slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Geological Time - really, really, really long! PowerPoint Presentation
Download Presentation
Geological Time - really, really, really long!

Loading in 2 Seconds...

play fullscreen
1 / 36

Geological Time - really, really, really long! - PowerPoint PPT Presentation


  • 94 Views
  • Uploaded on

Geological Time - really, really, really long!. Motion pictures are generally projected at 32 frames per second. Therefore, each frame (image) is on the screen for only split second- let each frame represent 100 years. Start movie at present and go back in time.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Geological Time - really, really, really long!' - gotzon


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Geological Time - really, really, really long!

  • Motion pictures are generally projected at 32 frames per second. Therefore, each frame (image) is on the screen for only split second- let each frame represent 100 years.
  • Start movie at present and go back in time.
  • The Declaration of Independence would show up 1/16 of a second into the movie.
  • The Christian era (BC-AD boundary) would be 3/4 of a second into the movie.
  • The most recent Ice Age would be 7 seconds into it.
  • The movie would run about 6 hours before we got to the end of the Mesozoic era (extinction of the dinosaurs).
  • We'd have to watch the movie for about 2 days to see the beginning of the Paleozoic era (macroscopic life).
  • The whole movie (to the beginning of geologic time on Earth) would be approximately 16 days long!
slide3

Geologic Time

Two ways to relate time in geology:

>

Relative

: Placing events in a

>

Relative

: Placing events in a

sequence based on their positions

sequence based on their positions

in the geologic record.

in the geologic record.

>

Chronologic

: Placing a specific

>

Chronologic

number of years on an event or rock

sample.

sample.

slide4

Geologic Time Scale

a combination of the two types of age

determinations

>

a

relative

sequence of lithologic units

-

established using logical principles

>

measured against a framework of

chronologic

dates.

slide5

Geologic Time and the "geologic column"

Geologic Time and the "geologic column"

Developed using logical rules to establish

relative sequences of events

Developed using logical rules to establish relative

sequences of events

-

-

superposition

-

-

cross-cutting relationships

-

-

original horizontality

-

-

lateral continuity

Added to as new information is obtained and

data is refined

refined

Use of fossils for correlation and age determination

-

-

Numerical Dates attached to strata after the

development of Radiometric techniques

-

-

Still being refined as more information

becomes available

slide8

Relative Dating Methods

determines the relative sequence of events.

>

which came first, which came last.

>

no numeric age assigned

6 Relative age principles:

>

Superposition

>

Original Horizontality,

>

Lateral continuity

>

Cross-cutting Relationships

>

Inclusions

>

Fossil succession.

Those in yellow are most useful

slide10

Law of Superposition

In undisturbed strata, the layer on the bottom is

In undisturbed strata, the layer on the bottom is

oldest, those above are younger.

slide11

Original Horizontality

Sediments are generally deposited as

horizontal layers.

Lateral Continuity

Sediment layers extend laterally in all

direction until they thin & pinch out as

theymeet the edge of the depositional

basin.

slide12

Charles Lyell

Charles Lyell

1st Principles of Geology text

-

included description and use of

-

>

principles of cross-cutting relationships

>

principles of cross-cutting relationships

>

principles of inclusions

>

principles of inclusions

relative time tools

relative time tools

slide13

Cross-cutting Relationships

That which cuts through is younger than the

Object that is cut

dike cuts through

granite is cut

slide15

Principle of Inclusions

Inclusions (one rock type contained in another rock type) are

older thanthe rock they are embedded in. That is, the younger

rock contains the inclusions

slide17

Faunal/Floral Succession

Fossil assemblages (groupings of fossils)

succeed one another through time.

slide18

• Correlation-

relating rocks in one location to those in

another using relative age stratigraphic

principles

-

-

Faunal Succession

-

Superposition

-

Lateral Continuity

-

-

Cross-cutting

-

-

slide19

Unconformities

surfaces

represent a long time.

a time when rocks were not

deposited or

a time when rocks were

eroded

Hiatus

the gap in time represented

in the rocks by an uncon-

formity

3 kinds

Angular Unconformity

Nonconformity

Disconformity

slide20

Disconformities

A surface of erosion or non-deposition between

Parallel sedimentary rock beds

of differing ages.

slide21

Angular Unconformities

Angular Unconformities

An

angular unconformity

is an erosional surface on tilted

or folded strata, over which younger strata have been deposited.

slide22

Nonconformities

A

nonconformity

is an erosional surface on igneous or

metamorphic rocks which are overlain by sedimentary rocks.

slide24

Counting lifetimes in the Bible

Comparing cooling rates of iron pellets.

Determine sedimentation rates & compare

Estimate age based on salinity of the ocean.

Age Estimates of Earth

all age estimates were off by billions of years

some were more off than others!

slide25

Absolute Dating Methods

Radioactive

Decay sequences

acts as an atomic clock

we see the clock at the end of its cycle

analogous to starting a stopwatch

allows assignment of numerical dates to

rocks.

Radioactive isotopes change (

decay

) into

daughter isotopes at known rates.

rates vary with the isotope

235

40

14

e.g., U , K , C, etc.

