. >> more now about these mammoth findings that come from kirk johnson, vice president and chief curator at the denver museum of nature and science who is feetured in the nova documentary. thanks for being with us. first, who stumbled upon this? >> it was a bulldozer operator named jesse steel who was pushing dirt in 2010 and ran his bolder right through a young female mammoth skel don. >> reporter: he obviously didn't know it and does the first best thing, called the museum? >> he didn't call the museum. he called the supervisor who called the property owner who called the museum and we went out and looked at the site. it was a beautiful little elephant. we thought that's great and as we looked around the site more we realized there was more than one elephant. there were bones all over the place. >> now we know this is one of the largest dig sites in american history. put it in perspective for us. how many bones did you find, and how much time? >> we dug for 69 total days. we had enough volunteers digging that we worked 3,200 person day efforts and found over 5,000 bones. i have one rig

. >> reporter: all right, kirk johnson from the denver museum of nature and science, thanks so much for your time. >> hey, my pleasure. thank you very much. >> ifill: "ice age death trap" airs tonight on "nova" on most pbs stations. >> woodruff: again, the major developments of the day. the republican presidential candidates headed west after mitt romney's resounding victory in florida. at least 73 people were killed in egypt when a soccer match erupted into a riot and stampede. and facebook gave formal notice that it's going public with a stock offering that could raise $5 billion. there's more about our "american graduate" series online. kwame holman has the details. kwame? >> reporter: join a live chat on friday at 1:30 pm eastern. we'll talk with victor rios, the college professor in tonight's report, and documentary photographer richard ross. find the details on our home page. and on our politics page, patchwork nation breaks down the votes for mitt romney and newt girich in different community types in florida. all that and more is on our web site, newshour.pbs.org. judy? >> woodr

. >> south dakota democrat tim johnson, who suffered a stroke several years ago, paying tribute to senator mark kirk who is now in fair condition at a chicago hospital. >>> this is "washington today" on c-span radio. we will continue the conversation. a look at the results from the florida primary. we will talk about jobs and manufacturing with congress member tim ryan. he is the democrat from the youngstown area. he is a member of the house bud budget committee. senator jim demint. he has a book. "now or never, saving america." thanks for being with us on this tuesday and a reminder. live coverage on c-span radio as we watch the results from florida. thanks for being with us on this tuesday. enjoy the rest of your evening. >>> coming up on c-span3, richard cordray, the head of the consumer financial protection bureau testifies on capitol hill. then, a senate hearing on u.s. domestic energy production. later, the defense department undersecretary for policy gives her last speech before stepping down on friday. >>> c-span's road to the white house political coverage takes you to the candidate events.