Question

scientist studies the seismograph data shown.



Wave Type Depth (km) Speed (km/s) Wave Type Depth (km) Speed (km/s)
P 1000 7 S 1000 5
P 1500 9 S 1500 5.4
P 2000 11 S 2000 5.8
P 2500 13 S 2500 6.2
P 3000 6 S 3000 0
P 3500 7 S 3500 -
P 4000 8 S 4000 -




What can the scientist most likely conclude about Earth’s structure from this data?


The crust transitions to the mantle approximately 1000-1500 km below Earth's surface.


The mantle transitions to the outer core approximately 1500-2000 km below Earth's surface.


The mantle transitions to the outer core approximately 2500-3000 km below Earth's surface.


The outer core transitions to the inner core approximately 3500-4000 km below Earth’s surface.

Answer 1

The mantle transitions to the outer core approximately 2500–3000 km below Earth's surface.

Reason: S-waves are present down to 2500 km but disappear at 3000 km (S = 0), and P-wave speed drops sharply at that depth. S-waves cannot travel through liquid, so this marks the solid (mantle) to liquid (outer core) boundary.