Here is a link detailing the geologic history of the mountains surrounding DF, the Trans-Mexican Volcanic Belt. 
http://www.mantleplumes.org/Mexico2.html

some beach trash photos of mine
http://www.flickr.com/photos/janesko/sets/72157623617823583/with/4549053547/

some Palo Alto dumpsters and trash
http://www.flickr.com/photos/janesko/sets/72157623800532879/with/4590435901/

-David Janesko