Energy
Drives earthquakes
and volcanic
eruptions
 Concentrated at
certain tectonic
settings
 Associated with the
Earth’s formation

Driving Forces on and within
the Earth?
Driving Forces within the Earth

Heat formation:
– Impact of asteroids and comets in Earth’s
early history
– Decay of radioactive elements
– Gravitational contraction
– Differentiation into layers
Artist Impression, NASA
Driving Forces on and within the
Earth?

Earth’s internal heat
– Flows within the mantle (largest volume of
Earth)
– Release in terms of volcanic activity and
earthquakes
– Long-term: continents, oceans and
atmosphere
– Movement of tectonic plates
Greg Houseman,
University of Leeds
Driving Forces on the Earth

Gravity: the attraction between bodies
– Segregating elements within the Earth
– Movement along the Earth’s surface
 landslides
– Movement within the Earth
 Subducting oceanic slab moving into the mantle
Landslide,
China
Driving Forces on the Earth

The Sun
– ¼ of the Sun’s energy reaches the Earth
– Evaporation
– Warming of atmosphere and hydrosphere
– Weather: movement of air from warm to
cooler areas
Formation of Solar System

What happened in the past and how is
this currently reflected?
– Gravitional force
– Variations of temperatures
– Rotation
– Composition of material
– Different states of matter
The Nebular Hypothesis
The solar system formation
A nebula is formed from
a collection of gases
(98%) and dust (2%)
 The mass rotates and is
held together by gravity.

Where do we see this in our
sky?
Third star down on
Orion’s belt
 Star nursery
 100 light years
across (1 light year
equals 6 trillion
miles)
 Reflection of dust
and hydrogen

Orion Constellation
Winter sky
constellation
 Hunter in Greek
mythology
 New stars in several
hundred million years

Nebula: Step I

Nebula exists and
through time:
– Contracts causing the
nebula to increase
temperature in center
and increase speed of
rotation
The Nebula
collapses: step 2

The collapsed mass
forms a proto-sun
and disc-shape
rotating mass of gas
and dust.

The Orion nebula
contains about 153
visible protoplanetary
disks

2-17 times larger than
our solar system
Rotation increases
 Temperature increases: 1,800,000 degrees
Fahrenheit
 Fusion begins

Protosun
Fusion
What does “to fuse” mean?
 Remember, what is the composition of the
nebula?
 Look on the periodic table
 What is the relation or difference between
Hydrogen and Helium?
 Can you predict what fuses?

Fusion

Hydrogen (1 proton) fuses with another
Hydrogen (1 proton) = Helium (2
protons)
E
= mc2
 E = energy
 m= mass (very small)
 c squared =speed of light
(186,000 miles/second)
Step 3: Sun Forms
The disk is “cleared
out” due to the
immense amount of
energy released.
 Dust and gases cool,
condense and
accrete forming
planetesimals.
 Defined orbits
around the sun

Earth’s internal heat from
formation
Our Sun
Collapsed disk not shown
 Sun is about 5 billion years
old
 5 billion years until a red giant
is formed

Step 4: Material Cools and
Condenses; planet formation
Temperature
differences with
respect from the sun
 Terrestrial planets
(closer)
 Jovian or gaseous
planets (farther
away)

Solar System
The first four planets are terrestrial (iron
and silicate)
 The last planets are composed of gases

Moon’s Formation
5:20
A large size planet ,
thought to be the
size of Mars, collided
with Earth- 4.4 billion
years ago
 The debris formed
the moon
 The impact, set the
Earth on its axis
 23 degrees

The Earth tilted
on its axis in
response to the
collision
The Early Earth





Hot
Homogenous
Crust as we know it,
not developed
4.6 billion years ago
Melted again due to
the collision of the
Mars size planet
Transitional Earth
Segregation of
elements by density
 Iron moves to the
center
 Gravitational pull and
rotation

Chemically distinct layers
Crust: oxygen and
silicon (70%)
 Mantle: iron,
magnesium, lower %
Si, O
 Core: iron and nickel

Physically Distinct Layers





Inner core: solid
Outer core: liquid
Mantle: capable of
flow
Asthenosphere: acts
like a hot plastic
Lithosphere: rigid
Lithosphere
Rigid layer that lies between the surface
and 60-100 miles
 “Floats” on the asthenosphere
 The tectonic plates are composed of
lithosphere

Lithosphere
Contains crust and upper mantle
Continental Crust





Less dense
Higher % of silicon
and oxygen
Lower % of iron and
magnesium
Thicker (15-25 miles)
30 % of Earth’s
surface
Oceanic Crust





More dense
Higher % of iron and
magnesium
Lower % of silicon and
oxygen
Thinner (5-7 miles)
70 % of Earth’s
surface
Asthenosphere

Relatively soft layer capable of flow that
lies below a depth of 60-100 miles (upper
mantle)
Dr. Railsback, University
of Georgia
The Mantle
Largest portion of the Earth
 Very rich in iron and magnesium
 Very poor in silicon and oxygen
 The mantle is solid but because of high
temperatures and pressures, it is soft
enough to flow
 The asthenosphere is part of the upper
mantle

The Core
Outer core-liquid which can flow and
generates the Earth’s magnetic field
 Inner core- solid and rotates faster than
the Earth
 Mostly iron, some nickel

Complex fields in the core
contribute to the dipole field
at the surface (UC Berkeley)
The magnetic field protects the
Earth from solar radiation
External Source of Earth’s Water
The collision of
comets with the
Earth’s surface
 As the ice hits the
warm Earth, the ice
melts to water
 Gravity holds the
water to the surface

Haley’s comet contains ices
and dust. The tail is created
by ice to sublimate to
steam.
Internal Source of Earth’s Water
Water vapor is
released during
volcanism
 Cooling of the hot
Earth involved intense
volcanism
 Water condenses

Formation of Atmosphere
Gas is expelled from
magma during
volcanic eruptions
 Nitrogen, carbon
dioxide, hydrogen,
sulfur dioxide and
water
 Early Earth’s
atmosphere did not
contain which gas?
Why?

History of the Earth
4.6 billion years old
Early Earth
 4.4 bya, formation of moon
 3.9 bya, oldest rock (sedimentary rock)

– sedimentary rocks are made-up of
fragments of preexisting rocks
– Sediments are carried and deposited by
water and wind
– implies the existence of weather and water

4.1 bya, age of particles within the
sedimentary rock
History of the
Earth
Fossil
Worm,
Cambrian
Sponge
3.5 bya, first bacteria
 3.2 bya, algae (product?)
 plants

– photosynthesis, by-product is oxygen
worms and jelly fish
Trilobite
 500 million years ago, Cambrian (life)
explosion: marine fauna; modern phyla:
sponges, mollusks (clams and snails),
echinoderms (sea urchins and stars),
anthropoda -trilobites(crabs, lobsters)

Earth as an
evolving system
Creation and early Earth
 Earth’s chemically and physically
distinct layers
 Atmosphere (air)
 Hydrosphere (water)
 Biosphere (plants and animals)

Summary
The Nebular Hypothesis
 Earth’s heat sources

– Radioactive decay
Think Quest
– Initial heat produced by collision of other
objects
Moon, water and gas formation
 Earth’s layers, differences and locations
 Importance of gravitational pull
