Download The Earth in Context

Physical Environment:
Earth Origin, Age &
Structure
EVPP 110 Lecture
Instructor: Dr. Largen
1
Topics








brief history of universe & earth
earth in context of solar system
age of earth
early ideas about physical features of earth
nature and origin of rocks
geologic time/dating rock & fossil record
components of earth system
structure of earth
2
Brief History of Universe & Earth

Universe
• Origin


Various theories
http://www.youtube.c
om/watch?v=4WF4Pq
DfRbI&feature=relat
ed
• Age

13.75 billion years, +/170 million years
• 3/1/10, in
Astrophysical Journal,
using data from Hubble
Space Telescope, using
technique called
gravitational lensing
3
Brief History of Universe & Earth

Universe
• Size


Expanding
~93 billion light
years in diameter
• 1 light year ≈ 10
trillion km
4
Brief History of Universe & Earth

Universe
• dynamic adolescence
5
Earth in context
of our solar system
6
Earth in context of our solar system

Origin of solar system
• solar nebula theory

Nebula collapsed under its own
gravity
• Nebula = giant, swirling cloud
of gas and dust
• sun

formed in center of collapsed
nebula
• temperature & density were high
enough for nuclear fusion to begin
• planets

formed from rest of swirling disk
7

Animation of origin of solar system at
http://www.classzone.com/books/earth
_science/terc/content/visualizations/es
0401/es0401page01.cfm?chapter_no=vis
ualization
8
Earth in context of our solar system

planets of solar system
• grouped as
 terrestrial

Jovian

Pluto =
(non-terrestrial)
dwarf planet
9
Earth in context of our solar system

Earth
10
Age of the Earth
11
Age of the Earth

Early ideas
• James Ussher (1581-1656)


Protestant Archbishop of
Armagh (Anglican Primate
of All Ireland)
volume 4 of his Annals
of the
World (1650)
• Earth was formed on
 Sunday, October 23, 4004 BC (Julian)
12
Age of the Earth

Current estimate
• ≈4.6 billion years
13
iClicker Question

The current estimate of the age of the
earth is ~
•
•
•
•
A. 4.6 million years
B. 4.6 billion years
C. 10 billion years
D. 20 billion years
14
iClicker Question 2

Is the earth older or younger than the
universe?
• A. older
• B. younger
15
Early ideas about
physical features of the
Earth
16
Early ideas about physical
features of the Earth

Early ideas
• unchanging
17
Early ideas about physical
features of the Earth

Catastrophism
• Earth’s surface is modified only by
periodic, violent disasters

attributed by some to divine origin
• enabled explanation of observations of
early geologists within framework of a
“young” earth
18
Early ideas about physical
features of the Earth

fundamental principles of modern
geology
• principle of superposition
• principle of original horizontality
• Principle of original lateral
continuity
• principle of uniformitarianism
19
Early ideas about physical
features of the Earth

Nicolaus Steno
(Danish,
1636-1686, anatomist, geologist,
and bishop)
• Formulated principles of
Superposition
 Original
Horizontality


Original Lateral
Continuity
20
Early ideas about physical features of
the Earth

principle of superposition
Oldest
Youngest
21
Early ideas about physical features
of the Earth

principle of original horizontality
22
Early ideas about physical features of
the Earth

principle of original lateral continuity
23
Early ideas about physical features of
the Earth

James Hutton (Scottish, 1726-1797)
• “father of modern geology”
• Wrote “Theory of Earth”
• formulated in 1785
 principle of
uniformitarianism
(gradualism)
• "the present is the key to the
past“
• geologic forces and processes -gradual as well as catastrophic -acting on the Earth today are
the same as those that have24
acted in the geologic past
Uniformitarianism

Present

Past
(fossilized/lithified/petrified)
Ripples in sand at
water shore
Sand dunes
Glacial deposits
(erratics)
25
Uniformitarianism

Present

Past
(fossilized/lithified/petrified)
Cracked mud
Impact crater
Alluvial fan (aka
river delta)
26
Early ideas about physical features of the Earth

Charles Lyell (British, 1797-1875)
• Wrote “Principles of
Geology”
• Popularized Hutton’s principle
of uniformitarianism
• Close/influential friend of
Charles Darwin
• Important work in fields of
stratigraphy and glacial
erractics
iClicker Question 3

In this diagram of unaltered layers
of sedimentary rock, rock found in
layer C would be ____________
than rock found in layer E
according to the principle of
superposition.
• A. older
• B. younger
28
iClicker Question 4
According to the principle of original horizontality,
if you discovered rock in which the layers were
vertical you would conclude that the layers
______________.
• A. were deposited in this manner and that the rock is
unaltered
• B. were deposited horizontally and the layers were
altered (tilted) some time after their formation
29
Nature and Origin of
Rocks
30
Nature and Origin of Rocks

three basic types
• Igneous
• Sedimentary
• Metamorphic
31
Nature and Origin of Rocks

Rock cycle
• A group of processes that produce igneous,
sedimentary and metamorphic rock
32
Animation of sediment deposition at
http://www.classzone.com/books/eart
h_science/terc/content/visualizations/
es0604/es0604page01.cfm?chapter_
no=visualization
33
Animation of formation of
metamorphic rock at
http://www.classzone.com/books/eart
h_science/terc/content/visualizations/
es0607/es0607page01.cfm?chapter_
no=visualization
34
Geologic Time
&
Dating the Rock & Fossil
Record
35
Geologic Time & Dating the
Rock/Fossil Record

geologic time
• expressed as
 relative time (relative age)
 absolute time (absolute age)
36
Geologic Time & Dating the
Rock/Fossil Record

geologic time
• expressed as
 relative time (relative age)
 absolute time (absolute age)
37
Geologic Time & Dating the
Rock/Fossil Record

relative time (relative age)
• Determined via a variety of types of
evidence, including, but not limited to,
Unconformities
 Index fossils
 Geologic correlation

