophism - most geologic change is slow and uniform; catastrophes can cause sudden changes
Explain how the principle of cross-cutting relationships can be used to determine the relative age of rock layers.
This law states that a fault or intrusion is younger than anything the fault or intrusion cuts through.
How do paleontologists determine the age of fossils?
Radiometric dating
If 600 grams of a radioactive isotope has a half-life of 2 days, how much (in grams) would remain after 4 days?
150 grams