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30 Oct 2010
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Jan 16 2009
EESA06
,}ÁZovZÁ}lvZo}v]ZÀ}]}v[
- }v]vvo](Wíõíî~tPvZWvP[
- Sea floor spreading 1960 (Hess)
- Polar wander paths for continents 1965
- Magnetic reversals and stripes 1965 (Vine)
- Mid-ocean ridges and hot spots
- Plate tectonics: 1967
- Oceanic vs. continental plates
- Collisional (obducting and subducting) margins and divergent (ridges)
Mid Ocean Ridges (MOR) and trenches
- Are actually volcanoes (shallow water) or ocean crust/floor
- Fractures divide mid ocean ridges into segments
- Trenches: very deep water
- A lot of volcanic and biological activity
- Zu}l[vu]vo}]
o t]v}vÁ]ZuPu]ZµZ[]lµ~ÀvP]vP}vvuo
in rocks as it rises up and cools on the ocean floor
o E.g. nickel, silver, copper, lead
o ,µPZ(}Ç[}(}vv]vPuo}vZ(o}}
o Important to driving ocean circulation
Harold Hess introduced idea of sea floor spreading (1962)
- ^(o}}DKZ[Ço]v}uvovvZ
- Oceanic crust spreads and pushes into subduction zones
- Basalt in crust gets melted and mixed to become magma
- Magma get less dense and will want to push up
- The younger the ocean, the hotter the basalt, oceans are shallowest at the middle portion
(ridge) as material is being recycled
- Older oceans have more dense rocks, so they are deeper
- Continental crust is the result of the subduction, melting of oceanic crust plus sea water
Magma
- The whiter (more silica) the lighter/less dense it is
- A lot of magnetic particles in the magma that are free to rotate but will point to the north pole
- Declination: orientation of magnetic particle with respect to magnetic north (e.g. if its pointing
south, its declination is 180degrees)
- Inclination: the dip of a particle affected by latitude (steeper dip closer to the poles)
- When magnetic particles become fixed in a rock, there is a record of where the land mass was
before it moved by measuring the inclination and declination µZv}Z}o}v[
move
- Magnetite: Acicular-shaped (needle-like)
- W]}]oUZZ[uPv](]o(o]~ÀoZ}µvÇ
o North becomes south, south becomes north
- Lava flow will show record of when the magnetic field reversed
- Magnetic stripes
o Magnetometer surveys of ocean floor identified patterns of anomalies on each side of
DKZ[
o Patterns matched pattern of magnetic reversals
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Document Summary

Collisional (obducting and subducting) margins and divergent (ridges) Are actually volcanoes (shallow water) or ocean crust/floor. A lot of volcanic and biological activity. l  k z in rocks as it rises up and cools on the ocean floor: e. g. nickel, silver, copper, lead, 2. Harold hess introduced idea of sea floor spreading (1962) Oceanic crust spreads and pushes into subduction zones. Basalt in crust gets melted and mixed to become magma. Magma get less dense and will want to push up. The younger the ocean, the hotter the basalt, oceans are shallowest at the middle portion (ridge) as material is being recycled. Older oceans have more dense rocks, so they are deeper. Continental crust is the result of the subduction, melting of oceanic crust plus sea water. The whiter (more silica) the lighter/less dense it is. A lot of magnetic particles in the magma that are free to rotate but will point to the north pole.

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