this is different then a caldera?
As this ignorant layman understands such things . . .
a caldera is a large . . . usually oblong/oval . . . area miles in dimensions which was once the site of a huge eruption spewing many cubic miles of material usually high into the atmosphere in a super volcano eruption.
I suppose some caldera are not super volcano sized.
There are often smaller eruptions in the same caldera after the main huge one originally forming it.
The caldera may form a rough bowl/depression shape . . . though there’s usualy ages enough of erosion, later smaller eruptions and perhaps other quake related deformations along with the vast size . . . and altered, quite varied landscape within them . . . that many caldera were not perceived to be caldera initially.
I think that’s about all I have off the top of my head. Perhaps someone that knows what I’ve tried to talk about much better can correct me.
Oh, the caldera is on the surface . . .
the magma or magma plume is usually quite deep . . . sometimes coming nearer the surface in the case of volcanoes.
. . . particularly say in Hawaii.