AST101H1 Lecture : 9.5-Geology of Venus, 9.6-Geology of Earth
2 Aug 2010
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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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Document Summary
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. Lacks small craters they burn up as they enter venus thick atmosphere. Abundant evidence of lava plains and many volcanic mountains. Outgassing supplies sulfur dioxide to the atmosphere the clouds contain sulfuric acid. Curst is quite contorted surface 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) Far too hot for any type of rain or snow.
