Earth's Internal Structure Flashcards
what is inside the earth?
layers of different composition formed by differentiation
how is earths volume distributed between the mantle, crust and core?
Crust: 1.4%
Mantle: 82.5%
Core: 16.1%
how is earths mass distributed between the mantle, crust and core?
Crust: <1%
Mantle: 68%
Core: 32%
How do we know about the continental crust?
We live on it
Erosion cuts through the layers
Drilling (to a few km depth)
How do we know about oceanic crust?
Sample the upper layers (seafloor, drilling ships)
Ophiolites on land provide cross-section
why does continental crust sit higher on the mantle than oceanic crust?
thickened continental crust -> high elevations
what is the average thickness of oceanic crust?
6km
what is the average thickness of continental crust?
35-40 km (max >70 km)
what is the composition of oceanic crust?
Mafic (Si,Mg, Fe)
what is the composition of continental crust?
Felsic (Si, Al)
what is the relative deformity of oceanic crust?
relatively undeformed
what is the relative deformity of continental crust?
deformed
what is the age of oceanic crust?
young (<200 Ma)
what is the age of continental crust?
older (max 4.4 billion years)
what is the density of oceanic crust?
Higher (~3.0 g/cm3)
what is the density of continental crust?
Lower (~2.7 g/cm3)
what are the typical rocks in oceanic crust?
Basalt, gabbro
what are the typical rocks in continental crust?
Varied, granite, gneiss
what is the extent of the mantle?
Moho to ~2900km depth
what is the composition of the mantle?
Ultramafic (Mg, Fe)
what is the density of the mantle?
3.3 g/cm3 to 5 g/cm3
↑with depth
what are the typical rocks in the mantle?
Peridotite (olivine-rich)
what is the extent of the core?
Radius ~3500 km
what is the composition of the core?
Outer core: Fe-Ni alloy (+ some O, Si, S)
Inner core: pure Fe