| Abbreviation | Definition |
|---|---|
| MGR | Marine Geology Repository |
| MGS | Maine Geological Survey |
| MGS | Maryland Geological Survey |
| MGS | Michigan Geological Survey |
| MGS | Mississippi Geological Society |
| MHT | Micro Hardness Tester |
| MIGI | Metadata Integration and Geodata Integrity |
| MIS | Mountain Ice Sheet |
| MISB | Mississippi Interior Salt Basin |
| MMRI | Mississippi Mineral Resources Institute |
| MNA | Mina, Nevada, Seismograph station |
| MNFI | Michigan Natural Features Inventory |
| MNT | Moist Nonacidic Tundra |
| MNT | Mount |
| MNT | Mountain |
| MNTP | Midewin National Tallgrass Prairie |
| MOB | Middle Of Beach |
| MORB | Mid Oceanic Ridge Basalt |
| MPRC | Minerals and Petroleum Reference Centre |
| MPT | mid(dle) pleistocene transition |