Transcript Historical Geology - Rice University -

Ch. 1 Dynamic and Evolving
Earth
ESCI 102
Spring 2005
ESCI 105
Intro Lab for Earth Science
Tues 1:00 - 4:00
105 Geological Labs
Mikala Beig
[email protected]
Earth is a Dynamic and
Evolving Planet
• changes in its surface
• changes in life
Earth is a System of
Interconnected Subsystems
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•
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Atmosphere (air and gases)
Hydrosphere (water, oceans, and ice)
Biosphere (plants and animals)
Lithosphere (Earth’s rocky surface)
Interior (mantle and core)
Interactions in Earth’s
Subsystems
Gases from
respiration
Transport
of seeds and
spores
Interactions in Earth’s
Subsystems
Wind erosion,
transport of water
vapor for
precipitation
Mountains
divert air
movements
Interactions in Earth’s
Subsystems
Source of sediment
Water
erosion, solution
of minerals
Historical Geology
• in historical geology we study
– changes in our planet
– how and why past events happened
– implication for today’s global ecosystems
• 3 main ideas of historical geology
– plate tectonics
– evolution
– uniformitarianism
Origins
• What do we want to know?
• how/when did the:
– universe form?
– solar system/Earth form?
– Moon form?
• what were early Earth conditions?
How Do We Know?
Origin of the Universe
• the Big Bang
– occurred 15 billion years ago
– model for the beginning of the universe
Building a Universe
- infinitely dense point
not governed by our
physical laws or time
- all matter and energy
contained in one point
http://rainbow.ldeo.columbia.edu/courses/v1001/7.html
Building a Universe
- instantaneous
filling of space with
all matter
http://rainbow.ldeo.columbia.edu/courses/v1001/7.html
Building a
Universe
•10-43 s - gravity separates from other
forces - 10-28 centimeters
•10-35 to 10-32 s - fundamental particles quarks and electrons - softball
•10-6 s - quarks combine into protons
and neutrons - solar system
•1 s - electromagnetic and weak nuclear
forces separate
•3 minutes - protons and neutrons
combine into atomic nuclei
•105 years - electrons join nuclei to
make atoms; light is emitted
•105-109 years - matter collapses into
clouds, making galaxies and stars
Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
Edwin Hubble
• Universe is continuously expanding
• Galaxy’s velocity is proportional to its distance
(galaxies that are twice as far from us move twice as
fast)
– taken every galaxy the same amount of time to move from a
common starting position to its current position
Hubble’s Evidence
• Doppler shifting - wavelength emitted by something moving
away from us is shifted to a lower frequency
• Sound of a fire truck siren - pitch of the siren is higher as the fire
truck moves towards you, and lower as it moves away from you
• Visible wavelengths emitted by objects moving away from us
are shifted towards the red part of the visible spectrum
• The faster they move away from us, the more they are
redshifted. Thus, redshift is a reasonable way to measure the
speed of an object (this, by the way, is the principal by which
radar guns measure the speed of a car or baseball)
• When we observe the redshift of galaxies outside our local
group, every galaxy appears to be moving away from us universe is expanding
Evidence for Big Bang
• Red shift - as light from distant galaxies approach earth there is
an increase of space between earth and the galaxy, which leads
to wavelengths being stretched
• In 1964, Arno Penzias and Robert Wilson, discovered a noise of
extraterrestrial origin that came from all directions at once radiation left over from the Big Bang
• In June 1995, scientists detected helium in the far reaches of the
universe - consistent with an important aspect of the Big Bang
theory that a mixture of hydrogen and helium was created at the
beginning of the universe
When Did the Universe Form?
• 10 to 20 billion years ago (15)
• How do we know?
– spreading (red shift)
– know distances, rates of
retreat, relative positions
– pervasive background
radiation of 2.7°C above
absolute zero is the
afterglow of the Big Bang
Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
How old is the universe?
• Speed x time = distance
• (distance of a particular galaxy) / (that galaxy’s
velocity) = (time)
– or
• 4.6x1026 cm / (1x109 cm/sec) = 4.6x1017 sec
• 4.6x1017 s x (hr/3600s) x (day/24hr) x (yr/365day)
= 15 billion years
Features of Our Solar System
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in a spiral arm of the Milky Way Galaxy
Sun, 9 planets
101 known moons (satellites)
a tremendous number of asteroids between
the orbits of Mars and Jupiter
• millions of comets and meteorites
• interplanetary dust and gases
Relative Sizes of the
Sun and Planets
Solar System Configuration
Origin of Our Solar System
Solar nebula theory
• cloud of gases and dust
• formed a rotating
disk
• condensed and
collapsed due to
gravity
• forming solar nebula
– with an embryonic Sun
– surrounded by a rotating cloud
Embryonic Sun and Rotating Cloud
• planetesimals have formed in the inner solar
system
• large eddies of gas and dust remain far from
the protosun
The Planets
• Terrestrial Planets
• Jovian Planets
– Jupiter
– Saturn
– Uranus
– Neptune
– Mercury
– Venus
– Earth
– Mars
• small, composed
of rock, with metal
cores
• large, composed
of hydrogen,
helium, ammonia,
methane,
relatively small
rocky cores
– Pluto?
Earth’s Very Early History
• started out cool about 4.6 billion years ago
– probably with uniform composition/density
• mostly:
– silicate compounds
– iron and magnesium oxides
• temperature increased from:
– meteorite impacts
– gravitational compression
– radioactive decay
• heated up enough to melt iron and nickel
Earth’s Differentiation
• differentiation = segregated into layers of
differing composition and density
• early Earth was
probably uniform
• molten iron and
nickel sank to form
the core
• lighter silicates
flowed up to form
mantle and crust
Forming the Earth-Moon System
• impact by Mars-sized or larger
planetesimal with young Earth
– 4.6 to 4.4 billion
years ago
– ejected large
quantity of hot
material
Forming the Earth-Moon System
• most of the
lunar material
– came from
the mantle of
the colliding
planetesimal
• material
cooled
– crystallized
into lunar
layers
Forming the Earth-Moon System
• most of the
lunar material
– came from
the mantle of
the colliding
planetesimal
• material
cooled
– crystallized
into lunar
layers
Moon
• light-colored
areas are lunar
highlands
– heavily
cratered
• provide striking
evidence of
massive
meteorite
bombardment
Earth—Dynamic Planet
• Earth was also subjected
– to the same meteorite barrage that pock-marked
the Moon
• Why isn’t Earth’s surface also densely
cratered?
- because Earth is a dynamic and evolving
planet: craters have long since been worn
away
Earth’s Interior Layers
• Crust - 5-90 km
thick
– continental and
oceanic
• Mantle
– composed
largely of
peridotite
– dark, dense
igneous rock
– rich in iron and
magnesium
• Core
– iron and a small
amount of nickel
Earth’s Interior Layers
• Crust - 5-90 km
thick
– continental and
oceanic
• Mantle
– composed
largely of
peridotite
– dark, dense
igneous rock
– rich in iron and
magnesium
• Core
– iron and a small
amount of nickel
• Lithosphere
– solid upper
mantle and crust
• Asthenosphere
– part of upper
mantle
– behaves
plastically and
slowly flows