Conical?
Which end do *YOU* mean by "top"
The start of the flow is the uphill end, in the Alcove (which is a bit conical, but more of a scoop shape). The core of the flow is the channel. The end of the flow is the conical distributory fan.
Many features on Earth have this conical form at the terminus e.g. in sandpits, grain silos, Death Valley, the Nile Delta...
Anywhere that stuff piles up from a sediment source.
If you're asking about the Alcove - well it's basically a hollow cone because everything is funnelling down into the channel.