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Lecture

9.5-Geology of Venus, 9.6-Geology of Earth


Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
C.B.Netterfield

Page:
of 2
9.5 Geology of Venus
-surface is searing hot with brutal pressure
-radius is only about 5% smaller than Earth
-Radar mapping: a way to study its geological features through the bouncing of radio waves off the
surface and using the reflections to create a 3-D images of the surface
-has some impact craters but far less than Mercury, the Moon or Mars
-the surface is about the same age everywhere
-surface of Venus is about 750 million years old
-no craters from the heavy bombardment remain
-lacks small craters Æ they burn up as they enter Venus· thick atmosphere
-volcanism is clearly important
-abundant evidence of lava plains and many volcanic mountains
-outgassing supplies sulfur dioxide to the atmosphere Æ the clouds contain sulfuric acid
-tectonic in origin
-curst is quite contorted ²surface appears to be fractured in a regular pattern
-other tectonic feature, coronae, point directly to mantle convection on Venus
-probably formed by hot, rising plumes in the mantle (may also push lava up to surface)
-lots of volcanoes around the coronae
-lack erosion on Venus compared to Earth
-far too hot for any type of rain or snow
²has virtually no wind or weather because of its slow rotation (once every 243 days)
-lack of plate tectonics suggests
-weaker mantle convection
-lithosphere somehow resists fracturing
-lack of plate tectonics because of its high surface temperature leading to loss of water and lithosphere
thickening
9.6 Geology of Earth
-remains volcanically and tectonically active
-outgassing Æ liquid because the temperatures are in range
-erosion by water and wind is explained by planet·s size, distance to Sun and rate of rotation
-rapid rotation drives erosion
-unique because of the style of tectonics
-(plate tectonics: the scientific theory that explains much of Earth·s surface geology as a result of the
slow motion of plates)
-earth·s lithosphere is broken into more than a dozen plates
-continental drift: the idea that continents gradually drift across the surface of the Earth
-seafloor spreading: explained how continents could move apart with time
-mantle material erupts onto the ocean floor Æ pushing apart the existing seafloor
-earth·s surface has two types of crust; seafloor crust, continental crust
-seafloor is thin, dense and younger than continental
Earth shaped by plate tectonics
-subduction: where a seafloor meets a continental plate
-generally offshore at the edge of a sloping continental shelf
-the denser seafloor crust of on pelage pushes under the less dense continental crust of another plate
Æ can from an ocean trench
-continental does not get recycled back into the mantle
-build up and push each other
-continental plates pull apart Æ crust thins Æ can create a large rift valley
-faults: places where plates slip sideways relative to each other
-fractures in the lithosphere
-when the plates don·t slip smoothly and their rough surface catch against each other Æ stress builds
up Æ rapid, violent shift Æ earthquake
-hot spot: -Hawaiian Islands Æ plate tectonics carries the Pacific plate over the hot spot, forming a
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chain of volcanic island
-about 200 million years ago, continents were a supercontient, Pangaea
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