Transcript Intro 1-2-3-4

INTRODUCTION TO OCEANOGRAPHY
Instructor: Prof. ANAMARIJA FRANKIĆ
Office Number: S-1-061
Office Hours: Posted on office door or by appointment
Telephone: 617-287-4415
Email Address: [email protected]
Web Page: http://alpha.es.umb.edu/faculty/af/frankic.hml
Department Website: http://www.es.umb.edu/
Oceanography is an
observationally driven field!
What are the independent
variables/parameters for the ocean?
What do they measure and what is
there use?
Geology: coastlines, bathymetry, movement of
tectonic plates
Chemistry: Carbon, Nitrogen, Iron, Oxygen…
Physics: T, U, V, S, SSH
Biology: Chl-a, Productivity, Zooplankton,
Phytoplankton, Fish and Egg counts, etc…
How was the ocean observed so far?
Lots of historical account of early
explorations – (see book).
HMS Challenger
http://www.amazon.com/gp/reader/0393317552/ref=sib_dp_pt/1
03-3317661-1512644#reader-page
International Observational Programs
Deep Sea Drilling Project - DSDP
1968, Glomar Challenger
Theory of
Plate
Tectonics
and much
more…
1985, Joides Resolution Replace G.
Challenger
International Observational Programs
The Joint Global Ocean Flux Study (JGOFS)
(launched in 1987 at a planning meeting in Paris)
The Operational Goal of JGOFS :
Spatial Scale: regional to global
Temporal Scale: seasonal to interannual
1) Fluxes of carbon between the atmosphere-surface ocean-ocean
interior.
2) Sensitivity to climate changes
International Observational Programs
The World Ocean Circulation Experiment
1990-1998
http://woce.nodc.noaa.gov/wdiu/
International Programme on Climate Variability and
Predictability, 1995-present
http://www.clivar.org/index.htm
http://www.clivar.org/publications/other_pubs/clivar_transp/index.htm
World Climate Research Programme
http://www.wmo.ch/web/wcrp/wcrp-home.html
US Programs sponsors:
http://www.nsf.gov/
e.g. GLOBEC http://www.pml.ac.uk/globec/
http://www.noaa.gov/
http://science.hq.nasa.gov/oceans/
http://www.onr.navy.mil/focus/ocean/habitats/default.htm
U.S. Coastal Observing Systems
http://www.csc.noaa.gov/coos/
Technologies for ocean observing
Remote Sensing/Satellite Imagery:
Geostationary Server -http://www.goes.noaa.gov/
Satellite significant events: http://www.osei.noaa.gov/
National Geophysical Data Center:
http://www.ngdc.noaa.gov/ngdc.html
Floating devices in the ocean:
Argo FLoats - http://www.argo.ucsd.edu/
Drifter Programs:
http://www.aoml.noaa.gov/phod/graphics/pacifictraj.gif
Remotely Operated Vehicles (ROVs) :
Amazing discoveries…
http://oceanexplorer.noaa.gov/technology/subs/rov
/rov.html
Automated Underwater Vehicles (AUVs) :
How do we define the science of Oceanography?
WHAT PEOPLE NEED TO KNOW ABOUT
OCEAN SCIENCES
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Ways of knowing – “Reflection on how we know what we believe will help
our understanding”
Human interactions – “Currently, the human species is significantly affecting
earth systems, but has the ability to choose its relationship with the
environment”
Ecosystems – “The survival and health of individuals and groups of
organisms are intimately coupled to their environment”
Earth system science – “The Earth as a whole acts as a complex set of
interacting systems with emergent properties”
Evolution & Biodiversity – “Evolution explains both the unity and diversity of
life”
Energy flow and transformation – “Energy transformation drive physical,
chemical, and biological processes. Total energy is conserved and flows to
more diffuse forms”
Conservation of mass – “Mass is conserved as it is transferred from one
pool to another”
Spatio-temporal relationships – “Choosing the appropriate reference frame
is the key to understanding one’s environment”
Beginnings
1. Earth’s formation
2. Earth’s timeline
Earth’s Formation
The Universe - formed 10-15 billion years ago
Currently referred to as the ‘Big Bang‘
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current theory is that the universe was formed from something
smaller than an atom
the atom exploded and everything was blown outward with great
heat and speed
Earth’s Formation
Our Solar System was formed 4.6 billion years ago
The Earth is assumed to be the same age
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At this time, Earth had a surface
~ known from radiometric dating of meteorites (uranium and
potassium)
We think water condensed on the planet 3.9 billion years ago
~ known from radiometric dating of sedimentary rocks that
formed by processes requiring water
Earth’s Formation
Where did oceans come from?
