2ND QT: Lesson 6 & 7 Flashcards
the time line of the History of the Earth, is based from the rock record
The Geologic Time Scale
how is geologic time divided?
Geologic time is subdivided into hierarchal intervals, the largest being Eon, followed by Era, Period, and Epoch, respectively.
Why are the names of the earth’s history from Europe?
they named the blocks of time from towns or other local places where the rock layers that represented
that time were found yuhh
When did the mass extinction event happen?
around 66.4 million years ago
what does the mass extinction of dinosaurs mark?
boundary between the Mesozoic Era (Age of the Reptiles) and the Cenozoic Era (Age of Mammals).
One of the first to recognize the correspondence of between rocks and time
Nicholas Steno (1638-1686)
Steno’s principles, foundation of stratigraphy? no need to memorize
superposition, original horizontality, and lateral continuity
One of the earliest attempts to subdivide the rock record into units of time was made by
Abraham Gottlob Werner, a German geologist
Werner divided the rock record into the following rock-time units (from oldest to youngest)
Primary, Secondary, Tertiary, and Quaternary
What did werner use to establish temporal
relationship among the rock units?
Principle of Superposition
Fossils are also useful in determining relative ages of rocks. Who noticed this?
William “Strata” Smith (1769 –1839)
recognized the utility of fossils in subdividing Geologic Time on the basis of fossils
Charles Lyell (1797 – 1875), British Lawyer and Geologist
He was able to subdivide the Tertiary by
examining the proportion of living vs. extinct fossils in the rock
The underlying reason for this definite and orderly succession of fossils in the rock record is
organic evolution
a sub-discipline of stratigraphy which deals with the use of fossils in correlation and establishing the relative ages of rocks.
Biostratigraphy
are marker fossils used to define periods of Geologic Time, and are useful in biostratigraphic correlation.
Index Fossils
index fossils are distinctive (can be easily identified and distinguished from other fossils, widespread
(Distribution is not confined to a few locality) and have limited geologic time range.
yes, they should be distinct, and widespread, and KJHDSHDKJF
The age of a rock, fossil, or other feature measured relative to another.
Relative Dating
The age of a rock in years
Absolute Dating (numerical dating)
Object of Relative Dating
*To place a geologic event in between two (or more) other geologic events.
*Does not tell the age of the event.
*Keep putting events in time, in relation to other events until the sequence spans geologic history.
*Some events can been seen throughout the world.
distinct layer of sediment
Stratum
plural of stratum
Strata
– the study of sedimentary layers
Stratigraphy
Water-borne sediments are deposited in horizontal layers.
.Original Horizontality
– when several layers of sedimentary rock are exposed, the oldest layer is at the
bottom of the pile and the youngest layer is at the top..
Superposition
- A surface within a sequence of layers where no deposition, and possibly
erosion, took place.
Unconformities
a. Disconformity
b. Angular Unconformity
c. Nonconformity
extra info on
If a rock fragment is found within another rock type, the fragment is older.
Inclusions
- A rock layer is always older than a feature that cuts through it
Cross-cutting Relations
Fossil Correlation
a. Based of evolution
b. Also relies of superposition
c. When a species becomes extinct, it does not reappear
The spontaneous disintegration of the nucleus of an atom.
Radioactive decay
a type of radioactive decay in which an atomic nucleus emits an alpha
particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and
transforms (or ‘decays’) into an atom with a mass number 4 less and atomic number 2 less
Alpha decay
a type of radioactive decay in which a beta particle (an
electron or a positron) is emitted
beta decay
the amount of time it takes for half of the atoms in a sample to decay.
absolute
Half-life
Characteristics of index fossils are:
–Abundant
–Easily identified
–Geographically widespread
–Occurs in a variety of rock types
–Short stratigraphic range (rapid rates of evolution)
:D
is the scientific study of the origin, history, and structure of Earth and the processes that
shape it.
Geology
the principle that states that all geologic change occurs suddenly
Catastrophism
Supporters of catastrophism thought that Earth’s features, such as mountains and seas,
formed during sudden events called
catastrophes
established a principle that is now known as
uniformitarianism.
James Hutton
the idea that the same geologic processes that shape Earth today have been
at work throughout Earth’s history.
Uniformitarianism
soo, Catastrophism or Uniformitarianism
bothh
4 eons
Hadean, Archean, Proterozoic, and
Phanerozoic
Hadean, Archean, and Proterozoic eons together are called
Precambrian time
Precambrian time makes up almost ____ percent of Earth’s history
90
The Phanerozoic Eon, the present eon, is divided into three eras
the Paleozoic, Mesozoic, and
Cenozoic.
Each era is subdivided into a number of
periods
periods divided into
epochs
At least ____ divisions of geologic time have ended in large mass extinction events
five
Precambrian time began with the
formation of Earth about 4.6 billion years ago
Toward the end of Precambrian time, where were earth;s land surfaces located?
near the poles and
covered in ice.
The Paleozoic Era began about
540 million years ago
The supercontinent _________ was breaking up
and the supercontinent Pangaea began forming.
Pannotia
Life diversified quickly and dramatically during the ___________, during which most major
groups of organisms first evolved.
Cambrian Explosion
The era ended about 250 million years ago with a _________________.
huge mass extinction event
During the Mesozoic Era, which began about 250 million years ago, Pangaea began _________
breaking up
Life during the Mesozoic was dominated by
dinosaurs
The Cenozoic Era began about 65 million years ago with the ________________ and
continues to the present.
Cretaceous mass extinction
Cenozoic period:
___________ split apart from North America and Europe, and the continents assumed their
current positions.
Greenland
The Indian subcontinent collided with Eurasia to form the
Himalayas
The collision of Africa and
Europe resulted in the
Alps
The Cenozoic Era is divided into two periods:
the Tertiary and the Quaternary
Quaternary stretches from about 2.6 million years ago to the __________.
present
The Quaternary has been characterized by an
ice age, with much of Europe, North America, and
Asia having been covered in thick sheets of ice
The evolution of modern humans occurred during the
late Quaternary
Any remains, trace or imprint of a plant or animal that has been preserved in Earth’s crust during
prehistoric times
Fossils
- Animal or plant remains buried quickly
- Bones, shells, and teeth usually become fossils because they are very hard and don’t rot as quickly as
softer parts - Usually takes millions of years for fossils to form
Conditions for fossilization
Types of fossilization
Replacement
Petrification
Carbonization
Bones or shells of organism are eventually broken down, which leaves a mold of the original organism
in the sediment
Replacement
Mineralized water fills pores and cavities of trees, deposits minerals, turns organic material
into rock slowly
Petrification
Overlying sediments flatten a plant and turn it into a thin, carbon film
Carbonization
example of petrification
petrified wood
NOT all fossils are index fossils
Index Fossils
If they can be recognized in the rock,
these fossils can be used to correlate rock in one area with rocks in a distant area
purpose of index fossilssssss
