Transcript Inside the Earth

Chapter One
Introduction
to Geology
Geology literally
means "study of the Earth."
Physical geology examines the materials and processes of the Earth.
Historical geology examines the origin and evolution of our planet
through time.
• Geology is an evolving science - the theory of plate tectonics was just accepted in
the 1960's.
•
•
Geology is an extremely controversial
science - the theory of evolution
(paleontology) is central to geology.
Geology seeks to understand the origin
of our planet and our place in the
Universe - answers to these questions
are also posed outside of the realm of
science.
History of Early Geology
Catastrophism (James Ussher, mid 1600s) - He interpreted that the Earth was
created at 4004 B.C. Subsequent workers then developed the notion of
catastrophism, which held that the the Earth’s landforms were formed over very
short periods of time.
Uniformitarianism (James Hutton, late 1700s) - He proposed that the
same processes that are at work today were at work in the past.
Summarized by “The present is the key to the past.” Hutton recognized
that time is the critical element to the formation of common geologic
structures. Uniformitarianism is a basic foundation of modern geology.
Although catastrophism was
abandoned, there is certainly
evidence that sudden events do
occur.
From space, Earth looks small, finite and fragile.
What's the first thing that
you notice about our planet
when you see this image?
The Earth is composed of several
integrated parts (spheres) that
interact with one another:
atmosphere
hydrosphere
solid earth (lithosphere)
biosphere
The Earth
System
Hydrosphere: Oceans are the most
prominent features of our (blue)
planet. The oceans cover ~71% of our
planet.
Atmosphere: the swirling clouds of
the atmosphere represent the very
thin blanket of air that covers our
planet. It is not only the air we
breathe, but protects us from harmful
radiation from the sun.
The Earth
System
Biosphere: includes all life on Earth concentrated at the surface. Plants
and animals don't only respond the
their environment but also exercise a
very strong control over the other
parts of the planet.
Solid Earth: represents the majority
of the Earth system. Most of the
Earth lies at inaccessible depths.
However, the solid Earth exerts a
strong influence on all other parts (ex.
magnetic field).
Theories of the Origin of the
Universe
• Theological “Theories”:
• Scientific Theories:
– Continuous creation
– Big Bang Theory – the commonly accepted
theory( given by Georges Lemaître in
1927)
The Big Bang theory
•
•
•
•
The theory that the universe was
expanding implies the universe must have
been smaller in the past than it is today.
It implies that the universe must have had
a beginning.
Astronomers today believe the universe
exploded outward from a single point.
This idea is known as the Big Bang theory.
The Big Bang theory
•
•
The Big Bang theory says the
universe began as a huge explosion
between 10 billion and 20 billion years
ago.
According to this theory, all matter
and energy started in a space smaller
than the nucleus of an atom.
Big “Bang Theory”
• Technically, there was no “bang”
• Technically, galaxies are not moving away
from each other
• Reality: space expands
– When there are more space between galaxies,
they “move” away from each other
– Analogy: dots on an expanding balloon
Evidence for the Big Bang
• Theory predicts an expanding universe
– Confirmed by Red Shift (Doppler effect) in
spectrum
• Theory predicts cosmic background
radiation
– Background radiation was discovered in
1964 by Arno Penzias and Robert Wilson,
who later won the Nobel Prize for this
discovery
Doppler Shift
• In the 1800s, Christian
Doppler discovered that
when the source of a
sound wave is moving, its
frequency changes.
• The change in sound you
hear is caused by a
Doppler shift.
• Doppler shift is related
to the net change
between the source of
the waves and the
observer.
Doppler Shift
• Doppler shift also
occurs with
electromagnetic
waves, such as
visible light, X-rays,
and microwaves.
• This phenomenon is
an important tool
used by
astronomers to
study the motion of
objects in space.
The expanding universe
•
•
The faster the
source of light is
moving away from
the observer, the
greater the
redshift.
The opposite
(blueshift) happens
when an object is
moving toward the
observer.
The expanding universe
•
•
Edwin Hubble in 1929
discovered that the
farther away a
galaxy was, the
faster it was moving
away from Earth.
This concept came to
be known as the
expanding universe.