Old Theory:
a) H2O came from big comets during period of
heavy bombardment
a) H2O locked up in minerals released from
differentiation and heating
Earth’s Formation
Where did oceans come from?
(cont’d)
New Theory:
a) Oceans still forming and H2O comes from many small
cometessimals that continually bombard the Earth
a) H2O came from big comets during period of heavy
bombardment
a) H2O locked up in minerals released from differentiation
and heating
Earth’s Timeline
Mother Earth formed 4.6 billion years ago..
What has happened during this time?
Earth’s Timeline
(cont’d)
Divide by 4.6 billion by 100 million years - makes Earth
46 years old
0-3 yrs
3 yrs
8-11 yrs
22-23 yrs
31 yrs
39th yr
41rst yr
no record
dated from rocks in Canada, Africa
and Greenland
1st living cells - primitive bacteria
oxygen production by cells begins
atmosphere has enough oxygen to
support life
first invertebrates-hard shelled fossils
primitive fish and corals
Earth’s Timeline
(cont’d)
41-42 yrs
43 yr
44 yr
45 yr
land plants, fish
reptiles, dinosaurs, sharks
dinosaurs dominate
dinosaurs die
1 yr ago
plants and flowers proliferate
7 mos. ago
25 days ago
6 days ago
1/2 hour ago
1 minute ago
insects, mammals, birds proliferate
first humans
homosapiens
1st recorded civilization
industrial revolution
 change Earth and relationship
with Earth for all time…
Earth
1. Coordinates
2. Earth’s Water
3. Earth’s Structure
Coordinates
Earth
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Highest mountain is Mt. Everest at 8840m above sea level
Lowest trench is the Mariana Trench (Pacific) at 11,000m
below sea level
Think of earth like a basketball - the
bumps would be the mountains and
the dimples would be the trenches.
Earth has a huge mass!!!
Coordinates
(cont’d)
Latitude and Longitude
Latitude
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Parallel to the equator
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Expressed as degrees N or S of the equator where equator = 0
Coordinates
(cont’d)
Latitude and Longitude
(cont’d)
Longitude
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Lines of longitude are meridians
Longitudinal lines are at a right angle to
latitudinal grid
0° longitude is known as the prime meridian
Goes right through Royal Observatory in
Greenwich, England
Greenwich Mean Time = ‘Universal Time’,
when sun is directly above 0 longitude
• Expressed as degrees E or W of prime meridian
where prime meridian = 0
Earth’s Water
How Earth's water reservoirs are connected
Connected by 2 processes:
evaporation and precipitation
See fig 1.18 (Intro 7e) or 2.13 (Fund. 4e)
Earth’s water reservoirs:
Oceans 97.2%
Lakes, rivers and inland seas 0.017%
Glaciers 2.14%
Atmosphere 0.001%
Ground H20 0.61%
Biosphere 0.005%
WORLDS WATER SOURCES:
Earth’s Structure
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Layered system (like an onion, concentric regions)
~ differentiation of mineral material
Not only Earth’s mineral
material, but also:
1. hydrosphere
2. biosphere
3. atmosphere
Earth’s Structure
(cont’d.)
