Download How old is the Earth? What is the Earth made of?

27 PLANET EARTH
Salt Lake
Temple granite
Top
When was this
granite
formed?
Don’t forget
to take
Exam 3!
Do all mineral
systems give
the same age
for this
granite?
If not what
events are they
recording?
PS 100 -- Chapter 27
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Sun is thought to be about 5 billion years
old
„ Rocks from the Moon have been dated at
4.6 billion years old
„
A.
B.
is thought to be the age of the Earth and
Moon
C.
Oldest rocks on Earth are about 4.0 billion
years old
Age Top
Age Base
K-Ar
Hornblende
500 ºC
30 my
30 my
K-Ar
Biotite
300 ºC
28 my
28 my
Fission Track
Zircon
225 ºC
20 my
10 my
Fission Track
Apatite
100 ºC
11 my
6 my
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Because the Moon is older than the
earth.
Earth & moon are about the same age,
but the Earth’s surface is constantly
reworked whereas the Moon’s surface is
not.
Because radiation exposure on the Moon
makes the rocks older.
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4
PS 100 -- Chapter 27
What is the Earth made of?
Why are Rocks on Earth Younger?
„
Closure T
PS 100 -- Chapter 27
… This
PS 100 -- Chapter 27
Mineral
Why were astronauts able to find older
rocks on the moon than any found on
Earth?
How old is the Earth?
„
Base
System
It has a Tectonic
System
„
It has a Hydrologic
System
Feldspar
„
Mostly Oxygen, Silicon, and Iron
Atoms combine to form “Minerals”
Quartz
„
Mica
„
PS 100 -- Chapter 27
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Minerals combine to form “Rocks”
PS 100 -- Chapter 27
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1
Common Igneous Rocks
What are the main types of Rocks?
„
IGNEOUS ROCKS – Form
from hot, liquid magma
„
SEDIMENTARY ROCKS –
Form as layered deposits in
oceans, lakes, and on land
„
GRANITE
„
„
„
„
„
BASALT
„
METAMORPHIC ROCKS –
Form when pressures,
temperatures and fluids
change rocks in the solid state
„
„
„
„
„
Why is granite generally lighter in color
than basalt or peridotite?
PS 100 -- Chapter 27
Because granite has lower
transition metal content
Because granite is full of air
pockets
Because granite has larger
grains
PS 100 -- Chapter 27
„
SHALE
„
SANDSTONE
„
CONGLOMERATE
„
LIMESTONE
„
„
„
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SLATE
„
„
Pebbles & cobbles
Precipitates out of
water
PS 100 -- Chapter 27
10
Formed from
Shale
Formed from
Sandstone
GNEISS
„
„
Sand-sized particles
QUARTZITE
„
„
Clay-sized particles
Why are Earth & Venus so
Different?
Common Metamorphic Rocks
„
8
Common Sedimentary Rocks
„
C.
Why is granite
generally lighter
in color than
basalt or
peridotite?
Lowest in Si
Highest in Fe,Mg
Highest Density
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PS 100 -- Chapter 27
B.
Lower in Si
Higher in Fe, Mg
Higher Density
PERIDOTITE
„
A.
High in Si
Low in Fe, Mg
Low Density
Formed from
Shale or Granite
MARBLE
„
Formed from
Limestone
PS 100 -- Chapter 27
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PS 100 -- Chapter 27
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2
Continents
Characteristics of Continents
Why does the Earth
have continents?
„
Because it has
WATER Water is
„
„
necessary to make granite,
and granite is what continents
are made of
„
and Plate tectonics to
pull sediment that contains
water down into the Earth
where it can combine to form
the minerals in granite
PS 100 -- Chapter 27
„
Composed mostly of
rocks high in silica
(granite, gneiss)
Low density
Rocks can be as old as 4
billion years
Rocks may be highly
deformed
Continents have several
distinct regions
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PS 100 -- Chapter 27
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Shield
Shield
Oldest part of
continent
„ Rocks highly
deformed
„ Roots of ancient
mountain belts
„ Sometimes called
the “basement”
„
Stable
Platform
Mountain
Belt
PS 100 -- Chapter 27
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PS 100 -- Chapter 27
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Stable Platform
„
„
„
PS 100 -- Chapter 27
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Relatively flat lying,
undeformed
sedimentary rocks
Broad domes and
basins
Sediments lie on top
of basement (rocks
found in shield)
PS 100 -- Chapter 27
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3
Mountain Belts
„
„
„
„
„
PS 100 -- Chapter 27
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Continental Shelf & Slope
Rugged Topography
Youngest part of
continent
Folded and faulted
rocks
Found along margins of
continents
May have active
volcanoes
PS 100 -- Chapter 27
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Ocean Basins
The Edge of the Continent
„
„
Continental Shelf is
the part of the
continent under water
Continental Slope is
the drop-off into the
deep ocean basin
PS 100 -- Chapter 27
„
„
„
„
„
21
Oceanic Ridges
„
„
„
„
„
Composed mostly of basalt
High density
Rocks younger than 200 million years
Rocks mostly undeformed
Ocean Basins have several distinct regions
PS 100 -- Chapter 27
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Abyssal Hills & Plains
Long underwater
mountain ranges
Common eruptions of
basalt
Youngest part of
ocean basin
High heat flow
Generally have a rift
valley along the crest
of the ridge
PS 100 -- Chapter 27
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PS 100 -- Chapter 27
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4
Trenches – narrow, deep, usually next to
the continents, & oldest part of ocean basin
PS 100 -- Chapter 27
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Ocean Islands & Seamounts
PS 100 -- Chapter 27
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How did all of these features form?
PS 100 -- Chapter 27
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