Assertion: terrestrial planet's material | /r/HasAspect | low densities
Facets:
value: relatively
type: DEGREE
Source sentences:
text: Near the surface the bonds are relatively long and "loose" and the predominant materials (olivine and similar ferromagnesian silicates) have relatively low densities (3.5 to 4.5 tims the density of water, which is much less than the average density of the Earth); but at greater depths the weight of the overlying material pushes the atoms closer together, making the bonds between them shorter and stiffer, thereby (1) increasing the density of the material (since the atoms are closer together they take up less room), (2) increasing the melting temperature (shorter bonds are stiffer and harder to break, which is a requirement for melting the minerals), and (3) increasing seismic wave velocities (shorter, stiffer bonds cause the impulse received by one atom to be transferred to the next atom at a more rapid rate).