Evidence for the Big Bang theory
•
•
In the 1960s, Arno
Penzias and Robert
Wilson were trying to
measure electromagnetic
waves given off by the
Milky Way.
The “noise” these
scientists found was the
cosmic microwave
background radiation
predicted by the Big Bang
theory.
Evidence for the Big Bang theory
•
•
The proportion of hydrogen to helium is
consistent with the physics of the Big Bang.
If the universe were significantly older, there
would be more heavy elements present
compared with hydrogen and helium.
Planetary systems
• A star with orbiting planets is called a
planetary system.
• Scientists now believe that planets are a
natural by-product of the formation of stars.
How the solar system formed
Nebular Hypothesis
• Scientists think that the solar system was formed out of
the same nebula (vast cloud of dust and gas that created
the Sun.
A diffuse, spherical slowly rotating nebula
begins to contract
As a result of contraction and rotation, a flat rapidly rotating
disc is formed with matter concentrated at the centre
Enveloping gas and dust form grains
that collide and clump together to form
protoplanets
SUN
The Sun is the Solar System's star, and by far its chief component. Its
large mass (332,900 Earth masses) produces temperatures and densities
in its core great enough to sustain nuclear fusion which releases
enormous amounts of energy, mostly radiated into space as
electromagnetic radiation. Also known as ‘yellow dwarf’ sun is one of the
brightest stars. Dimmer and cooler stars are known as red dwarfs. 85%
Stars are red dwarfs.
Terrestrial or inner planets: Mercury, Venus, Earth, Mars
Mercury: smallest planet, no satellite, large iron core, no atmosphere
Venus:close in size to Earth, (0.815 Earth mass) and like Earth, has a
thick silicate mantle around an iron core, a substantial atmosphere, it is
much drier than Earth and its atmosphere ninety times as dense, no
natural satellites, hottest planet, with surface temperatures over 4000C
most likely due to the amount of greenhouse gases in the atmosphere.
Earth:the largest and densest of the inner planets, is the only place
in the universe where life is known to exist, hydrosphere is unique
among the terrestrial planets. Earth's atmosphere is radically
different from those of the other planets, having been altered by
the presence of life to contain 21% free oxygen, has one natural
satellite, the moon, the only large satellite of a terrestrial planet in
the Solar System.
Mars: smaller than Earth and Venus (0.107 Earth masses), an
atmosphere of mostlyCO2, surface, peppered with vast volcanoes
such as Olympus Mons, red colour comes from iron oxide (rust) in its
soil, has two tiny natural satellites).
Asteroid belt: occupies the orbit between Mars and Jupiter,
thought to be remnants from the Solar System's formation that
failed to coalesce because of the gravitational interference of
Jupiter. Ceres is the largest body in the asteroid belt
Outer solar system: Gas giants or Jovian planets: not composed of
rock or other solid matter, mainly composed of hydrogen and helium
Jupiter:at 318 Earth masses, composed largely of hydrogen and helium.
Jupiter's strong internal heat creates a number of semi-permanent
features in its atmosphere, such as cloud bands and the Great Red spot.
Jupiter has 63 known satellites.
Saturn:distinguished by its rings, has several similarities to Jupiter,
such as its atmospheric composition. Although Saturn has 60% of
Jupiter's volume, it is the least dense planet in the Solar System. The
rings of Saturn are made up of small ice and rock particles. Saturn has
62 satellites
Ice Giants: Composed of water ammonia and methane ice
Uranus: lightest outer planet, 14 earth masses, 27 known satellites,
orbits the sun on its side with axial tilt over 90 degree.
Neptune: smaller but denser, 17 earth masses, 13 satellites
Inside the Earth
Composition (What it is made of)
• Crust
• Mantle
• Core
Earth’s Layers
• How are the earth’s
layers similar to an
egg?
• Shell=crust
• Egg white=mantle
• Yolk=core
Average density of the earth: 5.52
grams/cm3.
Continental Crust: 2.7 to 3.0
Oceanic crust: 3.0 to 3.3
Mantle (silicates): 3.3 to 5.7
Outer Core (liquid): 9.9 to 12.2
Inner Core (solid): 12.6 to 13.0
How do we know about the interior of the earth ?
