Earth Space Science Semester 2 Exam Review Part 3

Earth Space Science
Semester 2 Exam Review
Part 3
Uniformitarianism
-From the “Theory of Earth,” written by Scot James Hutton.
-Stated that the physical, chemical and biological laws that operate today also operated in the
past.
-In order to understand the past geology, we must study the present day processes.
Absolute Age
-Determining the number of years since the occurrence of a geologic event; such as the
formation of a rock or rock layer.
-Determined by Radioactive Dating
Relative Age
-Rocks are placed in their proper sequence or order in which they were formed.
-Only the chronological order of events can be determined.
-Relative Dating is another term used to explain Relative Age.
-Geologists study Igneous extrusions and intrusions as well as faults and unconformities
(geologic gap caused by erosion) to determine Relative Age.
-Index Fossils also help determine the Relative Age of Rocks. Index fossils must be a widely
distributed organism that briefly (millions of years) existed.
Correlation
-In order to create a worldwide geologic time scale, rocks of similar age in different areas need
to be matched up.
Cross-cutting Relationships
-A principle of Relative Aging.
-A rock formation like an igneous intrusion (dike, sill, and batholith) is younger than the
surrounding rock
formation that it cuts through.
-A fault is also younger than the rock that it cuts through.
-Faults and intrusions can also cut through each other as shown in illustrations. The fault and
intrusion shown as overlapping is the younger or most recent event.
Unconformity
-An area where an eroded rock is in contact with a newer rock layer.
-The rock below the unconformity is always older.
-Creates a geologic gap or break in the rock record where the erosion occurs.
Law of Superposition
-In any sequence of undisturbed rock layers (mostly sedimentary), each bed of rock is older than
the layers above and younger than the layers below.
Fossil Evidence
- Found on or in the Crust.
- Classified as Sedimentary.
-Index Fossils help determine the Relative Age of rocks.
-Provides us evidence of how life has changed over time.
-Provides us with a timeline or order of organisms living in certain time periods.
-Fossils are the preserved remains or traces of living organisms.
-Shows us that organisms over time have evolved and have become extinct.
-Provides us with evidence of Earth’s changing climate in the past.
Fossil Evidence (cont.)
-Includes types that are classified as Petrified (mineral replacement), Molds (hollow copy of the
shape), Casts (solid copy of the shape), Trace (prints, trails and burrows), Original Animal Parts
/Preserved Remains (Tar, Amber, Ice, Shells, and Teeth) and Carbon film.
Outcropping
-Where a mineral formation emerges and becomes exposed on the surface of the Earth.
Greenhouse Gas
-An atmospheric gas that contributes to the Greenhouse Effect by absorbing IR radiation which
in turn warms the Troposphere.
-Carbon Dioxide (CO2), Methane (CH4) and water vapor are gasses that are common examples.
-Deforestation of tropical rainforests and the burning of carbon fuels (transportation and
factories) add CO2 to the atmosphere.
- Animals add CH4 to the atmosphere.
-Recent increases in the production of greenhouse gasses may have contributed to increases in
global air temperatures.
Global Warming
-Recent temperature increase of the Troposphere and water temperatures that some scientists
attribute to the production and rise of greenhouse gasses.
Radioactive Dating
-Geologists use radioactive dating to determine the absolute ages of rocks.
-Geologists first determine the amount of a radioactive element in a rock.
-Geologists then compare that amount with the amount of the stable element that it decays
into.
- Examples of elements used in dating include Carbon -14, Uranium-238 and Potassium 40.
Half-life
-The half-life of a radioactive element (unstable element that emits radiation) is the time it takes
for half of the radioactive atoms to decay.
- As a radioactive element decays, its atoms breakdown to form atoms of another element. For
example, Potassium 40 decays and forms Argon 40.
Solar Radiation
-Radiation from the sun.
-An alternative energy source for human energy needs.
Use the principle of superposition to determine the relative age of surface features or rock layers.
-Review the “Determining Geologic Ages” lab illustrations.
-Review the teacher diagrams and quiz relating to superposition.
-Refer to the term “Relative Age” found towards the beginning of this document.
Use cross-cutting relationships to determine the relative age of rocks.
-Review the “Determining Geologic Ages” lab illustrations.
-Review the teacher diagrams and quiz relating to cross-cutting relationships.
-Refer to the term, “cross-cutting relationships” found towards the beginning of this document.
Describe the principle of uniformitarianism.
-A tenet of modern geology.
-It means that geologic processes occur over a very long period of time.
-Though the geologic processes appear to act slowly over time, their effects in the long term are
just as significant as when compared to a major catastrophic event.
-For example, erosion can occur slowly over time. The North American continent is “lowered
about 3 centimeters every 1,000 years.”
-The Earth has “experienced many cycles of mountain building and erosion” over the last 4.5
billion years.
-Refer to the term “uniformitarianism” found towards the beginning of this document.
Describe the principle of radioactive dating.
-Refer to the term “radioactive dating” found towards the beginning of this document.
-Carbon-14 is one type of Carbon found in our body. It is radioactive.
-When we die, no more carbon is added. The Carbon -14 decays and changes into Nitrogen -14.
-A scientist could measure the remains of the C-14 left in your body.
-C-14 has a half-life of only 5,730 years.
-“The percentage of radioactive atoms that decay remains the same but the number of
radioactive atoms decreases with each half-life.”
Select an appropriate method to determine the age of a rock.
-Sedimentary rock contains minerals from rocks of different ages making radioactive dating
inaccurate.
- Radioactive dating can be performed on igneous intrusions and extrusions.
- Law of Superposition and Cross-cutting principles can be used in conjunction with radioactive
dating.
Describe how fossil evidence can support the age of rocks.
-Geologists can also determine the relative age of a rock layer by finding index fossils in the
layer.
-Index fossils have to be widely distributed over large land masses.
-Index fossils can only exist over short periods of time (100’s of millions of years).
-Scientists use index fossils to match up similar rock layers in distant areas.
Identify a technique used by geologists to identify the age of events in Earth’s History.
-Geologists use radioactive dating to determine the absolute ages of rocks.
-Scientists also developed a Time Scale which is a record of life forms and geologic events.
-Relative Dating and Absolute Dating (radioactive dating) help determine the age of divisions on
the Geologic Time Scale.
Identify a greenhouse gas in the atmosphere.
-Carbon Dioxide and Methane gas are two greenhouse gasses that are produced by humans.
Explain how global temperature change may affect sea level.
-Some scientists predict that an increase of greenhouse gasses will contribute to warmer air and
water temperatures which in turn will melt polar ice caps which in turn will raise ocean sea
levels.