GeologyRocks

Welcome to the site.

It could be they're the remains of a flat area that's been eaten away by rivers, rather than being piled up. A photo would help.

Hi Ellz, welcome to geologyrocks!

WHich part of New Mexico is it you visited? I went to the Gaudalupes (sp?) last March for a fieldtrip.

The mountains in Southern New Mexico are caused by faulting and were once dipping quite steeply. This would have formed peaks. However, they have been tilted back to near horizontal by more recent tectonic events. So peaks like El Capitan are very nearly flat as the main sedimentary layers are also nearly flat. Most erosion occurs along these layers or at the edges of the layers, hence you get a flat-top mountain. Mountains with peaks are formed of twisted and contorted beds that are rarely horizontal.

Dan's explaination also works - especially the Canyons area of the States (Dry, Grand, etc Canyon).

A picture here would say a thousand words - I'll have to see about getting a whiteboard of some kind set up. Another thing to add to my to-do list

Hope this helps!

Jon