>

>

+

+

slide26

Decay

unstable nuclei in parent isotope emits

subatomic particles and transform into

another isotopic element (daughter).

does so at a known rate, measured in the

lab

Half-life

The amount of time needed for one-half of a

radioactive parent to decay into daughter

isotope.

Assumptions?-you bet

Cross-checks ensure validity of method.

slide27

All atoms are parent isotope or some

t

0

known ratio of parent to daughter

1 half-life period has elapsed, half of the

t

material has changed to a daughter

1

isotope (6 parent: 6 daughter)

2 half-lives elapsed, half of the parent

t

remaining is transformed into a daughter

2

isotope (3 parent: 9 daughter)

3 half-lives elapsed, half of the parent

remaining is transformed into a daughter

t

3

isotope (1.5 parent: 10.5 daughter)

We would see the rock at this point.

Rate of Decay

slide28

Radioactive Isotopes

Radioactive Isotopes

analogous to sand in an hour glass

analogous to sand in an hour glass

-

-

we measure how much sand there is

we measure how much sand there is

>

represents the

mass of elements

>

represents the

mass of elements

-

-

we measure the ratio of sand in the bottom to sand in the top

we measure the ratio of sand in the bottom to sand in the top

-

-

at the end (present)

at the end (present)

>

daughter (b) and parent (t)

>

daughter (b) and parent (t)

-

-

we know at what rate the sand falls into the bottom

we know at what rate the sand falls into the bottom

>

the half life of the radioactive element

>

the half life of the radioactive element

-

-

how long would it take to get the amount sand in the observed

how long would it take to get the amount sand in the observed

ratio starting with all of it in the top?

ratio starting with all of it in the top?

100

Parent

Parent

% parent remaining

Daughter

Daughter

50

25

13

time----------->

slide29

Five Radioactive Isotope Pairs

Five Radioactive Isotope Pairs

Effective

Dating Range

Minerals and

Isotopes

Half-Life

of Parent

Rocks That Can

(Years)

Parent

Daughter

(Years)

Be Dated

Uranium 238

Lead 206

4.5 billion

10 million to

Zircon

4.6 billion

Uraninite

Uranium 235

Lead 207

704 million

Muscovite

Thorium 232

Lead 208

14 billion

48.8 billion

Biotite

Potassium feldspar

Rubidium 87

Strontium 87

4.6 billion

10 million to

Whole metamorphic

4.6 billion

or igneous rock

Potassium 40

Argon 40

1.3 billion

100,000 to

Glauconite

4.6 billion

Muscovite

Biotite

Hornblende

Whole volcanic rock

slide30

Radiocarbon and Tree-

Ring Dating Methods

Carbon-14 dating is based on the

Carbon-14 dating is based on the

in an organic

ratio of C-14 to C-12

ratio of C-14 to C-12

sample.

sample.

>

Valid only for samples less than 70,000

>

Valid only for samples less than 70,000

years old.

years old.

>

Living things take in both isotopes of

>

Living things take in both isotopes of

carbon.

carbon.

>

When the organism dies, the "clock" starts.

>

When the organism dies, the "clock" starts.

Method can be validated by cross-checking with tree rings

slide32

Recognizing Patterns of change

Walther's Law

The vertical sequence is repeated by the horizontal

sequence

walking from A to B to C to the Coast you would encounter the

-

rocks that would be encountered by drilling a core into the

earth at any point (A, B, or C)

slide33

Facies Diagram

distribution of lithofacies (rock-types)

these are associated with their respective EOD

-

biofacies are similar but refer to fossils rather than

rock types

slide34

Eustasy, relative sea-level, and relative position

of lithofacies

Eustasy= changes in volume of water in ocean

lithofacies depend on

sea-level

-

land level

-

geometry of coast

-

sediment supply

-

Vail Curve

an attempt at global

correlation of

lithologies

for better production

-

of petroleum resources

-

slide35

Rock designations

Rock designations

Rock units called Lithostratigraphic units

Rock units called Lithostratigraphic units

-

described in terms of Group, Formation, & Member

-

described in terms of Group, Formation, & Member

>

each term has specific meanings in geological parlance

>

each term has specific meanings in geological parlance

Formation

Formation

-

a mappable lithostratigraphic unit

-

a mappable lithostratigraphic unit

>

has a location for identifying the type-section

>

has a location for identifying the type-section

>

has a rock designation describing the lithology

>

has a rock designation describing the lithology

-

sometimes not all the same lithology

-

sometimes not all the same lithology

>

in which case the term "Formation" takes the place of lithologic

>

in which case the term "Formation" takes the place of lithologic

type

type

Groups are composed of several formations

Groups are composed of several formations

Members are distinctive units within a formation

Members are distinctive units within a formation

-

group is largest and contains formations and members

-

group is largest and contains formations and members

-

formations are next and contain members

-

formations are next and contain members

slide36

Fundamental lithological units

Formation- a rock layer with distinctive characteristics that is mappable over a large are at “typical” map scales

1:62,500 or more commonly 1:24,000

Formations have Members

smaller layers that are unique that are not mappable over larger areas and won’t show up at typical map scales

Groups have formations; formations have members