Delineating all area above a certain contour line... What is this called?

[CoreyChin]

Hello,

If you were to take a certain elevation threshold (contour line) and select all area ABOVE that line, you might end up with a polygon that is essentially a mountain top. I work for a non-profit organization that works primarily in watersheds but we also work in places like the buffer area surrounding the Mt. Kilimanjaro National Park and the Foret des Pins in Haiti to restore and protect the land, where the project boundary is defined by an elevation threshold (roughly). 

A couple questions:

1. What is this area called? It's somewhat of an aggregation of upper watersheds, but surely not called a "watershed"...

2. Is there a tool in ArcGIS that delineates these cleanly? We currently create contour lines and select one line and extract it. Seems to work but wondering if there is a more direct method. 

Below is an example (not mine. From Wikipedia - Topographic Prominence) of the type of boundaries I am trying to describe.

[SteveLynch]

Corey

Have you looked at Contour shell and Contour shell up in the Contour tool?

Available in ArcGIS Pro 2.2+ and ArcGIS Desktop 10.6.1+

-Steve

[CoreyChin]

Thank you, Steve! I was not aware of Contour shell or shell up until now. 

Is there a name for this type of land area? Or is there any terminology that I should be aware of that might help describe it?