Classification according to chemical composition
4 concentric regions of
mineral material:
1. crust
2. mantle
3. outer core - molten
4. inner core - solid
Earth’s Structure
(cont’d.)
Classification according to chemical composition
1. Crust
Two types:
continental g granite – composed of
silicates rich in Na, K & Al
ocean g basalt – composed of
silicates rich in Ca, Mg & Fe
• represents 0.4% of Earth’s mass
• extends down to 75 km
Earth’s Structure
(cont’d.)
Classification according to chemical composition
2. Mantle
Three parts:
uppermost/middle/innermost
• Composed of Mg-Fe silicates
• represents 68% of Earth’s mass
• extends down from base of
crust to ~2,900 km
Earth’s Structure
(cont’d.)
Classification according to chemical composition
3. Core
Two parts:
Outer
Inner
• Composed of Fe & Ni
• Represents 28% of Earth’s mass
• Extends down from base of
mantle ~ 6400km
Earth’s Structure
(cont’d.)
Classification according to physical properties
(factor in temperature and pressure)
4 concentric regions:
1. lithosphere - rigid outer shell (crust & uppermost mantle)
• 100 - 150km thick
• does not change shape
Earth’s Structure
(cont’d.)
2. Asthenosphere - soft, flows over geologic time under the weight of
the lithosphere (small fraction of middle mantle)
• lithosphere ‘floats on top’
• zone where magma formed
• 200 – 350km thick
• easily deformed, can be pushed down by overlying lithosphere –
“plastic” – tar or asphalt
Earth’s Structure
(cont’d.)
Classification according to physical properties
3. Mesosphere - rigid but not as hard as lithosphere
• higher temp than asthenosphere, but not molten because of
compression pressure
• 4950km thick
Earth’s Structure
(cont’d.)
Classification according to physical properties
4. Core - outer is molten, inner is solid
Earth’s Structure
(cont’d.)
Isostacy
Principle that dictates how different parts
of the lithosphere stand in relation to each
other in the vertical direction
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Continental crust less dense (granitic) therefore rises higher
relative to ocean crust (basaltic)
•
Continents move up and down depending on weight on top (i.e.
from glaciers - ‘isostatic rebound’)
~
Continents pop up after glaciers melt
~
Canada and Scandinavia rising at a rate of 1m/100yrs
because the glaciers are receding
Earth’s Water
(cont’d.)
Five oceans:
1.
Atlantic – shallowest, greatest number of adjacent seasregional seas: i.e. Gulf of Mexico, Caribbean, Mediterranean,
North), has the largest freshwater input (i.e. Amazon, Congo,
Mississippi)
2.
Pacific – largest, deepest
3.
Indian – smallest, muddiest
4.
Arctic – covers N. Pole, saltiest
5.
Southern Ocean – coldest, most productive
(Some) OCEANS’ related FACTS:
 Our planet is actually the Ocean Planet - 77% of the Earth’s surface is covered
by oceans and seas. However, less than 10% has been investigated.
 Oceans provide more than 70% of oxygen we breathe
 80% of world’s plant and animal species live in oceans
 More than 60% of the current human population (5.8 billion) lives in the coastal
zones (~60 km wide), the areas representing only 8% of the Earth surface!
 ‘Poorest of the poor’ - 1.1 billion people ‘survive’ on less than 1$/day
 1 billion people rely on fish as the only daily source of protein
 Global climate change and the humans’ well being depend on the conditions and
health of the oceans;
 Poverty, hunger, diseases as well as casualties from natural disasters can be
alleviated by improving the health of the environment and by sustainable use and
management of the coasts and oceans!
Plate Tectonics
Horizontal Movement of
Earth’s Lithosphere
Plate Tectonics
1. The Theory of Plate Tectonics
2. Plate Boundaries
a) Spreading Centers
b) Subduction Zones
c) Transform Faults
3. Plate Movement
The Theory of Plate Tectonics
“Continental Drift” - theory* proposed by
Alfred Wagner, a German meteorologist (1915)
Explained by:
• geologic fit
• fossils
* Not accepted by scientific community
- no mechanism to explain plate movement
The Theory of Plate Tectonics
(cont’d.)
