Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative...
-
Upload
cleopatra-gibbs -
Category
Documents
-
view
214 -
download
0
Transcript of Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative...
![Page 1: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/1.jpg)
Earth’s HistoryThe Rock Record
![Page 2: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/2.jpg)
Topic 1 – Telling Time
• Kinds of Time– 2 types
1. Relative time – places an event in order by comparing it with other events
– Example: Sedimentary Rock layers» A – Oldest (Lower)» B – Middle Age» C – Youngest (Upper)
– Actual age not known, only relative!
•Relative time – place in a sequence
![Page 3: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/3.jpg)
Topic 1 – Telling Time2. Absolute time – specific age
–Example: Sedimentary Rock»Rock Layer B deposited 30 Ma (mega anna = million years ago)»B is 10 million years older than C»B is 5 million years younger than A
Rock Layer Absolute Age
A 35 Ma
B 30 Ma
C 20 Ma
Two things told with absolute time
1. Actual age
2. Length of time between events
-- used to determine rate of geologic process
![Page 4: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/4.jpg)
So... What’s the story?
List observations
Do not write down interpretations
![Page 5: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/5.jpg)
Finding Age with Relative Time
• Law of superposition – in a sequence of horizontal sedimentary rocks, the oldest in on the bottom
Originally Horizontal
YoungerYoungerTiming
Gra
nd
Ca
nyo
n,
Ariz
on
a,
Co
pyr
igh
t L
arr
y F
ello
ws
htt
p:/
/ww
w.e
art
hsc
ien
cew
orld
.org
/ima
ge
ba
nk/
sea
rch
/re
sults
.htm
l?Im
ag
eID
=h
mw
nq
6
OlderOlder
![Page 6: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/6.jpg)
Finding Age with Relative Time
http://www.classzone.com/books/earth_science/terc/content/investigations/es2903/es2903page03.cfm
![Page 7: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/7.jpg)
Finding Age with Relative Time
• What happened here?• Originally layers deposited
horizontally• Then they were tilted
USGS/Jennifer Loomis, TERCTilted limestone beds in the Mojave Desert, Californiahttp://www.classzone.com/books/earth_science/terc/content/investigations/es2903/es2903page04.cfm.
![Page 8: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/8.jpg)
Finding Age with Relative Time• Law of Cross-cutting
relationships – igneous rocks are younger than rocks that they intrude into
Cross-cutting
MOST recent
![Page 9: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/9.jpg)
Finding Age with Relative Time
• Law of (fragmented) Inclusion – Rock fragments found in another
rock must be older than the rock it is found in•Examples
– pebbles in a conglomerate– Sand grains in a sandstone
http://www.geology.sfasu.edu/rocks/conglomerate02.jpg
http://www.zionnationalpark.com/zioninfo/photos/Sandstone-2.jpg
![Page 10: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/10.jpg)
Finding Age with Relative Time
• Unconformity – break in the rock record– Eroded surface
then buried– Parts of rock
record missing like pages in a book
– Gap in geologic time
http://www.bamboo.hc.edu.tw/~sts/course-2003/course/textbook/text05/ch14/images/ch14-032.jpg
![Page 11: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/11.jpg)
Geologic Time
______________________
________________________
http://www.astro.lsa.umich.edu/users/cowley/grand33.jpg
250 Ma
600 Ma
TIMING: RELATIVE vs. ABSOLUTETIMING: RELATIVE vs. ABSOLUTE
![Page 12: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/12.jpg)
M. d’Alessio, 2004
Murder Mystery?
How is this picture explained using relative dating?
