Download Chemistry: Atoms First, McMurry and Fay, 1st Edition

Advanced structure of
the Earth
By
Doba D. Jackson, Ph.D.
Associate Professor of Chemistry
& Biochemistry
Huntingdon College
Outline of Lecture 1
• Part I: Matter & Matter changes
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Natural Science-Physical Science
Physical & Chemical Properties
Elements of Nature
Temperature, Pressure
Physical States of Matter
• Part II: Origin of the Universe and matter
– Big Bang (video)
– Formation of atoms, elements
– Formation of galaxies, our solar system
Outline of Lecture 1
• Part III: Structure & Components of Earth
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Earth’s Core
Earth’s Mantle
Earth’s Crust
Lithosphere
Asthenosphere
Rock Cycle (Sedimentary, Metamorphic, Igneous)
Plate Tectonic Theory (intro)
Geologic Time (intro)
Plate Tectonic theory
• Plate tectonic theory states that the lithosphere is
divided into rigid plates that diverge, converge, or slide
past each other as they move over the asthenosphere.
Plate Tectonic theory
The movements of the plates and the interactions
of plates along their boundaries cause volcanic
eruptions, earthquakes, the formation of mountain
ranges and ocean basins, and recycling of rock
material.
The Rock Cycle
• What is a rock?
– A rock is an aggregate of minerals.
Granite
Slate
Limestone
Quartzite
Conglomerate
Gneiss
The Rock Cycle
The Rock Cycle
• What are the characteristics of each of
the three major rock groups?
• Igneous rocks
result from the
crystallization of
magma or the
consolidation of
volcanic ejecta.
The Rock Cycle
• Sedimentary rocks are typically
deposited in layers formed by the:
– consolidation
of rock
fragments
– precipitation of
mineral matter
from solution
– compaction of
plant or animal
remains
The Rock Cycle
• Metamorphic Rocks- that result from the
alteration of other rocks;
– Metamorphic
rocks usually
form beneath
Earth’s surface,
by
• Heat
• Pressure
• Chemically active
fluids.
The Rock Cycle connects the internal and
external processes of the earth
Plate Tectonic theory
• Plate tectonic theory states that the lithosphere is
divided into rigid plates that diverge, converge, or slide
past each other as they move over the asthenosphere.
Plate Tectonics?
Plate interaction is a major factor that
determines when, where and what kind
of rock develops.
Geological Time
Radioactive Decay Example
14
C
6
Parent
14
N
7
Daughter
+
Nt
Equation: Ln
= -kt
N0
-N is the number of radioactive
atoms per minute per gram
Carbon
-N0 is the initial number of
radioactive atoms per and per
gram Carbon
-k is the decay constant for
carbon
-t is the age of the sample
0
β
-1
Half-life 14C is 5730 years
Radioactive Decay Example
14
C
6
Parent
14
N
7
Daughter
+
Nt
Equation: Ln
= -kt
N0
-N is the number of radioactive
atoms per minute per gram
Carbon
-N0 is the initial number of
radioactive atoms per and per
gram Carbon
-k is the decay constant for
carbon
-t is the age of the sample
0
β
-1
Half-life 14C is 5730 years
Radioactive Dating Methods
Parent
147Sm
Daughter Half-life
143Nd
106 billion years
87Rb
87Sr
238U
206Pb
40K
40Ar
235U
207Pb
234U
230Th
235U
231Pa
14C
3H
Samples Used
Rocks
50 billion years
Rocks
4.47 billion years Rocks
1.3 billion years Rocks
14N
704 million years
80,000 years
34,300 years
5,730 years
Rocks
Rocks
Rocks
Organic Fossils
3He
12.3 years
Organic Fossils
Geological Time
• Eon- Time periods around .5 to 1 billion
years.
• Era- Time periods between 100 million
and 500 million years. These occur within
Eons.
• Periods- Time periods between 10
million and 100 million years.
• Ages-
No
Early Evidence for Plate Tectonics:
Continental Drift Hypothesis
The idea that continents have moved in the past is not
new and goes back to the first maps, in which one
could see that the east coast of South America looks
like it fits into the west coast of Africa.
Pangaea
Supporting evidence for a
Continental Drift
1) Continental Fit- Outlines of coasts
closely approximate each other.
2) Fossil Evidence- Similar extinct plant
and animal fossils on different continents.
3) Glacial Evidence- Similar leftover tills in
rocks on different continents.
