GEO 110 Chapter Notes - Chapter 4: Continental Crust, Oceanic Crust, Plate Tectonics

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25 Jul 2016
Lecture 4
Earth’s Layers
-Earth’s crust is positioned above the asthenosphere
-The inner core is made of two minerals; iron and nickel, and its solid
-Temperature of about 6000 degrees celsius
-Beyond the core you have the mantel layer, upper and lower mantle, makes accounts for 80%
of volume of air
-Then the asthenosphere, ranges from 400 to 700km, and above that is the lithosphere(zone of
rock) which is 60 to 400 km depending on the land its found
-Two major crust, ocean and continental
Continental Crust: Made up of a combination of mineral (sial), silica, and aluminium, lighter in
weight, it is relatively warmer and lighter than the oceanic crust. It has great viscosity, so it flows
very slowly, if there is an eruption of a volcano the materials from the Continental crust have
great resistance, and solidifies within a short time
Oceanic Crust: Denser and cooler, made up of mafic composition, means that high amount of
magnesium, and iron, it has very low viscosity, very fluid. Minerals found within is the oceanic
crust is gabbros and basalt. It has a lot of water compared to the continental crust
Asthenosphere: Weak layer, plastic, fluid because of high temperatures
-Ocean and continental are in constant collision
The Core: The central part of it
-Move a few cm or inches per year
-It is imperceptible to the eye because it is a small change for continental movement
3 reasons for Continental Drift
Alfred Wegener: Began his theory about continental drifting,
1.Magma Convection: Magma will rise to the surface and it will push the continent upward so it
expands, when it cools it falls down.
2. Magama Upwelling: Magma is constantly upwelling, forcing its way through fishes and
cracks. causing continental drifts
3.Sea Floor Spreading: When two oceanic plates collide and cracks develop between them,
magma spews out, grows above the ocean and in some cases solidifies to form an island, or a
submerged land in the ocean, ex. Hawaii
Different types of plate boundaries:
Convergent plate boundaries: when two plates collide from opposite direction they exert
pressure at the point of convergence, causes rocks to crumbles, and be uplifted, and the result
is that mountains occur around fort lines. When fort mountain occur at the top of the mountain
they are describes as anticline, and the low line areas are syncline, these are one of the
features at convergent plate boundaries
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