Earth's Three Layers
Earth's coolest, thinnest, and least dense compositional layer, making up less than 1% of total planetary volume.
What is the crust?
The coarse-grained, silica-rich rock type that makes up the bulk of continental crust.
What is granite?
The two metallic elements that combine with silicon and oxygen to dominate the chemical composition of the mantle.
What are iron and magnesium (or Fe and Mg)?
The chemical symbols for the two predominant metallic elements that make up Earth's core.
What are Fe and Ni?
D=MV this physical property determined the layering of materials inside Earth.
What is density?
Earth's volumetric giant extending roughly 2,900 kilometers deep, containing about 84% of the planet's total volume.
What is the mantle?
The dense, dark igneous rock type that primarily forms the thin oceanic crust beneath ocean basins.
What is basalt?
The dense, ultramafic silicate rock, rich in iron and magnesium, that forms the chief constituent of the mantle.
What is peridotite?
The approximate density range of Earth's metallic core in g/cm^3.
What is 9.9 to 13.0 g/cm^3 (accept average around 12.0 g/cm^3)?
The geological process during early planetary history where molten materials separated into distinct layers based on density.
What is planetary differentiation?
The dense central sphere of our planet composed almost entirely of metallic iron and nickel.
What is the core?
The approximate average density of continental crust in g/cm^3, allowing it to float buoyantly above the mantle.
What is approximately 2.7 g/cm^3?
The approximate density range of the mantle in g/cm^3, spanning from its upper boundary down to the core boundary.
What is 3.3 to 5.7 g/cm^3?
The non-contact force acting at a distance that pulled dense metallic iron and nickel toward Earth's center during its molten stage.
What is gravity (or gravitational force)?
If molten quartz (2.65 g/cm^3), molten basalt (3.0 g/cm^3), and molten copper (8.96 g/cm^3) are mixed and allowed to settle, this material rests at the very bottom
What is molten copper?
The maximum distance in kilometers that humans have physically drilled into Earth's surface (less than 0.2% of the way to the center).
What is 12 kilometers (or approximately 7.5 miles)?
The typical thickness range in kilometers of oceanic crust.
What is 5 to 10 kilometers?
The energy waves generated by earthquakes that geologists analyze to reconstruct the composition and boundaries of Earth's interior.
What are seismic waves (or earthquake shockwaves)?
The physical state of matter of the outer core that causes an abrupt change in seismic wave behavior at 2,900 kilometers depth.
What is liquid (molten metal)?
The two primary early planetary heat sources that kept young Earth completely molten, enabling gravity to separate materials by density.
What are heavy bombardment and radioactive decay?
The sharp compositional boundary where seismic wave speeds abruptly jump as waves travel from crustal rock into dense mantle rock.
What is the Moho boundary (or Mohorovičić discontinuity)?
The physical reason oceanic crust sinks lower into the mantle than continental crust, creating low-lying ocean basins.
What is higher density (oceanic crust is denser at approximately 3.0 g/cm^3?
The deep planetary property that, together with elasticity, dictates how fast seismic waves travel through mantle rock.
What is density (rock density)?
The consistent mathematical trend in rock density observed as an observer moves from the outer crust all the way to the center of the core.
What is strictly increasing (density increases with depth)?
In three sealed boxes of identical volume, this specific physical property varies because internal elements have different atomic packing.
What is mass (or density)?