primary crater

primary crater

[′prī‚mer·ē ′krād·ər]
(geology)
An impact crater produced directly by the high-velocity impact of a meteorite or other projectile.
References in periodicals archive ?
They also found 248 small "splotches" which extended up to 30kms from the primary crater. rof Robinson said that his team found hundreds of similar splotches around other lunar craters - and that some of these were "directional."
The Davy chain is problematic; there's no obvious primary crater, and the craterlets are strung out in an arc.
Later spacecraft images showed that rays comprise rock powder ejected from the primary crater as well as ejecta churned up by secondary impacts.
These are now recognized as "secondary craters" made by chunks of ejecta splashed from the impact that created the primary crater. The rays themselves are patterns of ejecta.
Closer examination of these Copernicus secondaries reveals that they are more complicated than similarly sized primary craters. That is because of two factors: their shapes and their configurations.
The ejecta that form secondary craters travel only about 10% as fast as the cosmic projectiles that excavated the primary craters. So instead of digging deep and beautifully circular craters, the impact of ejecta often creates elongated gashes.

Full browser ?