Although it may not be obvious at first glance, the bay side of San Francisco is largely artificial. The huge increase in population associated with the California Gold Rush of the mid 1800s resulted in San Francisco becoming the major port on the west coast. In some cases, people seeking riches in the Sierra Nevada headed off to the mountains and simply abandoned their ships in San Francisco. Some of these ships ended up being used as landfill and, year after year, the shoreline along the northern and eastern sides of the city was modified.

The area where Market Street meets the Embarcadero was among the earliest areas to be extended into the bay, but landfill — a combination of sediment dredged from the bay with rubble — continued to be used to create new "land" for decades to come.

The map below* shows this modification quite nicely. Original creeks and streams are in blue, marshes in aqua-green, and modern landfill in pink.

What I like about this map is how the pink landfill areas highlight the old shoreline. Note where the original creeks and marshlands met the bay. What is now a relatively straight shoreline was once very irregular with several natural embayments. Mission Bay was once an actual bay. I find it fascinating to picture the city in this way — the way it was a little over a century ago.

The areas that are now landfill are important to consider not just as interesting history, but also in the context of earthquake hazards. Last week I discussed Bay Area seismic hazard preparedness and an important component of getting ready is to learn about how different types of land respond to the shaking.

The map above** was produced by the USGS and shows the liquefaction hazard — red is very high hazard, orange is high, yellow moderate, green low, and no color is very low. Liquefaction is essentially when loose sediment behaves like a fluid when shaken, which can result is serious damage to buildings and houses.

Note the correspondence between the red areas on the liquefaction hazard map with the map showing where landfill and old marshes are. While it may seem like solid ground when you are walking or driving on the street it's important to remember that the fill underneath is quite loose compared to actual bedrock.

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* This great map, and many more, can be found at the website for the Oakland Museum of California: http://museumca.org

** See the entire zoomable map, learn more about liquefaction hazard, and how the USGS made this map here.

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Credit: California High Speed Rail Authority

Starting with California's state-wide propositions, we have Proposition 1A: Safe, Reliable High-Speed Passenger Train Bond Act. The proposed train would zip from San Francisco to LA in a mere two and a half hours, if voters approve a $10 billion bond. QUEST did a TV story on the science and politics of the high-speed rail last year, and updated it in a web-only video for this year's election. Check out High-Speed Rail on the Ballot. And listen to QUEST's radio story, Fast Trains.

Next, Proposition 2: Standards For Confining Farm Animals. If passed, this proposition would require bigger crates for certain farm animals. It is mostly about animal cruelty, but has implications for human health – and California's egg industry. Listen to The California Report's coverage of the pros and cons of Proposition 2.

Proposition 7: Renewable Energy Generation, would require utilities to get 50% of their power from renewable sources. It sounds straightforward, but actually this one is controversial. Things are explained in this QUEST radio story, Big Solar on the Ballot.

Then we have Proposition 10: Alternative Fuel Vehicles and Renewable Energy, which combines funding for solar and wind energy research with consumer incentives to encourage the use of clean fuels. There is controversy, because the proposition gives extra bonus points to some alternative fuels, but not others. Check out the coverage by the California Report.

There are three measures across the Bay Area concerning open space: Measure WW in Alameda and Contra Costa counties, Measure P in Napa county and Measure T in Solano county. Listen to a discussion of these measures with the executive director of The Greenbelt Alliance, in this KQED Radio News story.

And in San Francisco, Proposition H lets voters decide whether the electric utilities should be publicly owned. This would give the city flexibility in terms of obtaining power from renewable energy sources, but it's hard to say how it would affect the price of electricity. Reporter Cy Musiker and Craig Miller, senior editor for KQED's Climate Watch series, debate Prop H in this segment from KQED Radio News.

Figure out your opinions on these science and environment issues – and check KQED's Election 2008 page, for additional election coverage. Then voice your opinions, with your vote, and your comments to this blog!

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