Plate Tectonics - evidence for theory of
continental drift Hess, Heezen and Tharp (1960’s)
found lithospheres plate boundaries, 3 types:
1) ridges (spreading centers)
2) trenches (subduction zones)
3) transform faults (plates sliding past one
another)
The Theory of Plate Tectonics
(cont’d.)
Lithospheric Plates
major plates:
1.
2.
3.
4.
5.
6.
7.
Pacific – 105 x106 km2
Eurasian - 70 x106 km2
Antarctic - 60 x106 km2
Australian - 45 x106 km2
S. American - 45 x106 km2
African - 80 x106 km2
N. American - 60 x106 km2
From Fundamentals of Oceanography, 5h edition, Duxbury
Duxbury, and Sverdup. The McGraw-Hill Companies
minor plates:
1.
2.
3.
4.
5.
6.
7.
8.
Cocos - 5 x106 km2
Phillipine - 6 x106 km2
Caribbean - 5 x106 km2
Nazca - 15 x106 km2
Arabian - 8 x106 km2
Indian - 10 x106 km2
Scotia - 5 x106 km2
Juan de Fuca - 2 x106 km2
Plate Boundaries
a) Spreading centers - ‘rift zones’ (cont’d.)
1) Convection cells form
•
Density differences – cool vs. hot
2) Convection cells cause frictional drag on lithosphere
3) Lithosphere stretches due to convective movement
4) Lithospheric crust weakens
Plate Boundaries
(cont’d.)
a) Spreading centers - ‘rift zones’ (cont’d.)
5) Faulting – break in overlying lithosphere
6) Magma flows upward
7) New lithospheric crust formed
Plate Boundaries
(cont’d.)
a) Spreading centers - ‘rift zones’ (cont’d.)
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Plates split apart -‘divergent plate’ boundary
New crust formed - ‘constructive’ plate
boundary
Evolution of a mid-ocean ridge system
1. Upwarping
2. Rift valley
3. Linear sea
4. Mid-ocean ridge system
Ex. 1 - oceans: mid Atlantic Ridge
east Pacific Rise
Ex. 2 - continents: E. Africa Rift Valley
Baikal Rift Valley
Plate Boundaries
(cont’d.)
b) Subduction zones
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Lithospheric Plates collide - ‘convergent’ plate boundary
Crust destroyed - ‘destructive’ plate boundary
Forms trenches and mountains
Plate Boundaries
(cont’d.)
b) Subduction zones (cont’d.)
3 types of subduction zones:
1. Ocean crust into continental crust – form trenches and
mountain ranges
Ex. a): Juan de Fuca plate into the N. American plate - forms Cascade Mtn. Range
Ex. b): Nazca plate into the S. American plate - forms Peru-Chile Trench and
the Andes Mtn. Range
Plate Boundaries
(cont’d.)
b) Subduction zones (cont’d.)
2. Ocean crust into ocean crust – forms trenches and island arcs
Ex. A): Philippine plate into the Pacific plate – formed the Marianna Trench
and the Marianna Island Arc system
Ex. B): N. American plate into the Caribbean plate and then the N. American
plate into the S. American plate – formed the Isthmus of Panama
Plate Boundaries
(cont’d.)
b) Subduction zones (cont’d.)
3. Continental crust into continental crust – form mountain ranges
Ex. A): Indian plate into the Eurasian plate – formed the Himalayas
Ex. B): Eurasian plate into the African plate - closing up of the
Mediterranean sea
Plate Boundaries
(cont’d.)
c) Transform faults
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Plates slide past one another
Lithospheric crust neither created nor destroyed - ‘conservative’ plate
boundary
Ex. A) Pacific plate sliding past N. American plate – forms the San Andreas Fault
Plate Movement
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New crust is created at spreading centers at a rate of approximately
1-10cm per year
Old crust is destroyed at the same rate at subduction zones
How do we know these rates? (Rate=distance/time)
Plate Movement
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(cont’d.)
