Chapter 11 - ESC1000 Flashcards
What is the principle of uniformitarianism?
Concept that the processes that have shaped the Earth in the past are essentially the same as those operating today.
What is catastrophism?
Concept that Earth was shaped by catastrophic events of a short-term nature.
What is numerical dating?
Date that specifies the actual number of years that have passed since the event occurred.
What is relative dating?
Date that results from placing the rocks in their proper sequence or order to determine the chronological order of events.
Who was James Hutton?
Famous Scottish physician from the 1700s who published his Theory of Earth that puts forward the fundamental principle of uniformitarianism.
Who was James Ussher?
Anglican archbishop from the mid 1600s who constructed a chronology of human and Earth history based on the bible in which he determined that Earth was only a few thousand years old.
Explain the difference between catastrophism and uniformitarianism.
Catastrophism views the processes that shape the Earth as short-term events while uniformitarianism views the processes that shape the Earth as slow and acting over long spans of time.
List the principles of relative dating.
Superposition, Original Horizontality, Lateral Continuity, Cross-Cutting Relationships, and Inclusions.
What is the principle of superposition?
States that in any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.
Who is Nicholas Steno?
Danish geologist from the 1600s that proposed the principles of superposition and original horizontality.
What is the principle of original horizontality?
Principle by which layers of sediment are generally deposited in horizontal position.
What is the principle of lateral continuity?
Principle which states that sedimentary beds originate as continuous layers that extend in all directions until they grade into a different type of sediment or thin out at the edge of a sedimentary basin.
What is the principle of cross-cutting relationships?
Principle which states that a rock or fault is younger than any rock or fault through which it cuts.
What is the principle of inclusion?
Principle which states that the rock mass that provided the inclusion is older than the rock mass containing the inclusion.
What are unconformities?
A surface that represents a break in the rock record, caused by erosion or nondeposition.
What is conformable?
Layers of rock that were deposited without interruption.
List the 3 types of unconformities.
Angular, Disconformity, and Nonconformity.
What is angular unconformity?
Unconformity in which strata below dip at an angle different from that of the beds above.
What does an angular unconformity indicates?
Indicates that during a pause in deposition, a period of deformation (folding or tilting), and erosion occurred.
What is a disconformity?
Is a gap in the rock record that represents a period during which erosion rather than deposition occurred. Beds above and below are parallel.
What is nonconformity?
An unconformity in which older metamorphic or intrusive igneous rocks are overlain by younger sedimentary strata.
How does a nonconformity form?
Older metamorphic and igneous rocks that originate deep below must experience a period of uplift. Once exposed at the surface the rocks are subject to erosion and undergo a renewed period of sedimentation.
What are fossils?
Remains and traces of organisms preserved from the geologic past.
What is paleontology?
Systematic study of the fossils and the history of life on Earth.
Why are fossils important in geology?
They can serve as tools for interpreting the geologic past. They can indicate past environmental conditions and help correlate rocks of similar ages that are in different places.
List the 5 types of fossils.
Permineralization, Molds and Casts, Carbonization and Impressions, Amber, and Trace Fossils.
Describe the process of permineralization.
Mineral-rich groundwater permeates porous tissue such as bone or wood, minerals precipitate out of the solution and fill pores and empty spaces.
Describe the process of a mold and a cast.
A structure is buried in sediment and then dissolved by underground water forming a mold. If the hollow spaces of the structure are filled with mineral matter, casts are created.
Describe the process of carbonization.
Fine sediment encases the remains of an organism. As time passes, pressure squeezes out the liquid and gaseous components and leaves behind a thin residue of carbon.
Describe the process of impressions.
If the film of carbon created in carbonization is lost, a replica of the surface may still show.
Describe the process of amber fossils.
Organism is trapped in tree resin and then it hardens over time.
Describe what are trace fossils.
They are traces of prehistoric life and they can be tracks (footprints), burrows, and gastroliths (stomach stones from dinosaurs).
What conditions favor preservation of an organism as a fossil?
Rapid burial where remains are protected from the surface environment and hard parts have better chance of preservation.
What is correlation?
The process of establishing the equivalence of rocks of similar age in different areas.
What is the principle of fossil succession?
Principle by which fossil organisms succeed one another in a definite and determinable order, and any time period can be recognized by its fossil content.
What is the difference between index fossils and fossil assemblages?
One is limited to a short period of time so they help matching rocks of the same age and the other requires a variety of fossils to establish the age of the bed.
What is an index fossil?
A fossil that is associated with a particular span of geologic time.
What is a fossil assemblage?
The overlapping ranges of a group of fossils collected from a layer.
What is nuclear decay?
Spontaneous decay of certain unstable atomic nuclei.
What are the 3 types of nuclear decay?
Alpha emission, Beta emission, and Electron capture.
Describe the alpha emission.
A particle composed of 2 protons and 2 neutrons is emitted from the nucleus. The atomic number drops by 2 and the mass number diminishes by 4.
Describe the beta emission.
A neutron decays to produce an electron plus a proton and then the electron is emitted. The atomic number increases by 1 and there is no change in mass number.
Describe the electron capture.
An electron is captured by the nucleus and combines with a proton and forms an additional neutron. The change in the atomic number drops by 1 and there is no change in mass number.
What is a parent isotope?
An unstable isotope.
What is a daughter isotope?
Isotopes resulting from the decay of the parent isotope.
What is radiometric dating?
Procedure of calculating the absolute ages of rocks and minerals that contain radioactive isotopes.
What is the half-life?
Time required for one-half of the atoms of a radioactive substance to decay.
What is radiocarbon dating?
Radiometric dating using carbon-14, a radioactive isotope of carbon that is produced in the atmosphere.
Explain how the carbon-14 dating works.
Carbon-14is produced in the atmosphere and absorbed by every living organism. As long the as the organism is alive it will continue to absorb and replace carbon-14. Carbon-12 is the most common and stable type of carbon and when an animal dies, gradually the carbon-14 decays by beta emission into nitrogen-14. By comparing the proportions of carbon-14 and carbon-12 in an organism, a radiocarbon date can be determined.
How far can radiocarbon dating be used?
As far as 70,000 years.
Why it is difficult to assign a reliable numerical date to a sample of sedimentary rock?
The rocks composing sedimentary strata are not the same age as they are the result of weathered down rocks from different ages.
How might a numerical date for a layer of sedimentary rock be determined?
Geologists must relate the strata to datable igneous masses.
What is the geologic time scale?
The division of Earth history into blocks of time.
What are the blocks of time of a geologic time scale?
Eon, Eras, Periods, and Epochs.
What are the 2 eons?
Phanerozoic and Precambrian.
What is the phanerozoic?
Eon containing abundant fossil evidence and it extended from the end of the Proterozoic eon (540 million years ago) to present.
How can the Precambrian be divided?
In Archean and Proterozoic.
What are the 3 eras of the Phanerozoic?
Paleozoic, Mesozoic, and Cenozoic.
How long does the Precambrian lasts?
From 541 million years ago to 4.6 billion years ago.
What does “zoic” means?
Life
