In the past the crater was flooded by lava, leaving only the outer rim intact. There are gaps in the eastern and western rims, leaving two "half-moon" mountainous formations facing each other across the relatively flat floor. There is a similar lava-flooded crater remnant attached to the southern rim of Thomson. The floor of Thomson has a number of secondary impacts that form short, linear streaks across the surface.
| Thomson | Latitude | Longitude | Diameter |
|---|---|---|---|
| J | 35.9° S | 169.6° E | 44 km |
| M | 35.7° S | 166.0° E | 119 km |
| V | 30.7° S | 162.2° E | 13 km |
| W | 30.2° S | 163.3° E | 17 km |