38
Geologic Time & Dating the
Rock/Fossil Record

Unconformity
• surface with very large time loss
• types
 angular unconformity
 disconformity
 nonconformity
39
Geologic Time & Dating the
Rock/Fossil Record

relative time (relative age)
• Unconformities

angular unconformity
• sedimentary over
folded/tilted sedimentary
40
Geologic Time & Dating the
Rock/Fossil Record

relative time (relative age)
• Unconformities

disconformity
• Sedimentary over eroded
sedimentary
41
Geologic Time & Dating the
Rock/Fossil Record

relative time (relative age)
• Unconformities

nonconformity
• sedimentary over eroded
igneous or metamorphic
42
Plate tectonics

Animation of formation of unconformity
boundary at
http://www.classzone.com/books/earth_s
cience/terc/content/visualizations/es2902
/es2902page01.cfm?chapter_no=visualiza
tion
Geologic Time & Dating the
Rock/Fossil Record

relative time
age)
(relative
• Index fossils
 fossils of “forms of
life which existed
during limited
periods of geologic
time and thus are
used as guides to
the age of the rocks
in which they are
preserved”
(www.usgs.gov)
44
Geologic Time & Dating the
Rock/Fossil Record

relative time
(relative age)
• Index fossils
45
Geologic Time & Dating the
Rock/Fossil Record

relative time (relative age)
• Geologic correlation

determining that rocks are the same formation (may
mean rocks are the same age)
46
Geologic Time & Dating the
Rock/Fossil Record

relative time (relative age)
• summary
47
Geologic Time & Dating the
Rock/Fossil Record

geologic time
• expressed as
 relative time (relative age)
 absolute time (absolute age)
48
Geologic Time & Dating the
Rock/Fossil Record

absolute time (absolute age)
• Role of radioactivity

some elements have isotopes
• version of an element with a different number
of neutrons than “normal” (=periodic table)

some isotopes are
• radioactive


unstable
“decay” into other elements by emitting
49
particles and energy
Geologic Time & Dating the Rock/Fossil
Record

Radioactive isotopes
• radioactive decay
 original radioactive
isotope (parent isotope)
decays into daughter
isotope
• rate of decay
 unique to each radioactive
isotope
 exponential
 determined by half-life
• amount of time it
takes for ½ of parent
isotope to decay into
daughter isotope
Geologic Time & Dating the
Rock/Fossil Record

Radiometric dating
• Method for determining the age of an object
based on the ratio of the amount of a particular
radioactive isotope relative to the amount of its
decay products
51
Half Lives of Some Radiometric
Isotopes
Radioactive
isotope
Rubidium 87
~Half life in
Product of
years
decay
48.6 billion Strontium 87
Thorium 232
14.0 billion
Lead 208
Uranium 238
4.5 billion
Lead 206
Uranium 235
0.7 billion
Lead 207
5730
Nitrogen 14
Carbon 14
52
Iclicker question 5

Half-life is…
• A. the amount of time it takes for one half
of your life to pass
• B. the amount of time it takes for all of a
given quantity of radioactive isotope to
decay
• C. the amount of time it takes for ½ of a
given quantity of radioactive isotope to
decay
Iclicker question 6

The larger the half-life, the
_________ the amount of time it takes
for a radioactive isotope to decay.
• A. shorter
• B. longer
Iclicker question 7

Assume you have a radioactive isotope
with a half-life of 1000 years and you
start with 600g of the material. How
much of the original material will you
have after 3000 years?
•
•
•
•
•
A. 600g
B. 300g
C. 150g
D. 75g
E. 37.5g
Components of the
Earth System - or
“Ecosphere”
56
Components of the Earth
System
Ecosphere or Earth System
Lithosphere
Atmosphere
Biosphere
Hydrosphere
57
Components of the Earth System

Ecosphere

Lithosphere

Hydrosphere
Ecosphere

Atmosphere

Biosphere
58
Earth’s Structure
59
Earth’s Structure

formally described two ways
• Composition/chemical-based
description
• Physical/mechanical-based
description
60
Earth’s Structure

Compositional/Chemical-based description
•
Crust
•Continental
•Thickness 10-70km, Density ~2.8g/cm3
•Granite (Al, Ca K-rich silicate)
•Oceanic
•Thickness 5-7km, Density ~3.0g/cm3
•Basalt (Fe, Mg-rich silicate)
•
Mantle
•Thickness ~2900km, Density ~3.2-5.0g/cm
•Iron-magnesium silicates
•
Core
•Thickness ~3500km, Density ~10g/cm3
•Mostly iron, some nickel
61
Earth’s Structure

Physical/Mechanical-based description
• Lithosphere
•Cool, rigid, brittle
• Asthenosphere
•Hot, weak, a “plastic solid” because
it flows over time
• Mesosphere
•Hot, solid (due to pressure)
• Outer core
•Hot, liquid iron-nickel (due to lower
pressure than inner)
• Inner core
•Hot, solid iron (due to high
62
Earth’s Structure
Physical/Mechanical-based
Compositional/Chemical-based descriptio
63
Earth’s Structure

Interior of earth
• trends in

temperature

pressure

density
64
The End
65