EESA06H3 Lecture Notes - Lecture 2: Hydrophone, Bathymetry, Ocean Deep
EESA06
LECTURE 2
How planet earth Evolves: Continental Drift vs Plate Tectonics
KEY POINTS
● Formation of planet Earth: 4,500 millions (4.5 billion) years before present
● ‘Continental drift’ and Pangea: 1912 (Alfred Wegener)
● ‘Sea floor spreading’ : 1962 (Harold Hess)
● ‘Magnetic stripes’ on the ocean floor and ‘wander paths’ for continents: 1965 (Fred Vine)
● Mid-ocean ridges and ‘hotspots’: 1965 (Tuzo Wilson)
● Computer reconstruction of pangea by Edward Bullard (1965)
● Plate tectonics and the Wilson cycle of supercontinents : 1967 (Tuzo Wilson), called a
‘revolution in Earth sciences’
*** important distinction between continental drift and plate tectonics
● Continental drift theory indicates that the continents themselves are moving (like large
ships plowing through ocean floor)
○ Guy who came up with this theory didn’t have any support
○ It was rubbished
○ Original suggestion that continents are on the move
● 60s is when we started exploring Earth
○ oceans cover 70% of planet
○ We don't see much of the geology
○ Mid 60s → development of geophysics
■ Ability to map what’s underneath oceans and underground using
electromagnetic waves (sound waves)
■ Bounce back from rocks
● Plate tectonics
○ Plates are moving
○ Continents are apart of larger plates and that’s why they’re moving
● Found that you can fit Europe and
Africa against south America and North
America
○ Vague observation, not
looked into that much
● Interested in the moon and the
craters on them
○ Long thought to be volcanic
○ But actually found to be
because of impact
● Laurentia
○ North america in the ancient
past
EESA06
LECTURE 2
○ Ancestral NA
● Thought rate of movement was fastest in Greenland
● People began to explore idea that Earth had expanded or contracted
● Reassembled pangea
● Form belts (colours)
● Different rocks identify different
paleoenvironments
○ Ex: coal
■ Need high
temperatures
■ Usually in
subtropical and tropical areas
○ Ex: salt
■ Dry climate
■ A lot of evaporation
■ Concentrated salt
in the water and if you have evaporation, can dry seas and produce thick
salt deposits
● Form quickly
● Toronto’s natural state is to be covered in ice for
most of the time
● Move sediment when they melt
● Thick sheets
EESA06
LECTURE 2
● Scratch surface of wherever they flow
→ have debris at bottom of the sheet
○ Striations
→ steep scratches left
by ice sheets
● Trench → very deep water
○ Associated with
subduction zones
● Sound source → aka chirp
systems
○ Emit high frequency
sound
● Sound waves go down
through floor of ocean and bounce
back
● Can map layers at bottom of
the ocean
● Hydrophone → picking up
reflected waves
● Sidescan low vehicle →
produces black and white image of ocean floor
○ Used for finding wrecks today
● Echo sounder→
gives water depths
○ Can figure out bathymetry → depth of something (ocean floor)
● Ocean floor has a lot of relief on it→ not
flat
● Two important features of ocean floor:
○ Mid ocean ridges
■ Geologists come from all
over the world to walk on it
■ To the rest of the world it
is deep underwater
Document Summary
How planet earth evolves: continental drift vs plate tectonics. Formation of planet earth: 4,500 millions (4. 5 billion) years before present. Continental drift" and pangea: 1912 (alfred wegener) Sea floor spreading" : 1962 (harold hess) Magnetic stripes" on the ocean floor and wander paths" for continents: 1965 (fred vine) Mid-ocean ridges and hotspots": 1965 (tuzo wilson) Computer reconstruction of pangea by edward bullard (1965) Plate tectonics and the wilson cycle of supercontinents : 1967 (tuzo wilson), called a. *** important distinction between continental drift and plate tectonics. Continental drift theory indicates that the continents themselves are moving (like large ships plowing through ocean floor) Guy who came up with this theory didn"t have any support. Original suggestion that continents are on the move. 60s is when we started exploring earth. We don"t see much of the geology. Ability to map what"s underneath oceans and underground using electromagnetic waves (sound waves) Continents are apart of larger plates and that"s why they"re moving.
