Interpreting Geologic Interpreting Geologic HistoryHistory

Introduction to Relative and Introduction to Relative and Absolute DatingAbsolute Dating

The Solar SystemThe Solar System

The solar system is the sun and all objects The solar system is the sun and all objects that orbit the sun under its gravitational that orbit the sun under its gravitational influence.influence.

The solar system formed approximately 5 The solar system formed approximately 5 billion years ago (4.6 billion years ago).billion years ago (4.6 billion years ago).

Evolution of the Solar SystemEvolution of the Solar System

At first there was a gas dust cloud (nebula) At first there was a gas dust cloud (nebula) that was released by the Big Bang Theory that was released by the Big Bang Theory or by an explosion of stars. or by an explosion of stars.

Gravitation stemmed from a shock wave Gravitation stemmed from a shock wave from an exploding star, caused the cloud from an exploding star, caused the cloud to condense into one or more mass to condense into one or more mass concentrations. concentrations.

99% of the nebula of our solar system 99% of the nebula of our solar system makes our sun.makes our sun.

The Nebular Model of the The Nebular Model of the Formation of the Solar SystemFormation of the Solar System

Relative Dating of Rock StrataRelative Dating of Rock Strata

Relative Dating is the determination of the Relative Dating is the determination of the age of a rock or event in relation to the age of a rock or event in relation to the age of other rocks or events.age of other rocks or events.

The composition, structure, position and The composition, structure, position and fossil content of Earth’s rocks provide fossil content of Earth’s rocks provide information about Earth’s geologic history.information about Earth’s geologic history.

Evidence in Earth’s rocks dates back Evidence in Earth’s rocks dates back approximately 4 billion years.approximately 4 billion years.

Review of the Rock CycleReview of the Rock CycleSee p.6 in your reference tableSee p.6 in your reference table

Formation of Rock StrataFormation of Rock Strata

The rock strata below, originally formed The rock strata below, originally formed from deposition (by water), compaction from deposition (by water), compaction and cementation. and cementation.

It was disturbed at some point in time by a It was disturbed at some point in time by a magma extrusion.magma extrusion.

Observing Rock StrataObserving Rock Strata

How do we use rock strata for relative dating?How do we use rock strata for relative dating? Always start at the bottomAlways start at the bottom

The lowest layer is the oldest. The lowest layer is the oldest. Pay attention to any Pay attention to any disturbancesdisturbances

A disturbance is anything that disrupts the layering of the A disturbance is anything that disrupts the layering of the parent rock.parent rock.

For example: look for faultsFor example: look for faults

folding or tiltingfolding or tilting

metamorphism (both contact metamorphism (both contact

and regional)and regional)

erosionerosion

Look for the disturbancesLook for the disturbances

Let’s Interpret Rock StrataLet’s Interpret Rock Strata

What are the order of events for the rock What are the order of events for the rock strata below?strata below?

Let’s Interpret Rock StrataLet’s Interpret Rock Strata What are the order of events for What are the order of events for

the rock strata below?the rock strata below?

Lab Activity #1: Geologic ProfilesLab Activity #1: Geologic Profiles

Please complete lab activity #1 titled: Please complete lab activity #1 titled: Geologic Profiles.Geologic Profiles.

When finished, please complete the When finished, please complete the following: questions 1-7 on pages 280-following: questions 1-7 on pages 280-281.281.

HW#1: July 11, 2011HW#1: July 11, 2011

Regent review book, read pages 284-Regent review book, read pages 284-286. Answer questions for Regents 286. Answer questions for Regents practice pages 286-287 questions 21-36. practice pages 286-287 questions 21-36. Answer all questions in your workbook. Answer all questions in your workbook.

IF we did not get to it, please complete IF we did not get to it, please complete questions 1-7 on pages 280-281 and questions 1-7 on pages 280-281 and pages 283-284 #8-20pages 283-284 #8-20

Study for your quiz.Study for your quiz.

Correlation by Use of Index FossilsCorrelation by Use of Index Fossils

Fossils are the remains or evidence of Fossils are the remains or evidence of former living things.former living things.

Some examples of fossils are:Some examples of fossils are: Bones Bones FootprintsFootprints ShellsShells Organic compounds (such as DNA)Organic compounds (such as DNA)

Correlation by Use of Index FossilsCorrelation by Use of Index Fossils

Index fossils are used to correlate rock Index fossils are used to correlate rock layers.layers.

An index fossil is an organism that livedAn index fossil is an organism that lived For a short period of timeFor a short period of time Over a large geographic areaOver a large geographic area

Index FossilsIndex Fossils

With minor exceptions, fossils are found With minor exceptions, fossils are found exclusively in sedimentary rock.exclusively in sedimentary rock.

They are rarely found in igneous and They are rarely found in igneous and metamorphic rock because fossils are metamorphic rock because fossils are usually destroyed by the melting of usually destroyed by the melting of igneous rock and by the heat and pressure igneous rock and by the heat and pressure associated with the formation of associated with the formation of metamorphic rocks. metamorphic rocks.