Magnetic anomalies in ocean crust...look at spreading centers
 paleomagnetism
 every so often Earth’s magnetic field flips (every 300K-500K years)

magnetic signal recorded in crust at spreading center as it’s formed, forms
bands of crust with either a weak or strong magnetic signal

determine rate of plate movement by distance of band from spreading center
divided by age of rock in band (r=d/t)
Plate Movement
(cont’d.)
Hot spots
 Emperor Sea Mount chain
 islands or sea mountains formed over hotspots
(fixed area where magma comes up)


lithosphere moves over hotspot and end up have volcanic mountain
over hotspot as well as a series of mountains in ‘front’ of hotspot
determine rate of plate movement by distance of mountain from
hotspot divided by age of rock in mountain (r=d/t)
Learning Objectives
Understand the processes that are continuously changing Earth’s
surface as lithospheric plates move relative to one another.
Identify the role of oceanic ridges, transform faults and deep-sea
trenches in defining the edges of lithospheric plates.
Understand the importance of asthenospheric thermal convection
in plate tectonics and the resulting compression or tensional forces
at the plate boundaries.
Explain the distribution of magnetic anomaly stripes, seismicity,
and volcanism in terms of the concept of global plate tectonics.
Calculate spreading rates of ocean basins.
Age of Ocean Crust
http://www.ngdc.noaa.gov/mgg/geology/geology.html
Creating new ocean crust
More evidence of plate moving..
Oceanic crust moves
away from MOR (Mid
Oceanic Ridge) and
cools and subsides
3-3
Destructive margins
Subduction zones
Constructive margins
Midocean ridges
Driving Mechanisms for Plate Motions
Type of boundary between plates:
Constructive margins  Mid ocean ridges
Destructive margins
 Subduction zones
Conservative margins  Transform faults
Conservative margins
Transform faults
Conservative margins
Transform faults
The San Andreas fault
in southern California
Hot Spots ?
3-3
• Mantle plumes originate deep within the
asthenosphere as molten rock which
rises and melts through the lithospheric
plate forming a large volcanic mass at a
“hot spot”.
Mantle Plume
Coral Reefs
Air view
Spreading rates
Geological Periods
Geological Periods
Precambrian
Cambrian
Ordovician
Silurian
Devonian
Early Carboniferous
Late Carboniferous
Permian
Triassic
Jurassic
Late Jurassic
Cretaceous
K/T extinction
Eocene
Miocene
Modern
Future World
Future
Future
4.6 B 514 Ma
458 Ma
425 Ma
390 Ma
356 Ma
306 Ma
255 Ma
237 Ma
195 Ma
152 Ma
94 Ma
66 Ma
50.2 Ma
14 Ma
570 Ma solidification
Gondwana, hard shell anim.
separation, coldest
Laurentia collides with Baltica
pre-Pangea, equatorial forests
western Pangea is complete
deserts, reptiles, major ext.
Life begins to rediversify,Pangea
Dinosaurs, Pangea starts to break
Pangea rifts apart, Atlantic
New oceans, India
end of dinosaurs
India collides with Asia
Modern look
+50 Ma N. Atlantic widens, Med. vanish
+100 Ma new subduction
+250 Ma new Pangea
Precambrian
break-up of the
supercontinent, Rodinia,
which formed 1100 million
years ago. The Late
Precambrian was an "Ice
House" World, much like the
present-day.
Source: www.scotese.com
Cambrian
Animals with hard-shells
appeared in great numbers
for the first time during the
Cambrian. The continents
were flooded by shallow
seas. The supercontinent of
Gondwana had just formed
and was located near the
South Pole.
