4. A Brief History of Geology
• James Ussher, Anglican
Archbishop of Armagh, Primate of
all Ireland, constructed a
chronology of human and Earth
history in the mid 1600s in which
he determined that Earth was
only a few thousand years old,
having been created in 4004 B.C.
5. A Brief History
of Geology
• Catastrophism, a
philosophy that
believed that Earth’s
landscapes had been
developed primarily by
great catastrophes
6. Birth of Modern
Geology
• James Hutton, published his Theory
of the Earth in the late 1700s
• Uniformitarianism, the physical,
chemical, and biological laws that
operate today have also operated in
the geologic past
9. Law of
Superposition
• Nicolaus Steno, (1636–1686), is
credited with being the first to
recognize a sequence of
historical events in an outcrop of
sedimentary rock layers.
• in an undeformed sequence of
sedimentary rocks, each bed is
older than the one above it and
younger than the one below.
14. Unconformities
• Conformable, rock that have been deposited without
interruption
• Unconformity, breaks in the rock record
• Three Types:
• Angular Unconformity
• Disconformity
• Nonconformity
34. Types of
Fossils
Molds and Cast
• Mold is a fossilized
imprint
• Cast are hardened
mineral matter that
forms in the shape of
the mold
35. Types of
Fossils
Carbonization
• The process of
transforming organic
material into a carbon
residue through a
combination of heat,
pressure, and time.
36. Types of
Fossils
Impression
• The organism’s original
bone or tissue is
removed by processes
after burial, such as
ground water flow
44. Principle of Fossil
Succession
• Fossil organisms
succeed one another in
a definite and
determinable order,
and therefore any time
period can be
recognized by its fossil
content.
45. Index Fossil
• Fossils that are
widespread
geographically and are
limited to a short span
of geologic time.
• Provides an important
method of matching
rocks of the same age.
50. Importance of
Fossils
• Can be an indicator of the
age of the rock
• Can be used as an
environmental indicator
• Can indicate the former
temperature of the water
51. Importance of Fossils
•Can be an indicator of the age of
the rock
•Can be used as an environmental
indicator
•Can indicate the former
temperature of the water
56. 3 Common
Types
Alpha Emission, 2
4
𝐻𝑒
• the emission of an alpha particle means
that the mass number of the isotope is
reduced by four and the atomic number
is decreased by two
57. Alpha Emission, 2
4
𝐻𝑒
•the emission of an alpha particle means
that the mass number of the isotope is
reduced by four and the atomic number is
decreased by two
58. 3 Common
Types
Beta Emission, −1
0
𝑒
• Because the electron has come from a
neutron, the nucleus contains one more
proton than before. Therefore, the
atomic number increases by one.
59. Beta Emission, −1
0
𝑒
•Because the electron has come from a
neutron, the nucleus contains one more
proton than before. Therefore, the atomic
number increases by one.
* Powell realized that the evidence for an ancient Earth is concealed in its rocks
* Interpreting Earth history is a prime goal of the science of geology
*today’s geological processes are the same in the past
*geological processes occur over a long period of time
*cited verifiable observations
To say that geological processes in the past were the same as those occurring today is not to suggest that they always had the same relative importance or that they operated at precisely the same rate
To establish a relative
time scale, a few basic principles or rules had to be discovered
and applied.
*Danish anatomist, geologist, and priest
Beneath the ocean, beds
A, B, C, and E were
deposited in that order
(law of superposition).
Uplift and intrusion of a sill (layer D).
We know that sill D is younger than
beds C and E because of the
inclusions in the sill of fragments
from beds C and E.
Next is the intrusion of dike F. Because the dike
cuts through layers A through E, it must be younger
(principle of cross-cutting relationships).
Layers A through F were tilted and
exposed layers were eroded.
Next, beds, G, H, I, J, and K were
deposited in that order atop the
erosion surface to produce an
angular unconformity. Because layer
H is a lava flow, superposition
applies to it as well as the
surrounding sedimentary beds.
An English engineer and canal builder
For example, an Age of Trilobites is recognized quite early in the fossil record. Then, in succession, paleontologists recognize an Age of Fishes, an Age of Coal Swamps, an Age of Reptiles, and an Age of Mammals
*Origin of the Earth
*First one-celled organism
*First multicelled organism
