Mar 200 Unit 1- Ch2
Evidence shows that periodic reversals of Earth's magnetic field have resulted in
a symmetrical pattern of normal and reverse magnetization in ocean crustal rocks
paleomagnetism
analyze magnetic particles in rocks to determine north and south direction and magnetic dip that is directly related to latitude
Which of the following is characteristic of oceanic-continental convergent plate boundaries?
andesitic volcanoes
Which of the following is characteristic of continental-continental convergent plate boundaries?
uplifted mountain ranges
Which of the following is characteristic of oceanic-oceanic convergent plate boundaries?
volcanic island arcs
highest to lowest severity of earthquakes
convergent most severe, transform, divergent
Wegener hypothesis (reason 1)
-continents can fit together (matching shoreline) that was once one large landmass= pangaea -split once masses started to drift -huge ocean= panthalassa surrounded pangaea
Magnetic Field
-determined where rocks first formed on earths surface -north and south pole: geological pole and magnetic pole do not match
plates
-major and micro plates -litho broken to pieces that float on asthenosphere
Plate tectonics
-new global geology -outermost part of Earth is composed of patchwork thin rigid plates that move horizontally with respect to one another (like iceberg floating on water) -continent's are mobile and move by controlled forces
magnetite deposits in sediment
-sediment surrounded by water allows magnetite to align with the field -sediment buried and solidifies into sedimentary rock, particles cant align themselves and they are moved -most reliable igneous rock have high [basalt]
deposits (300 MYA) indicates
1. was a global ice age 2. some continents that now are in tropics were once near one of the poles
Alfred Wegener
A German scientist who proposed the theory of continental drift; they move
What is a volcanic arc?
a row of volcanoes that forms on the overriding plate near a subduction zone
Where is the youngest ocean floor found?
along the crest of mid-ocean ridges
Wegener reason 2
chemistry of rocks and age of mountains are identical along edge of continents (formed at same time and place) EX: Appalachian MT rock similar to Caledonian Mt separated by ocean with similar rock
climate distribution
controlled by latitude
divergent vs convergent vs transform
d- move away c- move toward t- move side by side
What would happen to Earth if ocean floor were created at divergent boundaries at a faster rate than it is destroyed at convergent boundaries?
earth increase in volume
Wegener reason 3
fossils revealed from non-swimmers in a population (once on same land mass) EX: fossils of same aquatic reptile in South America and Africa separated by ocean
Wegener 4
glacial scarring- glaciers expand out from the center point of snow and rip apart land -the consistent flow of grooves through continents
change in magnetic polarity identified in rocks
gradual decrease in intensity of field of one polarity, followed by increase in intensity of other polarity
magnetic dip
increase with increasing latitude -dip angle reveals where rock originated
magnetite
its in magma and aligns with earth magnetic field bc magma and lava are fluid -molten material cools and records angle of earths magnetic field at that place and time (compass recording strength and orientation of earths magnetic field
divergent boundaries features
mid-ocean ridges and continental rift valleys
convergent boundaries features
ocean trenches and volcanoes
magnetic polarity reversals
polarity has reversed itself periodically throughout geologic time How? earth rotation= liquid iron outer core to generate magnetic field, flow of liquid iron is disturbed and twist field in opposite direction -takes about 5000 years
igneous rock
solidify from molten magma underground or after volcanic eruption at surface producing lava -contain magnetite (magnetic iron metal)