How do we use index fossils to How do we use index fossils to correlate rock layers?correlate rock layers?

Based on fossil evidence, determine the geologic period during which the unconformity formed.

Identify the coral index fossil that would most likely be found in the same layer as

the index fossil Ctenocrinus.

Lab Activity #2: Using Index Lab Activity #2: Using Index Fossils to Correlate RocksFossils to Correlate Rocks

Please complete lab activity #2.Please complete lab activity #2.

When finished, please complete questions When finished, please complete questions 8-15 on page 283 in your regent review 8-15 on page 283 in your regent review book.book.

HW#2: July 12, 2011HW#2: July 12, 2011

Answer questions for Regents practice Answer questions for Regents practice pages 299-300 questions 45-47. Answer pages 299-300 questions 45-47. Answer all questions in your workbook.all questions in your workbook.

IF we did not get to it, please complete IF we did not get to it, please complete pages 283-284 #8-20pages 283-284 #8-20

Study for your quiz.Study for your quiz.

Interpreting Geologic TimeInterpreting Geologic Time

Pages 8 and 9 of your reference table Pages 8 and 9 of your reference table shows the many geologic events and shows the many geologic events and different forms of life that evolved over different forms of life that evolved over 4600 million years.4600 million years.

Reference Table page 8Reference Table page 8

If you look at p. 8 it breaks down the 4600 If you look at p. 8 it breaks down the 4600 million years intomillion years into Eons (the broadest time category)Eons (the broadest time category) ErasEras PeriodsPeriods Epochs (the simplest and most specific time Epochs (the simplest and most specific time

category)category)

Reference Table p.9Reference Table p.9

Time distribution of index fossilsTime distribution of index fossils Important Geologic Events in New York Inferred Positions of Earth’s

Landmasses

Lab Activity #3: Geologic CalendarLab Activity #3: Geologic Calendar

Please complete the Geologic Calendar Please complete the Geologic Calendar Lab.Lab.

When finished, please complete questions When finished, please complete questions 47-52 page 295 (if there is time). If not 47-52 page 295 (if there is time). If not complete for homework.complete for homework.

HW#3: July 15, 2010HW#3: July 15, 2010

Complete the handout about geologic Complete the handout about geologic history.history.

We will go over this worksheet at the We will go over this worksheet at the beginning of tomorrow’s class (after your beginning of tomorrow’s class (after your quiz).quiz).

Study for your quiz.Study for your quiz.

Radioactive Decay (Half Life)Radioactive Decay (Half Life)

The principle of superposition and The principle of superposition and methods of correlation help to determine methods of correlation help to determine the relative age of rock layers, but do not the relative age of rock layers, but do not give their absolute age. give their absolute age.

Absolute age is expressed in scientific Absolute age is expressed in scientific units; such as years before the present.units; such as years before the present.

Isotopes and Radioactive DecayIsotopes and Radioactive Decay

Isotopes are unstable forms of an element Isotopes are unstable forms of an element that differ from its parent element by its that differ from its parent element by its mass.mass.

They emit particles and electromagnetic They emit particles and electromagnetic energy in a process called radioactive energy in a process called radioactive decay or nuclear decay thus changing into decay or nuclear decay thus changing into atoms of other isotopes and elements.atoms of other isotopes and elements.

Radioactive Decay DataRadioactive Decay DataPage 1 of Reference TablePage 1 of Reference Table

Half LifeHalf Life

The time required for half of the atoms in a given The time required for half of the atoms in a given mass of an isotope to decay is called the mass of an isotope to decay is called the half half lifelife of the isotope. of the isotope.

The half life of a radioactive isotope can be used The half life of a radioactive isotope can be used along with the ratio between the amount of the along with the ratio between the amount of the original isotope and the amount of its decay original isotope and the amount of its decay product to estimate the absolute age of a rock product to estimate the absolute age of a rock sample.sample.

This method is called radioactive This method is called radioactive (absolute)dating.(absolute)dating.

Lab Activity #4: The Half Life of Lab Activity #4: The Half Life of M&M’sM&M’s

Please complete lab activity #4.Please complete lab activity #4. When finished please answer questions When finished please answer questions

37-46 on p.290 in your regent review 37-46 on p.290 in your regent review book.book.

If you do not get to this, please complete If you do not get to this, please complete for homework.for homework.

HW#4, July 16, 2010HW#4, July 16, 2010

Please complete questions 35-41 on Please complete questions 35-41 on pages 298-299 in your regent review book.pages 298-299 in your regent review book.

If not completed in class, please answer If not completed in class, please answer questions 37-46 on p.290 in your regent questions 37-46 on p.290 in your regent review book.review book.

Study for your quiz. Have a great Study for your quiz. Have a great weekend.weekend.