By Katie Beck and Charlene Pele BBC World News America

Historians have always had the arduous task of finding scraps of history with which to tell us about the past, but today we are creating a vast wealth of information. So how will historians in the digital age decide what is important?

We know very little, for example, about the Sinagua. A people who lived in what is now Arizona, from the 8th to the 15th centuries.

Aside from their complex cliff dwellings they left behind few clues about how they lived, which makes piecing together a clear picture of their culture near impossible.

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Now, the opposite is true. The explosion of the internet has brought with it an amazing mass of information, being generated at an astounding pace.

Google founder Eric Schmidt says every two days we are creating as much information as we did from the dawn of civilization up until 2003. And this shift is changing the job of historians.

Proactive preservation

Instead of searching for scraps, historians are now confronted by an overwhelming amount of information and what is worth saving needs to be decided as we go along, according to Tom Scheinfeldt, from the Center for History and New Media in Virginia.

"You can't wait until grandma dies for instance to find the letters that she wrote to her sweetheart 50 years ago. That's not going to happen anymore.

"Those e-mails, those instant messages, those tweets, those Facebook status updates, those things are going away unless we actively try to preserve them," he says.

Not everyone may be proactive about saving their history but 24-year-old Melissa Bounoua tries. When she thought that Twitter was going to erase her past tweets she tweeted about her discontent.

With over 5,800 tweets she says some of them are very important to her.

"I was in the US in 2008 the day Obama got elected and I wanted to keep the tweets I wrote the night of the election."

Ms Bounoua now saves the tweets she wishes to keep as "Favourites" in her account.

"But I now have 150 favourites, and it's difficult to find my way."

Today, Ms Bounoua trusts Google and Twitter to save her history for her, at least for now.

"If you know what you were talking about you can find your old tweets on Google now."

However she acknowledges that her Tweets may not be permanent.

"In 50 years, if I needed them, I'm not sure I'd be able to get them."

Web shelf life

Physically this data might exist somewhere but the challenge is making it accessible to future historians.

Brewster Kahle realised this 14 years ago, and he set up the Internet Archive.

Everyone is producing history, everyone has access to history and everyone has to be a historian Tom Scheinfeldt

Based in San Francisco, it has already stored 150 billion web pages in a secure and easily accessible form.

Those pages would otherwise have disappeared, Mr Kahle says.

"The average life of a web page, as best as we can tell, is about 100 days before it is either updated or disappears.

"So, given the growth of the internet and the changing nature of the internet we can fairly certainly assume that most of the good stuff that has been on the net isn't there now," he says.

According to Matt Raymond of the Library of Congress the internet is changing the way in which we archive.

"We are not looking at shelf space, but server space," he says.

"We are grappling with digital migration as a means of preservation, rather than analogue, paper-based preservation. The Twitter archive ratchets up this activity enormously."

Twitter donated its digital archive of public tweets to the Library of Congress in April 2010.

But whose job is it to determine what is worth preserving? Mr Scheinfeldt thinks that we all need to learn to sift through this information with history in mind.

"Everyone needs to know how to look at a Wikipedia article and decide, is this a good article, is this article a bad article, is this source that it references authentic or is it not authentic.

"So not only is everyone producing history, everyone has access to history and everyone has to be a historian in the digital age."

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