Ordovician
During the Ordovician ancient
oceans separated the barren
continents of Laurentia,
Baltica, Siberia and
Gondwana. The end of the
Ordovician was one of the
coldest times in Earth
history. Ice covered much of
the southern region of
Gondwana.
Silurian
Laurentia collides with
Baltica closing the northen
branch of the Iapetus Ocean
and forming the "Old Red
Sandstone" continent. Coral
reefs expand and land plants
begin to colonize the barren
continents.
Devonian
By the Devonian the early
Paleozoic oceans were
closing, forming a "prePangea". Freshwater fish
were able to migrate from the
southern hemisphere
continents to North America
and Europe. Forests grew for
the first time in the
equatorial regions of Artic
Canada.
Early Carboniferous
During the Early
Carboniferous the Paleozoic
oceans between Euramerica
and Gondwana began to
close, forming the
Appalachian and Variscan
mountains. An ice cap grew
at the South Pole as fourlegged vertebrates evolved in
the coal swamps near the
Equator.
Late Carboniferous
By the Late Carboniferous
the continents that make up
modern North America and
Europe had collided with the
southern continents of
Gondwana to form the
western half of Pangea. Ice
covered much of the
southern hemisphere and
vast coal swamps formed
along the equator.
Permian
Vast deserts covered
western Pangea during the
Permian as reptiles spread
across the face of the
supercontinent.
Triassic
The supercontinent of
Pangea, mostly assembled by
the Triassic, allowed land
animals to migrate from the
South Pole to the North Pole;
and warm-water faunas
spread across Tethys. The
first mammals and dinosaurs
appeared;
Jurassic
By the Early Jurassic, southcentral Asia had
assembled. A wide Tethys
ocean separated the
northern continents from
Gondwana.
Subduction zone Rocky Mountains
Formation of the Rocky Mountains
http://wrgis.wr.usgs.gov/docs/parks/province/rockymtn.html
Late Jurassic
In the Late Jurassic the
Central Atlantic Ocean was a
narrow ocean separating
Africa from eastern North
America.
Cretaceous
During the Cretaceous the
South Atlantic Ocean
opened. India separated from
Madagascar and raced
northward on a collision
course with Eurasia. Notice
that North America was
connected to Europe, and that
Australia was still joined to
Antarctica.
K/T extinction
The bull's eye marks the
location of impact site of a
10 mile wide comet caused
global climate changes that
killed the dinosaurs and
many other forms of life. By
the Late Cretaceous the
oceans had widened, and
India approached the
southern margin of Asia.
Eocene
50 - 55 million years ago
India began to collide with
Asia forming the Tibetan
plateau and Himalayas
(destroying the last of
Tethys ocean). Australia,
which was attached to
Antarctica, began to move
rapidly northward.
Collision of continental crust
3-2
• Whereas oceanic ridges indicate tension,
continental mountains indicate compressional
forces are squeezing the land together.
Sedimentary Rocks Squeezed by Compression
Miocene
20 million years ago,
Antarctica was covered by
ice and the northern
continents were cooling
rapidly. The world has taken
on a "modern" look, but
notice that Florida and parts
of Asia were flooded by the
sea. Arabia moved away
from Africa forming Gulf of
Aden and Red Sea;
Last Ice Age
When the Earth is in its "Ice
House" climate mode, there
is ice at the poles. The polar
ice sheet expands and
contacts because of
variations in the Earth's orbit
(Milankovitch cycles). The
last expansion of the polar
ice sheets took place about
18,000 years ago.
Modern World
If we continue present-day
plate motions the Atlantic
will widen, Africa will collide
with Europe closing the
Mediterranean, Australia will
collide with S.E. Asia, and
California will slide
northward up the coast to
Alaska.
Future +100
Earth is ~ 4.6 bill
years old –
suggested cyclic of
500 mill year
pattern of
assembling and
disassembling the
land masses;
Future +250
The Wilson Cycle
The
Wilson
Cycle