Which is closer to the Earth’s center…

…the Kola Borehole or the Challenger Deep?

(Question on behalf of Iris, age 10. I can’t figure it out.)

I believe the Kola Borehole is deeper by 1,300 meters than The Challenger Deep according to this. One is measured from ground level and the other is measured from sea level. I assume that makes the hole closer to the earth’s core/center than the deep.

Definitely the Kola Borehole. Challenger Deep is near the equator, while Kola Borehole is near the pole. In fact, the surface at Kola is almost certainly closer to the center of the Earth than the bottom of the Challenger Deep.

seems the Kola wins.
The Deep is 11K from sea level. The Borehole is 12K in depth from the surface.
Looking up the elevation of a town near the Borehole, No idea how near. it may be around 5 m above sea level.

AFAICT, the question is not which is deeper from the top, but which hole’s bottom
is nearer the earth’s center.

Chronos took that into account, as I did not. Works both ways as is. But not if their positions were reversed.

From National Geographic -

. Earth’s diameter at the Equator is about 12,756 kilometers (7,926 miles). At the poles, the diameter is about 12,714 kilometers (7,900 miles). Earth’s equatorial bulge is about 43 kilometers (27 miles) .

The Kola borehole, being at the very north end of European Russia, is pretty much the winner.

Looking up the Challenger Deep led me to this fun site:

The Deep Sea

Happy scrolling.

While we’re at it with the bulge, the head of the Mississippi River is closer to the center of the Earth than the mouth is.

Paris (at the surface) is closer to the center of the Earth than the bottom of the Challenger Deep.

Interesting. I’ve been to the head of the Mississippi River; you can cross it on stepping stones where it flows out of Lake Itasca.

If you wanted to find the true source of the Mississippi, I think it would be one of the streams that flows into Lake Itasca. But there’s a nice park at the Lake, so everyone just kinda goes along with it.