Inundated crater, Buried crater, Blanketed crater, Covered crater, Filled crater

The many English terms all describe the same situation: an impact crater flooded, mantled or completely buried by some material.

Craters are natural sediment traps. Various sediments slowly build up inside them. These can come from above, such as ash or snow falling from the atmosphere. They can come from the side, such as material from the crater wall, worn down slowly or quickly in landslides. Or they can come through a breach in the rim: a river breaking through the rim carries its load into the crater. A worn-down or breached crater rim cannot stop lava flows from outside, either. So lava can also flood the crater, partly or completely.

Intense or long-lasting volcanism, or falling material, can in time bury a crater completely. Its site is then shown only by inherited relief or other signs.

Besides these scenarios, the ejecta blanket of a neighbouring crater can also mantle a crater.

The crater Alcott, shown on the plate, was flooded by fluid basalt lava flows from the neighbouring Mylitta Fluctus. To do so, they had to break through the crater rim at one point.

Flooded craters can help with dating where crater counting gives no result (because craters are placed at random). Ivanov and Head (2015) looked at the share of craters flooded by different lava plains that follow one another in the stratigraphic sequence. Data from Schaber et al. (1998) show that about 6% of the craters of Venus are flooded.

Of the craters that struck the older lava plains (lower in the sequence), 3% were flooded by these older lavas. Of the craters on the younger lava plains (lobate, higher in the sequence), however, lobate lavas flooded 33%.

Where fewer craters were flooded, the volcanic material was laid down faster, in more intense floods. Assuming a steady rate of crater formation, volcanism stayed active after the impact for only 3% of the craters in that area. Where a larger share of craters was flooded, the lavas must have flooded the surface over a much longer time, that is, with lower intensity (more slowly). Here volcanism was still active in the area after 33% of the impacts. So this method can estimate how long each lava plain took to form, that is, how long the volcanic activity lasted.