t5 fossils & the rock records
DESCRIPTION
T5 Fossils & the Rock Records. ...it’s as old as the hills. PowerPoint Notes created by S. Koziol Date : 12/1/2013 Revised : ?/?/??. Part 1 Objectives. Describe the geological time scale Distinguish among the following time scale divisions: eon, era, period & epoch. Time Scale. - PowerPoint PPT PresentationTRANSCRIPT
T5 Fossils & the Rock Records
...it’s as old as the hills.PowerPoint Notes created by S. Koziol
Date : 12/1/2013 Revised : ?/?/??
Part 1 Objectives
• Describe the geological time scale• Distinguish among the following time
scale divisions: eon, era, period & epoch.
Time Scale
The geologic time scale divides Earth’s history into units from its origin to the present.
Era Period Epoch Began (MYA)
Cenozoic
Quaternary
Holocene 0.011
Pleistocene 1.8
Tertiary
Pliocene 5.3
Miocene 23.8
Oligocene 33.7
Eocene 54.8
Paleocene 65
MesozoicCretaceous 144
Jurassic 206
Triassic 248
Paleozoic
Permian 290
Carboniferous Pennsylvanian 323
Carboniferous Mississippian 354
Devonian 417
Silurian 443
Ordovician 490
Cambrian 540
Precambrian time4600
Adapted from Modern Earth Science, 2002, Holt, Rinehart and Winston
Time Scale – To be Completed
Blank Time Scale
Time Scale Continued
Recent period
The most recent period is the Quaternary
EpochOn the geologic time scale, the smallest unit of
time is called an epoch - longer than an age and shorter than a period.
Phanerozoic Eon
The Phanerozoic Eon includes the Paleozoic, Mesozoic, and Cenozoic Eras
Eons
The Archean and Proterozoic are examples of eons
End of the Precambrian
The end of the Precambrian is marked by the appearance of organisms with hard parts.
Cloudina, the earliest known calcium carbonate
shell-bearing fossil.
Units of geologic time
Units of geologic time in order from shortest to longest
• epoch, period, era, eon
Era Period Epoch Began (MYA)
Cenozoic
Quaternary
Holocene 0.011
Pleistocene 1.8
Tertiary
Pliocene 5.3
Miocene 23.8
Oligocene 33.7
Eocene 54.8
Paleocene 65
Mesozoic
Cretaceous 144
Jurassic 206
Triassic 248
Paleozoic
Permian 290
Carboniferous Pennsylvanian 323
Carboniferous Mississippian 354
Devonian 417
Silurian 443
Ordovician 490
Cambrian 540
Precambrian time4600
Adapted from Modern Earth Science, 2002, Holt, Rinehart and Winston
PeriodsPeriods are defined
by the abundance or extinction of life-forms.
Eras vs. Periods
Erasare longer spans of time,
measured in hundreds of millions to billions of years. They are defined by differences in life-forms found in rocks.
Periodsare usually measured in terms
of tens of millions of years to hundreds of millions of years. They are defined by the life-forms that were abundant or became extinct during the time in which specific rocks were deposited.
Both are units of time on the geologic time scale.
Part 2 Objectives
• Apply the principles for determining relative age to interpret rock sequences.
• Describe an unconformity and how it formed within the rock record.
Oldest rock layerThe oldest rock layer in an undisturbed rock
sequence occurs at the bottom of the sequence
The Principle of Superposition
The principle of superposition states that, in an undisturbed sequence, the oldest rocks are at the bottom of the sequence and successive layers are younger than those below them.
Cross-cutting RelationshipsYou can use the principle of cross-cutting
relationships to infer that a fault or an intrusion is younger than the rock it cuts across.
CorrelationThe matching of rock layers from one
geographic area with those of another area is known as correlation.
Inferences and rock layers
Uniformitarianism
The principle of uniformitarianism states that the The principle of uniformitarianism states that the processes occurring today have been occurring processes occurring today have been occurring on Earth since it formed. However, the rate, on Earth since it formed. However, the rate, intensity, and scale with which these processes intensity, and scale with which these processes occur have changed.occur have changed.
UnconformityWhen part of the rock record is destroyed, the
erosional gap that forms is an unconformity.
Angular UnconformityThe gap in the rock record that occurs between
folded or uplifted rock layers and a sedimentary rock layer on top of them is called an angular unconformity.
Nonconformity
A buried erosional surface between a nonsedimentary rock and a sedimentary rock is called a nonconformity.
Part 3 Objectives
• Explain the several different methods used by scientists to determine absolute age.
• Describe how objects are dated by the use of certain radioactive elements.
• Explain how annual tree rings and glacial varves are used to date geological events.
½ LifeThe amount of time it takes for one-half of the original amount of
an isotope to decay is known as its half-life.
Half Lives for Radioactive Elements
½ Life Practice Sheet
Absolute datingRadiometric dating is used to determine the
absolute age of a rock
Key BedsA key bed contains distinctive material that
geologists can easily recognize in the rock record and use as a time marker.
Contrast relative-age dating and absolute-age dating.
Relative-age datingRelative-age dating places the
ages of rocks and the events that formed them in order, without exact dates. This is done by comparing one event with another or one rock with another rock.
Absolute-age datingIn contrast, absolute-age
dating determines the actual age of a rock, a fossil, or an object. This is done through radiometric dating, a process that determines the ratio of parent material to daughter product in a given sample of rock or fossil.
Part 4 Objectives
• Define fossil.• Explain several methods by which fossils
can be preserved.• Describe the characteristics of an index
fossil.• Discuss how fossils can be used to
interpret Earth’s past physical and environmental history.
Fossils Fossils are the remains or evidence of once-
living plants or animals. They provide clues about Earth’s past environmental conditions and evolutionary changes in organisms over time. They also help to correlate rock layers from one area to another.
Fossils (continued)
Fossil insects preserved in hardened tree sap are called amber.
Fossils (continued)
Molds, casts, coprolites, and petrified wood are all example of fossils
Fossils - original preservation
Mummified animals found in dry caves can be examples of fossils with original preservation.
Fossils - original preservation
Fossil insects can be found imbedded in amber, the hardened sap of prehistoric trees.
An insect imbedded in amber is an example of a fossil with original preservation.
Fossils (altered)
An example of a fossil with altered hard parts includes petrified wood
Trace Fossils
An example of a trace fossil includes worm trails.
PermineralizationIn the process of permineralization, pore spaces
within an organism’s shell are filled in with mineral substances.
Fossils - casts
A cast forms when the hollowed-out impression of a fossil organism becomes filled with minerals or sediment.
Fossils - molds
When the original parts of an organism in a sedimentary rock are weathered and eroded, a hollowed-out impression called a mold forms.
Index fossilsIndex fossils are useful to geologists if the fossils
have lived over a short period of time
Index vs. Trace Fossils
Index fossils are the remains of organisms
that can be used by geologists to correlate rock layers over large geographic areas or to date rock layers.
Trace fossils are not remains but indirect
evidence of organisms, such as imprints, trails, and burrows.
Both are similar in that they are types of fossils.
EvolutionThe adaptation of life-forms to changes in the environment is
known as evolution.
A process by which (generations of) organisms adapt to changes in their environments.