Download 103-03a-TimeWaterEarthXsect

GEOLOGIC TIME, WATER,
& EARTH CROSS SECTION
GEOL 1033
GEOLOGIC TIME Earth is 4.65 Ga old
• A diagrammatic
representation of the last
4.0 billion years of the
geological time scale of
the Earth showing the
different groups of
organisms that evolved
through time. Note that
man's presence on earth
represents just an
extremely small fraction
of the 3.5 billion year
history of life on Earth.
On a 24 hour clock, our
species, Homo sapiens,
appeared at 2 seconds
before midnight.
• Oceans probably existed
at about 4 Ga
• Life began in the oceans
GEOLOGIC TIME SCALE
• Geologic time terms:
Eon
Era
Period
Epoch
Age
• Two major divisions:
– Precambrian
(4.7 Ga - 544 Ma)
– Phanerozoic
(since 544 Ma)
• Ma = million years
• Ga = billion years
Hadean
• Be aware of the
Geologic Time
Scale in general.
• What is the
Carboniferous
Period?
• What is the
Jurassic Period?
• When did it begin?
• Why is it
important to
oceanography?
• What is the
Pleistocene Epoch?
• When did it begin
and end?
• Why is it
important to
oceanography?
GEOLOGIC TIME SCALE
Hadean
4.65
WATER DISTRIBUTION ON EARTH'S SURFACE
• The Pacific Ocean is by far
the largest ocean.
• "Antarctic Ocean" is
really part of the Pacific,
Indian, & Atlantic oceans
• Arctic Ocean is the
smallest.
• Antarctic and Greenland
ice caps have 1.5% of
Earth's surface water.
• Lakes, rivers, &
atmosphere have only
<0.1% of water!
?
Where is the
Arctic
Ocean?
HEMISPHERIC DISTRIBUTION OF LAND
• 71% of Earth's
surface is covered by
the oceans.
• A northern land
hemisphere
• A southern water or
ocean hemisphere
WATER DISTRIBUTION ON EARTH'S SURFACE
• ~98% of Earth's surface & near-surface water is in the
oceans as liquid or floating sea ice
• Frozen seawater:
• Excludes salts
• Leaves a cold brine as a residue
• Forms freshwater when it melts
• ~97% of Earth's surface & near-surface water is saline.
SOME CHARACTERISTICS OF THE WORLD’S OCEAN
• Oceanic water covers a surface area of
about 361 100 000 km2 or 3.611 x 108 km2
• Oceanic water volume equals about 1.37 x 109 km3
• Average depth of the oceans is about 3.8 km (~12,450').
• Average temperature of the oceans is about 4 deg. C.
• Average salinity is about 34.482 o/oo (=34.482 g/kg)
or about 3.5%
HYPSOMETRIC CURVE
Cumulative area of
Earth's surface
above a certain
depth or
elevation, e. g.,
29% is above sea
level & 71% is
below sea level.
2 major elevations:
– near sea level
– deep ocean floor
29%
71%
TILT OF EARTH'S ROTATIONAL AXIS
• 23.5 degree tilt of Earth's rotational axis exerts a
controlling influence on climates, ocean circulation, etc.
Earthquake P & S Body Waves
• Review earthquake wave propagation
before studying a cross section of Earth
•Compare the hammer/board, spring,
& rope models of P and S waves
CROSS SECTIONS OF EARTH
• Study of seismic waves from earthquakes indicate
– Core with 2 layers
• inner solid
• outer liquid
– Mantle with many layers
• lower lithosphere
• asthenosphere
• mesosphere
– Crust with 2 types
• continental
• oceanic
• Lithosphere includes:
– Crust
– Upper mantle
CROSS SECTIONS OF EARTH
• Core (2 layers)
Si, NA, K
• Mantle (3 layers)
• Crust (2 types)
Fe,Mg
Silica Models
Outer core is all liquid
CROSS SECTIONS OF EARTH
Lithospheric layers:
–
–
Crust (oceanic or continental)
Uppermost mantle
OCEAN-CONTINENTAL MARGIN CROSS SECTION
DOWN TO THE MESOSPHERE
OVERVIEW OF PLATE TECTONIC PROCESSES
Thermal Convection
TABLE SUMMARIZING EARTH CROSS-SECTION DATA
Name of Layer
Radius (km) Density
(g/cm2)
State of
Matter
Rock Name or
Composition
CRUST:
Continental
up to 60
2.7
solid
Oceanic
5-10
2.9
solid
Granitic
(more silica, SiO2)
Basaltic
(less silica, SiO2)
~3.1
~3.3
~4.5-8
solid
solid
solid
Iron- & magnesiumrich silicates
~8
>10
liquid
solid
Mostly Fe with some
Ni, S, & Si
MANTLE
Lithosphere
~100
Asthenosphere ~600
Mesosphere
~2,200
CORE:
Outer
2,200
Inner
1,300
ELEMENT ABUNDANCE IN THE CRUST and WHOLE EARTH
• Abundance of elements in the crust by percentage weight:
–
–
–
–
–
–
–
–
–
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium
all others
O
Si
Al
Fe
Ca
Na
K
Mg
47%
28
8
5
3.6
3
2.6
2
1.5
• Whole Earth order of abundance:
–
–
–
–
–
–
–
–
–
Iron
Oxygen
Silicon
Magnesium
Nickel
Sulfur
Calcium
Aluminum
all others
Fe
O
Si
Mg
Ni
S
Ca
Al
(incl. Na, K)
35%
30
15
13
2.4
2
1
1
<1
PERIODIC TABLE of the ELEMENTS
END OF FILE
Review Questions:
• What are the two most abundant elements in the crust?
________________ ________________
• What is the depth of the deepest earthquake? _______________
• Magma is rising from deep in the mantle beneath
mid-ocean ridges where seafloor __________________ occurs.
• Thermal convection in the ______________ may be the driving
mechanism for plate tectonics.
• The proto-Atlantic ocean basin began to form about
__________ Ma ago near the beginning of the Jurassic Period.
• The average salinity of seawater is _________________ o/oo
• The ___________ Ocean is the largest ocean on Earth.