Lecture 1 Geological Time Flashcards
What is Geological Time?
When things happen over long periods of time like mountains forming
How old is the Earth?
4.5 Billion years old
How long ago did life begin?
4 billion years ago
What signified the beginning of life on Earth?
Microbes evolving and their metabolism having effects on the composition of the oceans, atmosphere and surface sediments/soils
What life forms existed before mammals and humans?
Microbes like bacteria
What is Stratigraphy?
The study of the layering of rocks
What is the Principle of Superposition?
The principle that in stratigraphic succession of undisturbed strata, the oldest layer is at the bottom and successively higher layers are successively younger
What is the Principle of Original Horizontality?
The principle that sediment must originally have been deposited in layers that were nearly horizontal and parallel to the surface on which they were accumulating
What do tilted rocks indicate according to the Principle of Original Horizontality?
An episode of crustal disturbance after the time of deposition
What does the Principle of Original Lateral Continuity state?
That all strata extend in all directions until they terminate by thinning at the margins of the basin and end abruptly against some barrier to deposition, or grade laterally into different kind of sediment
What is Uniformitarianism or Actualism?
The idea that if you understand how a process occurs today it gives insight into how the process occurred in the past
What are some exceptions to Uniformitarianism/Actualism?
Long term changes ex. Evolution of the atmosphere
Short term changes ex. Catastrophic meteorite impacts
What are Unconformities?
Gaps in the geological record that formed because layers were not deposited for some time or layers were removed by erosion
What are the 3 types of Unconformities?
Angular, Disconformity, Nonconformity
What is a Nonconformity?
A surface erosion that separates younger sedimentary strata above older igneous or metamorphic rocks below
What is a Disconformity?
A surface of erosion in which the orientation of older strata, below, are parallel to younger strata above
What is an Angular Unconformity?
A surface of erosion between two groups of sedimentary rocks in which the orientation of the older strata, below are at an angle to the younger strata above
What is the Principle of Cross Cutting Relationships?
The principle that states the geological feature which cuts another is the younger of the two features
With inclusions which portion is always the oldest?
The inclusion
What is Bioturbidation?
The process whereby sediments are disturbed by organisms living on or in the sediment
What are Formations?
A package of rocks that are identifiable and different from the rocks around them
What is the Principle of Biologic Succession?
A principle that states that the life forms of each age in earth history were unique for particular periods, and that these unique fossil assemblages could allow geologists to correlate contemporaneous formations around the world
