Joe, I felt somewhat like you expressed about central peaks. When I read the comment about central peaks requiring a certain force I looked around on the moon and was surprised how many small creators didn’t have central peaks. There are also a lot of big creators with out central peaks either. So, I am still not satisfied that I know enough. You wrote Ø As stop-motion photography of something as tiny as a drop of water proves, when a drop falls into a pan of water for an instant it forms a crater and an interior peak -- all water, of course.< Ø < I love to watch that water drop too. I think you can see as well as I can that it requires a certain amount of liquidity or plasticity to make that central peak form. When a 1 km rock comes in at super hight speed it is not hard for me to imagine the punch it carries has the ability to turn rock into plastic for a short period. I just don’t know enough to say when or what threshold is required to meet those requirements. It was sure fun watching Shoemaker-Levey 9 punch into Jupiter though. So, I will keep gathering data on this as it comes along and maybe learn something along the way. Jim PS I remember watching Gene Shoemaker on TV shooting a high powered rifle from a high bluff down into a sandy wash then going down and inspecting the creators the bullet made. That was one techneque he used to study impact crators. --- On Wed, 1/28/09, Joe Bauman <josephmbauman@yahoo.com> wrote: From: Joe Bauman <josephmbauman@yahoo.com> Subject: Re: [Utah-astronomy] More on Upheaval Dome To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Wednesday, January 28, 2009, 11:55 AM Jim, I feel sure there can be interior peaks in relatively small impact craters; it probably depends on factors like the material that was hit and the mass of the incoming object. As stop-motion photography of something as tiny as a drop of water proves, when a drop falls into a pan of water for an instant it forms a crater and an interior peak -- all water, of course. -- Joe --- On Wed, 1/28/09, Jim Gibson <jimgibson00@yahoo.com> wrote: From: Jim Gibson <jimgibson00@yahoo.com> Subject: Re: [Utah-astronomy] More on Upheaval Dome To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Wednesday, January 28, 2009, 11:10 AM I was just recently reading about interior mountains (central peak) within impact creators on the moon. As I recall (be on guard) I remember one writer saying that there were no interior mountains in creators less than 60 miles across. It seems that it takes a certain amount of size hence pressure to create a central peak. Just seems interesting that Upheaval Dome is barely 3 miles across and has a central peak, or does it? Maybe it is just the angle of Kurt’s photo. Jim Gibson _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com