4) Rock layers sequences in different ages.
Scientists responsible for
Continental Drift hypothesis
• Abraham Ortelius (1596)- developed the first map and
theorized that continents drifted across oceans to their
present positions.
• Edward Suess (1885)- First to propose that continents
were connected based on fossil evidence. Named
southern continents as Gonwana.
• Alfred Wegener (1915)- credited for the continental
drift hypothesis. (Named supercontinent Pangaea)
• Harry Hess (1962)- revised the continental drift theory
into the Plate Tectonic theory.
Abraham Ortelius developed
the first map of the world
Ortelius was a world renown English
geographer in his day. He spent his life
making regional and continental maps.
Through lots of partnerships, and
traveling, he was able to develop the first
maps of the world.
Latin: Theater of the World
He suggested after
publishing his 33rd map
of the world: “The
America’s may had
originally been joined
together but later drifted
away by earthquakes
and floods” in 1578
Edward Suess
1831-1914
Edward Suess was the first
to provided fossil evidence
for the continental drift
hypothesis
Glossopteris flora- The fossil
flora that succeeds the Permian
glacial deposits of South Africa,
Australia, South America, and
Antarctica. It grew in a cold, wet
climates. Plants with elongate,
tongueshaped leaves
dominated the southern flora.
Austrian Geologist Edward Suess proposed
the southern continents were once
connected and used the term Gondwana
Alfred Wegener noted similarities
of rock sequences for southern
continents
Glacial Striations as evidence
for continents drifting
Glacial striations are
scratches or gouges cut
into bedrock by glacial (ice)
abrasion.
Glacial striations form when ice
picks up small rock fragments.
When the ice forms or melts on
rock, picks up small pieces of
rock or sand and it scratches
the surface of the rock as it
moves across it. Glacial
striations are usually multiple,
straight, and parallel lines .
Glacial Striations in bedrock
found in South America, India,
South Africa and Australia
Arrows on each picture
represent the direction
of melting of the ice
Notice India’s presence
The directions of the glacial striations indicate that
the southern continents were closer together at the
south pole.
Setback in the Continental Drift
Theory
• None of the scientist could reasonably
explain How could the continents drift?
Continental Shelf- region off
the ocean boundary where the
seafloor is shadow.
Mapping of seafloor’s
found no evidence of continents
drifting on liquid water.
Paleomagnetism studies of the
1950’s revived the debate
Where and how is Earth’s magnetic
field generated?
- Electrical currents in the
(liquid Iron) outer core
probably generate Earth's
magnetic field. The lines
of magnetic field
surrounding Earth
resemble those of a bar
magnet.
Paleomagnetism Rocks
North
Paleomagnetism is the
reminant magnetism of
ancient rocks.
Ancient rocks showed a
different orientation of
its magnetic field.
Lodestone, Magnetite,
Maghemite- iron containing
mineral rocks with magnetic
properties (Fe3O4).
South
Paleomagnetic data can be
used to construct the positions
of early continents
Rocks analyzed during the
same time period gave
different positions
of their magnetic poles.
Scientists assume the
position of the magnetic
pole has not changes over
millions of years, but the
position of the continents
have changed.
Paleomagnetic data can be
used to construct the positions
of early continents
Rocks analyzed during the
same time period gave
different positions
of their magnetic poles.
Scientists assume the
position of the magnetic
pole has not changes over
millions of years, but the
position of the continents
have changed.
Discovery and mapping of the
Mid-Atlantic Ridge
Paleomagnetic studies revealed
the existance of Earth’s magnetic
field reversals
Paleomagnetic studies revealed
the existence of Earth’s magnetic
field reversals in lava flows
Henry Hess proposed the theory
of Seafloor Spreading in 1962
• What is the theory of
seafloor spreading?
– He suggested that the
seafloor separates at
oceanic ridges, where
new crust is formed by
upwelling magma.
– As the magma cools,
the newly formed
oceanic crust moves
laterally away from the
ridge.
How was the theory of seafloor
spreading confirmed?
Another confirmation of
Seafloor Spreading theory is
the age of rocks on ocean floor
Sea floor spreading
is confirmed by
– the ages of fossils in
sediments overlying
oceanic crust
– radiometric dating of
rocks on oceanic
islands and floors.
Red- present to 48 mya
Yellow- 48-68 mya
Green 68-155 mya
Blue- 155-180 mya
Model for How Seafloor
Spreading Occurs
Plate Tectonics: A Unifying
Theory
• Overwhelming evidence in support of
plate tectonics led to its rapid
acceptance and elaboration since the
early 1970's.