1. Seismology studies
2. Gravity measurements
3. Magnetic studies
Types of seismic waves
1. P waves (compressional waves)
2. S waves or shear waves
P waves travel 1.7 times faster than S waves.
S waves can only travel in a solid medium
AS SEISMIC WAVES TRAVEL FROM MATERIAL OF ONE
SPEED AND DENSITY TO ANOTHER
THE INCIDENT WAVES ARE REFLECTED AND TRANSMITTED
(REFRACTED)
BOTH THE ANGLES AND SIZE (AMPLITUDE) OF THE WAVES
CHANGE, DEPENDING ON THE VELOCITY AND DENSITY
CHANGE
THIS EFFECT LETS US STUDY EARTH STRUCTURE
(AND IS USED IN LENSES, EYEGLASSES, ETC. FOR LIGHT)
Physical Structure of the Earth
(5 Layers)
• Lithosphere- rigid outer layer (crust)
• Asthenosphere- solid rock that flows
slowly (like hot asphalt)
• Mesosphere- middle layer
• Outer Core- liquid layer
• Inner Core- solid, very dense
The Crust
The Earth's Crust is like the
skin of an apple. It is very
thin in comparison to the
other three layers. The
crust is only about 3-5
miles (8 kilometers) thick
under the oceans (oceanic
crust) and about 25 miles
(32 kilometers) thick under
the continents (continental
crust).
The crust is composed of two rocks. The
continental crust is mostly granite. The oceanic
crust is basalt. Basalt is much denser than granite.
Because of this the less dense continents ride on
the denser oceanic plates.
Properties of the Crust
Continental Crust
Depth : 20 to 70 km, average 30 to 40 km
Composition: felsic, intermediate, and mafic igneous, sedimentary, and
metamorphic rocks
Age: 0 to 4 b.y.
Summary: thicker, less dense, heterogeneous, old
Oceanic Crust
Depth : ~7 km
Composition: mafic igneous rock (basalt & gabbro) with thin layer of
sediments on top
Age: 0 to 200 m.y.
Summary: thin, more dense, homogeneous, young
Oceanic and Continental Crust
The Mantle
The Mantle is the
largest layer of the
Earth at 2900 km thick.
The middle mantle is
composed of very hot
dense rock that flows
like asphalt under a
heavy weight. The
movement of the middle
mantle
(asthenosphere) is the
reason that the crustal
plates of the Earth
The Lithosphere
The crust and the upper layer of
the mantle together make up a
zone of rigid, brittle rock called the
Lithosphere.
The Lithospheric Plates
The crust of the Earth is broken into many pieces
called plates. The plates "float" on the soft, semirigid asthenosphere.
The Lithosphere
• Lithosphere=
the crust and
the uppermost
part of mantle
The Asthenosphere
• Asthenosphere= the fluid like portion of
the mantle that lies just below
lithosphere. The lithosphere “floats” on
the asthenosphere
Convection Currents
The middle mantle "flows" because of convection
currents. Convection currents are caused by the
very hot material at the deepest part of the
mantle rising, then cooling and sinking again -repeating this cycle over and over.
The Outer Core
The core of the
Earth is like a ball
of very hot
metals. The
outer core
is
so hot that the
metals in it are all
in the liquid state.
The outer core is
composed of the
melted metals of
nickel and iron.
The Inner Core
The inner core of
the Earth has
temperatures and
pressures so great
that the metals are
squeezed together
and are not able to
move about like a
liquid, but are
forced to vibrate in
place like a solid.
The Core
• Inner core:
The inner core is solid and unattached to the mantle,
suspended in the molten outer core. It is believed to
have solidified as a result of pressure-freezing which
occurs to most liquids when temperature decreases or
pressure increases.
