You know Mount Diablo. But do you know what kind of rock it's made of? Photo by Andrew Alden

If you’re like me, one highlight of your Christmas celebration is the consternating quiz that columnist Jon Carroll publishes in the San Francisco Chronicle every year. Acknowledging the greatness as well as the priority of the Carroll quiz, I am humbly pleased to bring a geological version to the pages of KQED Quest Science Blogs. The quiz is centered on the Bay Area, which in addition to its other virtues is a premier destination for Earth scientists.

There are 20 questions, each with one correct answer. Some answers may be found in my posts from this year. Some answers can be found on Google and others cannot, but you’re coolest if you don’t need to search. There is one big hint on this page.

And now the fine print: No prizes are awarded; answers will be added to this post on Boxing Day; until then please post questions, not answers, in the comments. All right? OK!

1. What is California’s state rock: gold, mariposite, quartz, serpentine?

2. How big was the 1906 San Francisco earthquake: 7.8, 8.0, 8.2, 9.0?

3. Which of these places is on the North American plate: Aptos, Bolinas, Colma, Davenport?

4. Which of these places is on the Pacific plate: San Francisco, San Jose, Santa Clara, Santa Cruz?

5. What is the highest magnitude earthquake that the Hayward fault is capable of: 6.7, 7.0, 7.5, 8.0?

6. Mount Tamalpais is primarily what rock type: blueschist, chert, marble, melange?

7. What mineral resource has NOT been produced in the Bay Area: coal, mercury, petroleum, uranium?

8. What fossils are NOT found in the Bay Area: ammonites, dinosaurs, hypsodonts, mammoths?

9. What fault continues north where the Hayward fault ends: Calaveras, Rodgers Creek, San Andreas, Zayante?

10. Mount Hamilton is primarily what rock type: gneiss, granite, graywacke, greenstone?

11. What fault continues north where the Concord fault ends: Flint Hills, Green Valley, Greenville, Maacama?

12. Which Spanish word tells you there was once a lime kiln here: calabaza, calavera, calera, calesitas?

13. The San Gregorio fault occurs onshore in what county?

14. Franciscan rocks are mapped in 14 different entities called what: belts, formations, melanges, terranes?

15. What rock type is at the top of Mount Diablo: basalt, harzburgite, rhyolite, schist?

16. Which entity allows personal fossil collecting: BLM, Caltrans, Coastal Commission, state parks?

17. Which North Bay mountain is an actual (former) volcano: Burdell, Konocti, St. Helena, Tamalpais?

18. Mount St. Helena is primarily what rock type: diatomite, serpentinite, slate, tuff?

19. What kind of ore was mined south of Livermore during World War II: iron, magnesium, uranium, vanadium?

20. Where is the Bay Area’s only geyser: Calistoga, The Geysers, Great America Park, Mount Diablo?

And here are the answers:

1. California’s state rock is serpentine, better known as serpentinite.

2. The 1906 San Francisco earthquake was magnitude 7.8.

3. Colma is east of the San Andreas fault and therefore on the North American plate.

4. Santa Cruz, conversely, is on the Pacific plate.

5. The Hayward fault is considered capable of a magnitude 7.5 earthquake.

6. Mount Tamalpais is primarily melange, an intimate mixture of metamorphic rocks.

7. To my knowledge, uranium has never been produced in the Bay Area.

8. No dinosaur fossils are known from the Bay Area.

9. The Rodgers Creek fault continues north where the Hayward fault ends.

10. Mount Hamilton is primarily graywacke, a variety of sandstone.

11. The Green Valley fault continues north where the Concord fault ends.

12. “Calera” is the Spanish term for a limekiln, where limestone is roasted into lime. You may now look up the other three words.

13. The San Gregorio fault occurs onshore only in San Mateo County, just missing San Francisco and Santa Cruz counties.

14. Franciscan rocks are mapped in 14 different entities called terranes.

15. The top of Mount Diablo consists mostly of basalt.

16. The Bureau of Land Management allows personal fossil collecting on the public lands it administers.

17. Mount Konocti, overlooking Clear Lake, is a former volcano, although the others contain volcanic rocks.

18. Mount St. Helena is primarily tuff, or volcanic sediments.

19. Magnesium ore, the mineral magnesite, was mined in the ultramafic rocks south of Livermore during World War II.

20. The Bay Area’s only geyser is in Calistoga, but it’s an artificial one that erupts in a drilled hole.

The Bay Area Geological Holiday Quiz 13 January,2012Andrew Alden

  • Mary Mactavish

    Wow, I knew far more than I expected (will research to make sure I was right), just because I’d internalized some of that without thinking about it. Still not as much as 80%, but more than 50%.

  • Anonymous

    Amazing, I actually got 15/20. Got 6, 7, 8, 15 and 19 wrong.



Andrew Alden

Andrew Alden earned his geology degree at the University of New Hampshire and moved back to the Bay Area to work at the U.S. Geological Survey for six years. He has written on geology for since its founding in 1997. In 2007, he started the Oakland Geology blog, which won recognition as "Best of the East Bay" from the East Bay Express in 2010. In writing about geology in the Bay Area and surroundings, he hopes to share some of the useful and pleasurable insights that geologists give us—not just facts about the deep past, but an attitude that might be called the deep present.

Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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