– The theory is widely accepted because it
explains so many geologic phenomena.
– Plate Tectonic Theory encompasses the
Seafloor Spreading Theory with thye
existance of Earthquakes and Volcanism.
– For these reasons, it is known as a unifying theory.
What are the main tenets of
Plate Tectonic Theory?
The Three Types of Plate
Boundaries
• Divergent Plate Boundaries- Spreading ridges
that occur where new lithosphere is forming
and older lithosphere is separating away.
• Convergent Plate Boundaries- Boundary where
older crust is destroyed and recycled to keep
the surface area of the earth the same.
• Transform Plate Boundaries- (or Transform
faults)- Changes one type of motion between
plates to another type of motion.
• History of Divergent
Boundaries
– Divergent boundaries
form when rising
magma beneath a
continent pushes
crust up to form
mountains, faults,
valleys and volcanic
activity
– As more continental
crust is broken,
valley’s form with
volcanic activity.
• History of Divergent
Boundaries
- As more continental
crust is broken,
valley’s form with
volcanic activity.
- (East African Rift
Valley)
- Continued spreading
splits apart the
continent and a
seaway develops (Red
Sea)
• History of Divergent
Boundaries
- Continued spreading
splits apart the
continent and a seaway
develops (Red Sea)
- Continued spreading, a
oceanic ridge system
develops (Mid-Atlantic
Ridge)
East African Rift Valley may be
the future Diverging plate
boundary
Red Sea may be the next MidAtlantic Ridge system
The Three Types of
Convergent Plate Boundaries
• Convergent boundaries are places where two
plates collide and one plate is subducted into
the asthenosphere.
• Oceanic-oceanic boundary is where two
oceanic plates collide, one ocean plate will
subduct beneath the margin of the other
plate.
• Oceanic-continental boundary is where an
oceanic plate and a continental plate
collide, the oceanic plate will subduct.
• Continental-continental boundary occurs
when two continents collide
Oceanic-Oceanic Convergent
boundaries
– One oceanic plate is subducted beneath the other and
a volcanic island arc forms on the non-subducted
plate
– An oceanic trench forms parallel to the volcanic
island arc where the subduction is taking place.
– The volcanoes result from rising magma produced by
the partial melting of the subducting plate.
Oceanic-Continental
Convergent Boundary
– An oceanic plate and a continental plate converge, with
the denser oceanic plate being subducted under the
continental plate.
– Just as with an oceanic-oceanic boundary, a chain of
volcanoes forms on the nonsubducted plate.
Continental-Continental Plate
Boundaries
– Two continents converge and the ocean floor
separating them is subducted, resulting in a collision
between the two continents. Neither plate will subduct.
– When the two continents collide, they are welded
together to form an interior mountain chain along a
zone marking the former site of subduction.
Transform Plate Boundaries
• Transform boundaries (also Transform Faults)
are boundaries along which plates slide
laterally past each other, which change one
type of motion between plates into another
type of motion.
Types of Plate Boundaries
Introduction to Chapter 3
• What is a mineral?
A mineral is
– Naturally
– Inorganic
– Crystalline solid
– Characteristic physical properties
– Specific chemical composition.
Matter, Atoms, Elements, and
Bonding
• What are the atomic number and atomic
mass of an atom?
– The number of protons in an atom’s nucleus
determines its atomic number, whereas an
atom’s atomic mass number is the total number
of protons and neutrons in the nucleus.
Matter, Atoms, Elements, and
Bonding
• Chemical bonding
– Atoms are joined to
one another by forces
known as bonding.
– Atoms of different
elements which are
bonded to one another
form compounds.
Types of Chemical Bonds
• Ionic Bonds
– Ionic bonds form when ions with opposite
electrical charges attract one another
Types of Chemical Bonding
• Covalent Bonds
– Covalent bonds atoms share electrons.
Native Elements vs Minerals
By definition native
elements are made
up of only one
chemical element,
such as:
– Gold (Ag)
– Silver (Ag)
– Aluminum (Al)
– Copper (Cu)
– Diamond (pure C)
Elements of the Earth’s Crust
• Why are there so few common minerals?
– Even though there are 92 naturally occurring
elements, only 8 of them are very common in
Earth’s crust.
– Most common minerals are made up of oxygen,
silicon, and one or more other elements.