LOW VELOCITY ZONES
Schematic view of the interior of Earth. 1.
continental crust - 2. oceanic crust - 3.
upper mantle - 4. lower mantle - 5. outer
core - 6. inner core - A: Mohorovičić
discontinuity - B: Gutenberg Discontinuity C: Lehmann discontinuity
1. Mohorovicic Discontinuity or ‘Moho”
Seismic velocities tend to gradually increase with depth in the mantle due
to the increasing pressure, and therefore density, with depth. However,
seismic waves recorded at distances corresponding to depths of around
100 km to 250 km arrive later than expected indicating a zone of low
seismic wave velocity. Furthermore, while both the P and S waves travel
more slowly, the S waves are weakened. This is interpreted to be a zone
that is partially molten. Alternatively, it may simply represent a zone
where the mantle is very close to its melting point for that depth and
pressure that it is very "soft." Then this represents a zone of weakness in
the upper mantle. This zone is called the asthenosphere or "weak
sphere."
MOHO
Lehman Siesmic Discontinuity / The
InnerCore
A sudden increase in P wave velocities
at a depth of 5150 km indicates the
presence of another discontinuity. This
velocity increase is consistent with a
change from a molten outer core to a
solid inner core.
Gutenberg
discontinuity
Lehman
discontinuity
Gutenberg
Seismic
Discontinuity/Core-Mantle
Boundary
Gutenberg (1914) explained that as the result of a molten core
beginning at a depth of around 2900 km, S waves could not penetrate
this molten layer and P waves were
(bent).
severely slowed and refracted
What Causes the Earth's Magnetic Field?
The outer core is a hot, electrically conducting liquid within which
convective motion occurs. This conductive layer combines with Earth's
rotation to create a dynamo effect that maintains a system of electrical
currents known as the Earth's magnetic field.
The discovery of the liquid outer core allowed another hypothesis: the
geodynamo. Iron, whether liquid or solid, is a conductor of electricity.
Electric currents would therefore flow in molten iron. Moving a flowing
electric current generates a magnetic field at a right angle to the
electric current direction (basic physics of electromagnetism). This
convective motion would displace the flowing electric currents thereby
generating magnetic fields. The magnetic field is oriented around the
axis of rotation of the Earth.
Practice Quiz Question
• Can you label the following layers?
What are the geologic landforms on
the earth ?
When you think of landforms, you might
think of mountains or valleys. These are
continental landforms, or landforms on
the continents.
Landforms are also found under the ocean’s
water. These are called oceanic
landforms.
Continental vs. Oceanic Landforms
• Canyon
• Valley
• Volcano
• Mountain range
• Low hills or plains
• Trench
• Rift
• Seamount
• Mid-ocean ridge
• Ocean basin and
abyssal plains
Plains
• Plains are large flat areas of land that
are relatively low. A plain found in the
ocean is called an abyssal plain.
• A mountain has high elevations with
steep sides and pointed tops. The top
of the mountain is a peak, or summit.
Circum-Pacific belt
Alpine-Himalayan Belt
Shield areas: Most stable parts of the continents. Rocks are as old
as 3.8 billion
Mountain range of the ocean : Ocean ridge system
65000 km continuous belt around the globe
Mid-Ocean Ridge
On the bottom of the ocean, there is a
central ridge, or mountain range, that
divides the ocean floor into two parts. This
underwater volcanic mountain is the midocean ridge. It is more than 50,000 km in
length
DID YOU KNOW?
The Earth’s longest mountain range is underwater ?
Valleys
• Valleys are low, narrow areas on Earth’s crust.
On land, valleys are usually formed by erosion.
• Valleys in the ocean are called a rift zone, or rift
valley. The most extensive rift valley is located
along the crest of the mid-ocean ridge
www.inewscatcher.com/timages/9f26ca47
ac9ab0
Canyon and Trenches
• A canyon has steep, rocky walls and is usually formed
by water erosion like the Grand Canyon.
• Ocean trenches have a much lower elevation than the
surrounding area and is caused by one plate sliding
under another plate.
Trenches
The many steep-sided canyons and deep,
narrow valleys in the bottom of the ocean
are trenches. Ocean trenches are the
deepest part of the ocean basin and are
deeper than any valley found on land.
Did you Know?
The Marianas Trench in the Pacific
Ocean is the deepest trench in the world. It is
nearly 7 miles (11 kilometers) below sea level.
Mount Everest is only 5.5 miles (9 kilometers)
above sea level.
visual.merriam-webster.com/.../ocean-floor.jpg
catastrophemonitor.com/public_html/images/art.
