Google overlaid digitised historical maps onto Google Earth to commemorate the annual Geography Awareness Week last week.

The “mash up” - technical speak for the mix of content - used maps from enthusiast David Rumsey and was aimed at educating users on the history of the world. It included content dating back to the 17th century so that users could compare the old and new world through a transparency slider found on the page.

“This morning was incredibly exciting for me: when I opened up Google Earth, there were 16 of my historical map features floating serenely on the Google Earth globe,” David Rumsey, wrote in a Google blog.

“The cartographers and explorers who made these historical maps hundreds of years ago would be amazed and thrilled to see their maps in Google Earth. For me it is a perfect example of creative reuse of historic materials that the Web, thanks to Google, is making possible.“

Google Earth also partnered with National Geographic to mix interactive geography quizzes with maps that test users' knowledge of Africa, which was the focus of this year’s Geography Awareness Week.

John Hanke, director of Google Earth and Maps, said: “Our work with David Rumsey to bring some of the finest privately held historical maps to users worldwide further demonstrates how Google Earth can serve as a dynamic tool for geographic discovery.”