MIT was reported to have calved subsequent to being rammed by a large iceberg. However from remote sensing, the ice fronts being rammed did not move out first which led us to detect the influence of seafloor on instability of MIT. Using Firn Air Content extracted from slightly grounded icebergs, laser altimetry, remote sensing, and seafloor topography data, grounding of the MIT caused by Mertz Bank is extracted. Mertz Bank is confirmed to control calving of the MIT at a cycle of ~70 years.