The depth of any crater in a solid planet or moon - whether it is an impact crater, a volcanic crater, or a subsidence crater - may be measured from the local surface to the bottom of the crater, or from the rim of the crater to the bottom.
The diagram above shows the full (side) view of a typical crater. Depth "A" measures from the surface to the bottom of the crater. Depth "B" measures from the mean height of the rim to the bottom of the crater.
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