Download Earth`s Layers

Earth’s Layers
7th Grade Earth Science Unit
Earth is made of 4 layers
•
Crust- thin outermost layer
– Continental crust is oldest, thickest, less dense and made of granite
– Oceanic crust is younger, thinner, denser and made of basalt
•
Mantle- 80 % 0f the volume of the earth.
– Upper mantle is rigid, below is the asthenosphere which is a plastic like layer on
which the tectonic plates float.
– There is a huge difference in temperature between the outer mantle and the
inner mantle.
– This difference in temperature sets up a convection current which is responsible
for the cracking and moving of the tectonic plates.
•
Outer Core- liquid layer directly below the mantle (Fe, Ni)
•
Inner Core- solid innermost layer of earth( Fe, Ni)
– Inner core is solid because the pressure is too great to allow it to be liquid
Andrija Mohorovicic
• Yugoslavian scientist, discovered in 1909 that
earthquake waves near the surface moved
slower than ones passing through the interior.
• Discovered that P-waves were deflected in the
interior.
• Decided the crust was less dense then the
mantle due to the fact that waves move faster
through denser material.
• Boundary b\w mantle and crust named Moho
discontinuity.
Lithosphere
• Made of the crust and upper layer of the
mantle
• Broken into 12 large pieces called Plates
Crust
• Where we live
• Made of basalts and granites
• 2 types– Oceanic b\w 3-5mi. Thick
• Is youngest, thinnest, more dense and made of
Basalt
– Continental ~25mi. Thick
• is oldest, thickest, less dense and made of granite
Temperature ranges b\w air temp. – 1600*F
Mantle
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Largest layer 1800mi. thick
Very hot dense rock (mostly S,O,Fe,Mg)
1600*F @ top and 4000*F @ bottom.
Consistency of asphalt
Convection Currents- are caused by the very hot
material at the deepest part of the mantle rising,
then cooling, sinking again and then heating,
rising and repeating the cycle over and over.
(responsible for movement of the plates)
Asthenosphere
• Layer below the lithosphere, zone of
asphalt like consistency (part of mantle
that flows)
Outer Core
• Made of iron and nickel in the liquid state
• 1800mi. under crust and is 1400mi. thick
• Temp. range b\w 4000*F and 9000*F.
Inner Core
• Pressure so great that metal core stays
solid.
• Starts @ 4000 mi. under crust, 800 mi.
thick
• Temp. may reach 9000*F
• Pressure ~ 45,000,000 pounds per sq. in.