A volcano is a mountain that
opens downward to a pool of
molten rock below the surface
of the earth. When pressure
builds up, eruptions occur.
Gases and rock shoot up
through the opening and spill
over or fill the air with lava
fragments. Eruptions can
cause lateral blasts, lava
flows, hot ash flows,
mudslides, avalanches, falling
ash and floods. Volcano
eruptions have been known to
knock down entire forests. An
erupting volcano can trigger
tsunamis, flashfloods,
earthquakes, mudflows and
rockfalls.
Seamounts
Volcanic cone shaped peaks that dot the
ocean floor are called seamounts. Most
are found in the Pacific Ocean.
Most seamounts began life as volcanoes
formed over hot spots in the ocean floor
Guyots
A guyot /ɡiˈoː/, also known as a tablemount, is an isolated underwater
volcanic mountain, with a flat top over 200 meters (660 feet) below
the surface of the sea.
Guyots are most commonly found in the Pacific Ocean. Guyots show
evidence of having been above the surface with gradual subsidence
through stages from fringed reefed mountain, coral atoll, and finally a
flat topped submerged mountain. Their flatness is due to erosion by
waves, winds, and atmospheric processes
What are the landforms on the
ocean floor?
The amazing ocean floor is made
up of three parts:
•the continental shelf
•the continental slope
•the deep blue sea
Continental Shelf
The edges of the continents slope down
from the shore into the ocean. The
part of the continent located under the
water is the continental shelf.
In some places the shelf is fairly shallow
and in other places it becomes very
deep.
The steep slope where the continental
shelf drops to the bottom of the ocean
floor is called the continental slope.
The depth of the water increases greatly
here.
Quick Quiz
1.
The ocean is a big, flat featureless plain.
True
false
2.
or
False
The steep part where the continental shelf slopes
down to the deepest part of the ocean is called the
continental slope.
True
true
or
False
3. What are the deepest parts of the ocean called?
a. Deep-sea trenches
b. Abyssal plains
c. Continents
d. Seamounts
Deep sea trenches
4. What is a seamount?
a. A scientist who studies the ocean floor
b. Deep-sea trench
c. A fancy seagull
d. A volcano that formed over a hot spot on the ocean
floor.
How can we classify and illustrate
natural processes as constructive or
destructive?
Constructive – Processes that create
landforms
Destructive – Processes that destroy
landforms
Natural Processes that can affect
Earth’s oceans and landforms
include:
• Weathering – a term used to describe
processes that break down rocks at or
near the surface of the earth. Water is an
important cause of weathering.
• Erosion – the movement of sediments and
soil by wind, water, and gravity
• Deposition – the dropping, or depositing,
of sediments by water, wind, or ice.
Deposition builds up new land on Earth’s
surface, like a delta at the end of a river or
the pile up of a sand dune in a desert.
• Landslides – mass movements of land due
to gravity.
• Volcanic Eruptions – Volcanoes can change the
Earth’s surface. When the magma erupts from
the volcano, the top of the mountain can be
changed. The lava and ash can destroy forests
and bury fields. Eruptions can even change
weather patterns.
• Earthquakes – vibrations on the surface of the
Earth caused by sudden movement in Earth,
often along a fault line. Large earthquakes can
cause landslides. Earthquakes under the ocean
can cause huge waves, called tsunamis that
destroy land and cause great damage on shore.
• Floods – rapid erosion can take place and move
soil and sediments away. When the flood
recedes, new sediment is left behind and can
build up rich soil deposits.
What are examples of ways natural
processes can be both destructive
and constructive?
Constructive
forces
Destructive
forces
Both
Kinds of forces
Acknowledged sources
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s%20of%20the%20Earth.ppt
2.www.livingston.org/15262082112049837/.../Inside_th
e_Earth.ppt
3.teacherweb.com/TX/FriendswoodJrHigh/So/EarthInterior.ppt
4.www.ichthus.info/PowerPoint/BigBangand-Beyond.ppt
5.www.cpo.com/home/.../2/.../PESChp28U
niverse3.ppt
6.www.pfm.howard.edu/astronomy/Universe.ppt
7. science.pppst.com/geology.html