SAN FRANCISCO - Google Inc. on Monday launched a new version of Google Earth that allows users to explore the oceans, view images of Mars and watch regions of the Earth change over time.

The new features mark a significant upgrade to Google Earth, a popular software program that provides access to the world's geographical information through digital maps, satellite imagery and the company's search tools.

Google Earth 5.0 was unveiled at the California Academy of Sciences in San Francisco, where former U.S. vice-president Al Gore, singer Jimmy Buffet and others spoke about its capacity to educate the public about global warming, ocean acidification and other threats to the planet.

"This is an extremely powerful educational tool," said Gore, who won a Nobel Peace Prize for his work raising awareness about climate change. "One of my fondest hopes is that people around the world will use Google Earth to see for themselves the reality of what's happening because of the climate crisis."

Google Earth has been downloaded more than 500 million times since it was launched in 2005. The software is available for free on Google's website. Researchers and organizations can purchase a more powerful version for $400.

John Hanke, director of Google Earth and Maps, said the idea of adding oceans came three years ago when a scientist pointed out that the software was missing the water that covers almost three-quarters of the Earth's surface.

Google Earth users can now plunge beneath the ocean's surface, explore three-dimensional images of the underwater terrain and view articles and videos about marine science contributed by scientists and organizations such as the National Geographic Society.

The Historical Imagery feature lets users see archive satellite images of individual locations to see how the region has evolved over time as a result of climate change and other forces. For example, viewers can observe how the largest glacier in Glacier National Park has melted over the past decade.

With Google Mars 3-D, users can view three-dimensional, satellite imagery of the red planet taken during NASA space expeditions.

A Halifax company is among the organizations that are providing a look at ocean terrain. Eco-Nova Productions Ltd. produces underwater television documentaries of shipwrecks from around the planet.

Users who click on the shipwrecks tab in the ocean layer of Google Earth are taken to sites that have been explored by Eco-Nova Productions and are able to view videos and other content generated by the company.

"With this latest version of Google Earth ... you can now dive into the world's oceans that cover almost three-quarters of the planet and discover new wonders that had not been accessible in previous versions of this magical experience," Gore said in a statement.

Google CEO Eric Schmidt said the oceans are often an overlooked piece of the climate change debate.

"About one-third of the carbon dioxide that we emit into the atmosphere ends up in the oceans," he said in a news release.

The new version also allows users to created narrated tours of places using the software's content and images.

"It's not just a fun demo," said Schmidt. "What it really is is a platform for science and research and literally understanding the future of the world."

Also featured in the new oceans layer of Google Earth is a National Geographic Magazine quiz and videos from the archives of Jacques Cousteau.

John Hanke, director of Google Earth and Maps, described the gap in oceans coverage as a "serious omission" in the company's online searchable replica of the planet.

The new feature was developed with the help of Sylvia Earle, an oceanographer and National Geographic's explorer-in-residence.

"For the first time, everyone from curious kids to serious researchers can see the world, the whole world, with new eyes," she said.