CHAPTER 19 Earth’s Evolution through Geologic Time
466
A. Big Bang
13.7 Ga
B. Hydrogen and
helium atoms
created
C. Our galaxy forms
10 Ga
D. Heavy elements
synthesized by
supernova
explosions
E. Solar nebula
begins to contract
4.7 Ga
F. As material collects
to form the protosun
rotation flattens nebula
G. Accretion of planetesimals
to form Earth and the
other planets
Earth
H. Continual bombardment
and the decay of radioactive elements
produces magma ocean
I. Chemical differentation
produces Earth’s
layered structure
J. Mars-size
object impacts
young Earth
4.6 Ga
K. Debris orbits
Earth and
accretes
L. Formation of Earth Moon system
4.5 Ga
M. Outgassing produces Earth’s
primitive atmosphere and ocean
FIGURE 19.4 Major events that led to the formation of early Earth.
466
A. Big Bang
13.7 Ga
B. Hydrogen and
helium atoms
created
C. Our galaxy forms
10 Ga
D. Heavy elements
synthesized by
supernova
explosions
E. Solar nebula
begins to contract
4.7 Ga
F. As material collects
to form the protosun
rotation flattens nebula
G. Accretion of planetesimals
to form Earth and the
other planets
Earth
H. Continual bombardment
and the decay of radioactive elements
produces magma ocean
I. Chemical differentation
produces Earth’s
layered structure
J. Mars-size
object impacts
young Earth
4.6 Ga
K. Debris orbits
Earth and
accretes
L. Formation of Earth Moon system
4.5 Ga
M. Outgassing produces Earth’s
primitive atmosphere and ocean
FIGURE 19.4 Major events that led to the formation of early Earth.