Download #2. Earth is 4.6 billion years old.

GG101 – Physical Geology
Dr. Fletcher
POST 721
[email protected]
956 2582
956-2582
Core
Concepts
Text – Lutgens and Tarbuck, 2009
You will
inherit
Earth.
•Three exams, 70% total
•In-class projects, homework, 25% total
•In-class participation and attendance, 5%
Big Island Field Trip
http://www.soest.hawaii.edu/coasts/lecture/gg101/index.html
How is science
done?
#1. Earth scientists
use repeatable
observations and
testable ideas to
understand and
explain our planet.
How old is Earth?
#2. Earth is 4.6
billion years old.
1
What is Earth?
How does Earth behave?
#3. Earth is a complex system of
interacting
g rock,, water,, air,, and
life.
#4. Earth is continuously
changing.
changing
What is special about Earth?
What is life's role on Earth?
#5. Earth is the
water planet.
planet
#6. Life evolves
on a dynamic
Earth and
continuously
modifies Earth.
2
What is the human relationship
to Earth?
#7 Humans
#7.
depend on Earth
for resources.
What are natural hazards?
#8 Natural
#8.
hazards pose
risks to humans.
What is the human impact on
Earth?
Some observations
about the Universe
#9 Humans
#9.
significantly alter
Earth.
3
Observations of
the universe
If the universe were infinite and
uniformly filled with stars and
galaxies, the sky should be
brilliantly lit at all times and
the radiation would heat Earth
and other celestial bodies
thousands of degrees.
Observations of
the universe
Those “stars” you see at
night – they are mostly
galaxies each with
billions of stars.
Is the universe infinite?
It gets dark at night because
the universe is not infinite.
Because it takes time for
light to travel from
distant galaxies to Earth
we see these galaxies as
they were in the past, not
as they are in the present.
g of distant
This image
galaxies is a look
backward in time.
“Olber’s Paradox”
Observations of
the universe
„
Edwin Hubble
Discovered
Galaxies beyond
the Milky Way and
the Cosmic
red shift –
Hubble’s Law
Red Shift
Red Or
Orange
ange Yellow Green Blue Indigo Violet
Retreating
g
light source
Stationary
y
light source
Approaching
pp
g
light source
Galaxies that are furthest away, are retreating faster. This is typical
of an expanding object.
Analogy of the ambulance, train
whistle, car on highway
•Most galaxies are red shifted
4
In an unchanging
universe galaxies would
move randomly with
respect to the Milky
Way (a) and there would
b no correlation
be
l ti
between distance and
rate of movement (b).
In an expanding
universe all galaxies
would be moving away
from each other (c) and
the recession velocity
would increase for
galaxies with greatest
distance (d).
15 km/sec
1mly
Measurements of the
red shift of distant
galaxies provide data
for calculating the
value of “Hubble’s
Constant” the cosmic
rate of expansion.
30 km/sec
2 mly
Edwin Hubble
Edwin Hubble calculated the rate (R) at which the universe is expanding.
R~15 km/sec for two galaxies that are separated by a distance (D) of
1 million light years (9.46x1018 km).
R= D/T
R t off expansion
Rate
i
= di
distance
t
between
b t
two
t
objects/time
bj t /ti
off expansion
i
This can be reorganized to T = D/R.
T=age of the universe!
Dividing D by R yields 6.3 x 1017 seconds or 1.99 x 1010 years.
About 20 billion years.
The Milky Way
Galaxy, one of
billions of other
galaxies in the
universe,
i
contains about
400 billion stars
and countless
other objects.
Why is it called
the “Milky Way?”
Improvements in estimating the rate of recession have lowered the probable age of
the universe to the range 13 to 14 billion years.
Therefore - the Universe had a beginning – The “Big Bang”
5
Origin of the Solar System
Solar Nebula
Hypothesis
The beginning of the
Solar System 6.9 billion
years ago –
nebula formation
An ancestral star –
ended its life: Red Giant
Explosion - Nebula
Formation of
a nebula
Nebula Collapse and Condensation
Rotation started by shockwaves
from a nearby explosion (?)
Because the solar nebula
was rotating, it contracted
into a disc, and the planets
formed with orbits lying in
nearly the same plane.
6
The spinning solar nebula
segregated into a cooling
outer
t accretion
ti disc
di off
rocky fragments and dust,
and the inner nebula core
that was to become the
Sun
Planetesimal accretion - ~5 to 4.6 billion yrs ago
Volatile compounds expelled from inner system
(He, H, CO2, H2O, N2, CO, NH3, CH4)
Inner system enriched in Fe, Si, O, Mg, Al, Ca + others
Inner Rocky Planets – Fe, Mg, Si, O, Ca, Na, K, Al (nonvolatile)
Outer Gas Giants – He, H, CO2, H2O, N2, CO, NH3, CH4 (Ices) (volatiles)
7
Comet Tempel, 19 seconds before impact
Dust tail from trajectory
Ion tail from solar radiation
Edgeworth-Kuiper belt
and
Oort Cloud
Oort Cloud and Edgeworth
Edgeworth-Kuiper Belt of comets
Inner Rocky Planets…………Outer Gas Giants
Mercury – no atmosphere
So heat is not retained
Daytime temp +230deg.,
But night temp -140deg.
8
Venus, heavy
g
greenhouse
effect,
enough to melt many
metals.
Carbon dioxide 96%
of atmosphere…temp
480 deg
Channels are formed by running water,
Probably from melting ice – not rainfall
9
Jupiter's Great
Red Spot - A
hurricane the size
of Earth lasting
several centuries
Does Jupiter have
a hard surface?
No hard planet
may allow for
different winds at
different speeds –
hence, banding
Saturn, in the center,
is shown with eight
g
of its moons.
The Uranian system showing Ariel in the
forefront, with Uranus rising behind.
Traversing clockwise from Ariel are the
satellites Umbriel, Oberon, Titania, Miranda,
and the small moon Puck.
10
Pluto. A rare
image of tiny
Pluto with its
moon Charon,
which is slightly
smaller than the
planet. Pluto
has not yet
been visited by
any spacecraft,
it remains a
mysterious
planet. Pluto's
surface is
believed to
reach
temperatures as
low as -240°C (400°F). From
Pluto's surface,
the Sun appears
as only a very
bright star.
Early Earth
Near Moon…
Earliest phase of
Earth heating
heating…
11
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