Lecture 1 - Introduction Flashcards
Are all plates rigid?
At depth plates do not have rigid structures.
Where are deformation, seismicity and volcanisms generally located?
Boundaries of rigid plates
How is topography determined?
Tectonism
What does topography determine?
Local climate
What are the two main feedback loops dictating topography?
Direct path - tectonics increase erosion rates by increasing elevation, relief and drainage areas
Indirect path - tectonics increases erosion rates by changing the climate
Where is the majority of the earth?
Below 4km below sea level (55%)
Where are topographic highs and lows in the ocean?
Ocean floor - topographic lows
Ocean ridges - topographic highs
What equation is used to quantify the age-depth relationship?
D = 2500 + 350 x t1/2
What does the mantle welling cause?
Partial melts because of drop in pressure. New thin (~5km) Oceanic crust is formed that moves away cm/yr
What heats the earth interior?
Heat trapped from the accretion of the earth and radiogenic heat
How is heat lost in the earths interior?
Convection - bringing rocks that were at depth up
Conduction - the rock is hot, the water is cool
What kind of heat flows occur in the lithosphere and in the asthenosphere?
Lithosphere - conductive
Asthenosphere - convective near adiabatic gradient
What is the density of the asthenosphere, oceanic lithosphere and continental lithosphere?
Asthenosphere - 3.23 gm/cm3
Oceanic lithosphere - 3.27 gm/cm3
Continental lithosphere - 3.15 gm/cm3
What happens to the oceanic crust on top of the underlying mantle?
It sinks as it is denser
The depth of oceans is controlled by the lithosphere thickness. Given that the amount of water has been constant since the Phanerozoic if higher spreading rates have been seen in the past (thinner lithosphere) what effect did this have on the sea level and when?
Higher sea level in Cretaceous