List observations From your observations make interpretations
Law of SuperpositionPrinciples of: Original Horizontality Cross-Cutting Rel. Inclusions Unconformities
![Page 13: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/13.jpg)
Topic 9 – Measuring Absolute Time
http://home.earthlink.net/~colorado_hiking/1_Hiking_topics/pics/bristleconepineT.jpg
4,862 – Prometheus
4,767 -- Methuselah
http://www.championtrees.org/champions/articles/AP21010.htm
• Tree rings can be used to measure specific dates– 1 ring = 1 year– Width of ring correlates to
temperature and rainfall– Wide ring = high temperature
and rain– Oldest tree is the bristle cone
pine
![Page 14: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/14.jpg)
Radioactive Elements & Absolute Time
• Radioactive decay used to date much farther back in time
• Some elements naturally “decay” in the nucleus– Radioactive decay occurs until a
stable element is formed
http://www.pbs.org/wgbh/nova/first/radiocarbonce.html
![Page 15: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/15.jpg)
Topic 12 – Half-Life
• Half-life = rate of decay–Time needed for ½ radioactive items to decay
•Ranges from seconds to billions of years
Radioactive material
Found in Half-life (years)
C-14 Wood, peat, coal , bones, shells
~5,700
K-40 Mica, feldspars ~1.3 billion
Rb-87 Mica, feldspars ~47 billion
U-235 Many rocks 713 million
U-238 Oldest igneous rocks
4.5 billion
![Page 16: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/16.jpg)
Fossil Preservation
• 1. Original Remains• Frozen• Resin (Amber)
– Sticky substance from evergreens– Usually insects
• Tar Pits– LaBrea
![Page 17: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/17.jpg)
Fossil Preservation
• Replaced Remains• Hard parts replaced by minerals• Usually done by groundwater
– Ex: petrified Wood
• Mold or Cast• Mold – shape of where fossil was• Cast – new material fills mold &
hardens– Ex: Shells
![Page 18: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/18.jpg)
Fossil Preservation• Trace Fossils• Evidence of life other than
remains – trails– Footprints– Burrows– copralites
http://www.delargy.com/images/2004_7_Colorado/dinosaur%20footprint.JPG http://csd.unl.edu/csd-esic/ResourceNotesImages/volume16/page-24.jpg
http://www.scienceviews.com/photo/thumb/SIA0651.jpg
![Page 19: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/19.jpg)
Topic 5 – Fossils as Evidence for Evolution• Oldest rocks with fossils show
simple life forms (only)• As time goes by, some simpler
life forms become more complex
• This process of change is called:EVOLUTION
• Theory of Evolution: Scientific explanation for the past and present diversity of lifehttp://www.thezreview.co.uk/posters/posterimages/e/evolution1.jpg
![Page 20: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/20.jpg)
Topic 5 – Fossils as Evidence for Evolution
• Charles Darwin – “The Origin of Species”, 1859
• - theory states that species evolve slowly over geologic time
• Modern science - species remain fairly constant for millenia, then abruptly change within a relatively short time, often less than 1 million years
http://earth.ast.smith.edu/courses/ast215/darwin.jpg
![Page 21: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/21.jpg)
Topic 6 – Index Fossils and Key Beds
• Index fossils (guide fossils)• Lived for a “short geologic”
time period in a lot of places• Allow dating of rock layers
with relative age3 Characteristics1. Easily recognized (unique)2. Found over large geographic area
– Continental drift theory evidence
3. Limited in time– Only lived over short period of time,
therefore, only found in FEW rock layers
http://www.paleocurrents.com/img/2002_09_13FI/HTML/138-3848_img_std.jpg
![Page 22: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/22.jpg)
Topic 6 – Index Fossils and Key Beds
• Key Bed• Single rock layer that acts like
an index fossil• Easily recognized• Large area
– Ex: Ash from volcanic eruptions• Iridium layer from Chicxulub impact
(K-T)
http://www.astro.uva.nl/encyclopedie/images/chicxulub.gif
Iridium Layer
Clay with high rare element (Ir) found in Mexico, Italy, Denmark & New Zealand
![Page 23: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/23.jpg)
Topic 7 – Rock Correlation
• Correlation: matching of rock layers from one area to another
• Index Fossils• Key Beds
• Allow correlating over great distances
Iridium LayerClay with high rare element (Ir) found in Mexico, Italy, Denmark & New Zealand
![Page 24: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/24.jpg)
Topic 8 – Other Uses for fossils
1. Determine relative age of rocks
2. Correlate rock layers3. Indicate past climate
• Ex: coal only from warm, swampy areas
4. Oil exploration• Microfossils – seen only with
microscope• Help correlate layers of rock to oil
rich layers in other places
![Page 25: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/25.jpg)
Topic 10 – Varves
• Varve• Any sediment that
shows a yearly cycle
• Sedimentary layers resemble tree rings
• Can date ~15,000 years ago– Often associated
with lakes annual turnover
![Page 26: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/26.jpg)
Geologic Timetable (p. 600-601)• Eon – greatest division of geologic time• Era – 2 or more of these form an eon• Period – basic unit of geologic time in
which a single type of rock system is formed (named for specific occurrence)
• Epoch – subdivision of a period• Age – subdivision of an epoch
– All changes based on significant changes in the fossil record
• The greater the changes, the larger division
• Fossil – ANY evidence of earlier life or environments preserved in rock record
![Page 27: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/27.jpg)
Geologic Timetable
• The geologic time scale can be represented in many ways
![Page 28: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/28.jpg)
![Page 29: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/29.jpg)
Geologic Timetable
![Page 30: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/30.jpg)
![Page 31: Earth’s History The Rock Record. Topic 1 – Telling Time Kinds of Time –2 types 1. Relative time – places an event in order by comparing it with other.](https://reader034.fdocuments.net/reader034/viewer/2022051621/56649e555503460f94b4cc3c/html5/thumbnails/31.jpg)
Geologic TimetableERA Attributes
Archean (Beginning Earth)Began ~4.6 Ga
Beginning of Earth, almost no fossils
Proterozoic (Earliest Life)
Began 2.5 Ga
Simple plants & animals (worms)No life on land
Paleozoic (Ancient Life)Began 570 Ma
Plant & Animal FossilsLand & Ocean
MesozoicBegan 250 Ma
Middle LifeAge of Reptiles (dinosaurs)
Cenozoic (Recent Life)Began 65 Ma
Age of Mammals