GEOLOGIC TIME, WATER, & EARTH CROSS SECTION GEOL 1033.
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Transcript of GEOLOGIC TIME, WATER, & EARTH CROSS SECTION GEOL 1033.
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
GEOLOGIC TIME SCALE• 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? 4.65
Hadean
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)
• Mantle (3 layers)• Crust (2 types)
Outer core is all liquid
Fe,Mg
Si, NA, K
Silica Models
CROSS SECTIONS OF EARTH
Lithospheric layers:– Crust (oceanic or continental)– Uppermost mantle
OCEAN-CONTINENTAL MARGIN CROSS SECTION DOWN TO THE MESOSPHERE
Ast
heno
sphe
re
OVERVIEW OF PLATE TECTONIC PROCESSES
Thermal Convection
TABLE SUMMARIZING EARTH CROSS-SECTION DATAName of Layer Radius (km) Density State of Rock Name or
(g/cm2) Matter Composition
CRUST:
Continental up to 60 2.7 solid Granitic
(more silica, SiO2)
Oceanic 5-10 2.9 solid Basaltic
(less silica, SiO2)
MANTLE
Lithosphere ~100 ~3.1 solid Iron- & magnesium-
Asthenosphere ~600 ~3.3 solid rich silicates
Mesosphere ~2,200 ~4.5-8 solid
CORE:
Outer 2,200 ~8 liquid Mostly Fe with some
Inner 1,300 >10 solid Ni, S, & Si
ELEMENT ABUNDANCE IN THE CRUST and WHOLE EARTH• Abundance of elements in the crust by percentage weight:
– Oxygen O 47%
– Silicon Si 28
– Aluminum Al 8
– Iron Fe 5
– Calcium Ca 3.6
– Sodium Na 3
– Potassium K 2.6
– Magnesium Mg 2
– all others 1.5
• Whole Earth order of abundance:– Iron Fe 35%
– Oxygen O 30
– Silicon Si 15
– Magnesium Mg 13
– Nickel Ni 2.4
– Sulfur S 2
– Calcium Ca 1
– Aluminum Al 1
– all others (incl. Na, K) <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.