Here's a breakdown:

* Earth's crust: The outermost layer, about 5-70 km thick.

* Earth's mantle: Extends from the base of the crust to about 2900 km deep. It's primarily solid rock, but it behaves like a very viscous fluid over long periods.

* Earth's outer core: Lies between 2900 km and 5150 km deep. It's composed of liquid iron and nickel.

* Earth's inner core: Extends from 5150 km to the Earth's center at about 6371 km. It's mostly solid iron and nickel, despite the immense heat and pressure.

Since 6000 km lies between the outer core's upper boundary and the inner core's lower boundary, it's located within the Earth's mantle.