In the upper crust, P-waves travel in the range per second (or lower) in soils and unconsolidated sediments, increasing to per second in solid rock. In the lower crust, they travel at about per second; the velocity increases within the deep mantle to about per second. The velocity of S-waves ranges from per second in light sediments and per second in the Earth's crust up to per second in the deep mantle. As a consequence, the first waves of a distant earthquake arrive at an observatory via the Earth's mantle.