L1: Geological Time Flashcards
What were the findings of Nicolaus Steno?
His investigations on rocks led to his theory on the 3 principles of stratigraphy: principle of superstition, principle of original horizontality, and the principle of original lateral continuity.
What are the 3 principles of stratigraphy?
- Principle of Superstition
- Principle of original horizontality
- Principle of original lateral continuity
Principle of Superstition
States that in any stratigraphic succession of undisturbed strata, the oldest layer is at the bottom, and successively higher levels are younger strata
What is strata?
- Strata are layers of rock, or sometimes soil. In nature, strata come in many layers. It is a term in sedimentary and historical geology
- These layers are laid down as sediment, often in the sea, and are slowly changed by pressure, heat and chemical action into rocks.
Principle of Original Horizontality
- Sediment must originally have been deposited in layers that were nearly horizontal and parallel to the surface on which they were accumulating
- Therefore, this shows that tilted rocks indicate an episode of crustal disturbance after the time of deposition
Principle of original lateral continuity
States that all strata extend in all directions until they terminate by thinning at the margins of the basin, end abruptly against some barrier to deposition, or grade laterally into different kinds of sediment
What were the findings of James Hutton
- Unconformities/actualism
- The present is the key to the past
What is Uniformitarianism or actualism
The past history of our globe being able to be explained by what can be seen happening now
“The present is the key to the past”
Looking at the now can reveal what has occurred in the past; interpreting rock exposures by observing present-day processes
Unconformities
The Earth’s surface underwent cyclical events and that sequences of rock often show hiatus’ in the rock record. ( this is unconformities)
Non-Conformity
A surface of erosion that separates younger sedimentary strata above older igneous or metamorphic rocks below
Disconformity
A surface of erosion in which the orientation of older strata (below) are parallel to the younger strata (above)
Angular
A surface of erosion between the 2 groups of sedimentary rocks in which the orientation of the older strata (below) are at an angle to the younger strata (above)
Inclusions
Fragments within larger rock masses that are older than the rock masses in which they’re inclosed
Charles Lyell extended Hutton’s theory by discussing what he called _______
Principle of cross cutting relationships
Fossils
- The remains of ancient organisms
- May include shells, teeth, bones, impressions, and animal tracks
- Most commonly found = shells of invertebrate animals (clams, oysters, ammonites)
Paleontology
The study of ancient life
Formation
Certain rock units
William Smith
Discovered Principle of Biological Succession
Principle of biological succession
Identifying particular assemblages of fossils contained within formations
Biostratigraphy / Principle of biological succession
Life forms of each age in Earth’s history were unique for particular periods, and that these unique fossil assemblages could allow geologists to correlate contemporaneous formations around the world
protons = _______
atomic #
What is a nucleus?
A nucleus contains protons (positive charges) and neutrons (neutral charge) and is surrounded by orbiting electrons (negative charge)
Protons + neutrons = ________
atomic mass
What are isotopes?
The same element with the same atomic # but has a different # of neutrons
When may we use biostratigraphy with dating rocks?
The actual age of rocks that cannot be dated isotopically can be ascertained by correlation
